Servlet复习第一天_JAVA_编程开发_程序员俱乐部

1.servlet定义: 运行在服务器端的java类.

2.servle生命周期

? ?<1>WEB容器创建Servlet实例

? ?<2>调用Servlet的init方法

? ?<3>多次调用Servlet的service方法(即Servlet是单例的)

? ?<4>WEB容器关闭时调用Servlet的destroy方法销毁Servlet

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3.Servlet配置

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class="java"><?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
	id="WebApp_ID" version="2.5">
	
	<context-param>
		<param-name>test2</param-name>
		<param-value>myServlet2</param-value>
	</context-param>
	
	<servlet>
		<servlet-name>MyServlet</servlet-name>
		<servlet-class>com.wr.servlet.MyServlet</servlet-class>
		<init-param>
			<param-name>test</param-name>
			<param-value>myServlet</param-value>
		</init-param>
		<load-on-startup>0</load-on-startup>
	</servlet>
	
	<servlet-mapping>
		<servlet-name>MyServlet</servlet-name>
		<url-pattern>/MyServlet</url-pattern>
	</servlet-mapping>
</web-app>

? ??

? ??monospace; line-height: 1.5; background-color: #fafafa;">load-on-startup: 配置Servlet的加载方式

? ? ? ? ? ? <1>值为负数时,访问当前Servlet时才创建Servlet实例

? ? ? ? ? ? <2>值位正数时,WEB应用加载时就创建Servlet实例, 值越小优先级越高,最先创建.

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package com.wr.servlet;

import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * Servlet implementation class MyServlet
 */
public class MyServlet implements Servlet{
	
	public MyServlet() {
		System.out.println("MyServlet.MyServlet()");
	}

	public void init(ServletConfig config) throws ServletException {
		// TODO Auto-generated method stub
		System.out.println("MyServlet.init()");
		String param = config.getInitParameter("test");
		System.out.println(param);
		ServletContext context = config.getServletContext();
		System.out.println(context.getInitParameter("test2"));
	}

	public ServletConfig getServletConfig() {
		// TODO Auto-generated method stub
		System.out.println("MyServlet.getServletConfig()");
		return null;
	}

	public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
		System.out.println("MyServlet.service()");
		// TODO Auto-generated method stub
		
	}

	public String getServletInfo() {
		System.out.println("MyServlet.getServletInfo()");
		// TODO Auto-generated method stub
		return null;
	}

	public void destroy() {
		System.out.println("MyServlet.destroy()");
		// TODO Auto-generated method stub
		
	}
	
}

??? ?ServletConfig: 当前Servlet的配置对象, 可以读取配置在Servlet中的初始化参数

? ? ?ServletContext: 当前WEB应用的上下文对象, 可以读取配置在WEB配置文件中的初始化参数