servlet的细节继续

1.需求：初始化任务，定时任务（定时发送邮件）

解决方法：通过<load-om-startup>配合线程知识搞定

在配置web.xml文件后

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>test</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>ServletTest</servlet-name>
    <servlet-class>ServletTest</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ServletTest</servlet-name>
    <url-pattern>/ServletTest</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>MyInitServlet</servlet-name>
    <servlet-class>com.myservlet.MyInitServlet</servlet-class>
<load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>MyInitServlet</servlet-name>
    <url-pattern>/MyInitServlet</url-pattern>
  </servlet-mapping>

</web-app>

 可以实现定时发送邮件功能

MyInitServlet.java：

package com.myservlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class MyInitServlet
 */
@WebServlet("/MyInitServlet")
public class MyInitServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public MyInitServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }
    public void init() throws ServletException{
        System.out.println("init has been used");
        System.out.println("创建数据库，表，读取数据参数");
        //创建一个线程
        SendEailThred sendemail =new SendEailThred();
        sendemail.start();
    }

}

Thread..java

package com.myservlet;

public class SendEailThred extends Thread{
@Override
public void run(){
    int i=0;
    while(true){
    try {
        Thread.sleep(10*1000);
        System.out.println("We have send No."+(++i)+"  email");}
catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
    }}
}
}

实现的结果：

<load-on-startup><load-om-startup>可以设置启动顺讯

下面的utf-8将会被写死

重点说明;全局配置

实现结果;

MyServlet1.java

package com.hello;

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

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class MyServlet1
 */
//@WebServlet("/MyServlet1")
public class MyServlet1 extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public MyServlet1() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        
        
        String encoding=this.getServletConfig().getInitParameter("encoding");
//        response.setCharacterEncoding(this.getServletConfig().getInitParameter("encoding"));
        response.setCharacterEncoding(encoding);
        PrintWriter out=response.getWriter();
        out.print("编码是"+encoding);
//         response.getWriter().println("hello,world!"+new java.util.Date().toString());
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        this.doGet(request, response);    
    }

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>test</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>MyServlet1</servlet-name>
    <servlet-class>com.hello.MyServlet1</servlet-class>
    <init-param>
    <param-name>encoding</param-name>
    <param-value>utf-8</param-value>
    </init-param>
  </servlet>
  <servlet-mapping>
    <servlet-name>MyServlet1</servlet-name>
    <url-pattern>/MyServlet1</url-pattern>
  </servlet-mapping>
</web-app>

 可以使用枚举遍历;