org.springframework.http.converter
Class AbstractHttpMessageConverter<T>

java.lang.Object
  extended by org.springframework.http.converter.AbstractHttpMessageConverter<T>
All Implemented Interfaces:
HttpMessageConverter<T>
Direct Known Subclasses:
AbstractWireFeedHttpMessageConverter, AbstractXmlHttpMessageConverter, ByteArrayHttpMessageConverter, MappingJacksonHttpMessageConverter, ResourceHttpMessageConverter, StringHttpMessageConverter

public abstract class AbstractHttpMessageConverter<T>
extends Object
implements HttpMessageConverter<T>

Abstract base class for most HttpMessageConverter implementations.

This base class adds support for setting supported MediaTypes, through the supportedMediaTypes bean property. It also adds support for Content-Type and Content-Length when writing to output messages.

Since:
3.0
Author:
Arjen Poutsma, Juergen Hoeller

Field Summary
protected  Log logger
          Logger available to subclasses
 
Constructor Summary
protected AbstractHttpMessageConverter()
          Construct an AbstractHttpMessageConverter with no supported media types.
protected AbstractHttpMessageConverter(MediaType... supportedMediaTypes)
          Construct an AbstractHttpMessageConverter with multiple supported media type.
protected AbstractHttpMessageConverter(MediaType supportedMediaType)
          Construct an AbstractHttpMessageConverter with one supported media type.
 
Method Summary
 boolean canRead(Class<?> clazz, MediaType mediaType)
          Indicates whether the given class can be read by this converter.
protected  boolean canRead(MediaType mediaType)
          Returns true if any of the supported media types include the given media type.
 boolean canWrite(Class<?> clazz, MediaType mediaType)
          Indicates whether the given class can be written by this converter.
protected  boolean canWrite(MediaType mediaType)
          Returns true if the given media type includes any of the supported media types.
protected  Long getContentLength(T t, MediaType contentType)
          Returns the content length for the given type.
protected  MediaType getDefaultContentType(T t)
          Returns the default content type for the given type.
 List<MediaType> getSupportedMediaTypes()
          Return the list of MediaType objects supported by this converter.
 T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
          Read an object of the given type form the given input message, and returns it.
protected abstract  T readInternal(Class<? extends T> clazz, HttpInputMessage inputMessage)
          Abstract template method that reads the actualy object.
 void setSupportedMediaTypes(List<MediaType> supportedMediaTypes)
          Set the list of MediaType objects supported by this converter.
protected abstract  boolean supports(Class<?> clazz)
          Indicates whether the given class is supported by this converter.
 void write(T t, MediaType contentType, HttpOutputMessage outputMessage)
          Write an given object to the given output message.
protected abstract  void writeInternal(T t, HttpOutputMessage outputMessage)
          Abstract template method that writes the actual body.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

logger

protected final Log logger
Logger available to subclasses

Constructor Detail

AbstractHttpMessageConverter

protected AbstractHttpMessageConverter()
Construct an AbstractHttpMessageConverter with no supported media types.

See Also:
setSupportedMediaTypes(java.util.List)

AbstractHttpMessageConverter

protected AbstractHttpMessageConverter(MediaType supportedMediaType)
Construct an AbstractHttpMessageConverter with one supported media type.

Parameters:
supportedMediaType - the supported media type

AbstractHttpMessageConverter

protected AbstractHttpMessageConverter(MediaType... supportedMediaTypes)
Construct an AbstractHttpMessageConverter with multiple supported media type.

Parameters:
supportedMediaTypes - the supported media types
Method Detail

setSupportedMediaTypes

public void setSupportedMediaTypes(List<MediaType> supportedMediaTypes)
Set the list of MediaType objects supported by this converter.


getSupportedMediaTypes

public List<MediaType> getSupportedMediaTypes()
Description copied from interface: HttpMessageConverter
Return the list of MediaType objects supported by this converter.

Specified by:
getSupportedMediaTypes in interface HttpMessageConverter<T>
Returns:
the list of supported media types

canRead

public boolean canRead(Class<?> clazz,
                       MediaType mediaType)
Indicates whether the given class can be read by this converter.

This implementation checks if the given class is supported, and if the supported media types include the given media type.

Specified by:
canRead in interface HttpMessageConverter<T>
Parameters:
clazz - the class to test for readability
mediaType - the media type to read, can be null if not specified. Typically the value of a Content-Type header.
Returns:
true if readable; false otherwise

canRead

protected boolean canRead(MediaType mediaType)
Returns true if any of the supported media types include the given media type.

