The struts tag library used by the Struts tag library JSP window component consists of four types of tags: 2. Bean tag: Manage Bean 3. Logical tag: Used to control flow in JSP page: HTML tag: use To generate an HTML tag, display data in the form, programming the URL using the session ID 5. Template tag: Use a dynamic template to construct a normal format page 2.1 bean tag this tag library contains the new bean, access bean and its properties Mark. 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 defines the tag in four subcategories: Create and copy the BEAN's tag script variable definition tag bean translation mark message international tag 2.1.1 Bean replication tag can define a new bean, you can copy the existing bean, you can also There is a bean replication attribute.
Mark is used:
Define new string constants
Copy existing beans to new defined bean objects
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 defined. If the value attribute is not set, this property must set the properties name of the Bean defined by the Property Name property, used to define new beans
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Scope of the 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, the request scope is another bean:
Scope = "Page" Toscope = "request" />
2.1.2 Define 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.
The tag will retrieve a resource response and introduce a script variable and a string type page scope property. This resource can be a page, an ActionForward or an external URL. versus
Differently, the resource response is stored in the bean of a page scope instead of writing 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.
Marking will retrieve resources in web applications and introduce a script variable and page scope attributes for inputStream or string types. If a problem occurs while retrieving resources, an exception is generated. The property is as follows:
Property Description 14
ID script variable and page scope to define the name of the name Name resource relative path 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.
2.1.3 Displaying bean properties
The tag library is defined.
Tags to deliver the properties of the bean to the packaged JSP page write. This tag is
Similar, 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, it will generate a request time anomalies when discovered attributes, otherwise returns NULL
E.g:
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.
2.1.4 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.
Struts framework is used for internationalization
Tags, as well as the Locale and ResourceBundle classes defined in the Java.util packet to implement the Java2 platform support for these tasks. 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 a web-inf / class directory, the file name is
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ApplicationResources.properties, 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.
The 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
2.2 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:
Conditional logic
repeat
Forward / Redirect Response
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2.2.1 Conditional Logic
Struts has three types of conditional logic. The first category can compare the size of the following entities and a constant:
cookie
Request parameters
Parameters of beans or beans
Request header
This type of tag is listed below:
Mark function
Returns true if the constant is equal to the defined entity
Returns true if the constant is not equal to the defined entity
Returns true if the constant is greater than or equal to the defined entity
Returns true if the constant is less than or equal to the defined entity
Returns true if the constant is less than the defined entity
Returns true if the constant is greater than the defined entity
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:
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
In one
Cookie The cookie specified by this property will be checked whether there is a request header specified by this property by this property will be checked whether there is a request parameter specified by this attribute that the request parameter specified by this property will be checked whether there is a name if there is no Property property, then this property is available. The specified bean will be checked if it exists. 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:
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" ).
2.2.2 Repeat marker
Defined in the logical tag library
Tag, it 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
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Java.util.map or an array. There are three ways to define this collection:
Use run time expressions to return a collection of attribute collections
The collection is defined as beans and use the Name property to specify the name of the storage attribute.
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, the search range from the page to the application scope Type is the type of page scope bean, for example:
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.
2.2.3 Forwarding and Redirecting Tags
Forward mark
The 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
The 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:
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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 the value of the query parameter paramscope paramname defined Bean search range
At least one property in Forward, HREF, or PAGE is to be specified when using this tag to indicate which resource will be redirected.
2.3 HTML tag
The Struts HTML tag can be roughly divided into the following functions:
Display form elements and input controls
Display error message
Show other HTML elements
2.3.1 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 can be
