(Reprinted from IBM DeveloperWorks China website Java Zone, http://www-900.ibm.com/developerWorks/java/j-struts/index.shtml)
Malcolm Davis Consultant February 2001
Content: Introduction JSP is the use of too many Java MVC MVC Model 2 Struts in my HTML. Sample Sample Funds, Struts, Final Comment Reference Resources Author
This article describes Struts, which is a Model-View-Controller implementation using servlet and JavaServer Pages technology. Struts helps you control changes in the web project and improve the level of specialization. Although you may never use Struts to implement a system, you can use some of these ideas for your future servlet and JSP webpage implementation.
Introduction Primary school students can also post HTML web pages on the Internet. However, primary school students' web pages and professional development websites have quality. Web designers (or HTML developers) must understand colors, users, production processes, webline layouts, browser compatibility, image creation, and JavaScript, and more. The beautiful website needs to do a lot of work, most Java developers pay more attention to create a beautiful object interface, not the user interface. JavaServer Pages (JSP) technology provides web designers and Java developers with a link.
If you have developed a large web application, you understand the meaning of changing the word. "Model - View - Controller" (MVC) is a design pattern used to help you control changes. The MVC weakens the coupling between the business logic interface and the data interface. Struts is an MVC implementation that uses Servlet 2.2 and JSP 1.1 tags (belonging to J2EE specification) as part of the implementation. Although you may never use Struts to implement a system, you know that Struts may allow you to use some of the ideas for the JSP implementation of your later servlet.
In this article, I will discuss the advantages and disadvantages of the web page with a JSP file, which may be what you are familiar. Then I will discuss strut and explain how it controls changes in your web project and improves the level of specialization. Finally, I will re-develop this simple JSP file, I have taken into account in web designers and changes during the development process.
A JSP file is a Java Servlet JavaServer Page (JSP) file is just another way of reviewing the servlet. The concept of JSP file allows us to view Java servlet as an HTML page. JSP eliminates the annoying PRINT () statement that often appears in the Java code. The JSP file is first preprocessed as .java files, then compile to .class files. If you are using Tomcat, you can view the pre-processed .java files in the Work directory. Other containers may store .java and .class files in other locations; this location is related to the container. Figure 1 illustrates the process from the JSP file to the servlet.
Figure 1. Process from JSP files to servlet
(This is clearly different from Microsoft's Active Server Page (ASP). ISP is compiled into memory, not compiled into a separate file.) Simple independent JSP files in small JSP applications, often see data, Business logic and user interfaces are combined in a code module. In addition, applications typically include logic used to control application flow. Listing 1 and Figure 2 show a simple JSP file that allows users to join a mailing list. Listing 1. Join.JSP - a simple request and response JSP file <% @ page language = "java"%>
<% @ page import = "business.util.validation"%>
<% @ page import = "business.db.mailinglist"%>
<%
String Error = "";
String email = Request.getParameter ("email");
/ / Is there an email address?
IF (email! = null) {
// Verify input ...
IF (Business.util.Validation.issalidemail (email)) {
// Storage input ...
Try {
Business.db.mailingList.addemail (email);
} catch (exception e) {
Error = "Error adding email address to system." E;
}
IF (Error.Length () == 0) {
%>
/ / Redirect to Welcome Page ...
<%
}
} else {
/ / Set the error message and resume the web page
Error = Email "IS Not a Valid Email Address, please try again."
