Properties ORM

实现

最近突发奇想，java使用properties时每次都要调用getProperty方法获取配置信息，有时还要转换类型，这有点不方便，于是就自己实现了一个从properties到类的映射功能，方便读取配置信息。实现原理非常简单，利用java的反射功能找到类的所有公共字段，然后利用字段名作为key从properties中查找value，再将value转换为字段对应的类型。注意，类字段必须为public，且字段名必须与配置key一致，类无需getter\setter，因为字段都是public

/**
 * 通过反射实现properties到java类文件的映射，目前支持类型:boolean,byte,short,int,float,double,long,string，
 * java bean字段名必须与properties配置key一致，且必须为public
 * @author lhl
 *
 * 2015年7月7日下午2:54:50
 */
public class ConfigParser 
{
	/**
	 * 从类路径加载配置并映射到类
	 * @param file
	 * @param clas
	 * @throws IllegalStateException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 * @throws IOException 
	 */
	public static void parseFromClassPath(String file, Class<?> clas) throws IllegalStateException, IllegalArgumentException, IllegalAccessException, IOException
	{
		Properties prop = loadFromClassPath(file);
		assignment(clas, prop);
	}
	
	/**
	 * 从类路径加载配置
	 * @param file
	 * @return
	 * @throws IOException 
	 */
	private static Properties loadFromClassPath(String file) throws IOException
	{
		Properties prop = new Properties();
		try (InputStream inStream = ConfigParser.class.getClassLoader().getResourceAsStream(file))
		{
			prop.load(inStream);
		}
		return prop;
	}
	
	/**
	 * 给字段赋值
	 * @param obj
	 * @param prop
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	private static void assignment(Class<?> obj, Properties prop) throws IllegalArgumentException, IllegalAccessException
	{
		Field[] allFields = obj.getFields();
		for (Field field : allFields)
		{
			Class<?> type = field.getType();
			String fieldName = field.getName();
			String value = prop.getProperty(fieldName);
			if (type == boolean.class)
			{
				field.setBoolean(obj, Boolean.parseBoolean(value));
			}
			else if (type == byte.class)
			{
				field.setByte(obj, Byte.parseByte(value));
			}
			else if (type == short.class)
			{
				field.setShort(obj, Short.parseShort(value));
			}
			else if (type == int.class)
			{
				field.setInt(obj, Integer.parseInt(value));
			}
			else if (type == float.class)
			{
				field.setFloat(obj, Float.parseFloat(value));
			}
			else if (type == double.class)
			{
				field.setDouble(obj, Double.parseDouble(value));
			}
			else if (type == long.class)
			{
				field.setLong(obj, Long.parseLong(value));
			}
			else if (type == String.class)
			{
				field.set(obj, value);
			}
		}
	}
}

测试类：

/**
 * @author lhl
 *
 * 2015年7月30日下午5:53:13
 */
public class TestConfig
{
	public static String fieldA;
	public static byte fieldB;
	public static short fieldC;
	public static int fieldD;
	public static boolean fieldE;
	public static float fieldF;
	public static double fieldG;
	public static long fieldH;
}

测试配置文件app.properties：

fieldA=this is first  field
fieldB=2
fieldC=3
fieldD=4
fieldE=true
fieldF=5
fieldG=6
fieldH=7

使用方法：

ConfigParser.parseFromClassPath("app.properties", TestConfig.class);