JavaWeb-利用Enumeration获取初始化参数

JavaWeb-利用Enumeration获取初始化参数

要点
- getInitParameter()方法：public java.lang.String getInitParameter(java.lang.String name)
- getInitParameterNames()方法：public java.util.Enumeration getInitParameterNames()

getInitParameter()方法概述：public java.lang.String getInitParameter(java.lang.String name)
返回上下文定义的变量的值，如果变量不存在，返回null。
见ServletConfig.getInitParameter(java.lang.String)。
getInitParameterNames()方法概述：public java.util.Enumeration getInitParameterNames()
返回上下文定义的所以变量的枚举函数，如果空则返回空枚举函数。

首先在web.xml设置全局参数：

<?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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 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 -->
    <context-param>        
        <param-name>user</param-name>
        <param-value>root</param-value>        
    </context-param>   

    <context-param>        
        <param-name>password</param-name>
        <param-value>xieth123456</param-value>        
    </context-param>  

    <context-param>        
        <param-name>adress</param-name>
        <param-value>china</param-value>        
    </context-param>  
    <!-- 全局参数 -->

    <servlet>
        <servlet-name>HitServlet</servlet-name>
        <servlet-class>com.org.web.HitWebDemo</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>HitServlet</servlet-name>
        <url-pattern>/Hit</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>EServlet</servlet-name>
        <servlet-class>com.org.web.EnumDemo</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>EServlet</servlet-name>
        <url-pattern>/Enum</url-pattern>
    </servlet-mapping>

</web-app>

EnumDemo.java

package com.org.web;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;
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 EnumDemo extends HttpServlet {

    private List<Map<String, String>> list = new ArrayList<>();

    @Override
    public void init(ServletConfig config) throws ServletException {

        ServletContext servletContext = config.getServletContext();
        Enumeration<String> enumeration = servletContext.getInitParameterNames();

        while (enumeration.hasMoreElements()) {
            Map<String, String> map = new HashMap<>();
            String name = enumeration.nextElement();
            map.put("name", name);
            map.put("value", servletContext.getInitParameter(name));
            list.add(map);
        }

    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

        resp.setContentType("text/html;charset=gb2312");

        PrintWriter out = resp.getWriter();


        Iterator it = list.iterator();

        while (it.hasNext()) {
            Map<String, String> map = (Map<String, String>) it.next();
            out.println("<h3>" + map.get("name") + ":" + map.get("value")
                    + "</h3>");
        }


    }

}

运行结果：