java 对象（List/Map/Set）转json类

package com.ciecc.utils;

import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.bict.test.UserTest;
public class JsonUtil {
	private static Log log = LogFactory.getLog(JsonUtil.class);
	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 void main(String args[]) {
		List<UserTest> userList = new ArrayList<UserTest>();
		userList.add(new UserTest("linbo","北京服装学院",25));
		StringBuilder sb = new StringBuilder();
		System.out.println(list2json(userList));
	}
}