package com.ha.servlet;

import java.io.IOException;
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class LifeServlet implements Servlet{
    public LifeServlet(){
        System.out.println("1、实例化");
    }

    public void init(ServletConfig servletConfig) throws ServletException {
        System.out.println("2、初始化");
    }

    public ServletConfig getServletConfig() {
        return null;
    }

    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("3、接收请求，响应结果");
    }

    public String getServletInfo() {
        return null;
    }

    public void destroy() {
        System.out.println("4、销毁");
    }
    
}

执行shutdown.bat，这个tomcat的窗口里面会一闪而过的打印销毁的内容

二、特性

2.1线程安全问题

Servlet在访问之后，会执行实例化操作，创建一个Servlet对象。而我们Tomcat容器可以同时多个线程并发访问同一个Servlet，如果在方法中对成员变量做修改操作，就会有线程安全的问题。

代码解释，两个人以上同时访问：

package com.ha.servlet;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class SafeServlet extends HttpServlet {
    private String message = "";

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //假设1、接收参数
        //2、调用业务逻辑 得到登录结果
        message = "登录成功";//登录失败！
        PrintWriter printWriter = resp.getWriter();
        printWriter.println(message);

    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
}