自定義監聽器類來加載web.xml中的系統屬性 和xxx.properties文件屬性

1：配置web.xml文件

<?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_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>SpringMVC</display-name>
  <welcome-file-list>
    <welcome-file>webpage/index.html</welcome-file>
    <welcome-file>webpage/index.htm</welcome-file>
    <welcome-file>webpage/index.jsp</welcome-file>
    <welcome-file>webpage/default.html</welcome-file>
    <welcome-file>webpage/default.htm</welcome-file>
    <welcome-file>webpage/default.jsp</welcome-file>
  </welcome-file-list>

    <context-param>
        <param-name>USERNAME</param-name>
        <param-value>liufukin</param-value>
    </context-param>

    <listener>
        <listener-class>system.InitListener</listener-class>
    </listener>

  <servlet>
    <servlet-name>springmvc</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/classes/springAnnotation-mvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>springmvc</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>

</web-app>

2：創建自定義監聽器類InitListener來加載web.xml中的系統屬性 和xxx.properties文件屬性

package system;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import util.LoadProperties;

/**
 * @author Kin.Liufu
 * @created 2016-1-25
 * @describe 
 */
public class InitListener implements ServletContextListener{

    public void contextDestroyed(ServletContextEvent sce) {  
        System.out.println("web exit ... ");  
    }
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("system init .......");
        //加載web.xml中的配置信息
        System.out.println(sce.getServletContext().getInitParameter("USERNAME"));
        //加載.properties配置文件的信息，但是需要LoadProperties這個靜態類的支持
        System.out.println(LoadProperties.getProperty("config.properties", "userPwd", "liufu"));
    }
}

3：加載xxx.properties屬性文件需要LoadProperties的支持，所以就自己寫了一個加載properties文件的工具類

import java.io.IOException;
import java.io.InputStream;
import java.util.Hashtable;
import java.util.Locale;
import java.util.Properties;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public class LoadProperties {

    private static Logger loger = Logger.getLogger(LoadProperties.class);
    private static Hashtable<String, Properties> htProp = new Hashtable<String, Properties>();

    public static String getProperty(String properties, String key)
            throws IOException {
        Properties p = getProperties(properties);
        return p.getProperty(key)!=null ? p.getProperty(key).trim() : null;
    }

    public static Properties getProperties(String properties)
            throws IOException {

        loger.info("start to read the properties file");
        Properties p = (Properties) htProp.get(properties);
        if (p == null) {
            LoadProperties.retrieveKeyMap(properties);
            p = (Properties) htProp.get(properties);
            if (p == null) {
                throw new IOException("Can't retrieve specified properties: "
                        + properties);
            }
        }
        loger.info("end to read the properties file");
        return p;
    }

    public static String getProperty(String properties, String key, String defaultValue)
    {
        try{
            Properties p = getProperties(properties);
            return p.getProperty(key,defaultValue);
        }
        catch(Exception e)
        {
        }
        return defaultValue;
    }

    public static String getProperty(String properties, String key,
            Locale locale) throws IOException {
        String langName = locale.toString();
        return getProperty(properties, key + "_" + langName);
    }

    public static void refresh(String properties) throws IOException {
        retrieveKeyMap(properties);
    }

    private static void retrieveKeyMap(String propertyFileName) throws IOException {
        Properties p = new Properties();

        InputStream is = LoadProperties.class.getResourceAsStream("/" + propertyFileName);
        if (is == null) {
            is = LoadProperties.class
                    .getResourceAsStream(propertyFileName);
            if (is == null) {
                is = ClassLoader.getSystemResourceAsStream(
                        propertyFileName);
            }
        }
        if (is == null) {
            loger.log(Level.INFO, "Resource file cannot be found: " + propertyFileName);
        } else {
            p.load(is); // throw IOException
            is.close();
            htProp.put(propertyFileName, p);
        }
    }
}