Struts framework

sequence

After two weeks of unremitting efforts, it has finally completed the introduction of the overall architecture and core label library of Strtus. From hard to Struts and HTML tags, you can solve some small problems involving Struts, which can help others, and your help and my efforts are not open, but I want it to give those who want to learn, is being Learn and have learned from different benefits. I know that I am a newbie, but I will use a hundred times effort to continue in this field to in-depth and scalability learning and research. At the same time, it is like what I said, we will use the actual action to prove that we will provide you with the help.

This chapter is suitable for reference materials, not only contains detailed and clear introductions for Struts's overall architecture and main components, but also a detailed introduction to the Struts label library that many people pay attention to, it can be said that it is your hand. Information can be used to perform reference. When you are unclear, you can query here. For your query, I made a directory.

Since the open source software is evolving, this is impossible to be the final version, I will continue to add content and new features. For example, Strus1.1 NESTED TAG, but due to many reason, the speed will not be too fast, this requires everyone's help, I hope everyone will participate in some information.

Finally, I sincerely thank JAG, Banq, Steelg, Holn, Seven Herbs, there is also a mixed-blood, or not him, I will complete this information earlier, but he has exercised my will again.

I have tried my best to avoid errors in the text or code, but people are not finished, and omissions are always inevitable. If you have discovered the mistakes, such as the wrong or wrong code, I would like to feed it to me, which will help others solve the problems, and continue to improve this set of information. My email is: Tyrones@cmmail.com QQ: 36983608

I hope this information can bring you help!

Midnight, August 26, 2002

table of Contents

sequence

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table of Contents

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Struts framework

1. Struts compression package content .........................................................................

2. Struts Architecture (Model - Window - Controller) .....................................................

3. Struts framework components ......................................................................... 4

3.1 Struts configuration file ........................................................................ 5

3.2 ActionServlet class ........................................................................ 7

3.3 Actionmapping Class ........................................................................ 9

3.4 Action class ...............................................................................

3.5 Actionform class ......................................................................... 10

3.6 ActionForward class ...................................................................................

3.7 Error handling .....................................................................................................

Struts tag library

4. Struts Tag Library ...............................................................................................................

4.1 Bean Marker ...................................................................................................................

4.1.1 Bean replication marker .......................................................................

4.1.2 Defining a script variable mark .............................................................................

4.1.3 Showing bean properties ................................................................................................................... ...................................... 15

4.2 Logic Markers .....................................................................................................

4.2.1 Conditional Markers ........................................................................... 16

4.2.2 Repeat marker ...........................................................................

4.2.3 Forwarding and redirect markers .....................................................................

4.3 HTML marker .................................................................................................................

4.3.1 Display form elements and input controls ...............................................................

4.3.2 Shows the mark of the error message ................................................................ 23

4.3.3 Other HTML markers .................................................................... 24

4.4 Template mark .................................................................................. 24

Struts framework

The Struts framework has the advantages of module, flexibility, and reuse of the components, and simplifies the development of MVC-based web applications.

This chapter discusses the Struts architecture in detail. We will see how Struts clearly define control, transaction logic, and appearance, simplifying the development of application processes. We will also introduce how the class provided by Struts makes development work more simple, including:

l Control the program process

l Classs that implement and execute program transaction logic

l The custom tag library makes it easier to create and verify the HTML form.

1. Struts compressed package content

Folder Jakarta-Struts-1.0.2 contains two directories, libs, and webapps. In the lib directory, you can use Struts to create an application is the required file:

Document Description JDBC2_0-stdext.jar contains a JDBC2.0 Optional Package API class. If we want to use the data resources provided by Struts, you need to copy this file to web-inf / lib with all Java classes in the Struts. Also need to be copied to web-inf / lib * .tld tag library descriptor file, describe custom tags in multiple Struts tag libraries. Also copy to Web-Inf / Lib

There is a file under the WebApps directory:

Web application description Struts-Blank.war A simple web application Struts-documentation.war contains all Struts Documents Struts-Example.war strut Struts-Example.War Struts Struts-EXERCISETAGLIB.WAR is mainly used to customize label libraries Increase and use the test page, but you can also demonstrate how to use the struts tag Struts-Template.war contains a simple example of the Struts template tag. Struts-upload.war is a simple example of how to use the struts framework to upload files.

2.Struts architecture

Let us observe the components in the Struts frame from the angle of the MVC

Three parts of the frame: model, window and controller.

model

In the Struts framework, the model is divided into two parts:

l system internal state

l You can change the status of the status (transaction logic)

The internal state is usually represented by a set of ActInform JavaBean. These beans may be self-contained and have a continuous state depending on the design or application complexity, or data (from a database) is only available when needed.

Large applications are typically encapsulated transaction logic (operation) in method, which can be called the bean call. For example, shopping cart bean, it has information about purchasing goods, there may be a checkout () method to check the user's credit card, and send information to the warehouse. In a small program, the operation may be embedded in the Action class, which is part of the controller role in the Struts framework. This method is very suitable when logic is simple.

It is recommended that users separate transaction logic (what to do) with the role (decision to do) played by the Action class.

Windows

Established by JSP, Struts contains extended custom label libraries to simplify the process of created a fully international user interface.

Controller

In Struts, the basic controller component is an instance servert in the ActionServlet class, and the actually used servlet is defined by a set of mappings (described by the ActionMApping class) in the configuration file.

