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Java Web学习笔记-Servle生命周期

时间:2017-01-07 23:41:22      阅读:651      评论:0      收藏:0      [点我收藏+]

Servlet会在服务器启动或第一次请求该Servlet的时候开始生命周期,在服务器停止的时候结束生命周期.

无论请求多少次Servlet,最多只有一个Servlet实例.多个客户端并发请求Servlet时,服务器会启动多个线程分别执行该Servlet的service()方法.

 

package com.helloxr.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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 LifeCycleServlet extends HttpServlet {
    
    /**
     * 
     */
    private static final long serialVersionUID = 9898777879L;
    public static double startPoint = 0;
    
    /**
     * Constructor of the object.
     */
    public LifeCycleServlet() {
        super();
    }

    /**
     * Destruction of the servlet. <br>
     */
    public void destroy() {
        this.log("执行 destroy方法 ...");
        startPoint = 0;
    }

    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        this.log("执行 doGet() 方法 ...");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>个人所得税计算</TITLE></HEAD>");
        out.println("<link rel=‘stylesheet‘ type=‘text/css‘ href=‘../css/style.css‘>");
        out.println("  <BODY>");
        out.println("<div align=‘center‘><br/><fieldset style=‘width:90%‘><legend>个税计算器</legend><br/>");
        out.println("<form method=‘post‘>");
        
        out.println("<div style=‘line‘>");
        out.println("   <div class=‘leftDiv‘>您的工资为</div><div align=‘left‘ class=‘rightDiv‘><input type=‘text‘ name=‘income‘>单位:元<div>");
        out.println("</div><br/>");
        
        out.println("<div style=‘line‘");
        out.println("  <div class=‘leftDiv‘></div><div align=‘left‘ class=‘rightDiv‘><input type=‘submit‘ value=‘  计算个税  ‘ class=button></div>");
        out.println("</div>");
        out.println("</form>");
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

    /**
     * The doPost method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to post.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        this.log("执行 doPost() 方法 ...");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
        out.println("<HTML>");
        out.println("  <HEAD><TITLE>个人所得税计算</TITLE></HEAD>");
        out.println("<link rel=‘stylesheet‘ type=‘text/css‘ href=‘../css/style.css‘>");
        out.println("  <BODY>");
        out.println("<div align=‘center‘><br/>");
        out.println("<fieldset style=‘width:90%‘><legend>个税计算器</legend><br/>");
        
        try{
            double income = new Double(request.getParameter("income"));
            
            double charge = income - startPoint;
            double tax = 0;
            
            if(charge <= 0) {tax = 0;}
            if(charge > 0 && charge <= 500) {tax = charge * 0.05;}
            if(charge > 500 && charge <= 2000) {tax = charge * 0.1 - 25;}
            if(charge > 2000 && charge <= 5000) {tax = charge * 0.15 - 125;}
            if(charge > 5000 && charge <= 20000) {tax = charge * 0.2 - 375;}
            if(charge > 20000 && charge <= 40000) {tax = charge * 0.25 - 1375;}
            if(charge > 40000 && charge <= 60000) {tax = charge * 0.30 - 3375;}
            if(charge > 60000 && charge <= 80000) {tax = charge * 0.35 - 6375;}
            if(charge > 80000 && charge <= 100000) {tax = charge * 0.4 - 10375;}
            if(charge > 100000) {tax = charge * 0.45 - 15375;}
            
            out.println("<div style=‘line‘>");
            out.println("   <div class=‘leftDiv‘>您的工资为</div><div class=‘rightDiv‘>" + income + " 元</div>");
            out.println("</div>");
            out.println("<div style=‘line‘>");
            out.println("   <div class=‘leftDiv‘>您应纳税</div><div class=‘rightDiv‘>" + tax + "元</div> ");
            out.println("</div><br/>");
            out.println("<input type=‘button‘ onclick=‘history.go(-1);‘ value=‘纳税光荣 逃税可耻 返回‘ class=button>");
            
