In-depth understanding of the working principle and main functions of the Struts2 framework

Understanding the operating principles and core features of the Struts2 framework requires specific code examples

Struts2 is an open source web application framework based on Java and is a subsequent version of the Struts framework. It provides an MVC (Model-View-Controller) architecture for developing maintainable and extensible web applications. It is very important for developers to understand the operating principle and core features of Struts2.

1. The operating principle of Struts2

Struts2 is based on the MVC architecture. Its operating principle mainly includes the following steps:

1. The client sends a request: When the user is When you enter a URL or click a link in the browser, the browser sends an HTTP request to the server.

2. The server receives the request: After the server receives the request, it will find the corresponding Struts2 controller based on the configuration information in the configuration file.

3. The controller processes the request: The controller will decide which method of which Action class to execute based on the information in the request and the configuration information in the configuration file.

4. Action class handles requests: Action class is the core component in the Struts2 framework, which is responsible for processing specific business logic. The controller will call the corresponding method of the Action class.

5. Return the view result: After the Action class method is executed, a result view will be returned. The view result is a JSP page or other type of view used to present the results to the user.

6. Return response: The server will return the view result to the browser as a response, and the browser will render the interface based on the content of the response.

2. Core features of Struts2

1. Core classes: The Struts2 framework has some core classes, such as Action, Interceptor, and Result. The Action class is responsible for processing business logic, the Interceptor class is responsible for intercepting and performing corresponding operations before and after request processing, and the Result class is responsible for generating the result view.

2. Interceptor stack: The interceptor stack in the Struts2 framework is a collection of interceptors used to process requests. Each interceptor can perform some operations before and after request processing, such as verifying user permissions, recording logs, etc.

3. Data binding: The Struts2 framework supports data binding, which can automatically bind request parameters to the properties of the Action class. Through data binding, developers do not need to manually handle request parameters, making development more convenient.

4. Internationalization support: The Struts2 framework provides internationalization support, which can easily implement multi-language applications. Developers only need to write resource files in different languages, and the Struts2 framework will automatically load the corresponding resource files according to the user's locale.

5. Form verification: The Struts2 framework provides the form verification function, which can verify the data entered by the user. Developers only need to define corresponding verification rules in the Action class, and the Struts2 framework will automatically perform verification based on the rules and return verification results.

The following uses a simple example to demonstrate the operating principle and core features of the Struts2 framework.

First, create an Action class, named HelloWorldAction, with the following code:

public class HelloWorldAction {
    private String name;
    private String message;
    
    public String execute() {
        message = "你好，" + name + "！";
        return "success";
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    public String getMessage() {
        return message;
    }
}

Then, create a JSP page, named hello.jsp, with the following code:

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Struts2示例</title>
</head>
<body>
    <form action="hello" method="post">
        <input type="text" name="name" />
        <input type="submit" value="提交" />
    </form>
    
    <span>${message}</span>
</body>
</html>

Finally, create a configuration file named struts.xml to configure the Action class and result view. The code is as follows:

<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN" "http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
    <package name="default" extends="struts-default">
        <action name="hello" class="com.example.HelloWorldAction">
            <result>/hello.jsp</result>
        </action>
    </package>
</struts>

When running this example, first start the server and deploy the above code to the server. Then enter the URL in the browser, and an input box and a submit button will be displayed. After the user enters their name and clicks the submit button, the Struts2 framework will automatically call the execute() method of the HelloWorldAction class and display the result view to the browser.

Through the above examples, we can understand the operating principles and core features of the Struts2 framework. The MVC architecture, interceptor stack, data binding, internationalization support, form validation and other features of the Struts2 framework provide developers with a convenient and efficient development method, which is worthy of in-depth study and application by developers.

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