3. Components in the Struts framework

(Because the ROSE tool has not been downloaded, only this picture can be found, it illustrates a certain problem, especially ActionerRors, but it does not contain ActionMapping, JSP, and Tag Library, there is time to replace it.)

The components used in the frame:

ActionServlet Controller ActionClass Contains Transaction Logic ActionForm Display Module Data ActionMApping Help Controller to Map to ActionForward Use to indicate Observed Object ActionError Used to Storage and Recycling Error The Struts Tag Library can reduce the development display hierarchy

Let's take a look at the roles and responsibilities they play in the framework.

3.1 Struts Profile

This is the strew-config.xml that combines the Struts component: struts-config.xml. Defaults

/Web-inf/struts-config.xml. Profiles can be defined:

l Global forward

l actionmapping class

l actionform bean

l JDBC data source

Configure global forwarding

Global forwarding is used to create logical name mappings between JSP pages. Forwarding can be obtained by an instance that calls an operation map, for example:

ActionMappingInstace.FindForward ("LogicalName");

Example of global forwarding: (All example I have not explained, one is that the combination table can be understood, the second is that most of the examples from the series four, you should take a look after the experiment, then look at it)

Property Description Name Global Forwarded Name Path Path and Target URL

Configuring actionmapping

The ActionMapping object helps process control within the framework, which can map the request URI to the Action class and associate the Action class with the ActionForm bean. ActionServlet uses these mappings internally and transfers control to an instance of a specific Action class. All Action classes use the Perform () method to implement a specific application code, return an ActionForward object, including the target resource name of the response forwarding. E.g:

TYPE = "BOOKAATION" name = "bookform"

Scope = "request"

INPUT = "/ createbook.jsp">

Property Description The relative path of the PATH Action class NAME is connected to the Action BEAN of the Action BEAN Type connected to the Action of the Action Class of this map (can be included) Scope ActionForm Bean scope (request or session) prefix is ​​used to match the request The prefix of the parameter and the bean property is used to match the suffix attribute scope of the request parameter to the bean property. The fully qualified name of the class of the classname actionMapping object is org.apache.struts.Action.ActionMapping input input to the path to enter the form, pointing to the Control Unknown, which must return to the BEAN, set to True, the operation will be used as all unselected The default operation validate of the ActionMapping URI is set to TRUE, before calling the Perform () method on the Action object, the ActionServlet will call an actionform bean's validate () method for input check.

With elements, the logical name of the resource can be defined, which is the target of the Action class's response to be forwarded.

Property Description ID ID ClassName ActionForWard class fully qualified name, the default is org.apache.struts.Action.ActionForward Name Operation class Access ActionForward When the logical name path response forwarding the path of the target resource of the forward, the ActionServlet is used by the ActionServlet SendRedirect () method to forward resources

Configuring an actionform bean

The ActionServlet uses ActionForm to save the request parameters, these beans correspond to the name in the HTTP request parameter, the controller passes the request parameters to the ActionForm bean instance, and then transfer this instance to the Action class. example:

Property Description ID ClassName ActionForm Bean's fully qualified name, the default value is the name of the org.apache.struts.Action.ActionFormBean Name form BEAN in the relevant scope, this property is used to associate bean with actionmapping's fully qualified name of the TYPE class

Configure JDBC data sources

Use the elements to define multiple data sources.

Property Description ID The Id KEY Action class uses this name to find the name of the class that connects Type to implement the JDBC interface

The following property requires the element definition, is not used in the framework 1.1 version, but you can use the element. example:

TYPE = "org.apache.struts.util.GenericDataSource"

AutoCommit = "True"

Description = "EXAMPLE DATA SOLRE Configuration"

Driverclass = "org.test.mm.mysql.driver"

Maxcount = "4"

MinCount = "2"

URL = "JDBC: mysql: // localhost / test"

User = "struts"

Password = "wrox" />

Property Description Description Data Source Description AutoCommit Data Source The default Auto Update Database Mode DriverClass Data Source is used to display the class of the JDBC driver interface logintimeout database login time, in seconds. Maxcount. Most Established connection Number of connections MINCOUNT To create the minimum number of connections Password database Access password Readonly Create a read-only connection USER access database username URL JDBC URL

By specifying the keyword name, the Action class can access the data source, such as:

Javax.sql.datasource DS = servlet.finddataSource ("contool");

Javax.sql.connection con = ds.getConnection ();

3.2 ActionServlet class

The controller component in the frame is an org.apache.struts.Action.ActionServlet class implementation, this class is an extension of the javax.servlet.http.httpservlet class.

The Struts Controller's basic function is: 1. Intercepting the user's HTTP request 2. Map the request to the corresponding Action class, if this is the first request received by this class, the instance will be initialized

Capacity. 3. Create or discover an ActionForm bean instance (see if the configuration file is defined), then transplant the request process to

Bean.4. Call the perform () method of the Action instance and use Actioform Bean, Action Mapping object, Request

Pass with the Response object. Such as: Public ActionForWord Perform (ActionMapping Mapping, ActionForm, httpservletRequest Request, HttpservletResponse response) 5.Perform Returns an ActionForWord object, which is connected to the appropriate JSP page.

