JSON实用类，用来实现对象和JSON字符串的互相转换

import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * JSON实用类
 * 用来实现对象和JSON字符串的互相转换
 *
 * @author aven
 * @date 2015-01-14
 */
public class JSONUtil {

	public static String object2json(Object obj) {
		StringBuilder json = new StringBuilder();
		if (obj == null) {
			json.append("\"\"");
		} else if (obj instanceof String || obj instanceof Integer
				|| obj instanceof Float || obj instanceof Boolean
				|| obj instanceof Short || obj instanceof Double
				|| obj instanceof Long || obj instanceof BigDecimal
				|| obj instanceof BigInteger || obj instanceof Byte) {
			json.append("\"").append(string2json(obj.toString())).append("\"");
		} else if (obj instanceof Object[]) {
			json.append(array2json((Object[]) obj));
		} else if (obj instanceof List) {
			json.append(list2json((List<?>) obj));
		} else if (obj instanceof Map) {
			json.append(map2json((Map<?, ?>) obj));
		} else if (obj instanceof Set) {
			json.append(set2json((Set<?>) obj));
		} else {
			json.append(bean2json(obj));
		}
		return json.toString();
	}

	public static String bean2json(Object bean) {
		StringBuilder json = new StringBuilder();
		json.append("{");
		PropertyDescriptor[] props = null;
		try {
			props = Introspector.getBeanInfo(bean.getClass(), Object.class)
					.getPropertyDescriptors();
		} catch (IntrospectionException e) {
		}
		if (props != null) {
			for (int i = 0; i < props.length; i++) {
				try {
					String name = object2json(props[i].getName());
					String value = object2json(props[i].getReadMethod().invoke(
							bean));
					json.append(name);
					json.append(":");
					json.append(value);
					json.append(",");
				} catch (Exception e) {
				}
			}
			json.setCharAt(json.length() - 1, ‘}‘);
		} else {
			json.append("}");
		}
		return json.toString();
	}

	public static String list2json(List<?> list) {
		StringBuilder json = new StringBuilder();
		json.append("[");
		if (list != null && list.size() > 0) {
			for (Object obj : list) {
				json.append(object2json(obj));
				json.append(",");
			}
			json.setCharAt(json.length() - 1, ‘]‘);
		} else {
			json.append("]");
		}
		return json.toString();
	}

	public static String array2json(Object[] array) {
		StringBuilder json = new StringBuilder();
		json.append("[");
		if (array != null && array.length > 0) {
			for (Object obj : array) {
				json.append(object2json(obj));
				json.append(",");
			}
			json.setCharAt(json.length() - 1, ‘]‘);
		} else {
			json.append("]");
		}
		return json.toString();
	}

	public static String map2json(Map<?, ?> map) {
		StringBuilder json = new StringBuilder();
		json.append("{");
		if (map != null && map.size() > 0) {
			for (Object key : map.keySet()) {
				json.append(object2json(key));
				json.append(":");
				json.append(object2json(map.get(key)));
				json.append(",");
			}
			json.setCharAt(json.length() - 1, ‘}‘);
		} else {
			json.append("}");
		}
		return json.toString();
	}

	public static String set2json(Set<?> set) {
		StringBuilder json = new StringBuilder();
		json.append("[");
		if (set != null && set.size() > 0) {
			for (Object obj : set) {
				json.append(object2json(obj));
				json.append(",");
			}
			json.setCharAt(json.length() - 1, ‘]‘);
		} else {
			json.append("]");
		}
		return json.toString();
	}

	public static String string2json(String s) {
		if (s == null)
			return "";
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < s.length(); i++) {
			char ch = s.charAt(i);
			switch (ch) {
			case ‘"‘:
				sb.append("\\\"");
				break;
			case ‘\\‘:
				sb.append("\\\\");
				break;
			case ‘\b‘:
				sb.append("\\b");
				break;
			case ‘\f‘:
				sb.append("\\f");
				break;
			case ‘\n‘:
				sb.append("\\n");
				break;
			case ‘\r‘:
				sb.append("\\r");
				break;
			case ‘\t‘:
				sb.append("\\t");
				break;
			case ‘/‘:
				sb.append("\\/");
				break;
			default:
				if (ch >= ‘\u0000‘ && ch <= ‘\u001F‘) {
					String ss = Integer.toHexString(ch);
					sb.append("\\u");
					for (int k = 0; k < 4 - ss.length(); k++) {
						sb.append(‘0‘);
					}
					sb.append(ss.toUpperCase());
				} else {
					sb.append(ch);
				}
			}
		}
		return sb.toString();
	}

	public static <T> T json2Object(String jsonString, Class<T> pojoCalss) {
		if (pojoCalss == null || jsonString == null || jsonString.trim().isEmpty()){
			return null;
		}
		try {
			T pojo = (T)pojoCalss.newInstance();
			Field[] fields = pojo.getClass().getDeclaredFields();

