ServletContextListener实现全局配置装载入内存-优快云博客

本文介绍如何通过ServletContextListener在应用启动时加载配置，并通过JSP页面访问这些配置。使用自定义XML配置文件并借助Dom4J进行解析。

(2011-03-27 19:34:06)

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杂谈

分类： java和数据库

1.定义ServletContextListener

public class ApplicationLoader implements ServletContextListener{

    private String ip;
    private String port;
    private String username;
    private String password;
    private String server;

    public void contextInitialized(ServletContextEvent arg0) {

        //装载配置文件
        this.loadXmlConfig();

        // 将配置文件里的值装入context属性,这样可以在JSP,SERVLET里调用
        ServletContext context = arg0.getServletContext();
        context.setAttribute("ip", this.ip);
        context.setAttribute("port", this.port);
        context.setAttribute("username", this.username);
        context.setAttribute("password", this.password);
        context.setAttribute("server", this.server);

    }

     public void loadXmlConfig() {
        //获取配置文件路径, 定义在系统环境变量中
        String xmlFile = System.getenv(Constants.ENVNAME);

        //Dom4J方式获取XML文件的节点值
        List<String> retList = null;
        retList = Dom4JParser.readNodeText(new File(
                xmlFile+"/ibiconfig/xml/amconfig.xml"),"//host/ip");
        if(null != retList){
            for(String temp:retList){
                this.ip = temp;
            }
        }

        //Dom4J方式获取XML文件的节点值
        retList = Dom4JParser.readNodeText(new File(
                xmlFile+"/ibiconfig/xml/amconfig.xml"),"//host/port");
        if(null != retList){
            for(String temp:retList){
                this.port = temp;
            }
        }

        //Dom4J方式获取XML文件的节点值
        retList = Dom4JParser.readNodeText(new File(
                xmlFile+"/ibiconfig/xml/amconfig.xml"),"//host/authentication/username");
        if(null != retList){
            for(String temp:retList){
                this.username = temp;
            }
        }

        //Dom4J方式获取XML文件的节点值
        retList = Dom4JParser.readNodeText(new File(
                xmlFile+"/ibiconfig/xml/amconfig.xml"),"//host//authentication/password");
        if(null != retList){
            for(String temp:retList){
                this.password = temp;
            }
        }

        //Dom4J方式获取XML文件的节点值
        retList = Dom4JParser.readNodeText(new File(
                xmlFile+"/ibiconfig/xml/amconfig.xml"),"//host//authentication/server");
        if(null != retList){
            for(String temp:retList){
                this.server = temp;
            }
        }
    }

2.修改WEB-INF/web.xml, 启用前面定义的listener

<listener>
        <listener-class>com.machome.system.ApplicationLoader</listener-class>
    </listener>

3.在JSP页面里可以调用listener装入的变量值

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<br />
<%=getServletContext().getAttribute("ip")%> <br />
<%=getServletContext().getAttribute("username")%> <br />
<%=getServletContext().getAttribute("password")%> <br />
</body>
</html>

4.自定义XML配置文件

<?xml version="1.0" encoding="UTF-8"?>

<root>
    <host>
         <ip>192.168.0.101</ip>
         <port>8080</port>
         <authentication>
             <username>macg</username>
             <password>008421</password>
             <server>EDASERVE</server>
         </authentication>
    </host>
</root>

前面采用的是读取环境变量获取XML文件路径,我们应该把这个配置文件的路径设到环境变量中.这里不赘述.
你也可以直接采用文件物理路径,访问更简单些,但路径做死在程序里,不好修改.