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;
}
}