关于JSON的Java类库挺多的，但有时候不希望在项目里边引入这些JAR包，所以需要自己实现一些简单的工具类。本例就属于这种情况。本例中使用Java的反射机制，将简单的POJO对象转换成JSON字符串。

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/**
* 将字符串首字母大写
* @param str
 * @return
 */
private static String transform(String str) {
	if (str == null || str.length() < 1) {
		return "";
	}
	return str.substring(0, 1).toUpperCase() + str.substring(1);
}

/**
 * 将POJO对象转换成JSON格式的字符串
 * @param obj
* @return
 */
public static String pojo2Json(Object obj) {
	if (obj == null) {
		return "";
	}
	Class clazz = obj.getClass();
	Field[] fields = clazz.getDeclaredFields();
	StringBuilder buff = new StringBuilder();
	buff.append("{");
	for (Field f : fields) {
		try {
			String methodName = "get" + transform(f.getName());
			Object value=clazz.getDeclaredMethod(methodName).invoke(obj, null);
			buff.append("\"");
			buff.append(f.getName());
			buff.append("\":");
			if(value==null){
				buff.append("\"\",");
				continue;
			}
			if(value instanceof Boolean){
				buff.append((Boolean)value);
				buff.append(",");
			}else if(value instanceof Number){
				buff.append((Number)value);
				buff.append(",");
			}else if(value instanceof Date){
				buff.append("\"");
				buff.append(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format((Date)value));
				buff.append("\",");
			}else{
				buff.append("\"");
				buff.append(value.toString());
				buff.append("\",");
			}
		} catch (SecurityException e) {
			//e.printStackTrace();
		} catch (NoSuchMethodException e) {
			//e.printStackTrace();
		} catch (IllegalArgumentException e) {
			//e.printStackTrace();
		} catch (IllegalAccessException e) {
			//e.printStackTrace();
		} catch (InvocationTargetException e) {
			//e.printStackTrace();
		}
			
	}
	if (buff.length() > 1) {
		buff = buff.deleteCharAt(buff.length() - 1);
	}
	buff.append("}");
	return buff.toString();
}