}
} else {
Email = "";
}
%>
join mailing list </ title></p>
<p></ hEAD></p>
<p><body></p>
<p><font color = red> <% = error%> </ font> <br></p>
<p><h3> Enter Your Email to join the group </ h3></p>
<p><form action = "join.jsp" Name = "joinform"></p>
<p><Input Name = "email" id = "email" value = <% = email% >> </ input></p>
<p><Input Type = Submit Value = "Submit"></p>
<p></ form></p>
<p></ body></p>
<p></ html></p>
<p>Figure 2. In a simple request and response, the JSP file sets the data, controls the process of the next web page and creates HTML</p>
<p>This mailing list JSP file is an independent and autonomous module that completes all tasks. Only code not included in this JSP file is the actual verification code included in IsValideMail () and the code to store the email address into the database. (ISVALIDEMAIL () method seems to be of course selection in reusable code, but I have seen the isvalidemail () code directly embedded in the web page. The advantages of a single page method are easy to understand, and it is also easy to build. In addition For a variety of graphical development tools, it is also easy. Join.jsp's activity displays the open input web page. Read the value of Email from the form parameter. Verify the email address. If the email address is valid:</p>
<p>Add this address to the database. Redirect to the next page. If the email address is invalid:</p>
<p>Set an error message. Re-display Join.jsp containing the error message. Frequency of single page</p>
<p>The writers of HTML and Java strong coupling JSP files together must be both web designers and Java developers. The result is usually either a very bad Java code, either a grunge web page, sometimes even Java code and web pages are very bad. The shortcomings of Java and JavaScript have gradually become bigger with web pages, and it is easy to think of some JavaScript. This script may be confused with Java code when JavaScript appears in a web page. An example of possible confusion is to verify the Email domain using JavaScript using the client. The embedded process logic understands the entire process of the application, and you must browse all the web pages. Imagine the intricate logic of the website with 100 webpages. In addition to the worse appearance, the HTML tag, Java code, and JavaScript code are set in a web page and make debugging quite difficult. Strong coupling changes business logic or data may involve each web page. Aesthetics is in a large web page, this code style looks messy. When I was developed by Microsoft ASP, I often saw a 1000-line web page. Even with color syntax shows that reading and understanding these codes is still more difficult.</p>
<p>Please don't join too much Java code in my HTML in Listing 1, not having a lot of HTML in the Java code, but there is a lot of Java code in the HTML file. From this point of view, in addition to allowing web designers to write Java code, I don't actually do anything. However, we are not all; in JSP 1.1, we get a new feature called "tag".</p>
<p>The JSP tag is just a way to extract the code from the JSP file. Some people regard JSP tags as a macro of the JSP file, which is included in the servlet used for this tag. (Macro's view is largely correct.) For the same reason, I don't want to see HTML tags in the Java code, and I don't want to see Java code in the JSP file. The entire starting point of JSP technology is to allow web designers to create servlets without entanglement of Java code. The tag allows Java programmers to extend JAVA code into HTML to extend JSP files. Figure 3 shows the general concepts of extracting code from the JSP page and put them in a JSP tag.</p>
<p>Figure 3. JSP tag</p>
<p>Listing 2 is an example in which the function of the Struts tag is used. In Listing 2, the normal HTML <form> tag is replaced with a struts <form: form> tag. Listing 3 shows the results of the browser received HTML. The browser gets HTML <form> tags, but with additional code, such as JavaScript. Additional JavaScript activates the Email address domain. The <form: form> tag code for the server is created, and the web design personnel will no longer contact JavaScript. Listing 2. Struts Form tag <form: form action = "join.do" FOCUS = "email"></p>
<p><form: text property = "email" size = "30" maxlength = "30" /></p>
<p><form: Submit property = "submit" value = "submit" /></p>
<p></ form: form></p>
<p>Listing 3. Send to the browser results HTML</p>
<p><form name = "joinform" method = "post" action = "join.do; jsessionid = ndj71hjo01"></p>
<p><input type = "name =" email "maxlength =" 30 "size =" 30 "value ="> "></p>
<p><Input Type = "Submit" name = "submit" value = "submit"></p>
<p></ form></p>
<p><script language = "javascript"></p>
<p><! -</p>
<p>Document.joinform.Email.focus ()</p>
<p>// -></p>
<p></ script></p>
<p>Precautions for JSP tags:</p>
