Rest对象转换为json时，value值为null，key是否需要返回逻辑

1、注册自定义转换配置：

import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.collect.ImmutableList;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;

@Configuration
public class WebConfiguration  {

    @Bean
    public MappingJackson2HttpMessageConverter mappingJacksonHttpMessageConverter() {
        final MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        ObjectMapper mapper = converter.getObjectMapper();
        // 为mapper注册一个带有SerializerModifier的Factory，此modifier主要做的事情为：设置空值处理序列化对象，针对空值做处理，防止值为空，key也显示为空
        mapper.setSerializerFactory(mapper.getSerializerFactory().withSerializerModifier(new MyBeanSerializerModifier()));
        converter.setSupportedMediaTypes(ImmutableList.of(MediaType.APPLICATION_JSON, MediaType.APPLICATION_JSON));
        return converter;
    }
}

2、定义序列化逻辑对象：

import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializationConfig;
import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;
import com.fasterxml.jackson.databind.ser.BeanSerializerModifier;

import java.util.List;

public class MyBeanSerializerModifier extends BeanSerializerModifier {

    private JsonSerializer