3.从context-param获取：（视频下载） （全部书籍）
马克-to-win：用context-param存放的参数，本个web应用中的任何servlet，jsp都可以获得。
例：1.3.1
ServletHello1.java：
package com;
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 ServletHello1 extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
ServletContext servletContext = getServletContext();
String jd = servletContext.getInitParameter("zhangsan");
System.out.println(jd);
}