<p>The JSP tag requires a container running JSP 1.1 or higher. The JSP tag is running on the server without explaining the client as the HTML tag. The JSP tag provides the appropriate code reuse mechanism. HTML and JavaScript can be added to the web page using a JSP mechanism called include. However, developers often create huge JavaScript library files, which are included in the JSP file. As a result, the HTML page that is returned to the client is much larger than the required HMTL page. The correct usage of include only HTML code segments that generate it such as header and footer. The JSP tag makes the development role more specialized by extracting Java code.</p>
<p>Model - View - Controller (MVC) JSP tag only solves some problems. We have to handle issues such as verification, process control, and update applications. This is where the MVC works. MVC helps solve some of the problems encountered by the single module method by dividing the problem into three categories:</p>
<p>The Model model contains the core function of the application. The model encapsulates the status of the application. Sometimes the only function it contains is status. It doesn't know anything about the view or controller. View view provides a representation of the model. It is the appearance of the application. The view can access the model's read method, but the write method cannot be accessed. In addition, it doesn't know anything about the controller. The view should be notified when changing the model. The Controller controller responds to the user's input. It creates and sets the model. MVC model 2Web proposes some unique challenges to software developers, the most obvious is the stateless connection of clients and servers. This stateless behavior makes the model difficult to change the notification view. On the Web, in order to find changes to the application status, the browser must re-query the server.</p>
<p>Another major change is different from the techniques used by the view and implementation models or controllers. Of course, we can generate HTML using Java (or Perl, C / C or other languages). This method has several disadvantages:</p>
<p>Java programmers should develop services instead of HTML. You need to change the code when changing the layout. Services should be able to create a web page to meet their specific needs. Web designers cannot participate directly in web development. HTML in the ejection code is difficult.</p>
<p>For the web, you need to modify the standard MVC form. Figure 4 shows the MVC's web rewrite, usually also known as MVC Model 2 or MVC 2.</p>
<p>Figure 4. MVC Model 2</p>
<p>One of Struts, MVC 2 is a set of collaborative classes, servlets, and JSP tags that make up a reusable MVC 2 design. This definition indicates that struts is a frame, not a library, but Struts also contains a wealth of tag libraries and utility classes independent of the framework. Figure 5 shows an overview of Struts.</p>
<p>Figure 5. Struts Overview</p>
<p>Struts overview</p>
<p>CLIENT BROWSER Creates an event from each HTTP request from the client browser. The Web container will respond with an HTTP response. The Controller controller receives a request from the browser and decides where to send this request. For Struts, the controller is a command design pattern implemented by a servlet. Struts-config.xml file configuration controller. Business logic logic updates the status of the model and helps control the flow of applications. For Struts, this is done by the Action class "thin" packaging as the actual business logic. The status model of the Model represents the status of the application. Business object updates the status of the application. The ActionForm bean represents the status of the model in the session stage or the request grade, not in the persistence. JSP files read information from Actionform Bean using JSP tags. View view is a JSP file. There is no process logic, no business logic, and there is no model information - only the tag. The tag is one of the factors that make Struts different from other frameworks (such as Velocity).</p>
<p>Detailed analysis of Struts Figure 6 shows a simple UML diagram of the org.apache.struts.Action package. Figure 6 shows the simplest relationship between ActionServlet, ACTIONFORM (Form State), and Action (Model Wrapper).</p>
<p>Figure 6. UML diagram of the relationship between Command (ActionServlet) and MODEL (ACTION & ActionForm)</p>
<p>ActionServlet class Do you still remember the day of the function map? At that time, you will map some input events to a function pointer. If you are familiar with this, you will put the configuration information in a file and load this file at runtime. The function pointer array once is a well-programmed way to use C language. Now much now, we have Java technology, XML, J2EE, and more. The Struts controller is a servlet that maps events (events typically http post) to classes. As you expected - the controller uses the configuration file to make you don't have to hardcode these values. The time changed, but the method is still. ActionServlet is the COMMAND section implemented by the MVC, which is the core of this framework. ActionServlet (Command) creates and uses Action, ActionForm, and ActionForward. As mentioned earlier, the struts-config.xml file