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Java

JsonView Null to Empty String

Spring에서 JsonView 사용 시 공통으로 null인 필드를 empty string으로 리턴해야 할 필요가 있는 경우가 있습니다. 이런 경우 ObjectMapper를 상속받은 Custom ObjectMapper를 이용한 HttpMessageConverter를 통해 해결할 수 있습니다. 1.NullSerializer 구현

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

import java.io.IOException;

public class NullSerializer extends JsonSerializer<Object> {
    @Override
    public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {
        jsonGenerator.writeString("");
    }
}

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.core.JsonProcessingException;

import com.fasterxml.jackson.databind.JsonSerializer;

import com.fasterxml.jackson.databind.SerializerProvider;

import java.io.IOException;

public class NullSerializer extends JsonSerializer<Object> {

@Override

public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {

jsonGenerator.writeString("");

}

2.CustomObjectMapper 구현

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ser.DefaultSerializerProvider;

public class CustomObjectMapper extends ObjectMapper {
    public CustomObjectMapper() {
        DefaultSerializerProvider.Impl sp = new DefaultSerializerProvider.Impl();
        sp.setNullValueSerializer(new NullSerializer());
        this.setSerializerProvider(sp);
    }
}

import com.fasterxml.jackson.databind.ObjectMapper;

import com.fasterxml.jackson.databind.ser.DefaultSerializerProvider;

public class CustomObjectMapper extends ObjectMapper {

public CustomObjectMapper() {

DefaultSerializerProvider.Impl sp = new DefaultSerializerProvider.Impl();

sp.setNullValueSerializer(new NullSerializer());

this.setSerializerProvider(sp);

}

3.HttpMessageConverter 추가

@Bean
public MappingJackson2HttpMessageConverter converter() {
    CustomObjectMapper com = new CustomObjectMapper();
    MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
    converter.setObjectMapper(com);
    return converter;
}

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    converters.add(converter());
    super.configureMessageConverters(converters);
}

public class JsonViewResolver implements ViewResolver {
  @Override
  public View resolveViewName(String viewName, Locale locale)	throws Exception {
  	MappingJackson2JsonView view = new MappingJackson2JsonView();
  	return view;
  }
}

@Bean

public MappingJackson2HttpMessageConverter converter() {

CustomObjectMapper com = new CustomObjectMapper();

MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();

converter.setObjectMapper(com);

return converter;

}

@Override

public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {

converters.add(converter());

super.configureMessageConverters(converters);

}

public class JsonViewResolver implements ViewResolver {

@Override

public View resolveViewName(String viewName, Locale locale) throws Exception {

MappingJackson2JsonView view = new MappingJackson2JsonView();

return view;

}

글쓴이 SilverNine, 5 년전