在微服务项目中，可将这个转换类放在公共模块(commons)下，在整个项目中都生效

1、使用spring boot默认的Jackson

package com.miswu.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.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

import java.io.IOException;

/**
 * @author mis_wu
 * @date 2022/3/3 11:05
 * json转换配置
 * 说明:开发开中会查询到null值,在转json时不希望存在null,而是将null转换为空字符串 ""
 */
@Configuration
public class JacksonConfig {
    @Bean
    @Primary
    @ConditionalOnMissingBean(ObjectMapper.class)
    public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder){
        ObjectMapper objectMapper = builder.createXmlMapper(false).build();
        objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {

            @Override
            public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
                jsonGenerator.writeString("");
            }
        });
        return objectMapper;
    }
}

2、使用阿里巴巴的FastJson

导入依赖:

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.35</version>
</dependency>

package com.miswu.config;

import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;

/**
 * @author mis_wu
 * @date 2022/3/8 15:01
 * 如果项目中使用FastJson可以使用此配置类
 */
@Configuration
public class AliFastJsonConfig extends WebMvcConfigurationSupport {
    @Override
    protected void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        FastJsonConfig config = new FastJsonConfig();
        config.setSerializerFeatures(
                //保留map空的字段
                SerializerFeature.WriteMapNullValue,
                //将String类型转换成""
                SerializerFeature.WriteNullStringAsEmpty,
                //将Number类型转换成0
                SerializerFeature.WriteNullNumberAsZero,
                //将List的null转换为[]
                SerializerFeature.WriteNullListAsEmpty,
                //将Boolean类型的null转换为false
                SerializerFeature.WriteNullBooleanAsFalse,
                //避免循环引用
                SerializerFeature.DisableCircularReferenceDetect
        );
        converter.setFastJsonConfig(config);
        //converter.setDefaultCharset(Charset.forName("UTF-8"));
        converter.setDefaultCharset(StandardCharsets.UTF_8);
        ArrayList<MediaType> mediaTypeList = new ArrayList<>();
        //解决中文乱码问题,相当于controller上的@RequestMapping中加了个属性produces="application/json"
        mediaTypeList.add(MediaType.APPLICATION_JSON);
        converter.setSupportedMediaTypes(mediaTypeList);
        converters.add(converter);
    }
}