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In-depth analysis of the operating mechanism of the Struts2 framework

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Release： 2024-01-05 15:36:54

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In-depth analysis of the operating mechanism of the Struts2 framework

In-depth analysis of the working principle of the Struts2 framework

Struts2 is an excellent Java Web application development framework, which provides MVC (Model-View-Controller) mode based on development method to help developers build and maintain web applications more quickly. Understanding the working principle of the Struts2 framework is very important for developers. This article will help readers gain an in-depth understanding of the working principle of the Struts2 framework through detailed analysis and specific code examples.

MVC pattern
MVC pattern is a software design pattern that divides the application into three core components: Model, View and Controller. The model represents the data and business logic of the application, the view is responsible for presenting data to the user, and the controller handles user requests and updates the model and view.
The working principle of Struts2
The working principle of the Struts2 framework is based on the Front Controller design pattern. The core component DispatcherServlet acts as a controller and is responsible for processing all user requests. The following is the workflow of the Struts2 framework:

(1) The user sends a request to the server, and the Web container (such as Tomcat) starts the Struts2 FilterDispatcher filter after receiving the request.

(2) FilterDispatcher filter intercepts the request and passes it to the core controller DispatcherServlet.

(3) DispatcherServlet maps to the corresponding Action class and method according to the requested URL.

(4) Before calling the Action method, the Struts2 framework will execute the interceptor (Interceptor) chain. Interceptors can preprocess requests, such as verifying user identity, checking user permissions, etc.

(5) Call the Action method to process the request, and determine the next jump or output result based on the return value of the method.

(6) The Struts2 framework selects the corresponding result view based on the return value of the Action method. If the return is a string, Struts2 will parse it into a logical view name, and then find the corresponding physical view through the view parser.

(7) The result view will be rendered and returned to the user.

Specific code examples
In order to better understand the working principle of Struts2, the following is a simple code example:

(1) Front-end page (index. jsp)

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Struts2 Example</title>
</head>
<body>
    <h1>Welcome to Struts2 Example</h1>
    <form action="hello" method="POST">
        <input type="text" name="name" placeholder="Enter your name" required>
        <button type="submit">Say Hello</button>
    </form>
</body>
</html>

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(2) Action class (HelloAction.java)

package com.example;

import com.opensymphony.xwork2.ActionSupport;

public class HelloWorldAction extends ActionSupport {
    private String name;

    public String execute() {
        return SUCCESS;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

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(3) Struts2 configuration file (struts.xml)

<!DOCTYPE struts PUBLIC
        "-//Apache Software Foundation//DTD Struts Configuration 2.5//EN"
        "http://struts.apache.org/dtds/struts-2.5.dtd">

<struts>
    <package name="default" extends="struts-default">
        <action name="hello" class="com.example.HelloWorldAction">
            <result>/hello.jsp</result>
        </action>
    </package>
</struts>

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(4) Result view ( hello.jsp)

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Hello, Struts2</title>
</head>
<body>
    <h1>Hello, <s:property value="name"/>!</h1>
    <!-- 其中<s:property>是Struts2的标签，用于显示Action类的属性值 -->
</body>
</html>

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Through the above example, we can see how the entire Struts2 works: the user enters his or her name on the front-end page and submits the form. The request is intercepted by the DispatcherServlet, the core controller of the Struts2 framework, and mapped to HelloAction. The execute method of the class. After that, Struts2 will execute the interceptor chain and call the Action method to process the request. In the execute method of HelloWorldAction, the SUCCESS string is returned, indicating that the request was successfully processed. Then, Struts2 will select the corresponding result view hello.jsp for rendering, and display the returned name attribute value through the tag.

Conclusion:
Through an in-depth analysis of the working principle of the Struts2 framework, we understand its design based on the MVC pattern and the role of core components. Using concrete code examples, we demonstrate how the Struts2 framework works and is configured. Understanding how Struts2 works will help us better use this framework for web application development.

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