Servlet的生命周期
Servlet的生命周期是由tomcat服务器来控制的。
1 构造方法：
创建servlet对象的时候调用。默认情况下，第一访问servlet就会创建servlet对象只创建一次。说明servlet对象在tomcat中是单实例的。
2初始化 init方法
当创建完servlet对象的时候会调用init()方法,只调用一次。
1>ServletConfig对象
获取serlvet初始化参数
调用的时候用
this.getInitParameter(参数名)
2>ServletContext对象
获取上下文信息
A 获取全局参数
ServletContext sc= this.getServletContext()
sc.getInitParameter("ecode");
sc.getContextPath() 项目路径 --项目名字
sc.getRealPath() 发布路径 --发布后在tomcat中的路径
3 调用服务 service 方法 其中就包含doGet doPost等方法
每次发送请求的时候调用。可以调用n次。
4 销毁 destory 方法
销毁servlet对象的时候调用，停止服务器或者重新部署的web项目的时候销毁servlet就会调用destory方法
package com.bw.reg.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.bw.reg.bean.Users;
import com.bw.reg.service.ServiceImpl;
public class LoginServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public LoginServlet() {
super();
System.out.println("这里是构造方法");
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
System.out.println("销毁");
// Put your code here
}
/**
* 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 {
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>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.print(" This is ");
out.print(this.getClass());
out.println(", using the GET method");
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
*
*/
//这里是service方法
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
boolean isLogin = false;
//设置编码类型
request.setCharacterEncoding("UTF-8");
//获取登入时输入的用户名和密码
String username = request.getParameter("username");
String password = request.getParameter("pwd");
//创建users的对象
Users users = new Users();
//给users的对象设置登入时输入的用户名和密码
users.setUserName(username);
users.setPwd(password);
//登入时的查找
ServiceImpl serImpl = new ServiceImpl();
isLogin = serImpl.find(users);
if(isLogin){
System.out.println("登入成功！！");
}else {
System.out.println("登录失败");
}
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
System.out.println("这里是初始化方法");
}
}