@Use of jsonserialize annotation

Use scenarios

In development , We serialize the object as JSON To the front end , Sometimes our Some or some fields Require special treatment , For example, we have a date field , We hope that the date will be NULL Do not return to the front end NULL And return as Hang in the air Etc , Or we have some status fields , We need to return the information corresponding to the status to the front end , At this point, we need to customize the serialization of fields . This is it. @JsonSerialize Usefulness

nullsUsing usage

Suppose there is one in our project Date Type field , Our requirement is when this field is NULL when , When serializing data, we serialize it into " Hang in the air "( The front end can also be used , Suppose the front end is lazy hhh)

 @ApiModelProperty(" Completion time ")
 private Date finishTime;

First step , Let's first write a specified processing class

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

import java.io.IOException;
import java.util.Date;

// Inherit JsonSerializer
public class DateJsonSerialize extends JsonSerializer<Date> {
    
 		
    // rewrite serialize Method 
    @Override
    public void serialize(Date date, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
    
        // Custom handling 
        jsonGenerator.writeString(" Hang in the air ");
    }
}

The second step , Add @JsonSerialize annotation , And use nullsUsing attribute , That is, when this field is NULL Use our custom parsing class to serialize this field ( Note that when this field is not NULL Do not execute this configuration )

	@ApiModelProperty(" Completion time ")
    @JsonSerialize(nullsUsing = DateJsonSerialize.class)
    private Date finishTime;

test

take finishTime Set to NULL, Then test the query , Serialize as Hang in the air

using usage

When the field is not NULL Custom serialization method when , The usage is the same as above

    @ApiModelProperty(" Completion time ")
    @JsonSerialize(using = XXX.class) // Custom serialization class 
    private Date finishTime;

For detailed examples, please refer to