configures the Command. When you create a web project, you will extend Action and ActionForm to resolve specific issues. File Struts-Config.xml Indicates how the ActionServlet uses these extensions. This approach has several advantages: the entire logic process of the application is stored in a hierarchical text file. This makes it easier to view and understand it, especially for large applications. Web designers don't have to pay great way to read Java code to understand the application's process. Java developers also do not have to recompile the code after the change process. You can add a Command feature by extending an ActionServlet. Actionform class ActionForm maintains the session status of the web application. ActionForm is an abstract class that must create subclasses of this class for each input form model. When I said the input form model, it means that Actionform represents the general sense of the HTML form setting or update. For example, you may have a useerActionform set by the HTML form. The Struts framework will do the following:</p>
<p>Check if the userActionform exists; if there is no existence, it will create an instance of this class. Struts will set the status of the useerActionform using the appropriate domains in HttpservletRequest. There is not much annoying request.getParameter () call. For example, the STRUTS framework extracts FNAME from the request stream and calls useerActionform.setFName (). The Struts framework updates its status before passing the UseractionForm to the business packaging UserAction. Before passing it to the Action class, Struts also calls the userActionForm to make a form verification. Note: This is not always wise. Other web or services may use UseractionForm, in these places, verification may vary. Perform status verification in the UserAction class may be better. UserActionform can be maintained in the session level. Note:</p>
<p>Struts-config.xml file controls the mapping relationship between the HTML form request and the ActionForm. Multiple requests can be mapped to UseractionForm. The useerActionForm can map across multiple pages to perform operations such as the wizard. The Action class Action class is a packaging of business logic. The use of the Action class is to convert HTTPSERVLETREQUEST to business logic. To use Action, create its subclass and override the process () method. ActionServlet (Command) passes the parameterized class to ActionForm using the Perform () method. There is still not much annoying request.getParameter () call. When the event progresses to this step, the input form data (or HTML form data) has been extracted from the request stream and transferred to the actionform class. Note: Please pay attention to simplicity when expanding the Action class. The Action class should control the process of the application without controlling the logic of the application. We can provide greater flexibility and reusability by placing business logic in separate packages or EJBs. Another way to consider the Action class is Adapter design mode. The use of Action is to "convert the interface interface to another interface required to the client. ADAPTER allows the class to work together. If there is no Adapter, these classes cannot work together because of incompatible interfaces." (Excerpted from GOF Design Patterns - Elements of Reusable Oo Software. The client in this example is an ActionServlet, which does not know anything about our specific business interface. Therefore, Struts provides a service interface that it understands, namely Action. By extending Action, we have kept our business interface to keep compatible with the Struts business interface. (A interesting discovery is that Action is a class rather than an interface). The Action started to be an interface, but later turned into a class. It's really gold. Error class UML map (Figure 6) also includes ActionError and ActionerRRORS. ActionError encapsulates a single error message. ActionerRORS is a container of an ActionError class, and View can use tags to access these classes. ActionError is the way Struts keeps an error list. Figure 7. UML diagram of the relationship between Command (ActionServlet) and Model (Action)</p>
<p>The ActionMapping class input event is usually occurring in the HTTP request form, and the servlet container converts the HTTP request to HttpServletRequest. The controller view the input event and assign the request to an Action class. Struts-config.xml determines which Action class calling Controller calls. Struts-config.xml configuration information is converted to a set of actionMApping, while the latter is placed in the ActionMAppings container. (You may have not noticed this, the class ends with S is the container) ActionMApping contains information about how a specific event is mapped to a particular action. ActionServlet (Command) passes ActionMApping to the Action class via Perform (). This allows the Action to access information for controlling the flow. ActionMappingsActionMappings is a collection of an actionMApping object.</p>