ActionServlet configuration

We need to declare an actionServlet in Web.xml and configure it to be loaded. The following is an initialization parameter that can be configured:

Parameter Default Value Description Application Null Application Resource Collection Class Buffersize 4096 File Uploaded Buffer Size Config /Web-inf/Struts-Config.xml Profile Location and Name Content Text / HTML Default Content Type Debug 0 Program Debugging Level Detail 0 Program Debugging Details Factory Null Message Resource Factory, Used in Internationalization Interpretation Message Resources FORMBEAN Org.Apache.Struts.Action.ActionFormBean Package Actionform Bean Information Class name forward Org.apache.struts.Action. class name locale true ActionForward package ActionForward object information is true, a local object is stored in the user session information for mapping org.apache.struts.action.ActionForward package ActionMapping class name maxFileSize multipartClass org 250M maximum size of the uploaded file. Apache.struts.Action.ActionForward Processes the name of the class of multi-part requests NOCACHE FALSE HTTP header to be set to the Prohibition Capital Null True Set to True, and return null Tempdir as a servlet parameter for invalid information keywords. The work directory processing download file is the temporary work directory VALIDATE TRUE to use the new format profile Vallidating True to effectively analyze the configuration files, the standard servlet can meet the needs of users.

When the URI of the first received a specific request, the ActionServlet instantiates the appropriate Action class, and the ActionServlet stores a reference in servlet in the Action class instance. When instantiated, the Action class will be temporarily stored.

ActionServlet also provides some methods that use the Action class to access resources such as data sources and forwarding targets.

ACTIONSERVLET method

ActinServlets provide a group of methods that can be used by Action objects.

All information for the Struts API can be found in Struts-Documentation.war. Dynamic add or delete, these methods only affect the current instance of the application:

Public Void AddFormbean (ActionformBean Formbean)

Public Void RemoveFormBean (ActionformBean Formbean)

Public Void Addforward (ActionForward ActionForward)

Public Void RemoveForward (ActionForward ActionForward)

Public void addmapping (actionMapping actionmapping)

Public void removemapping (actionMapping actionmapping)

Find objects according to the name:

Public ActionFormBean FindFormbean (String Name)

Public ActionForward FindForward (String Name)

Public anctionMAPPING FINDMAPPING (String Name)

Used to process data sources:

Public Void AddDataSource (String Key, DataSource DS)

Public DataSource FindataSource (String Key)

We can also:

l Use the destroy () method to end ACTIONSERVLETL Use the Reload () method to reload the information from the Struts profile.

3.3 ActionMApping class

The relevant information mapped to a specific Action is stored in an actionMApping. ActionServelt transmits actionMApping to the Perform () method of the ActionMApping, Action will use an actionMApping's FindForward () method, this method returns an actionforward that specifies the name, so that ACTION Completed local forwarding. If you do not find a specific ACTIONFORWARD, you will return a NULL.

Public ActionForward FindForward (String Name)

You can dynamically add ACTIONFORWARD in the mapping:

Public Void Addforward (ActionForward Forward)

You can return to form beans associated with mapping:

Public string getName ()

Remove the mapping attribute domain (session or request)

Public string getscope ()

3.4 Action class

The Action class truly implements the application's transaction logic, which is responsible for processing the request. After receiving the request, the ActionServlet will:

l Select the appropriate action for this request.

l If you need, create an instance of an action

l Call an perform () method

If an ActionServlet does not find a valid map, it calls the default Action class (defined in the configuration file). If you find the ActionServlet forward to the appropriate actionMApping class, this action uses actionMapping to find local forwarding, then get an actionMApping property. The ActionServlet also transmits the ServletRequest object or HTTPServletRequest object according to the signature of the servlet environment and the overform () method.

All Action classes expand the org.apache.struts.Action.Action class, and override a perform () method defined in the class. There are two perform () methods:

Handling non-HTTP (general) request:

Public ActionForward Perform (ActionMapping Action,

ACIONFORM FORM,

ServletRequest Request,

ServletResponse response)

THROWS IOEXCEPTION, ServletException

Handle HTTP request:

Public ActionForward Perform (ActionMapping Action,

ACIONFORM FORM,

HTTPSERVLETREQUEST REQUEST,

Httpservletresponse response

THROWS IOEXCEPTION, ServletException

The Action class must program as "thread security" because the controller will share the plural simultaneous request to share the same instance, according to the design of the Action class, you need to pay attention to the following points:

l You cannot use instances or static variables to store status information for specific requests, which share global resources across the request in the same operation.

l If the resources you want to access (such as JavaBean and Session Variables) need to be protected when parallel access, then access is synchronous

Method of Action class

In addition to the perform () method, there is also the following methods:

You can get or set the area associated with the request:

Public Locale getLocale (httpservletRequest request)

Public void setlocale (HttpservletRequest Request, Locale Locale)

Get a message resource for your application:

Public MessageResources getResources ()

Check if the user clicks on the "Cancel" button on the form, if yes, True will be returned:

Public Boolean ISCANCELED (HTTPSERVLETREQUEST REQUEST)

When an application error occurs, the Action class can store error messages using the following method:

Public Void SaveErrors (HttpservletRequest Request, ActionerRors Error)

The ActionError instance is used to store an error message, which stores the ActionError object in the request attribute list under the error key. The JSP page can display these error messages by using the custom tag defined in the Struts tag library. We will introduce later.

3.5 Actionform class

The framery assumes that the user creates an actionform bean for each form in the application, and the framework will do the following before the bean defined in the Struts-Config.xml file is called before the action class:

l In the associated keyword, it checks the user session of the Bean instance for the appropriate class, if there is no Bean available in the session, it will automatically create a new bean and add it to the user's session.

l For each parameter corresponding to the bean property name, the Action calls the corresponding setting method.

l When Action Perform () is called, the latest ActionForm bean is transmitted to it, and the parameter value can be used immediately.

