JavaWeb-利用Enumeration获取初始化参数

JavaWeb-利用Enumeration获取初始化参数

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

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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。

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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：

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