Package org.springframework.http.converter

Class AbstractHttpMessageConverter<T>

java.lang.Object

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

Type Parameters:

T - the converted object type

All Implemented Interfaces:

HttpMessageConverter<T>

Direct Known Subclasses:

AbstractGenericHttpMessageConverter, AbstractWireFeedHttpMessageConverter, AbstractXmlHttpMessageConverter, ByteArrayHttpMessageConverter, ObjectToStringHttpMessageConverter, ProtobufHttpMessageConverter, ResourceHttpMessageConverter, SourceHttpMessageConverter, 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, Sebastien Deleuze

Field Summary

Fields

Modifier and Type	Field	Description
protected final org.apache.commons.logging.Log	logger	Logger available to subclasses.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractHttpMessageConverter()	Construct an AbstractHttpMessageConverter with no supported media types.
protected	AbstractHttpMessageConverter(Charset defaultCharset, MediaType... supportedMediaTypes)	Construct an AbstractHttpMessageConverter with a default charset and multiple supported media types.
protected	AbstractHttpMessageConverter(MediaType supportedMediaType)	Construct an AbstractHttpMessageConverter with one supported media type.
protected	AbstractHttpMessageConverter(MediaType... supportedMediaTypes)	Construct an AbstractHttpMessageConverter with multiple supported media types.

Method Summary

Modifier and Type	Method	Description
protected void	addDefaultHeaders(HttpHeaders headers, T t, MediaType contentType)	Add default headers to the output message.
boolean	canRead(Class<?> clazz, MediaType mediaType)	This implementation checks if the given class is supported, and if the supported media types include the given media type.
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)	This implementation checks if the given class is supported, and if the supported media types include the given media type.
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.
Charset	getDefaultCharset()	Return the default character set, if any.
protected MediaType	getDefaultContentType(T t)	Returns the default content type for the given type.
List<MediaType>	getSupportedMediaTypes()	Return the list of media types supported by this converter.
final T	read(Class<? extends T> clazz, HttpInputMessage inputMessage)	This implementation simple delegates to readInternal(Class, HttpInputMessage).
protected abstract T	readInternal(Class<? extends T> clazz, HttpInputMessage inputMessage)	Abstract template method that reads the actual object.
void	setDefaultCharset(Charset defaultCharset)	Set the default character set, if any.
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.
final void	write(T t, MediaType contentType, HttpOutputMessage outputMessage)	This implementation sets the default headers by calling addDefaultHeaders(org.springframework.http.HttpHeaders, T, org.springframework.http.MediaType), and then calls writeInternal(T, org.springframework.http.HttpOutputMessage).
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

Methods inherited from interface org.springframework.http.converter.HttpMessageConverter

getSupportedMediaTypes

Field Details

logger

protected final org.apache.commons.logging.Log logger

Logger available to subclasses.

Constructor Details

AbstractHttpMessageConverter

protected AbstractHttpMessageConverter()

Construct an AbstractHttpMessageConverter with no supported media types.

See Also:

• setSupportedMediaTypes(java.util.List<org.springframework.http.MediaType>)

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 types.

Parameters:

supportedMediaTypes - the supported media types

AbstractHttpMessageConverter

protected AbstractHttpMessageConverter(Charset defaultCharset,
 MediaType... supportedMediaTypes)

Construct an AbstractHttpMessageConverter with a default charset and multiple supported media types.

Parameters:

defaultCharset - the default character set

supportedMediaTypes - the supported media types

Since:

4.3

Method Details

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 media types supported by this converter. The list may not apply to every possible target element type and calls to this method should typically be guarded via canWrite(clazz, null. The list may also exclude MIME types supported only for a specific class. Alternatively, use HttpMessageConverter.getSupportedMediaTypes(Class) for a more precise list.

Specified by:

getSupportedMediaTypes in interface HttpMessageConverter<T>

Returns:

the list of supported media types

setDefaultCharset

public void setDefaultCharset(@Nullable
 Charset defaultCharset)

Set the default character set, if any.

Since:

4.3

getDefaultCharset

@Nullable
public Charset getDefaultCharset()

Return the default character set, if any.

Since:

4.3

canRead

public boolean canRead(Class<?> clazz,
 @Nullable
 MediaType mediaType)

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(@Nullable
 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,
 @Nullable
 MediaType mediaType)

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(@Nullable
 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,
HttpMessageNotReadableException

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

HttpMessageNotReadableException - in case of conversion errors

write

public final void write(T t,
 @Nullable
 MediaType contentType,
 HttpOutputMessage outputMessage)
                 throws IOException,
HttpMessageNotWritableException

This implementation sets the default headers by calling addDefaultHeaders(org.springframework.http.HttpHeaders, T, org.springframework.http.MediaType), and 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

addDefaultHeaders

protected void addDefaultHeaders(HttpHeaders headers,
 T t,
 @Nullable
 MediaType contentType)
                          throws IOException

Add default headers to the output message.

This implementation delegates to getDefaultContentType(Object) if a content type was not provided, set if necessary the default character set, calls getContentLength(T, org.springframework.http.MediaType), and sets the corresponding headers.

Throws:

IOException

Since:

4.2

getDefaultContentType

@Nullable
protected MediaType getDefaultContentType(T t)
                                   throws IOException

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

Throws:

IOException

getContentLength

@Nullable
protected Long getContentLength(T t,
 @Nullable
 MediaType contentType)
                         throws IOException

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

Throws:

IOException

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 actual object. Invoked from read(java.lang.Class<? extends T>, 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 HTTP output message to write to

Throws:

IOException - in case of I/O errors

HttpMessageNotWritableException - in case of conversion errors