读取 jpa 的配置文件.添加自己的属性.

package com.freewebsys.sns.common;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.Iterator;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.dom4j.Document;
import org.dom4j.DocumentFactory;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.xml.sax.SAXNotRecognizedException;
import org.xml.sax.SAXNotSupportedException;

public class SysConfUtil {

	/**
	 * @param args
	 * @throws MalformedURLException
	 */
	public static void main(String[] args) throws MalformedURLException {
		// TODO Auto-generated method stub
		System.out.println(getConfigValue("mail.host"));
		// System.out.println(getConfigValue("mail.username"));
	}

	private static Document document = null;

	static {
		Enumeration<URL> xmls;
		SAXReader reader = new SAXReader(DocumentFactory.getInstance());
		try {
			xmls = Thread.currentThread().getContextClassLoader()
					.getResources("META-INF/persistence.xml");
			if (xmls.hasMoreElements()) {
				URL configURL = xmls.nextElement();
				document = reader.read(configURL.openStream());
			}
		} catch (Exception e) {
			System.out.println("加载配置失败：" + e.getMessage());
		}
		// System.out.println(document.selectSingleNode("@name=mail.host"));
	}

	@SuppressWarnings("unchecked")
	public static String getConfigValue(String name) {
		System.out.println(document.getRootElement().getName());
		// /*[name()='persistence']/*[name()='persistence-unit']/*[name()='properties']/*[name()='property']
		// 得到根节点
		Element root = document.getRootElement();
		// 得到persistenceUnit
		Element persistenceUnit = root.element("persistence-unit");
		// 得到下面的属性
		Element properties = persistenceUnit.element("properties");
		// 对属性进行循环，找到自定义的配置
		for (Iterator<Element> i = properties.elementIterator("property"); i
				.hasNext();) {
			Element property = i.next();
			if (property.attributeValue("name") != null
					&& property.attributeValue("name").equals(name)) {
				// 如果有这个属性返回value
				return property.attributeValue("value");
			}
		}
		return "";
	}
}

 经过 测试 可以读取 配置文件.并且 打成 jar 包之后 也可以读取到配置文件.

在 properties 下面添加 自己的属性就 property

就可以读取了..比如我添加了. 邮件的配置.