org.springframework.web.accept

## Class ContentNegotiationManager

- java.lang.Object
- - org.springframework.web.accept.ContentNegotiationManager

- All Implemented Interfaces:
    ContentNegotiationStrategy, MediaTypeFileExtensionResolver

      public class ContentNegotiationManager
      extends Object
      implements ContentNegotiationStrategy, MediaTypeFileExtensionResolver

  This class is used to determine the requested media types of a request by delegating to a list of ContentNegotiationStrategy instances. The strategies must be provided at instantiation or alternatively if using the default constructor, an instance of `HeaderContentNegotiationStrategy` will be configured by default.

  This class may also be used to look up file extensions associated with a MediaType. This is done by consulting the list of configured `MediaTypeFileExtensionResolver` instances. Note that some ContentNegotiationStrategy implementations also implement MediaTypeFileExtensionResolver and the class constructor accepting the former will also detect if they implement the latter. If you need to register additional resolvers, you can use the method `addFileExtensionResolvers(MediaTypeFileExtensionResolver...)`.

  Since:
    3.2
  Author:
    Rossen Stoyanchev

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `ContentNegotiationManager()` Create an instance with a `HeaderContentNegotiationStrategy`.
    `ContentNegotiationManager(ContentNegotiationStrategy... strategies)` Create an instance with the given ContentNegotiationStrategy instances.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addFileExtensionResolvers(MediaTypeFileExtensionResolver... resolvers)` Add MediaTypeFileExtensionResolver instances.
    `List<String>` | `getAllFileExtensions()` Delegate to all configured MediaTypeFileExtensionResolver instances and aggregate the list of all known file extensions.
    `List<String>` | `resolveFileExtensions(MediaType mediaType)` Delegate to all configured MediaTypeFileExtensionResolver instances and aggregate the list of all file extensions found.
    `List<MediaType>` | `resolveMediaTypes(NativeWebRequest webRequest)` Delegate to all configured ContentNegotiationStrategy instances until one returns a non-empty list.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### ContentNegotiationManager

          public ContentNegotiationManager(ContentNegotiationStrategy... strategies)

      Create an instance with the given ContentNegotiationStrategy instances.

      Each instance is checked to see if it is also an implementation of MediaTypeFileExtensionResolver, and if so it is registered as such.

      Parameters:
        `strategies` - one more more ContentNegotiationStrategy instances

    - #### ContentNegotiationManager

          public ContentNegotiationManager()

      Create an instance with a `HeaderContentNegotiationStrategy`.

  - ### Method Detail

    - #### addFileExtensionResolvers

          public void addFileExtensionResolvers(MediaTypeFileExtensionResolver... resolvers)

      Add MediaTypeFileExtensionResolver instances.

      Note that some `ContentNegotiationStrategy` implementations also implement `MediaTypeFileExtensionResolver` and the class constructor accepting the former will also detect implementations of the latter. Therefore you only need to use this method to register additional instances.

      Parameters:
        `resolvers` - one or more resolvers

    - #### resolveMediaTypes

          public List<MediaType> resolveMediaTypes(NativeWebRequest webRequest)
                                            throws HttpMediaTypeNotAcceptableException

      Delegate to all configured ContentNegotiationStrategy instances until one returns a non-empty list.
      Specified by:
        `resolveMediaTypes` in interface `ContentNegotiationStrategy`
      Parameters:
        `webRequest` - the current request
      Returns:
        the requested media types or an empty list, never `null`
      Throws:
        `HttpMediaTypeNotAcceptableException` - if the requested media types cannot be parsed

    - #### resolveFileExtensions

          public List<String> resolveFileExtensions(MediaType mediaType)

      Delegate to all configured MediaTypeFileExtensionResolver instances and aggregate the list of all file extensions found.
      Specified by:
        `resolveFileExtensions` in interface `MediaTypeFileExtensionResolver`
      Parameters:
        `mediaType` - the media type to resolve
      Returns:
        a list of extensions or an empty list, never `null`

    - #### getAllFileExtensions

          public List<String> getAllFileExtensions()

      Delegate to all configured MediaTypeFileExtensionResolver instances and aggregate the list of all known file extensions.
      Specified by:
        `getAllFileExtensions` in interface `MediaTypeFileExtensionResolver`
      Returns:
        a list of extensions or an empty list, never `null`