			String simpleName = "";
			for (Field f : fields) {
				try{
					if (f.getName() == null) {
						continue;
					}
					if (f.getModifiers() > 2) {
						continue;
					}
					f.setAccessible(true);
					simpleName = f.getType().getSimpleName();

					String propName = "\"" + f.getName() + "\":";
					Integer idx = jsonString.indexOf(propName);
					if (idx == -1){
						continue;
					}
					Integer idxStart = idx + propName.length();
					if (jsonString.length() < idxStart){
						continue;
					}

					String valStart = jsonString.substring(idxStart, idxStart+1);
					if (valStart.equals("[")){
						valStart = "]";
					}else if (valStart.equals("{")){
						valStart = "}";
					}else{
						if (!valStart.equals("\"")){
							valStart = ",";
						}
					}
					String propValue = null;
					Integer idxEnd = -1;
					if (valStart.equals(",")){
						idxEnd = jsonString.indexOf(valStart, idxStart);
						if (idxEnd == -1){
							continue;
						}
						propValue = jsonString.substring(idxStart, idxEnd);
					}else{
						idxEnd = jsonString.indexOf(valStart, idxStart + 1);
						if (idxEnd == -1){
							continue;
						}
						propValue = jsonString.substring(idxStart + 1, idxEnd);
					}

					if (propValue == null){
						continue;
					}
					if (simpleName.equals("String") || simpleName.equals("Object")) {
						f.set(pojo, propValue);
						continue;
					}
					if (simpleName.equals("Long") || simpleName.equals("long")) {
						f.set(pojo, getLong(propValue));
						continue;
					}
					if (simpleName.equals("Integer") || simpleName.equals("int")) {
						f.set(pojo, getInteger(propValue));
						continue;
					}
					if (simpleName.equals("Boolean")) {
						f.set(pojo, getBoolean(propValue));
						continue;
					}
					if (simpleName.equals("Double")) {
						f.set(pojo, getDouble(propValue));
						continue;
					}
					if (simpleName.equals("Float")) {
						f.set(pojo, getFloat(propValue));
						continue;
					}
					if (simpleName.equals("Byte")) {
						f.set(pojo, getByte(propValue));
						continue;
					}
					if (simpleName.equals("List")) {
						f.set(pojo, getList(propValue));
						continue;
					}
				}catch(Exception ex){
					ex.printStackTrace();
				}
			}
			return pojo;
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}

	public static Long getLong(String propValue){
		Long val = 0L;
		try{
			val = Long.parseLong(propValue);
		}catch(Exception el){}
		return val;
	}

	public static Integer getInteger(String propValue){
		Integer val = 0;
		try{
			val = Integer.parseInt(propValue);
		}catch(Exception el){}
		return val;
	}

	public static Boolean getBoolean(String propValue){
		Boolean val = ("1".equals(propValue) || "true".equalsIgnoreCase(propValue));
		return val;
	}

	public static Double getDouble(String propValue){
		Double val = 0D;
		try{
			val = Double.parseDouble(propValue);
		}catch(Exception el){}
		return val;
	}

	public static Float getFloat(String propValue){
		Float val = 0F;
		try{
			val = Float.parseFloat(propValue);
		}catch(Exception el){}
		return val;
	}

	public static Byte getByte(String propValue){
		Byte val = 0;
		try{
			val = Byte.parseByte(propValue);
		}catch(Exception el){}
		return val;
	}

	public static List<String> getList(String propValue){
		List<String> valList = new ArrayList<String>();
		if (propValue != null && !propValue.trim().isEmpty()){
			try{
				String[] aptEvents = propValue.replace("\"", "").toLowerCase().split(",");
				valList = java.util.Arrays.asList(aptEvents);
			}catch(Exception ex){
				ex.printStackTrace();
			}
		}
		return valList;
	}

	public static void main(String[] args) {
		String json = JSONUtil.object2json(new Data());
		System.out.println(json);
	}
}