ActionForm class extension org.apache.struts.Action.Actionform class, the BEAN created by program developers can include additional properties, and ActionServlet may use reflection (allowing recycling information from loaded objects) to access it.

The ActionForm class provides another means of handling errors, providing two methods:

Public ActionerRors Validate (ActionMappin Mapping,

ServletRequest request)

Public ActionerRors Validate (ActionMappin Mapping,

HttpservletRequest Request)

You should override the validate () method in your own bean, and set the validate of the element in the configuration file to True. Before the ActionServlet calls the Action class, it calls validate (), if the ActionerRors returned is not null, ActinForm will store ActionerRors in the request attribute list based on the error keyword.

If the returned is not NULL, and the length is greater than 0, the instance is stored in the requested attribute list according to the error key, and then the ActionServlet will be forwarded to the target pointing to the INPUT property of the configuration file element.

If you need to perform a specific data validity check, it is best to do this in the Action class, not in the ActionForm class.

Method RESET () can restore the properties of the bean to the default value: public void reset (actionMapping mapping, httpservletRequest request)

Public Void Reset (ActionMapping Mapping, ServletRequest Request)

A typical actionFrom bean only has a method of setting with a read method (Getxxx) without transaction logic. Only simple input check logic, the purpose of use is to store the latest data entered in the relevant form so that the same web page can be regenerated while providing a set of error messages so that the user can modify the incorrect input data. It is really checking data validity to check the Action class or the appropriate transaction logic bean.

3.6 ActionForward class

The purpose is to forward the processing results of the Action class to the destination.

The Action class gets the handle of the ActionForward instance, and then use three methods to return to the ActionServlet, so we can use Findforward ():

l ActionServlet obtains a global forwarding according to the name

l ActionMAppin instance is transmitted to the Perform () method, and found a local forwarding according to the name

The other is to call the following constructor to create an example of themselves:

Public anctionforward ()

Public ActionForward (String Path)

Public ActionForward (String Path, Boolean Redirect)

3.7 Error handling

Struts provides two classes to handle errors: ActionerRRORS and ActionError, they all expand org.apache.struts.Action. ActionerRORS saves a collection of ActionError objects, each represents an independent error message. Each ActionError contains a keyword, which is mapped to the error message stored in the resource file, and this resource file is specified in the ActionServlet initialization parameter.

ActionError class

The ActionError class defines a set of overloaded constructors to create an error message, the first constructor method uses a string as a parameter, for example:

Actionerror Error = New Actionerror ("Error.INvalid");

Example Error maps an error message in the application resource file:

Error.INValid = invalid number

If you use , users will see the bold invalid number.

Another Java.Text.MessageFormat class can specify a replacement string in the message, for example:

Error.invalid = invalid number {0}

Create an error message:

ActionError Error = New Actionerror ('Error.invalid', New Double (-1));

JSP page display: Invalild Number -1

There is also a wrong keyword for a specific message:

Public string getKey ()

There is also an array of replacement strings:

Public String [] getValues ​​()

ActionError class

The ActionError class is not independently errors, which are always stored in the ActionerRors object. The ActionerRors object saves a collection of ActionError classes and their specific attribute values, we can use our own defined attribute values, or use ActionerRors.global_ERROR. Below is an error handling in Perform () of the typical Action class:

MyForm Form = (MyForm) Form;

IF (Number == -1) {

ActionerroS Errors = new actionerrors ();

ActionError Error = New ActionError ("Error.INvalid", New Double (-1));

Errors.Add (ActionerRors.global_Error, Error);

SaveerRors (Req, Errors);

String infut = mapping.getinput ();

Return New ActionForward (Input);

}

ActionerRors have the following useful methods:

Method Description clear () Clear all error messages EMPTY () If the ActionerrorS object is empty, it returns true get () returns an error message. If there is no parameters, all information will return Properties as an Iterator object () Returns the item containing the name of the property name, these attributes have at least one error size () returns the number of errors (intensity)

Struts tag library

4.Struts Tag Library

The Struts tag library used by JSP window components consists of four types of tags:

l bean tag: Manage Bean in JSP page

l Logic tag: Control flow in the JSP page

l HTML tag: Used to generate an HTML tag, display data in the form, program the URL using the session ID

l Template tag: Use dynamic template to construct a page of normal format

4.1 bean tag

This tag library contains tags for defining new beans, accessing beans, and its properties. The STRUTS framework provides a variety of custom tags to process JavaBean in the JSP page. These tags are packaged in a normal tag library, define its tag library descriptor in file struts-bean.tld. The bean tag library will define the tag in four subcategories:

l Create and copy the tag of bean

l Script variable definition tag

l bean translation mark

l Message Internationalization Mark

4.1.1 Bean Copy Mark

You can define a new bean, you can copy the existing bean, you can also replicate properties from the existing bean.

tag is used:

l Define new string constants

l Copy existing beans to new defined bean objects

l Copy the properties of the existing bean to create new beans

Tag properties:

Property Description ID The new defined bean script variable name, you must set the Type definition to introduce the class Value of the script variable to assign a new object Name target bean name for the ID attribute. If the value attribute is not set, this property must set the properties name of the Bean defined by the Property Name property to define the scope of the new Bean Scope source bean. If there is no setting, the search range is the scope of the slave page scope to the application scope TOSCOPE target bean. If there is no setting, the default value is a page scope

For example: Define a bean:

source bean is copied in the page scope to the other bean in the request scope:

Scope = "Page" Toscope = "request" />

4.1.2 Defining the tag of scripting variables

Define and generate script variables from multiple resources, including cookies, request parameters, HTTP headers, and more. The property is as follows:

Property Description ID Script Variable and Type Name of Page Scheme Properties To Define Name Cookie / Header / Parameters Multiple If this property sets any value, all matched cookies are accumulated and stored in a cookie [] Array) type bean. If there is no setting, specifying the first value of the cookie will be the value of the cookie type if the value is not matched, the default value specified by this property is returned.

