Hello Servlet

最新推荐文章于 2023-05-25 11:02:31 发布

原创最新推荐文章于 2023-05-25 11:02:31 发布 · 161 阅读

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本文通过两个具体的Servlet实例，FirstServlet和LastServlet，展示了Servlet的基本结构及其生命周期方法的使用。FirstServlet通过synchronized关键字确保了线程安全，并在init方法中进行了初始化设置，在doGet方法中实现了业务逻辑处理。

package cn.et;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class FirstServlet 
	extends HttpServlet 
	/*
	 * import javax.servlet.SingleThreadModel;
	 * 可实现SingleThreadModel标记接口，用于解决Servlet的线程安全问题(多个用户访问时，可创建多个Servlet)
	 * 非标准的解决方案，不建议使用，逐渐过时，建议使用synchronized解决线程安全问题
	 */
	/*implements SingleThreadModel*/ {
	private static final long serialVersionUID = 1L;
    public FirstServlet() {
        super();
    }
    private int n;
    //在第一次创建 Servlet 时被调用,可以简单地创建或加载一些数据，这些数据将被用于 Servlet 的整个生命周期
    public void init(ServletConfig config) throws ServletException {
		super.init(config);
		n=0;
		System.out.println("FirstServlet init方法被调用");
	}
	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		synchronized (this) {
			n++;
			try {
				Thread.sleep(1000*2);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			response.getOutputStream().write(("Hello Servlet "+n).getBytes());
		}
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}

}

package cn.et;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class LastServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
  
    public LastServlet() {
        super();
    }

    public void init(ServletConfig config) throws ServletException {
		super.init(config);
		System.out.println("LastServlet init方法被调用");
	}
	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.getOutputStream().write("Hello Servlet".getBytes());
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}


}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>ServletExample1_HelloServlet</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <description></description>
    <display-name>FirstServlet</display-name>
    <servlet-name>FirstServlet</servlet-name>
    <servlet-class>cn.et.FirstServlet</servlet-class>
   	<!-- 
   	配置Servlet初始化优先级 值可以是大于等于0的整数，数字越小优先级越高
   	配置load-on-startup后(0~∞)，Servlet不再被访问时创建，而是Web服务器启动时Servlet被创建
   	 -->
    <load-on-startup>0</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>FirstServlet</servlet-name>
    <url-pattern>/FirstServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>LastServlet</display-name>
    <servlet-name>LastServlet</servlet-name>
    <servlet-class>cn.et.LastServlet</servlet-class>
     <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>LastServlet</servlet-name>
    <url-pattern>/LastServlet</url-pattern>
  </servlet-mapping>
</web-app>

index.html

<html>
	<head></head>
	<body>
		Hello Servlet
	</body>
</html>