javascript当中null和undefined的==和===的比较

1.用init-param获取：

例：1.1.1

ServletHello1.java：
package com;
import java.io.IOException;
import java.io.PrintWriter;
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 {
        String salary = getInitParameter("zhangsan");
        System.out.println("salary is "+salary);
    }
}

在web.xml中加入：

<servlet>
        <servlet-name>ServletHello1</servlet-name>
        <servlet-class>com.ServletHello1</servlet-class>
             <init-param>
                 <param-name>zhangsan</param-name>
                 <param-value>1000</param-value>
             </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>ServletHello1</servlet-name>

文章转载自原文：https://blog.csdn.net/mark_to_win/article/details/84784926