Fastjson：深入理解SerializerFeature的数据格式转换特性详细解析

package com.fastjson;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.junit.Test;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.serializer.SerializerFeature;

import lombok.AllArgsConstructor;
import lombok.Data;

public class FastjsonFormat {
private static Word word;

private static void init() {
word = new Word();
word.setA("a");
word.setB(2);
word.setC(true);
word.setD("d");
word.setE("");
word.setF(null);
word.setDate(new Date());

List<User> list = new ArrayList<User>();
User user1 = new User();
user1.setId(1);
user1.setOld("11");
user1.setName("用户1");
user1.setAdd("北京");
User user2 = new User();
user2.setId(2);
user2.setOld("22");
user2.setName("用户2");
user2.setAdd("上海");
User user3 = new User();
user3.setId(3);
user3.setOld("33");
user3.setName("用户3");
user3.setAdd("广州");

list.add(user3);
list.add(user2);
list.add(null);
list.add(user1);

word.setList(list);

Map<String, Object> map = new HashMap<>();
map.put("mapa", "mapa");
map.put("mapo", "mapo");
map.put("mapz", "mapz");
map.put("user1", user1);
map.put("user3", user3);
map.put("user4", null);
map.put("list", list);
word.setMap(map);
}

public static void main(String[] args) {
init();
useSingleQuotes();
writeMapNullValue();
useISO8601DateFormat();
writeNullListAsEmpty();
writeNullStringAsEmpty();
sortField();
prettyFormat();
writeDateUseDateFormat();
beanToArray();
showJsonBySelf();

Person person = new Person(null, 28, new String[] { "", "明明" },
new BodyInfo[] { new Height(188), new Weight(150) });
System.out.println(person);

// 去null值
System.out.println(JSON.toJSONString(person));

// 美化,format
System.out.println(JSON.toJSONString(person, SerializerFeature.PrettyFormat));
}

/**
* 9:自定义 格式化输出 显示值为null的字段 将为null的字段值显示为""
* DisableCircularReferenceDetect:消除循环引用
*/
private static void showJsonBySelf() {
System.out.println(JSON.toJSONString(word));
System.out.println(JSON.toJSONString(word, SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue,
SerializerFeature.WriteNullStringAsEmpty, SerializerFeature.DisableCircularReferenceDetect,
SerializerFeature.WriteNullListAsEmpty));
}

/**
* 8: 将对象转为array输出
*/
private static void beanToArray() {
word.setMap(null);
word.setList(null);
System.out.println(JSON.toJSONString(word));
System.out.println(JSON.toJSONString(word, SerializerFeature.BeanToArray));
}

/**
* 7: WriteDateUseDateFormat:全局修改日期格式,默认为false。
*/
private static void writeDateUseDateFormat() {
word.setMap(null);
word.setList(null);
System.out.println(JSON.toJSONString(word));
JSON.DEFFAULT_DATE_FORMAT = "yyyy-MM-dd";
System.out.println(JSON.toJSONString(word, SerializerFeature.WriteDateUseDateFormat));
}

/**
* 6: PrettyFormat
*/
private static void prettyFormat() {
word.setMap(null);
word.setList(null);
System.out.println(JSON.toJSONString(word));
System.out.println(JSON.toJSONString(word, SerializerFeature.PrettyFormat));
}

/**
* SortField:按字段名称排序后输出。默认为false 这里使用的是fastjson：为了更好使用sort field
* martch优化算法提升parser的性能，fastjson序列化的时候，
* 缺省把SerializerFeature.SortField特性打开了。 反序列化的时候也缺省把SortFeidFastMatch的选项打开了。
* 这样，如果你用fastjson序列化的文本，输出的结果是按照fieldName排序输出的，parser时也能利用这个顺序进行优化读取。
* 这种情况下，parser能够获得非常好的性能。
*/
private static void sortField() {
System.out.println(JSON.toJSONString(word));
System.out.println(JSON.toJSONString(word, SerializerFeature.SortField));
}

/**
* 5: WriteNullStringAsEmpty:字符类型字段如果为null,输出为"",而非null
* 需要配合WriteMapNullValue使用，现将null输出
*/
private static void writeNullStringAsEmpty() {
word.setE(null);
System.out.println(JSONObject.toJSONString(word));
System.out.println("设置WriteMapNullValue后：");
System.out.println(JSONObject.toJSONString(word, SerializerFeature.WriteMapNullValue));
System.out.println("设置WriteMapNullValue、WriteNullStringAsEmpty后：");
System.out.println(JSONObject.toJSONString(word, SerializerFeature.WriteMapNullValue,
SerializerFeature.WriteNullStringAsEmpty));
}

/**
* 4: WriteNullListAsEmpty:List字段如果为null,输出为[],而非null
* 需要配合WriteMapNullValue使用，现将null输出
*/
private static void writeNullListAsEmpty() {
word.setList(null);
System.out.println(JSONObject.toJSONString(word));
System.out.println("设置WriteNullListAsEmpty后：");
System.out.println(JSONObject.toJSONString(word, SerializerFeature.WriteMapNullValue,
SerializerFeature.WriteNullListAsEmpty));
}

/**
* 3: UseISO8601DateFormat:Date使用ISO8601格式输出，默认为false
*/
private static void useISO8601DateFormat() {
System.out.println(JSONObject.toJSONString(word));
System.out.println("设置UseISO8601DateFormat后：");
System.out.println(JSONObject.toJSONString(word, SerializerFeature.UseISO8601DateFormat));
}

/**
* 2: WriteMapNullValue:是否输出值为null的字段,默认为false
*/
private static void writeMapNullValue() {
System.out.println(JSONObject.toJSONString(word));
System.out.println("设置WriteMapNullValue后：");
System.out.println(JSONObject.toJSONString(word, SerializerFeature.WriteMapNullValue));
}

/**
* 1: UseSingleQuotes:使用单引号而不是双引号,默认为false
*/
private static void useSingleQuotes() {
System.out.println(JSONObject.toJSONString(word));
System.out.println("设置useSingleQuotes后：");
System.out.println(JSONObject.toJSONString(word, SerializerFeature.UseSingleQuotes));
}

}

interface BodyInfo {

}

@Data
@AllArgsConstructor
class Height implements BodyInfo {
int height;
}

@Data
@AllArgsConstructor
class Person {
String name;
int age;

String[] nickNames;

BodyInfo[] bodyInfos;
}

@Data
@AllArgsConstructor
class Weight implements BodyInfo {
int weight;
}

@Data
class User {
private int id;
private String name;
private String add;
private String old;
}

@Data
class Word {
private String d;
private String e;
private String f;
private String a;
private int b;
private boolean c;
private Date date;
private Map<String, Object> map;
private List<User> list;
}