Spring mvc : Changing default Response format from xml to json

Question

I have gone through other similar asked questions but nothing worked for me.

All my API's return JSON as response by Default:

Because of some XML API, i had to add jackson-xml

    <dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
    </dependency>

Now by default "Without accept header" All responses are XML.

I would like to have JSON as default Response format .

As stated in the doc here:

https://spring.io/blog/2013/05/11/content-negotiation-using-spring-mvc

I implemented the following config :

@Override
    public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
        configurer.favorPathExtension(false).favorParameter(true).parameterName("mediaType").ignoreAcceptHeader(true)    
                .useJaf(false).defaultContentType(MediaType.APPLICATION_JSON)
                .mediaType("xml", MediaType.APPLICATION_XML).mediaType("json", MediaType.APPLICATION_JSON);
    }

Case 1: if i make the ignoreAcceptHeader(true) then everything is JSON even the XML API returning JSON.

Case 2: when ignoreAcceptHeader(false) is then default is XML.

I forget to mention my API's look like this:

@RequestMapping(value = "/getXml", method = RequestMethod.GET)
public ResponseEntity<String> getXml( HttpServletRequest request)
        throws JAXBException {
    return returnXml();
}

I am quite lost here, All i want is Default(Without AcceptHeader) should be JSON. (API returns XML as String)

And when Accept Header : "Application/xml" is defined then response should be XML.

Any advice would be of great help.

Thanks.

Answer 1

In general if you want to get json response you need an jackson-databind module:

<dependency> 
    <groupId>com.fasterxml.jackson.core</groupId> 
    <artifactId>jackson-databind</artifactId> 
    <version>${json-jackson-version}</version> 
</dependency> 

and then you have to define a MappingJackson2HttpMessageConverter in your configuration:

@Configuration
@EnableWebMvc
public class WebAppMainConfiguration extends WebMvcConfigurerAdapter {

    @Override 
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) { 
        converters.add(new MappingJackson2HttpMessageConverter());

        [..] 
        super.configureMessageConverters(converters); 
    }

    [...]
}

In your case, you can implement your own AbstractGenericHttpMessageConverter so you can switch in this converter between different concrete converters depending on media type.

Check the method AbstractGenericHttpMessageConverter#writeInternal(..)