E.g:

The script variable name is MyCookie, the name of the cookie for creating this property is UserName.

The script variable name is MyHeader, the name of the request header is accept-language.

The script variable name is MyPatameter, and the name of the request parameter it saves is also myParameter.

tag will retrieve a resource response and introduce a script variable and a string type page scope. This resource can be a page, an ActionForward or an external URL. Unlike , the resource response is stored in the bean of a page scope, not written to the output stream. The property is as follows:

Property Description ID Script Variables and Page Scheme Properties of To Definition Page An internal resource forward Forward an actionforward href's full URL

E.g:

The name of the script variable is MyInClude, and the response to retrieve is from the resource myjsp? X = 1.

Tag will retrieve resources in the web application and introduce a script variable and page scope attribute of the InputStream or string type. If a problem occurs while retrieving resources, an exception is generated. The property is as follows:

Property Description ID Script Variable and Name Name Name Name The relative path of Name resources INPUT If this property does not exist, the type of resource is a string

E.g:

The name of the script variable is MyResource, the name of the resource to retrieve is MyResource.xml.

4.1.3 Displaying Bean Attributes

The tag is defined in the tag library to deliver the properties of the bean to the packaged JSP page write. This tag is similar to , the properties are as follows:

Property Description Name The name of the name to display by the property displayed by the property is Property. If this attribute class has java.beans.propertyEditor, getastext () or TSTRING method will call Scope Bean's scope, if no settings are set, search range is from page to application scope Filter If set true, all specials in attributes HTML characters will be converted to the appropriate entity reference IGNORE If false is set, a request time is generated when an attribute is found, otherwise returns NULL, for example:

FILTER = "true" />

MyBean's property MyProperty will be displayed, the scope is a request, and if any HTML special characters are found, it will be converted to the corresponding entity reference.

4.1.4 Message markers and internationalization

The STRTUS framework supports internationalization and localization. Users define their own area in their computer, when the web application needs to output a message, it will reference a resource file, all messages in this file use the appropriate language. An application may provide a lot of resource files, each file provides messages written in different languages. If you do not find the resource file of the selected language, you will use the default resource file.

The Struts Framework supports internationalization uses the tag, and the support of these tasks to implement the Java2 platform using the Locale and ResourceBundle classes defined in the Java.util packet. Java.Text.MessageFormat class definitions can support messages. With this feature, developers do not need to understand the details of these classes to internationalize and set messages.

Internationalization and localization with STRTUS:

The first step To define the name of the resource file, this file will contain all messages that will appear in the program with the default language. These messages are stored in the form of "keyword-value" as follows:

Error.validation.Location = The Entered Location Is Invalid

This file needs to be stored under the path of the class, and its path is to transmit to the ActionServlet as a parameter as a parameter, and the path format should comply with the standard naming specification for the full Java class. For example, if the resource file is stored in the web-inf / class directory, the file name is ApplicationResources.properties, then the parameter value that needs to be passed is ApplicationResources. If the file is in web-inf / classs / com / test, the parameter value should be com.test. ApplicationResources.

In order to achieve internationalization, all resource files must be stored in the directory where basic resource files are located. The basic resource file contains messages written in the local language in the default regional language - local language. If the name of the basic resource file is ApplicationResources.Properties, the name of the resource file written in other specific languages ​​should be ApplicationResources_xx.properties (xx is ISO code, such as English is en). So these files should contain the same keyword, but the value of the keyword is written in a particular language.

The area initialization parameters of the ActionServlet must be transmitted with a TRUE value so that ActionServlet stores a region object of a particular user computer under an action.locale_key keyword in the user session. You can now run an international Web site that automatically displays in accordance with the area on the user's computer.

We can also use a specific string to replace some messages, just like Java.Text.MessageFormat: error.invalid.number = the number {0} is Valid

We can replace the string {0} to any number we need. Tag properties are as follows:

Property Description The property name of the area object stored in the Key resource file defines the area object stored in the LOCALE user session. If there is no setting, the default value is an action.locale_key bundle in the application context, store the name of the properties of the resource object. If this property is not set, the default value is an action.Message_Key Arg0 The first replacement parameter value arg1 second replacement parameter value arg2 third replacement parameter value arg3 fourth replacement parameter value

For example: a message defined in the resource file:

Info.mykey = the number in {0}, {1}, {2}, {3}

We can use the following message tag:

This information mark output to the JSP page will be displayed as: The NumBers Entered Area 5, 6, 7, 8