<p>Look at the Mail List Sample Let's take a look at how the Struts solves these problems that troubles join.jsp. The rewritten scheme consists of two projects. The first item contains the logical part of the application, which is independent of the web application. This independent layer may be a public service layer implemented by EJB technology. For convenience of explanation, I created a package called Business on the ANT build process. Several reasons prompted us to use independent business layers: Divided the responsibility of individual envelopers to delegate responsibility within the development group. This also helps to improve the responsibility of developers. Universal We envisage developers as a business software. Place it in another package make it more like a universal. This package may be universal, or it may be developed by another group inside the organization. Avoid unnecessary buildings and unit tests. Separate build processes help to avoid unnecessary buildings and unit tests. Using interface development When developing and avoiding unnecessary coupling, it helps to think about problems from the views of the interface. This is an extremely important aspect. When developing your own business pack, these business classes should not be concerned that the web application performs calls, or the stand-alone application executes calls. Therefore, you should avoid any references to the Servlet API or Struts API call in the business logic layer. Stability is not every organization, every week, even a month. Therefore, the stable interface point is important when developing. It is impossible to think that the web project should also be in the change phase because the business package is in a change phase.</p>
<p>Business Building Note I use the Ant build project and run unit test with JUnit. Business.zip contains everything you need to build a business project, except for Ant and Junit. This package will build a class, run unit test, create a Java document, and JAR file, and finalize all of these content to a zip file to send to customers. As long as you make some modifications to build.xml, you can deploy it to other platforms. Business.jar is located in the Web Download section, so you don't have to download and build this business package.</p>
<p>The second project of the Web project is a web application developed with Struts. You will need a container that meets JSP 1.1 and Servlet 2.2 specification. The fastest introductory method is to download and install Tomcat 3.2 (see Reference Resources). Before there is a Struts 1.0 release, I suggest you get the latest version from the Jakarta project (see Resources). This is a big problem for me. I can't make sure that my web project sample can work with Struts you downloaded. Struts is still changing, so I have to update my project frequently. In this project, I am using jakarta-struts-20010105.zip. Figure 8 shows the structure of this web project. If you have installed Ant, run this version will create a WAR file called JoinStruts.war, you can always deploy this file.</p>
<p>Figure 8. Structure of the web project</p>
<p>Listing 4 shows the converted JSP file called Joinmvc.jsp. This file is from the original 50 line to 19 lines and now does not contain any Java code. From the perspective of web designers, this is a huge improvement. Listing 4. Joinmvc.jsp - Revitalize simple JSP</p>
<p><% @ page language = "java"%></p>
<p><% @ Taglib Uri = "/ Web-INF / STRUTS.TLD" prefix = "struts"%></p>
<p><% @ Taglib URI = "/ Web-INF / STRUTS-FORM.TLD" prefix = "form"%></p>
<p><html></p>
<p><HEAD></p>
<p><title> <struts: message key = "join.title" /> </ title></p>
<p></ hEAD></p>
<p><body bgcolor = "white"></p>
<p><form: errors /></p>
<p><h3> Enter Your Email to join the group </ h3></p>
<p><form: form action = "join.do" FOCUS = "email"></p>
<p><form: text property = "email" size = "30" maxlength = "30" /></p>
<p><form: Submit property = "submit" value = "submit" /></p>
<p></ form: form></p>
<p></ body></p>
<p></ html></p>
<p>The change in the web page is the list of changes that have changed after using the Struts tag library:</p>
<p>Import</p>
<p><% @ Taglib Uri = "/ Web-INF / STRUTS.TLD" prefix = "struts"%> The <% @ page import? used for Java code is replaced with <% @ Taglib URI for the STRUTS tag library? . text</p>
<p><struts: message key = "join.title" /> The resource property file contains the text of Join.Title. In this case, the ApplicationResources property file contains this name value. This makes the string easier to view and internationalize. error</p>
<p><form: error or actionform builds an error message to display. These error messages can also be included in the properties file. ApplicationResources also provides a method of formatting errors to set ERROR.Header and Error.Footer. HTML form</p>
<p><form: form action = "join.do" FOCUS = "email"></p>
