java读取properties文档

两种方法：
第一种：用jdk自带的类

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

import org.apache.log4j.Logger;

/**
 * 常量配置类，从指定文件读取常量
 */
public class ConfigurableContants {
	private static final Logger logger = Logger.getLogger(ConfigurableContants.class);

	public static Properties properties = new Properties();

	public static void init(String propertyFileName) {
		InputStream in = null;
		try {
			
   //InputStream inStream =new FileInputStream("sys.properties");
   // this.getClass().getResourceAsStream("/sys.properties"); 
   //Test.class.getClassLoader().getResourceAsStream("sys.properties")        

in = ConfigurableContants.class.getResourceAsStream(propertyFileName);
			if (in != null)
				properties.load(in);
		} catch (IOException e) {
			logger.error("load " + propertyFileName + " into Contants error");
		} finally {
			if (in != null) {
				try {
					in.close();
				} catch (IOException e) {
					e.printStackTrace(e);
				}
			}
		}
	}

	public static String getProperty(String key, String defaultValue) {
		return properties.getProperty(key, defaultValue);
	}

	public static Object setProperty(String key, String Value) {
		return properties.setProperty(key, Value);
	}
}

第二种：用commons-configuration.jar为我们提供的方法
参考这个方法http://javamy.iteye.com/blog/252619