java对象转json

import java.util.Map;

import java.beans.BeanInfo;

import java.beans.IntrospectionException;

import java.beans.Introspector;

import java.beans.PropertyDescriptor;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.math.BigDecimal;

import java.text.SimpleDateFormat;

import java.util.*;

public class JSON1 {

    private static final String quote = "\"";

    private static final String braceL = "{";

    private static final String braceR = "}";

    private static final String middleBraceL = "[";

    private static final String middleBraceR = "]";

    private static final String comma = ",";

    private static final String colon = ":";

    private static final String defaultDateFormat = "yyyy-MM-dd HH:mm:ss";

    public static String toJsonString(Object obj) {

        return toJsonString(obj, defaultDateFormat);

    }

    public static String toJsonString(Object obj, String dateFormat) {

        StringBuilder sb = null;

        try {

            sb = parseObject(obj, dateFormat);

        } catch (IntrospectionException e) {

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            e.printStackTrace();

        }

        if (null != sb && sb.length() > 0 && sb.substring(sb.length() - 1).equals(comma)) {

            sb = new StringBuilder(sb.substring(0, sb.lastIndexOf(comma)));

        }

        return sb == null ? "" : sb.toString();
    }

    public static StringBuilder parseObject(Object object, String dateFormat) throws IntrospectionException, InvocationTargetException, IllegalAccessException {

        StringBuilder sb = new StringBuilder();

        if (canGetValue(object)) {

            sb.append(getSimpleValue(object, dateFormat));

        } else if (object instanceof List) {

            //遇到list

            sb.append(middleBraceL);

            List list = (List) object;

            for (Object o : list) {

                sb.append(parseObject(o, dateFormat)).append(comma);

            }

            if (list.size() > 0) {

                sb = new StringBuilder(sb.substring(0, sb.lastIndexOf(comma)));

            }

            sb.append(middleBraceR);

        } else if (object instanceof Map) {

            //遇到map

            sb.append(braceL);

            Map map = (Map) object;

            Set<Map.Entry> entrySet = map.entrySet();

            for (Map.Entry entry : entrySet) {

                sb.append(quote).append(entry.getKey()).append(quote).append(colon);

                sb.append(parseObject(entry.getValue(), dateFormat)).append(comma);

            }

            if (map.size() > 0) {

                sb = new StringBuilder(sb.substring(0, sb.lastIndexOf(comma)));

            }

            sb.append(braceR);

        } else if (object.getClass().isArray()) {

            //遇到数组

            sb.append(middleBraceL);

            List list = Arrays.asList(object);

            for (Object o : list) {

                sb.append(parseObject(o, dateFormat)).append(comma);

            }

            if (list.size() > 0) {

                sb = new StringBuilder(sb.substring(0, sb.lastIndexOf(comma)));

            }

            sb.append(middleBraceR);

        } else {

            //其他正常plain对象

            BeanInfo beanInfo = Introspector.getBeanInfo(object.getClass()); // 获取类属性

            PropertyDescriptor[] pds = beanInfo.getPropertyDescriptors();

            sb.append(braceL);

            for (PropertyDescriptor pd : pds) {

                if (pd.getName().equals("class")) {

                    continue;

                }

                String key = pd.getName();

                Method readMethod = pd.getReadMethod();

                Object result = readMethod.invoke(object, null);

                sb.append(quote).append(key).append(quote).append(colon);

                sb.append(parseObject(result, dateFormat)).append(comma);

            }

            if (pds.length > 1) {

                sb = new StringBuilder(sb.substring(0, sb.lastIndexOf(comma)));

            }

            sb.append(braceR);

        }

        return sb;

    }

    private static StringBuilder getSimpleValue(Object val, String dateFormat) {

        if (null == val) {

            return new StringBuilder("null");

        }

        StringBuilder sb = new StringBuilder();

        if (needQuote(val)) {

            sb.append(quote);

            if (val instanceof Date) {

                SimpleDateFormat sf = new SimpleDateFormat(dateFormat);

                sb.append(new StringBuilder(sf.format(val)));

            } else {

                sb.append(val);

            }

            sb.append(quote);

        } else {

            sb.append(val);

        }

        return sb;

    }


    private static boolean needQuote(Object object) {

        return object instanceof String || object instanceof Date;

    }


    private static boolean canGetValue(Object object) {

        return object instanceof Boolean || object instanceof Character ||

                object instanceof Byte || object instanceof Short ||

                object instanceof Integer || object instanceof Double ||

                object instanceof Long || object instanceof Date ||

                object instanceof BigDecimal || object instanceof Float ||

                object instanceof String || null == object;

    }


    public static void main(String[] args) {

        //  String[] ss = {"sdf", "dfd"};

        // System.out.println(ss.getClass().isArray());

        User user = new User(20, "yujun", "男");

        User subUser = new User(2, "yuxx", "女");

        user.setSubUser(subUser);

        List<User> users = new ArrayList<User>();

        User user1 = new User(1, "a", "n");

        User user2 = new User(2, "b", "v");

        User user3 = new User(3, "c", "n");

        User user4 = new User(4, "d", "v");

        user4.setSubUser(user);

        users.add(user1);

        users.add(user2);

        users.add(user3);

        users.add(user4);


        Map<String, Object> m = new HashMap<String, Object>();

        m.put("a", "dfsdf");

        m.put("b", user);

        m.put("c", users);

        m.put("date", new Date());

        //list
        System.out.println(toJsonString(users));

        //map
        System.out.println(toJsonString(m));

        //other obj
        System.out.println(toJsonString(user));

    }

}

class User {
    private Integer age;
    private String name;
    private String sex;
    private User subUser;

    public User() {
    }

    public User(Integer age, String name, String sex) {
        this.age = age;
        this.name = name;
        this.sex = sex;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public User getSubUser() {
        return subUser;
    }

    public void setSubUser(User subUser) {
        this.subUser = subUser;
    }
}