通过ServletContext和ServletConfig获取全局和局部参数配置信息

1、LoginServlet.java

package com.keke.servlet;

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

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {
	
	public void init() throws ServletException {
		//通过ServletConfig获取局部参数配置信息
		ServletConfig servletConfig = this.getServletConfig();
		String username = servletConfig.getInitParameter("username");
		String password = servletConfig.getInitParameter("password");
		//通过ServletContext获取全局参数配置信息
		ServletContext servletContext =this.getServletContext();
		String encoding = servletContext.getInitParameter("encoding");
		//username=张三,password=123456
		System.out.println("username="+username+",password="+password);
		//encoding=UTF-8
		System.out.println("encoding="+encoding);
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		this.doPost(request, response);
	}
	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
	
	}
	
	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		super.destroy();
	}

}

2、web.xml

<?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_3_0.xsd" id="WebApp_ID" version="3.0">
	
	<!-- 全局参数配置 -->
	<context-param>
		<param-name>encoding</param-name>
		<param-value>UTF-8</param-value>
	</context-param>

	<!-- 注册servlet -->
	<servlet>
		<servlet-name>loginServlet</servlet-name>
		<servlet-class>com.keke.servlet.LoginServlet</servlet-class>
		<!-- 局部参数配置 -->
		<init-param>
			<param-name>username</param-name>
			<param-value>张三</param-value>
		</init-param>
		<init-param>
			<param-name>password</param-name>
			<param-value>123456</param-value>
		</init-param>
	</servlet>	
	<servlet-mapping>
		<servlet-name>loginServlet</servlet-name>
		<url-pattern>/login</url-pattern>
	</servlet-mapping>
	
  	<welcome-file-list>
   	 	<welcome-file>index.jsp</welcome-file>
  	</welcome-file-list>
  	
</web-app>