<p>JSP <form> tags and properties replace HTML <form> tags and properties. <form action = "join.jsp" name = "join"> has been changed to <form: form action = "join.do" focus = "email">. HTML <Input> Tags have been replaced with <form: text />. HTML <Submit> Tags have been replaced with <form: submit />. Model - Session Status Joinform extends ActionForm and contains form data. The form data in this example only has an email address. I have added a write method and reading method to the email address for framework access. For convenience of explanation, I rewrite the validate () method and use the Struts tracking function. Struts will create Joinform and set status information. Model - Business Logic As mentioned before, Action is an interface between the controller and the actual business object. JoinAction wrapped in call to Business.jar, which was originally in the join.jsp file. JoinAction's Perform () method lists in Listing 5. Listing 5. - JoinAction.Perform () Public ActionForward Perform (ActionMapping Mapping,</p>
<p>Actionform Form,</p>
<p>HTTPSERVLETREQUEST REQUEST,</p>
<p>Httpservletresponse response</p>
<p>THROWS IOException, servletexception {</p>
<p>// Extract the properties and parameters we will use</p>
<p>JOINFORM JOINFORM = (JOINFORM) Form;</p>
<p>String email = joinform.getemail ();</p>
<p>ActionerroS Errors = new actionerrors ();</p>
<p>// Store input ....</p>
<p>Try {</p>
<p>Business.db.mailingList.addemail (email);</p>
<p>} catch (exception e) {</p>
<p>// Record the log, print the stack</p>
<p>// Disconnect the wrong back to the user</p>
<p>Errors.Add ("email", new actionerror ("error.mailing.db.add"));</p>
<p>}</p>
<p>// If you need any messages, save the specified error message key to</p>
<p>// HTTP request for use in <struts: errors> tag.</p>
<p>IF (! errors.empty ()) {</p>
<p>SaveerRors (Request, Errors);</p>
<p>// Return to the initial form</p>
<p>Return (maping.getInput ())));</p>
<p>}</p>
<p>// Transfer control to the 'Success' URI specified in Action.xml</p>
<p>Mapping.Findforward ("Success"));</p>
<p>}</p>
<p>Note: Perform () returns a class called an ActionForward that does this class notify the controller what to do next. In this example, I use the mapping that is incorporated from the controller to determine the next step. The controller I have modified the JSP file and create two new classes: A class is used to include form data, a class to call the business package. Finally, I integrate them by modifying profile struts-config.xml. Listing 6 shows the Action elements I added, this element is used to control the process of JoinMvc.jsp. Listing 6. Action configuration <action path = "/ join"</p>
<p>Name = "joinform"</p>
<p>TYPE = "Web.mailingList.joinAction"</p>
<p>Scope = "request"</p>
<p>INPUT = "/ joinmvc.jsp"</p>
<p>Validate = "True"></p>
<p><forward name = "success" Path = "/ welcome.html" /></p>
<p></ action></p>
<p>The Action element describes a mapping from the request path to the corresponding Action class, which should use these classes to handle requests from this path. Each request type should have a corresponding action element to describe how to handle the request. For Join Request:</p>
<p>Joinform is used to accommodate form data. Because Validate is marked as True, Joinform will try to perform self-authentication. Web.mailingList.joinAction is an Action class to handle requests to this mapping. If everything goes well, the request will go to Welcome.jsp. If a business logic failure occurs, the process will return to Joinmvc.jsp, which is a web page that originally issued a request. Why is this so? In the Action Element of Listing 6, there is an attribute called INPUT whose value is "/jinmvc.jsp". In my joinaction.perform () (as shown in Listing 5), if the business logic fails, Perform () returns an actionforward and as mapping.getInput () as a parameter. The getInput () in this example is "/joinmvc.jsp". If the business logic fails, it will return to Joinmvc.jsp, which is the first page that was originally issued.</p>
<p>The comparison before and after using Struts is as seen in Figure 9, has a significant increase in complexity and layers. No longer there is a direct call from the JSP file to the Service layer.</p>
<p>Figure 9. Comparison before and after Struts</p>
<p>Struts Advantages</p>
<p>The use tag feature of the JSP tag mechanism is a reusable code and abstract Java code from the JSP file. This feature is well integrated into JSP-based development tools, which allows you to write code with tags. Why should the tag library have an inventive wheel or a tag library? If you can't find the tag you want in the library, then you will define it. Also, if you are learning JSP tag technology, Struts provides you with a starting point. Open source You can get all the advantages of open source, such as you can view the code and check each person of the library to check the code. Many people can check very well. MVC implementation If you want to create your own MVC implementation, Struts can increase your knowledge. Management problem spatial rules are excellent ways to solve problems and make problems manageable. Of course, this is a double-edged sword. The problem is getting more complicated, and more and more management is needed. Struts Disadvantages</p>
