Differences and precautions of fastjson, jackjson and gson

transformation

 Prepare one vo
@Data
public class Person implements Serializable {
    private Integer id;
    private BigDecimal amount;
    private BigDecimal amountNUll;
    private String name;
    private String P;// Just a capital letter 
    private String XYZabc;// continuity 3 Capital letters 
    private String XYNULL;
    private Date createTime;


    public Person(Integer id, String name, Date createTime) {
        this.id = id;
        this.name = name;
        this.createTime = createTime;
    }
}

1、string turn object

 	String json = "{\"XYZabc\":\"XYZ\",\"amount\":8.88,\"createTime\":1654931545521,\"id\":1,\"name\":\"DZL\",\"p\":\"PPP\"}";
        //  The way 1:  take json String to Java object 
        Person person = JSON.parseObject(json,Person.class);
        System.out.println("fastjson：java object ->>>"+person);

        //  The way 2:  take json String to Java object 
        Person newPerson2 = JSONObject.parseObject(json, Person.class);
        System.out.println("fastjson：java object ->>>"+newPerson2);

        System.out.println("=========================================================");
        ObjectMapper objectMapper = new ObjectMapper();
        try {
            Person jackPerson = objectMapper.readValue(json, Person.class);
            System.out.println("java object ->>>"+jackPerson);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }

        System.out.println("=========================================================");

        final Gson gson = new Gson();

        Person gsonPerson = gson.fromJson(json, Person.class);
        System.out.println("java object ->>>"+gsonPerson);

• jackjson I can't make it in capital P,XYZabc Such a property key, All need to be changed to lowercase ,fast and gson No big problem
• gson incognizance 1654931545521 Such timestamp

2、object turn string

 	Person person = new Person(1,"DZL",new Date());
        person.setP("PPP");
        person.setXY("XYZ");
        person.setAmount(new BigDecimal("8.88"));

        //  The way 1： Convert object to json character string 
        String json = JSON.toJSONString(person);
        System.out.println("fast json character string 1->>>"+json);
        System.out.println("=========================================================");
        //  The way 2： Convert object to json character string 
        String json2 = JSONObject.toJSONString(person);
        System.out.println("fast json character string 1->>>"+json2);

        System.out.println("=========================================================");

        ObjectMapper objectMapper = new ObjectMapper();
        try {
            String jackStr = objectMapper.writeValueAsString(person);
            System.out.println("jack json character string ->>>"+jackStr);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        System.out.println("=========================================================");

        Gson gson = new Gson();
        String gsonStr = gson.toJson(person);
        System.out.println("gson json character string ->>>"+gsonStr);

result

fast json character string 1->>>{"XYZabc":"XYZ","amount":8.88,"createTime":1654931545521,"id":1,"name":"DZL","p":"PPP"}
=========================================================
fast json character string 1->>>{"XYZabc":"XYZ","amount":8.88,"createTime":1654931545521,"id":1,"name":"DZL","p":"PPP"}
=========================================================
jack json character string ->>>{"id":1,"amount":8.88,"amountNUll":null,"name":"DZL","createTime":1654931545521,"p":"PPP","xyzabc":"XYZ","xynull":null}
=========================================================
gson json character string ->>>{"id":1,"amount":8.88,"name":"DZL","P":"PPP","XYZabc":"XYZ","createTime":"Jun 11, 2022 3:12:25 PM"}

difference
1、 String and BigDecimal If the value of all is null,fastjson, and gson No printing by default ,jack It is printed by default
2、 Attribute names are capitalized , Like a P,fast,jack It's lowercase ,gson Still capitalized ;
3、 Attribute names such as XYZabc The first letter 2 A capital letter ,fast and gson Keep it as it is. ,fast All lowercase

3、array turn json

  public static void fast_list2str_test(){
        List<Person> personList = new ArrayList<>();
        personList.add(new Person(1,"DT",new Date()));
        personList.add(new Person(2,"DT1",new Date()));
        personList.add(new Person(3,"DT2",new Date()));
        String json = JSONObject.toJSONString(personList);
        System.out.println("fast json->>>"+json);
    }
    public static void jack_list2str_test()  {
        ObjectMapper objectMapper = new ObjectMapper();
        List<Person> personList = new ArrayList<>();
        personList.add(new Person(1,"DT",new Date()));
        personList.add(new Person(2,"DT1",new Date()));
        personList.add(new Person(3,"DT2",new Date()));
        String json = null;
        try {
            json = objectMapper.writeValueAsString(personList);
        } catch (JsonProcessingException e) {
            throw new RuntimeException(e);
        }
        System.out.println("json->>>"+json);
    }
    public static void gson_list2str_test(){
        Gson gson = new Gson();
        List<Person> personList = new ArrayList<>();
        personList.add(new Person(1,"DT",new Date()));
        personList.add(new Person(2,"DT1",new Date()));
        personList.add(new Person(3,"DT2",new Date()));
        String json = gson.toJson(personList);
        System.out.println("json->>>"+json);
    }

4、json turn array

5、 notes

5.1、 Sort

// fastjson
 Class plus 
@JSONType(orders = {"id","name","XYZabc","createTime"})

// jacckjson
    @JsonProperty(index = 2)
    private String channel

5.2、 Exempt or include

• fast
  // When serializing , Immunity realName
  @JSONField(serialize=false)
  public String realName;

@JSONType(ignores ={“id”,“sex”})
public class I'm a class

@JSONType(includes={“name”,“sex”})
public class I'm a class

• jack
• gson

5.3、 format

• fast Name it
  @JSONField(name=“gender”)
  public String sex;

• jackjson
  @JsonFormat(pattern =“yyyy-MM-dd HH:mm:ss”)
  private LocalDateTime createTime;

• fastjson
  @JsonFormat(pattern =“yyyy-MM-dd HH:mm:ss”)
  private LocalDateTime createTime;

5.4、 Print if not empty ( Ignore null)

// jackjson
@JsonIgnore
private LocalDateTime createTime;

@JsonIgnore
public LocalDateTime getCreateTime(){
	return createTime;
}

//  fastjson
@JSONField(serialize = false)
private String name;
 Or use include above the class , Elimination and other methods 

//  gson
 @Expose
    private String user;

5.5、 Mapping aliases

1）、fastjson

	@JSONField(name="person_name")
	private String name;

	@JSONField(name="person_age")
	private Integer age;

2）、jackjson

@JsonAlias({“n”,“Name”})
private String name;

3）、gson

@SerializedName(“Name”)
private String name;
@SerializedName(“Pwd”)
private String pwd;