作用:将返回实体类中的属性如果为null  变成""

package com.example.micrweb.config;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.io.IOException;

/**
 * @author hrui
 * @date 2023/11/23 3:00
 */
@Configuration
public class JacksonConfiguration {

    /**
     * 将返回值json格式化的时候,如果为null 变成""
     * 因SpringBoot 返回默认用jackjson格式化
     * 而jackson中JacksonAutoConfiguration
     * 类已经自动配置了一个 ObjectMapper Bean
     * 这里对ObjectMapper重新定义
     */
    @Bean
    public ObjectMapper objectMapper(){
        ObjectMapper objectMapper=new ObjectMapper();
        //设置null序列化时  为""
        objectMapper.getSerializerProvider()
                .setNullValueSerializer(new JsonSerializer<Object>() {
                    @Override
                    public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
                        jsonGenerator.writeString("");
                    }
                });
        return objectMapper;
    }
    //JacksonAutoConfiguration
}

例如

配置之后