ServletConfig对象和它在开发中的应用场

package cn.itcast;

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

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//servletConfig对象：用于封装servlet的配置信息
//在实际开发，有一些东西不适合在servlet中写死，这类数据就可以通过配置方式给servlet，例如
//servlet采用哪个码表、servlet连接哪个库，servlet哪个配置文件
public class ServletDemo extends HttpServlet {

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

        // 得到指定的
        String value = this.getServletConfig().getInitParameter("data1");
        System.out.println(value);

        // 得到所有的
        Enumeration e = this.getServletConfig().getInitParameterNames();
        while (e.hasMoreElements()) {
            String name = (String) e.nextElement();
            String value1 = this.getServletConfig().getInitParameter(name);
            System.out.println(name+"..="+value1);

        }

    }

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

    }

}

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 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_2_5.xsd">
    <display-name></display-name>
    <servlet>
        <servlet-name>ServletDemo</servlet-name>
        <servlet-class>cn.itcast.ServletDemo</servlet-class>

        <init-param>
            <param-name>data1</param-name>
            <param-value>xxxxxx</param-value>
        </init-param>
        <init-param>
            <param-name>data2</param-name>
            <param-value>yyyyy</param-value>
        </init-param>
        <init-param>
            <param-name>data3</param-name>
            <param-value>dddddd</param-value>
        </init-param>
        <init-param>
            <param-name>data4</param-name>
            <param-value>aaaaaa</param-value>
        </init-param>
    </servlet>

    <servlet-mapping>
        <servlet-name>ServletDemo</servlet-name>
        <url-pattern>/servlet/ServletDemo</url-pattern>
    </servlet-mapping>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>