4.2 Logical Tag

The mark of the logical library can be used to process appearance logic without the need to use the Scriptlet. The Struts Logic Tag library contains tags that can be conditionally generated, looped in an object collection, repeatedly generating output text, and application process control. It also provides a set of tags that handle flow control in the JSP page. These tags are encapsulated in the file named Struts-Logic.TLD. The mark defined by the logical tag library can perform the following three functions:

l condition logic

l repeat

l Forward / redirect response

4.2.1 Conditional Logic

Struts has three types of conditional logic. The first category can compare the size of the following entities and a constant:

l cookie

l request parameters

L bean or bean parameters

l request header

This type of tag is listed below:

Tag function If the constant is equal to the defined entity, return true If the constant is not equal to the defined entity, return True If the constant is greater than or equal to the defined entity, return True if constant Less than or equal to the defined entity, return True If the constant is less than the defined entity, return True If the constant is greater than the defined entity, return TRUE

All markers of this class have the same properties

Property Description Value To make a comparison of the name of HTTP cookies to compare the HTTP request header of the comparison HTTP request header name Parameter To make comparison HTTP request parameters Name Name If you want to make a bean or bean Attribute, then this property represents the name of the BEAN's name Property to compare the name of the name Scope BEAN, if no scope is specified, its search range is from the page to the application

E.g:

The entered name is someamename

The value of the request parameter named "Name" is "Somename".

The value of bean.prop is Greater Than 7

It is determined whether there is a bean named "bean" in the scope of the page, which has a PROP attribute, whether the value of this property is greater than 7. If this property can be converted to a value, the numerical comparison is performed, otherwise the string is compared.

The second type of condition tag defines two tags:

l

l

Their function is to determine if a specific item is present before calculating the marker. The attributes and attribute values ​​of the tag determine the item to be checked.

Property Description Cookie The cookie specified by this property will be checked whether there is a request header specified by the header by this property will be checked whether there is a request parameter specified by this attribute that will be checked whether there is a name if there is no Property property, then The bean specified by this property will be checked. If set, the bean and bean properties will be checked. Property Checks if there is a name specified by the Name property specified by the specified property Scope If the name of the bean is specified, this is the scope of the bean. If you do not specify a scope, the search range is from the page to the application scope. Role Checks whether the current confirmed user belongs to a special role user check whether the current confirmed user has a specific name

E.g:

The Bean Property Bean.prop is present

The tag determines whether there is a bean named "bean" in the page scope, this bean has a PROP property.

The third type of condition mark is more complicated, and these markers check the contents of the mark according to the results of the template match. In other words, these tags determine if the value of a specified item is a substring of a particular constant:

l

l

These tags allow the JSP engine to calculate the marker main body when the matching or no discovery is found. The property is as follows:

Property Description Cookie The name of the HTTP cookie to compare Header to compare the name of the HTTP header of the HTTP header Parameter to compare the name Name to compare the name Name to compare the properties of the bean or bean, this property is the user designated The name of the bean Location If the value of this property is set, the specified location (index value) will match Scope If the bean is compared, this property specifies the scope of the bean. If this parameter is not set, the search range is the constant value of the property name Value to be compared from the page to the application scope of Property.

E.g:

The parameter name is a sub-string of the string xyz from index 1

The mark checks if the request parameter named "name" is a sub-string of "XYZ", but the sub-string must start from the "XYZ" index position 1 (that is, the sub-string must be "y" or "yz" ). 4.2.2 Repeat marker

The tag is defined in the logical tag library, which can repeat the content of the marker according to the number of elements in a particular set. The type of collection can be java.util.iterator, java.util.collection

Java.util.map or an array. There are three ways to define this collection:

l Use the runtime expression to return a collection of attribute sets

l Define the collection as a bean and use the Name property to specify the name of the storage attribute.

l Use the Name property to define a bean and use the Property property to define a BEAN property that returns a collection.

The collection of current elements is defined as a bean of a page scope. The attributes are as follows, all of these properties use runtime expressions.

Property Description Collection If the Name property is not set, it specifies the name of the set ID page scope to repeat the set ID page scope, which saves the name of the current element's handle indexed page Schedule JSP bean name, it contains The current index of the collections after each repeated completion, the maximum number of times Name is the name of the set of bean, or a bean name, which is defined by the Property property, is a set of Offset Repeat Start Location Index Property as a collection of bea property. Name Scope If the bean name is specified, this property sets the BEAN's scope. If there is no setting, search range from the page to the application scope type TYPE Type for the currently defined page scope bean

E.g:

Collection = "<% = myList%>"

TYPE = "java.lang.integer"

OFFSET = "1"

Length = "2">

<% = currentint%>

The code will use the first element in the list to repeat two elements and allow the current element to use the script variable of the page scope and the Java.lang.integer type. That is, if MYLIST contains elements 1, 2, 3, 4, etc., the code will print 1 and 2.

4.2.3 Forwarding and Redirecting Tags

Forward mark

tag can forward the response to the redirect to a specific global ActionForward. The type of ActionForward determines whether to use the pageContext forward response or use SendRedirect to redirect the response. This marker has only one "name" property to specify the name of the global ActionForward, for example:

Redirect tag

tag is a powerful tool that can perform HTTP redirection. According to the specified different properties, it can achieve redirection in different ways. It also allows developers to specify query parameters for redirect URLs. The property is as follows:

Property Description Forward Mapping the ActionForward HREF resource of the resource relative path The relative path name, request, session, or program property of the Name Map type, which contains a big redirect URL (if no Property is set) The Name-Value parameter on the property). Or the bean name with the MAP type attribute, which contains the same information (no provosty attribute) the name of the bean property of the Property Map type. The name of the bean is specified by the Name property. Scope If the name of the bean is specified, this property specifies the range of search beans. If there is no setting, search range from the page to the application scope paramid define the name of the name of the specific query parameter paramname string type, which contains the value of the query parameter (if the paramproperty property is not set); or a bean name, Its property (specified in the paramproperty property) contains the name of the query parameter value paramproperty string bean property, which contains at least Forward, HREF or PAGE when the value of the query parameter paramese paramname defined bean uses this tag. A property in order to indicate which resource will be redirected to the response.

