Spring mvc：将默认的响应格式从xml更改为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(..)

Answer 2

As you have set ignoreAcceptHeader to true and favorPathExtension to false, spring will rely on other alternatives for content negotiations. Means it will look URL parameter which you have configured XML and JSON

so as @stan pointed /getXml?mediaType=xml will should return xml response else it will default to json(defaultContentType(MediaType.APPLICATION_JSON))

Answer 3

For me, adding

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {

    @Override
    public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
        configurer.defaultContentType(MediaType.APPLICATION_JSON_UTF8);
    }

}

solved the problem.

Now by default all RestController s return JSON, if no Accept header in the request. Also if Accept: application/xml header is passed, then result is XML.

Also, worth reading: https://spring.io/blog/2013/05/11/content-negotiation-using-spring-mvc