Parameters:
mediaType - the media type to read, can be null if not specified. Typically the value of a Content-Type header.
Returns:
true if the supported media types include the media type, or if the media type is null

canWrite

public boolean canWrite(Class<?> clazz,
                        MediaType mediaType)
Indicates whether the given class can be written by this converter.

This implementation checks if the given class is supported, and if the supported media types include the given media type.

Specified by:
canWrite in interface HttpMessageConverter<T>
Parameters:
clazz - the class to test for writability
mediaType - the media type to write, can be null if not specified. Typically the value of an Accept header.
Returns:
true if writable; false otherwise

canWrite

protected boolean canWrite(MediaType mediaType)
Returns true if the given media type includes any of the supported media types.

Parameters:
mediaType - the media type to write, can be null if not specified. Typically the value of an Accept header.
Returns:
true if the supported media types are compatible with the media type, or if the media type is null

read

public final T read(Class<? extends T> clazz,
                    HttpInputMessage inputMessage)
             throws IOException
Read an object of the given type form the given input message, and returns it.

This implementation simple delegates to readInternal(Class, HttpInputMessage). Future implementations might add some default behavior, however.

Specified by:
read in interface HttpMessageConverter<T>
Parameters:
clazz - the type of object to return. This type must have previously been passed to the canRead method of this interface, which must have returned true.
inputMessage - the HTTP input message to read from
Returns:
the converted object
Throws:
IOException - in case of I/O errors

write

public final void write(T t,
                        MediaType contentType,
                        HttpOutputMessage outputMessage)
                 throws IOException,
                        HttpMessageNotWritableException
Write an given object to the given output message.

This implementation delegates to getDefaultContentType(Object) if a content type was not provided, calls getContentLength(T, org.springframework.http.MediaType), and sets the corresponding headers on the output message. It then calls writeInternal(T, org.springframework.http.HttpOutputMessage).

Specified by:
write in interface HttpMessageConverter<T>
Parameters:
t - the object to write to the output message. The type of this object must have previously been passed to the canWrite method of this interface, which must have returned true.
contentType - the content type to use when writing. May be null to indicate that the default content type of the converter must be used. If not null, this media type must have previously been passed to the canWrite method of this interface, which must have returned true.
outputMessage - the message to write to
Throws:
IOException - in case of I/O errors
HttpMessageNotWritableException - in case of conversion errors

getDefaultContentType

protected MediaType getDefaultContentType(T t)
Returns the default content type for the given type. Called when write(T, org.springframework.http.MediaType, org.springframework.http.HttpOutputMessage) is invoked without a specified content type parameter.

By default, this returns the first element of the supportedMediaTypes property, if any. Can be overridden in subclasses.

Parameters:
t - the type to return the content type for
Returns:
the content type, or null if not known

getContentLength

protected Long getContentLength(T t,
                                MediaType contentType)
Returns the content length for the given type.

By default, this returns null, meaning that the content length is unknown. Can be overridden in subclasses.

Parameters:
t - the type to return the content length for
Returns:
the content length, or null if not known

supports

protected abstract boolean supports(Class<?> clazz)
Indicates whether the given class is supported by this converter.

Parameters:
clazz - the class to test for support
Returns:
true if supported; false otherwise

readInternal

protected abstract T readInternal(Class<? extends T> clazz,
                                  HttpInputMessage inputMessage)
                           throws IOException,
                                  HttpMessageNotReadableException
Abstract template method that reads the actualy object. Invoked from read(java.lang.Class, org.springframework.http.HttpInputMessage).

Parameters:
clazz - the type of object to return
inputMessage - the HTTP input message to read from
Returns:
the converted object
Throws:
IOException - in case of I/O errors
HttpMessageNotReadableException - in case of conversion errors

writeInternal

protected abstract void writeInternal(T t,
                                      HttpOutputMessage outputMessage)
                               throws IOException,
                                      HttpMessageNotWritableException
Abstract template method that writes the actual body. Invoked from write(T, org.springframework.http.MediaType, org.springframework.http.HttpOutputMessage).

Parameters:
t - the object to write to the output message
outputMessage - the message to write to
Throws:
IOException - in case of I/O errors
HttpMessageNotWritableException - in case of conversion errors