使用Jackson做對象與json之間的相互轉換

public class JsonUtil {
	private static JsonUtil ju;
	private static JsonFactory jf;
	private static ObjectMapper mapper;
	private JsonUtil(){}
	
	public static JsonUtil getInstance() {
		if(ju==null) ju = new JsonUtil();
		return ju;
	}
	
	public static ObjectMapper getMapper() {
		if(mapper==null) {
			mapper = new ObjectMapper();
		}
		return mapper;
	}
	
	public static JsonFactory getFactory() {
		if(jf==null) jf = new JsonFactory();
		return jf;
	}
	
	/**
	 * 將bean對象轉換爲json字符串，如obj可以爲List
	 * 
	 * /
	public String obj2json(Object obj) {
		JsonGenerator jg = null;
		try {
			jf = getFactory();
			mapper = getMapper();
			StringWriter out = new StringWriter();
			jg = jf.createJsonGenerator(out);
			mapper.writeValue(jg, obj);
			return out.toString();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if(jg!=null) jg.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return null;
	}
	
	/**
	 * 將json數據轉換爲bean對象
	 * 
	 * /
	public Object json2obj(String json,Class<?> clz) {
		try {
			mapper = getMapper();
			return mapper.readValue(json,clz);
		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return null;
	}
}