- 第一次加载这个servlet程序时（选择右边的servlet程序，注意servlet程序没有main函数，因此执行的是run as servlet Application ）,同时执行init()方法
- 然后开始输入servlet网址，注意不用加java或者php，加了反而运行不了，这是会先执行service()方法，在执行doget()方法；
- 然后点击计算，开始得到个人所得税部分，这个时候显示执行service()方法，在执行dopost()方法；
- 最后，关闭tomcat，执行destory()方法；
init()方法和destory()方法只会执行一次，而service每次都会执行
个人所得税代码
package com.helloweenvsfei.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 = -7197419401412129310L; private static double startPoint = 0; @Override public void init() throws ServletException { this.log("执行 init() 方法 ... "); ServletConfig conf = this.getServletConfig(); startPoint = Double.parseDouble(conf.getInitParameter("startPoint")); } @Override protected void service(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException { this.log("执行 service() 方法 ... "); super.service(arg0, arg1); } @Override 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><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=90%><legend>个税计算器</legend><br/>"); try{ // 从参数中获取的工资数目 double income = new Double(request.getParameter("income")); // 应纳税部分 double charge = income - startPoint; // 缴税 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(); } @Override 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("<link rel='stylesheet' type='text/css' href='../css/style.css'>"); out.println("<HTML><HEAD><TITLE>个人所得税计算</TITLE></HEAD>"); out.println("<div align='center'><br/><fieldset style=90%><legend>个税计算器</legend><br/>"); out.println("<form method='post' action='LifeCycleServlet'>"); 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("</BODY>"); out.println("</HTML>"); out.flush(); out.close(); } @Override public void destroy() { this.log("执行 destroy() 方法 ... "); startPoint = 0; } }