4.3 HTML tag

The Struts HTML tag can be roughly divided into the following functions:

l Display form elements and input controls

l Display error message

l Display other HTML elements

4.3.1 Display Form Elements and Input Controls

Struts is closely linked with the HTML form with the ActionForm Bean defined for formal operations. The name of the form input field is corresponding to the attribute name defined in the ActionForm Bean. When the form is first displayed, the input field of the form is transplanted from the ActionForm Bean. When the form is submitted, the request parameter will be transplanted to the Actionform Bean instance.

All the following properties can be used to define the JavaScript event processor using the following properties.

The attribute description ONBLUR field lost the focus onchange field lost the focus and the value was changed. The onclick field was changed by the mouse Click the onfocus field. The onfocus field is received by the mouse to receive the input focus onkeyDown field has focus and the key Press the onkeypress field with the focus and key Press. The onkeyup field has a focus and the key is released to the onmidown mouse pointer points to the field and click the OnMouseMove Mouse Pointer to point to the field and move the onmouseout mouse pointer to the control, but the pointer is moving the ONMOUSEOVER mouse pointer in the element, but pointers Move the onmouseup mouse pointer inside the element points to the field, and release the mouse button

Other general properties that can be defined in

elements are:

Property Description AccessKey Defines the Shortcut Key Style Definition of the Enter Field Style StyleSyleClass Defines the Tab Index Input Field Tabindex Enter the Tab Up.

Form mark

tag is used to display HTML tags, you can specify the name of the AcitonForm Bean and its class name. If these properties are not set, you need to have a configuration file to specify an actionMApping to indicate which JSP page currently entered, and the Bean name and class retrieved from the map. If you do not find the specified name in the scope specified by ActionMapping, you will create and store a new bean, otherwise the found bean will be used.

The tag can include a sub-tag corresponding to various HTML input fields. tag properties are as follows:

Property Description Action is related to a form. In the configuration, this operation is also used to identify the name of the HTTP method Name and form-related Actionform Beans that require initialization focus in the encoded type FOCUS form associated with the form of an ActionForm Bean EncType form. If this property does not set this property, the name of the bean will get the JavaScript event handler when reset from the configuration information, the JavaScript event handle Scope, the JavaScript event handle, the JavaScript event handle Scope search for the range of Actionform Beans. If there is no setting, you will get the format of the format STYLECLASS for the format of the format of the Style table Type ActionForm Bean. If there is no setting, it will be obtained from the configuration file.

E.g:

The operation path associated with the form is ValidateEmployee, and the form data is passed through POST. For this form, additional information, such as the bean name type, the scope of the scope, is retrieved from the form specified by the form:

TYPE = "com.example.validateexample"

Name = "Empform"

Scope = "request"

Input = "/ employeeinput.jsp">

If the configuration file contains the above information, and requesting the URI * .do is mapped to the ActionServlet, the name, type, and scope of action-related Actionform Beans are Empform, Com.example.employeform, request. These properties can also be used. Tag properties are defined.

The following tags must be nested in the tag

Button and cancellation

tag Displays a button control; tag Displays a cancel button. The property is as follows:

Property Description Property defines the tag on the name of the request parameter that returns to the server when the form is submitted

Reset and submission tag

and tags can display HTML reset buttons and submitting buttons.

Text and text zone tag

and Tags respectively HTML text boxes and text areas, the properties are as follows:

Property Description Property Defines the name of the request parameter that is sent back to the server when the form is submitted, or to determine the name of the reality name Name property of the text element, which determines the text box and the text area. value. If there is no setting, the name of the ACTIONFORM associated with this embedder form tag has the following properties:

Property Description MaxLength enters the size of the maximum number of characters Size text box (number of characters)

Mark a unique property is as follows:

Attribute describes the number of rows of rows in the ROWS text area column number

Check box and check box tag

Tags can display check box controls. Tags You can display the HTML checkbox control, request the object to get the getParameterValues ​​() call used when passing the check box name will return a string array. The property is as follows:

Attribute describes the name of the Name Bean, its property is used to determine if the check is displayed in the selected status display. If there is no setting, the name of the ActionFrom Bean associated with this embedded form will be used. The name of the Property check box is also the bean property name that determines if the check box is displayed in the selected status. In the case of the check box, this property must be an array. Value When the check box is selected to return to the server's request parameter

E.g:

A checkbox called Married, returns a "y" when the form is submitted.

File tag

tag can display HTML file controls. The property is as follows:

The property describes the name of the name bean, and its properties will determine the content displayed in the file control. If not set, the name of the ACTIONFORM BEAN associated with the embedded form is defined. The name of the request parameter sent back to the server when the form is submitted, and the bean property name used to determine the display content in the file control. ACCEPT The content type set of the server can handle. It will also filter the tags on the Value button on the optional file type in the Customer Browser dialog, which can browse files in the local file system.

Single button tag

tag is used to display the HTML radical button control, the property is as follows:

The property describes the name of the Name Bean, which is used to determine if the radio button is displayed in the selected state. If there is no setting, the name of the ActionFrom Bean associated with this embedded form will be used. Property When the form is submitted to the name of the request parameter of the server, and the name value of the bean property used to determine if the radio button is displayed in the selected state, the value returns to the server when the single-select button is selected.

Hidden tag

Property Description Name bean's name, its property is used to determine the current value of the hidden element. If there is no setting, the name of the ActionFrom Bean associated with this embedded form will be used. Property defines the name of the request parameter sent back to the server when the form is submitted, and the name value of the bean property used to determine the current value of the hidden element is used to initialize the value of hidden input elements.

Password mark

tag can display the HTML password control, the properties are as follows:

The property describes the name of the maximum number of characters that MaxLength enters the name bean, which will be used to determine the current value of the cryptographic element. If there is no setting, the name of the ActionFrom Bean associated with this embedded form will be used. Property defines the name of the request parameter that is sent back to the server when the form is submitted, and the name of the bean property used to determine the current value of the password element is displayed, if the corresponding bean property has been set, this The property determines whether the size of the content size field of the password is displayed.

tag can display HTML selection controls, the properties are as follows:

Property Description MultiPle indicates whether this selection control allows the name of the NAME BEAN, which is determined which. If there is no setting, the name of the ActionFrom Bean associated with this embedded form will be used. Property defines the name of the request parameter that is sent back to the server when the form is submitted, and the name of the Name of the bean property to determine which option needs to be selected, the number of options that can be displayed simultaneously VALUE is used to indicate the option to be selected.

Option tag (this element needs to be nested in tag)

Tag Use to display the HTML option element collection, the properties are as follows:

The property describes the name of the Collection Bean collection, which is stored in the properties of a scope. The number of options is the same as the number of elements in the collection. The Property property can define the bean property used by the option value, and the LabelProperty property definition option tag is used to specify the bean stored in a scope, this bean is a collection of strings and can define The tag of the element (if the flag is not the same) LabelProperty is used in common with the Collection property, and the bean stored in a scope is defined. This bean will return a string collection that can be used to write < HTML: OPTION> Element Value Attribute Name If this is the only specified property, it defines the bean stored in a scope. This bean will return a string collection that can be used to write The value of the value of the element Property This property is used in conjunction with the Collection property, defines the NAME attribute of each independent bean to display the option value. If it is not used together with the Collection property, this property defines the property name (if there is a Name property) specified by the Name property, or defines an actionform bean, this bean will return a collection to write an option value.

Let's take a look at some examples of this tag:

Labelproperty = "optionLabel" />

The tag assumes that there is a collection of optioncollection in a scope that contains some independent beans with optionValue properties, each with the value of an option. The flag of each option is defined by the BEAN's OptionLabel property property.

OptionValues ​​represents a bean stored in a scope, it is a string collection that can be used to write an option value, while OptionLabels represents a bean stored in a scope, it is also a string A collection that can be used to write an option sign. 4.3.2 Display the mark of the error message

tag can be combined with ActionerRORS to display the error message. This tag first reads the message key ERRORS.HEADER from the resource file of the current area, and then displays the text of the message. Next it will cycle in the ActionerRRORS object (usually as a request parameter in the action.error_key keyword), read the message keyword of a single ActionError object, read and format the corresponding message from the resource file of the current area. And display them. It then reads the message corresponding to the ErrorS.footer keyword and is displayed.

By defining the Property property to filter the message to display, the value of this attribute should correspond to the keyword of the ActionError object in the ActionerRROR object. The property is as follows:

Property Description BUNDLE represents the name of the application scope attribute, which contains message resources. The default value ACIion.Message_Key Locale represents the name of the session scope attribute, which stores the currently logged in area information. Its default is that Action.Error_Key Name indicates the name of the request attribute, which stores an ActionerRors object. Its default is the action.Error_Key Property property specifies the keyword to store each independent ActionError object in the ActionerRORS object, which can be filtered

example:

Display all errors in the collection.

Shows errors stored in miss.name keywords.

4.3.3 Other HTML tags

The Struts HTML tag also defines the following tags to display other HTML elements:

l : Show HTML elements

l : Display image tag

l : Display HTML link or anchor

l : Create a URI without an anchor tag

For details of these tags, please refer to the Struts documentation.

4.4 Template tag

The dynamic template is a powerful means of modular web page layout design. The Struts Template Tag Library defines custom tags to implement dynamic templates.

Insert tag

Tags can insert a dynamic template in the application's JSP page. This tag has only one template property that defines a template JSP page. To insert a page of the template, there are multiple tags to specify, and these tags are defined as the main content of the tag.

Placement mark

tag is the tag internal use to specify the resource inserted into the template. The property is as follows:

Property Description Content Defines the content to be inserted, such as a JSP file or an HTML file Direct If this setting is true, the content specified by the Content property is displayed directly on the JSP instead of the name Role if the content to be inserted. This property is set, and the content can be performed only when the current legitimate user has a specific role.

Get marker

Use the tag to retrieve the resources to the JSP page by the tag in the template JSP page. The property is as follows: Property Description Name The name Role of the content inserted by the tag Role If this property is set, only the current retrieval can be performed when the current legal user has a specific role.

Use template tag

First write a template JSP page, it will be used by all web pages:

<% @ Taglib Uri = "/ Template" prefix = "template"%>