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: