How do Java Servlets work with JSP?-javaTutorial-php.cn

How do Java Servlets work with JSP?

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Release： 2024-04-17 09:03:01

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Java Servlets and JSPs work together to handle HTTP requests, where the Servlet is responsible for processing the request and generating the response, while the JSP creates dynamic HTML output through embedded Java code. The two collaborate: 1. Servlet processes requests and generates data. 2. JSP accesses the data generated by the Servlet and creates an HTML page. 3. In the Servlet-JSP architecture, Servlet handles business logic, while JSP displays data.

Java Servlet如何与JSP协同工作？

Collaboration of Java Servlet and JSP

Introduction

Servlet and JSP are Two core technologies in Java web development. Servlets are Java applications used to handle HTTP requests and responses, while JSP is a Java templating technology used to create dynamic content that can be displayed on a Web page. This tutorial explores how Servlets and JSPs work together and provides a practical example.

Handling Requests

When a client sends an HTTP request to a Web server, the server dispatches the request to the appropriate Servlet. Servlets are responsible for processing requests and generating responses. It can access HTTP request and response objects and perform tasks such as retrieving data from a database or generating HTML pages.

Collaboration of JSPs

JSP pages embed Java code that dynamically generates HTML output. When a JSP page is displayed to a Web browser, the server first compiles the JSP code into a Servlet. The compiled servlet is then instantiated and executed, basically like a regular servlet.

Servlet-JSP architecture

In the traditional Servlet-JSP architecture, Servlet is responsible for processing business logic and generating HttpServletResponse objects. This response object is then used as input to an expression in the JSP page. The JSP page retrieves data from the HttpServletResponse object and generates an HTML page.

Practical case

Example Servlet

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/GetUserServlet")
public class GetUserServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // 获取请求参数
        String username = request.getParameter("username");

        // 从数据库中获取用户对象
        User user = getUserFromDB(username);

        // 将用户对象存储在请求属性中
        request.setAttribute("user", user);
    }
}

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Example JSP

<%@ page import="com.example.User" %>
<%@ page contentType="text/html" pageEncoding="UTF-8" %>

<!DOCTYPE html>
<html>
<body>
    <h1><%= user.getUsername() %></h1>
    <p><%= user.getEmail() %></p>
</body>
</html>

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Interaction

When the client sends a GET request to /GetUserServlet, the Servlet will retrieve the user object with the specified user name from the database. It then stores the user object in the request attribute. JSP pages use this request attribute to display the user's information.

Conclusion

Servlets and JSPs work together through an interactive process in which the Servlet handles the request and generates data, and the JSP uses the data to generate dynamic HTML output. This architecture provides a powerful foundation for creating interactive and dynamic web applications.

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