Servlet--ServletContext(三)获取web.xml配置参数

Servlet--ServletContext(三)获取web.xml配置参数
一、ServletContext作用之获取配置文件参数 1、获取配置文件实例：

package test07_3context;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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 WebServlet extends HttpServlet {

@Override
public void init() throws ServletException {
// TODO Auto-generated method stub
System.out.println("=========在控制台输出Web配置信息=========");

//获取ServletContext
ServletContext app = getServletContext();
//获取web配置的信息
System.out.println("①、通过参数名称获取Web配置的信息");
String names = app.getInitParameter("name");
System.out.println("name的值："+names);
String ages = app.getInitParameter("age");
System.out.println("age的值："+ages);
System.out.println("--------------------");
//通过遍历方式获取web配置的信息
System.out.println("②、通过Enumration遍历方式获取web配置的信息");
Enumeration<String> en = app.getInitParameterNames();
while(en.hasMoreElements()){
String key = en.nextElement();
System.out.println("key的值为："+app.getInitParameter(key));
}

}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.println("===========在网页输出Web配置信息==========="+"<br/>");

out.println("①、通过参数名称获取Web配置的信息"+"<br/>");

ServletContext ap = getServletContext();
String nm = ap.getInitParameter("name");
out.print("name的值："+nm+"<br/>");
String ag = ap.getInitParameter("age");
out.print("age的值："+ag+"<br/>");

out.println("②、通过Enumration遍历方式获取web配置的信息"+"<br/>");
Enumeration<String> eu = ap.getInitParameterNames();
while(eu.hasMoreElements()){
String ke = eu.nextElement();
out.print("key的值为："+ap.getInitParameter(ke)+"<br/>");
}

}

}

2、配置文件参数

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">

 <!-- servletContext获取web配置的参数如下有name和age两个参数 --> <context-param> <param-name>name</param-name> <param-value>我的家乡在中国</param-value> </context-param> <context-param> <param-name>age</param-name> <param-value>65</param-value> </context-param> <servlet>    <description>This is the description of my J2EE component</description>    <display-name>This is the display name of my J2EE component</display-name>    <servlet-name>WebServlet</servlet-name>    <servlet-class>test07_3context.WebServlet</servlet-class>    <load-on-startup>1</load-on-startup>  </servlet>  <servlet-mapping>    <servlet-name>WebServlet</servlet-name>    <url-pattern>/WebServlet</url-pattern>  </servlet-mapping></web-app>

3、测试 启动该项目，在浏览器中输入测试地址：http://127.0.0.1:8080/test07_3/WebServlet  测试结果： A、控制台结果：
B、网页端结果：