json-lib date对象转json ，加入自定义日期格式处理

import net.sf.json.JSONObject;
import net.sf.json.JsonConfig;
import net.sf.json.processors.JsonValueProcessor;

public class DateJsonValueProcessor implements JsonValueProcessor {
	public static final String DEFAULT_DATE_PATTERN = "yyyy-MM-dd HH:mm:ss";
	private DateFormat dateFormat;

	/**  
	 * 构造方法.  
	 *  
	 * @param datePattern 日期格式  
	 */
	public DateJsonValueProcessor(String datePattern) {
		try {
			dateFormat = new SimpleDateFormat(datePattern);
		} catch (Exception ex) {
			dateFormat = new SimpleDateFormat(DEFAULT_DATE_PATTERN);
		}
	}

	public Object processArrayValue(Object value, JsonConfig jsonConfig) {
		return process(value);
	}

	public Object processObjectValue(String key, Object value,
			JsonConfig jsonConfig) {
		return process(value);
	}

	private Object process(Object value) {
		if (value == null) {
			value = new Date();   //为null时返回当前日期，也可以返回"",看需要
		}
		return dateFormat.format((Date) value);
	}

	public static String map2JSonStr(Map map) {
		JsonConfig jsonConfig = new JsonConfig();
		DateJsonValueProcessor beanProcessor = new DateJsonValueProcessor(
				DEFAULT_DATE_PATTERN);
		jsonConfig.registerJsonValueProcessor(Date.class, beanProcessor);

		JSONObject jsonObject = JSONObject.fromObject(map, jsonConfig);

		return jsonObject.toString();
	}	
	
	//将对象转换为json string，使用上面定义的的日期格式
	@SuppressWarnings("unchecked")
	public static JSONObject obj2JsonObj(Object obj) {
		JsonConfig jsonConfig = new JsonConfig();
		DateJsonValueProcessor beanProcessor = new DateJsonValueProcessor(
				DEFAULT_DATE_PATTERN);
		jsonConfig.registerJsonValueProcessor(Date.class, beanProcessor);

		JSONObject jsonObject = JSONObject.fromObject(obj, jsonConfig);

		return jsonObject;
	}
}