java的json轉化工具類

作WebService 時須要傳遞JSON格式，導入的包老是出錯，因此參考網上的資源作了一個JSON工具類。

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

public class JsonUtil {
	/**
	 * 將Object類型的對象轉化爲JSON
	 * 
	 * @param object
	 * @return 
	 */
	public static String objectToJson(Object object) {
		StringBuilder json = new StringBuilder();
		if (object == null) {
			json.append("""");
		} else if (object instanceof String || object instanceof Integer
				|| object instanceof Character || object instanceof Float
				|| object instanceof Boolean || object instanceof Short
				|| object instanceof Double || object instanceof Long
				|| object instanceof Byte) {
			json.append("\"").append(stringToJson(object.toString()))
					.append("\"");
		} else if (object instanceof Map) {
			json.append(mapToJson((Map<?, ?>) object));
		} else if (object instanceof Object[]) {
			json.append(arrayToJson((Object[]) object));
		} else if (object instanceof Collection<?>) {
			json.append(collectionToJson((Collection<?>) object));
		} else {
			json.append(beanToJson(object));
		}
		return json.toString();
	}

	/**
	 * 將集合類型的對象轉化爲JSON
	 * 
	 * @param collection
	 * @return 
	 */
	public static String collectionToJson(Collection<?> collection) {
		StringBuilder json = new StringBuilder();
		json.append("[");
		if (collection != null && collection.size() > 0) {
			for (Object object : collection) {
				json.append(objectToJson(object));
				json.append(",");
			}
			json.setCharAt(json.length() - 1, ']');
		} else {
			json.append("]");
		}
		return json.toString();
	}

	/**
	 * 將一個Map類型的對象轉化爲JSON
	 * 
	 * @param map
	 * @return 
	 */
	public static String mapToJson(Map<?, ?> map) {
		StringBuilder json = new StringBuilder();
		Iterator it = map.keySet().iterator();
		json.append("{");
		if (map != null && map.size() > 0) {
			while (it.hasNext()) {
				Object object = it.next();
				json.append(objectToJson(object));
				json.append(":");
				json.append(objectToJson(map.get(object)));
				json.append(",");

			}
			json.setCharAt(json.length() - 1, '}');// 將最後一個逗號改成"}"
		} else {
			json.append("}");
		}
		return json.toString();
	}

	/**
	 * 將一個Bean類型的對象轉化爲JSON
	 * 
	 * @param bean
	 * @return 
	 */
	public static String beanToJson(Object bean) {
		StringBuilder json = new StringBuilder();
		Class cl = bean.getClass();
		json.append("{");
		Field[] fields = cl.getDeclaredFields();
		for (Field f : fields) {
			try {
				StringBuilder fieldName = new StringBuilder(f.getName());
				fieldName.setCharAt(0,
						Character.toUpperCase(fieldName.charAt(0)));
				Method method = cl.getDeclaredMethod(
						"get" + fieldName.toString(), null);// 獲取類中的get方法
				json.append(objectToJson(method.invoke(bean, null)));
                                String value = objectToJson(method.invoke(bean,nu));
                                if(value != null && !value.equals("")){
                                json.append("\"");
                                json.append(f.getName());
                                json.append("\"");
                                json.append(":");
                                json.append("\"");
                                json.append(value);
                                json.append("\"");
                                json.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();
			}
		}
		json.setCharAt(json.length() - 1, '}');// 將最後一個逗號改成"}"
		return json.toString();
	}

	/**
	 * 將數組轉化爲JSON
	 * 
	 * @param array
	 * @return 
	 */
	public static String arrayToJson(Object[] array) {
		StringBuilder json = new StringBuilder();
		json.append("[");
		if (array != null && array.length > 0) {
			for (Object object : array) {
				json.append(objectToJson(object));
				json.append(",");
			}
			json.setCharAt(json.length() - 1, ']');
		} else {
			json.append("]");
		}
		return json.toString();
	}

	/**
	 * 將String類型的對象轉化爲JSON
	 * 
	 * @param s
	 * @return 
	 */
	public static String stringToJson(String string) {
		StringBuilder json = new StringBuilder();
		if (string == null) {
			return "";
		}
		for (int i = 0; i < string.length(); i++) {
			char ch = string.charAt(i);
			switch (ch) {
                        case '"': json.append("\\\""); break;
			case '\\':
				json.append("\\\\");
				break;
			case '\b':
				json.append("\\b");
				break;
			case '\f':
				json.append("\\f");
				break;
			case '\n':
				json.append("\\n");
				break;
			case '\r':
				json.append("\\r");
				break;
			case '\t':
				json.append("\\t");
				break;
                         case '/': json.append("\\/"); break;
			default:
				if (ch >= '\u0000' && ch <= '\u001F') {
					String ss = Integer.toHexString(ch);
					json.append("\\u");
					for (int k = 0; k < 4 - ss.length(); k++) {
						json.append('0');
					}
					json.append(ss.toUpperCase());
				} else {
					json.append(ch);
				}
			}
		}
		return json.toString();
	}
}

參考的文章是 http://www.cnblogs.com/scottpei/archive/2009/11/20/1606785.html