        }catch(Exception e){
            out.println("请输入数值类型数据.<input type=‘button‘ onclick=‘history.go(-1);‘ value=‘返回‘ class=button>");
        }
        out.println("  </BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }

    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException if an error occurs
     */
    @Override
    public void init() throws ServletException {
        this.log("执行 init() 方法 ...");
        ServletConfig config = this.getServletConfig();
        startPoint = Double.parseDouble(config.getInitParameter("startPoint"));
    }
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException{
        this.log("执行 service() 方法 ...");
        super.service(request, response);
    }

}

 

web.xml的配置如下:

<servlet>
    <servlet-name>LifeCycleServlet</servlet-name>
    <servlet-class>com.helloxr.servlet.LifeCycleServlet</servlet-class>
    <init-param>
        <param-name>startPoint</param-name>
        <param-value>1600</param-value>
    </init-param>
  </servlet>
<servlet-mapping>
    <servlet-name>LifeCycleServlet</servlet-name>
    <url-pattern>/servlet/LifeCycleServlet</url-pattern>
  </servlet-mapping>

 

Tomcat控制台的部分输出:

一月 07, 2017 10:28:35 下午 org.apache.catalina.core.ApplicationContext log
信息: LifeCycleServlet: 执行 init() 方法 ...
一月 07, 2017 10:28:35 下午 org.apache.catalina.core.ApplicationContext log
信息: LifeCycleServlet: 执行 service() 方法 ...
一月 07, 2017 10:28:35 下午 org.apache.catalina.core.ApplicationContext log
信息: LifeCycleServlet: 执行 doGet() 方法 ...
一月 07, 2017 10:29:03 下午 org.apache.catalina.core.ApplicationContext log
信息: LifeCycleServlet: 执行 service() 方法 ...
一月 07, 2017 10:29:03 下午 org.apache.catalina.core.ApplicationContext log
信息: LifeCycleServlet: 执行 doPost() 方法 ...
一月 07, 2017 10:29:22 下午 org.apache.catalina.core.StandardServer await
信息: A valid shutdown command was received via the shutdown port. Stopping the Server instance.
一月 07, 2017 10:29:22 下午 org.apache.coyote.AbstractProtocol pause
信息: Pausing ProtocolHandler ["http-apr-8080"]
一月 07, 2017 10:29:22 下午 org.apache.coyote.AbstractProtocol pause
信息: Pausing ProtocolHandler ["ajp-apr-8009"]
一月 07, 2017 10:29:22 下午 org.apache.catalina.core.StandardService stopInternal
信息: Stopping service Catalina
一月 07, 2017 10:29:22 下午 org.apache.catalina.core.ApplicationContext log
信息: SessionListener: contextDestroyed()
一月 07, 2017 10:29:22 下午 org.apache.catalina.core.ApplicationContext log
信息: ContextListener: contextDestroyed()
一月 07, 2017 10:29:22 下午 org.apache.catalina.core.ApplicationContext log
信息: LifeCycleServlet: 执行 destroy方法 ...
一月 07, 2017 10:29:22 下午 org.apache.coyote.AbstractProtocol stop
信息: Stopping ProtocolHandler ["http-apr-8080"]
一月 07, 2017 10:29:23 下午 org.apache.coyote.AbstractProtocol stop
信息: Stopping ProtocolHandler ["ajp-apr-8009"]
一月 07, 2017 10:29:23 下午 org.apache.coyote.AbstractProtocol destroy
信息: Destroying ProtocolHandler ["http-apr-8080"]
一月 07, 2017 10:29:23 下午 org.apache.coyote.AbstractProtocol destroy
信息: Destroying ProtocolHandler ["ajp-apr-8009"]

 

LifeCycleServlet运行效果:

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Java Web学习笔记-Servle生命周期

原文:http://www.cnblogs.com/datapool/p/6260569.html

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