<p>The development of Struts is still in the initial stage. They are working hard to the release version 1.0, but as with any 1.0 versions, it is impossible to do it. This frame is still changing in a variety of changes. Struts 1.0 varies greatly compared to Struts 0.5. In order to avoid the use of the method that does not agree, you may need to download the latest Struts over one day. In the past 6 months, I witnessed the Struts library increased from 90k to 270K. Due to changes in Struts, I have to modify my example several times, but I don't guarantee that my example works with Struts you downloaded. Does the correct abstraction level Struts provide the correct abstraction level? What is the correct abstraction level for web designers? This is a problem with the text with $ 64K. In the development of a web page, should we let the web designers visited the Java code? Some frameworks (such as velocity) should not, but it provides another web development language to make us learn. Restrict access Java in UI development has certain rationality. Most importantly, if web designers use a little Java, he will use a lot of Java. In the development of Microsoft ASP, I always see this situation. In ASP development, you should create a COM object, then write a small amount of ASP scripts to link these COM objects. However, ASP developers will use ASP scripts crazy. I will hear this, "Since I can write COM objects with VBScript, why should I wait for COM developers to create it?" By using the tag library, Struts helps limit the Java code required in the JSP file. Quantity. Logic Tag is a library that manages conditionally generated output, but this does not prevent UI developers from fanatizing the Java code. Whether you decide which type of framework you want to use, you should know the environment you want to deploy and maintain the framework. Of course, this task is really difficult to do. Limited Scope Struts is a web-based MVC solution that must be implemented with HTML, JSP files, and servlets. The J2EE application supports Struts that requires Servlet containers that support JSP 1.1 and Servlet 2.2 specification. This is far from which you can solve all your installation issues unless Tomcat 3.2 is used. I am installing this library with Netscape Iplanet 6.0, I encountered a lot of problems, and it is the first application server that meets J2EE. I recommend that you access the archive of the Struts user mailing list when you encounter problems (see Reference Resources). The complexity is also introduced into several parts of several parts. There is no doubt that you must understand that struts must accept certain training. As the changes continue to join, this is sometimes very frustrating. Welcome to this website. Where can I still point out other issues, for example, where the controller's client verification, how can the workflow and dynamic policy mode? However, this is now too easy to become a problem of phenomenon, some problems are irrelevant, or these issues should be issued for 1.0 issues. With the continuous efforts of the Struts team, Struts may have these features when you read this article, or it will have these features soon.</p>
<p>Struts's prospects in this new era development, everything has become very fast. In less than five years, I have witnessed from CGI / Perl to ISAPI / NSAPI, and then use VB's ASP, until the current Change of Java and J2EE. Sun is trying to reflect new changes to the JSP / Servlet architecture, as they are the same as the change made by the Java language and the API. You can get a new draft of JSP 1.2 and Servlet 2.3 specification from Sun's website. In addition, a standard JSP tag library is about to appear; for links to these specifications and tag libraries, see Reference Resources. The final comment Struts uses tags and MVC to solve certain major problems. This method helps to increase the reusability and flexibility of the code. By dividing problems into smaller components, you have more opportunity to reuse code when there is a change in technical space or problem space. In addition, Struts enables web designers and Java developers to focus on their best aspects. However, while strongness is enhanced, it also means complexity increases. Struts is much more complicated than a simple single JSP page, but for larger systems, Struts actually helps manage complexity. In addition, I don't want to write my own MVC implementation, but I just want to know a such implementation. Whether you will use Struts, review this Struts framework (sorry, it should be library) will make you a better understanding of the JSP file and servlet, and how to combine them for your next Web project. The positive image wing pillar is an indispensable part of the wing structure, and Strut may become an indispensable part of your next web project.</p>
<p>Reference resource</p>
