SpringBoot定义返回json的形式，默认字段为空字符串，所有数据都为string类型

在项目中新建个类即可。

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 com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
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;

@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;
    }

    /**
     * Jackson全局转化long类型为String，解决jackson序列化时long类型缺失精度问题
     * Jackson全局转化Integer类型为String
     * Jackson全局转化Double类型为String
     * * @return Jackson2ObjectMapperBuilderCustomizer 注入的对象
     * */
    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() {

        return jacksonObjectMapperBuilder -> jacksonObjectMapperBuilder
                .serializerByType(Long.class, ToStringSerializer.instance)
                .serializerByType(Long.TYPE, ToStringSerializer.instance)
                .serializerByType(Integer.class, ToStringSerializer.instance)
                .serializerByType(Integer.TYPE, ToStringSerializer.instance)
                .serializerByType(Double.class, ToStringSerializer.instance)
                .serializerByType(Double.TYPE, ToStringSerializer.instance);
    }
}