How to ignore “null” or empty properties in json,

问题:

I'm trying to return only the properties that have values, but the null ones are also being returned.

I know that there's an annotation that does this ( @JsonInclude(Include.NON_NULL) ), but then I need these in every single entity class.

So, my question is: Is there a way to configure this globally through spring config? (avoiding XML, preferably)

EDIT: It seems that this question has been considered a duplicate, but I don't think so. The real question here is how to configure it through spring config, which I couldn't find in other questions.

回答1:

If you are using Spring Boot, this is as easy as:

spring.jackson.serialization-inclusion=non_null

If not, then you can configure the ObjectMapper in the MappingJackson2HttpMessageConverter like so:

@Configuration
class WebMvcConfiguration extends WebMvcConfigurationSupport {
    @Override
    protected void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        for(HttpMessageConverter converter: converters) {
            if(converter instanceof MappingJackson2HttpMessageConverter) {
                ObjectMapper mapper = ((MappingJackson2HttpMessageConverter)converter).getObjectMapper()
                mapper.setSerializationInclusion(Include.NON_NULL);
            }
        }
    }
}

回答2:

If you use jackson ObjectMapper for generating json, you can define following custom ObjectMapper for this purpose and use it instead:

<bean id="jacksonObjectMapper" class="com.fasterxml.jackson.databind.ObjectMapper">
   <property name="serializationInclusion">
      <value type="com.fasterxml.jackson.annotation.JsonInclude.Include">NON_NULL</value>
   </property>
</bean>

回答3:

The programmatic alternative to Abolfazl Hashemi's answer is the following:

/**
 * Jackson configuration class.
 */
@Configuration
public class JacksonConfig {

    @Bean
    public ObjectMapper buildObjectMapper() {
       return new ObjectMapper().setSerializationInclusion(Include.NON_NULL);
    }
}

This way, you're basically telling to the Spring container that, every time an ObjectMapper is used, only properties with non-null values are to be included in the mappings.

回答4:

In newer versions of Spring Boot (2.0+), use:

spring.jackson.default-property-inclusion=non_null