使用Spring WebMVC REST控制器基于Accept标头的不同响应实体主体

Question

I have a controller with a method signature like this

@RequestMapping(value = "/{project:[A-Z0-9_+\\.\\(\\)=\\-]+}", method = RequestMethod.GET)
public ResponseEntity<Object> lookupProject(@PathVariable String project,
        @RequestParam(value = "fields", required = false) String fields,
        @RequestParam(value = "asList", required = false, defaultValue = "false") boolean asList);

I am returning for JSON a Collection<Object> or Map<String, Object> . This isn't suitable for XML. I'd rather return a Project object.

Is there a clean way to determine which content type will be produced? The work-around would be another method which produces XML only and returns the Project object. I'd rather like to avoid duplicate code.

I am on Spring 3.1.3-RELEASE.

Answer 1

According to Spring documentation, your produces param will return content based on the Accept, ie

@RequestMapping(value="/someUrl/", produces="application/*")
public Project someControllerMethod(...)

If the method takes in application/xml, the method will produce XML, if application/json, it will produce json, etc.

You just need marshallers set up for the appropriate object types.

Documentation here:

http://static.springsource.org/spring/docs/3.1.x/javadoc-api/org/springframework/web/bind/annotation/RequestMapping.html#produces ()

Answer 2

Content type to be produced will depend on type acceptable by the client.One solution for this is already mentioned, using produces attribute.Another solution is using ContentNegotiatingViewResolver, which can resolve views based on accept header or other mechanism.

Refer the documentation http://static.springsource.org/spring/docs/3.0.x/javadoc-api/org/springframework/web/servlet/view/ContentNegotiatingViewResolver.html

Example: http://www.mkyong.com/spring-mvc/spring-3-mvc-contentnegotiatingviewresolver-example/

Answer 3

尽管我认为Dardo的解决方案是最好的，但是您可以使用XMLHttpMessageConverter检查对象类型，如果它是Project对象，则可以进行不同的转换。

Answer 4

In Spring Framework 4.1 you can use a ResponseBodyAdvice to modify the value returned from an @ResponseBody or ResponseEntity method just before it is written out.

See http://docs.spring.io/spring-framework/docs/4.1.0.RC2/javadoc-api/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyAdvice.html .

Answer 5

I ended up in splitting in two methods.

Public methods have been renamed to lookupAsType . Both delegate/return

String[] fieldsArray = StringUtils.split(fields, ',');
return lookup(project, fieldsArray, asList, mediaType);

The new method lookup has the same code s before but contains not an if clause for the media types.

if (mediaType.equals(MediaType.APPLICATION_JSON)) {
    body = projectValues;
} else if (mediaType.equals(MediaType.APPLICATION_XML)) {
    body = new Project(projectValues);
} else {
    throw new NotImplementedException("Project lookup is not implemented for media type '" + mediaType + "'");
}

The bad thing is that MediaType is not a enum but an ugly class.