<p>You can download the code used herein: Business.zip is used to build business.jar files, JoinStruts.zip is used to build JoinStruts.war files. For documents, installation instructions, and downloads about Struts, see the home page of Struts. You can download the most recent Struts from the Jakarta project. If you want to get started, I suggest you download the reference to the JSP Servlet implementation Tomcat 3.2. If you use a container other than Tomcat, visit the Struts user mailing list to get the help of installing Struts in your specific environment. To get information not included in the Document or Install Guide, see the Struts User Mail List Archive File. The Apache Mail list archive contains Struts information that archives with other information. To understand more information that will build and test the process, see "Incremental Development With Ant and Junit". See Proposed Final Draft for Java Servlet 2.3 and JavaServer Pages 1.2 Specifications. See Standard Tag Library for JavaServer Pages, JSR # 000052.</p>
<p>About the author Malcolm G. Davis lived in Alabama Birmingham City, he was president in his own consulting company. He claims to be a Java officer. He will go to the long run in the leisure time of promoting Java, or play with your child. You can contact Malcolm via Malcolm@Nuearth.com.</p></div><div class="text-center mt-3 text-grey">
转载请注明原文地址:https://www.9cbs.com/read-8691.html</div><div class="plugin d-flex justify-content-center mt-3"></div><hr><div class="row"><div class="col-lg-12 text-muted mt-2"><i class="icon-tags mr-2"></i><span class="badge border border-secondary mr-2"><h2 class="h6 mb-0 small"><a class="text-secondary" href="tag-2.html">9cbs</a></h2></span></div></div></div></div><div class="card card-postlist border-white shadow"><div class="card-body"><div class="card-title"><div class="d-flex justify-content-between"><div><b>New Post</b>(<span class="posts">0</span>)
</div><div></div></div></div><ul class="postlist list-unstyled">
</ul></div></div><div class="d-none threadlist"><input type="checkbox" name="modtid" value="8691" checked /></div></div></div></div></div><footer class="text-muted small bg-dark py-4 mt-3" id="footer"><div class="container"><div class="row"><div class="col">CopyRight © 2020 All Rights Reserved
</div><div class="col text-right">Processed:
<b>0.058</b>, SQL:
<b>9</b></div></div></div></footer><script src="./lang/en-us/lang.js?2.2.0"></script><script src="view/js/jquery.min.js?2.2.0"></script><script src="view/js/popper.min.js?2.2.0"></script><script src="view/js/bootstrap.min.js?2.2.0"></script><script src="view/js/xiuno.js?2.2.0"></script><script src="view/js/bootstrap-plugin.js?2.2.0"></script><script src="view/js/async.min.js?2.2.0"></script><script src="view/js/form.js?2.2.0"></script><script>
var debug = DEBUG = 0;
var url_rewrite_on = 1;
var url_path = './';
var forumarr = {"1":"Tech"};
var fid = 1;
var uid = 0;
var gid = 0;
xn.options.water_image_url = 'view/img/water-small.png';
</script><script src="view/js/wellcms.js?2.2.0"></script><a class="scroll-to-top rounded" href="javascript:void(0);"><i class="icon-angle-up"></i></a><a class="scroll-to-bottom rounded" href="javascript:void(0);" style="display: inline;"><i class="icon-angle-down"></i></a></body></html><script>
var forum_url = 'list-1.html';
var safe_token = 'ckhv7SrBrIyZ0wlGwN8LQ6JK0G8vMA0lwF4vMdfHDAcnZ6qOtwBMM38sOogKe567LAZh8hvNLJHsYwiXIhTQYA_3D_3D';
var body = $('body');
body.on('submit', '#form', function() {
var jthis = $(this);
var jsubmit = jthis.find('#submit');
jthis.reset();
jsubmit.button('loading');
var postdata = jthis.serializeObject();
$.xpost(jthis.attr('action'), postdata, function(code, message) {
if(code == 0) {
location.reload();
} else {
$.alert(message);
jsubmit.button('reset');
}
});
return false;
});
function resize_image() {
var jmessagelist = $('div.message');
var first_width = jmessagelist.width();
jmessagelist.each(function() {
var jdiv = $(this);
var maxwidth = jdiv.attr('isfirst') ? first_width : jdiv.width();
var jmessage_width = Math.min(jdiv.width(), maxwidth);
jdiv.find('img, embed, iframe, video').each(function() {
var jimg = $(this);
var img_width = this.org_width;
var img_height = this.org_height;
if(!img_width) {
var img_width = jimg.attr('width');
var img_height = jimg.attr('height');
this.org_width = img_width;
this.org_height = img_height;
}
if(img_width > jmessage_width) {
if(this.tagName == 'IMG') {
jimg.width(jmessage_width);
jimg.css('height', 'auto');
jimg.css('cursor', 'pointer');
jimg.on('click', function() {
});
} else {
jimg.width(jmessage_width);
var height = (img_height / img_width) * jimg.width();
jimg.height(height);
}
}
});
});
}
function resize_table() {
$('div.message').each(function() {
var jdiv = $(this);
jdiv.find('table').addClass('table').wrap('<div class="table-responsive"></div>');
});
}
$(function() {
resize_image();
resize_table();
$(window).on('resize', resize_image);
});
var jmessage = $('#message');
jmessage.on('focus', function() {if(jmessage.t) { clearTimeout(jmessage.t); jmessage.t = null; } jmessage.css('height', '6rem'); });
jmessage.on('blur', function() {jmessage.t = setTimeout(function() { jmessage.css('height', '2.5rem');}, 1000); });
$('#nav li[data-active="fid-1"]').addClass('active');
</script>
