org.springframework.http.converter.json

Class MappingJackson2HttpMessageConverter

java.lang.Object

org.springframework.http.converter.AbstractHttpMessageConverter<java.lang.Object>

org.springframework.http.converter.json.MappingJackson2HttpMessageConverter

All Implemented Interfaces:

GenericHttpMessageConverter<java.lang.Object>, HttpMessageConverter<java.lang.Object>

public class MappingJackson2HttpMessageConverter
extends AbstractHttpMessageConverter<java.lang.Object>
implements GenericHttpMessageConverter<java.lang.Object>

Implementation of HttpMessageConverter that can read and write JSON using Jackson 2's ObjectMapper.

This converter can be used to bind to typed beans, or untyped HashMap instances.

By default, this converter supports application/json. This can be overridden by setting the supportedMediaTypes property.

Tested against Jackson 2.3; compatible with Jackson 2.0 and higher. Note that tests failed with Jackson 2.4 on Android 2.2 (API Level 8) and older versions. Jackson 2.4 uses APIs not available on those platforms.

Since:

1.0.1

Author:

Arjen Poutsma, Keith Donald, Rossen Stoyanchev, Roy Clarkson

Field Summary

Fields

Modifier and Type	Field and Description
static java.nio.charset.Charset	DEFAULT_CHARSET

Constructor Summary

Constructors

Constructor and Description
MappingJackson2HttpMessageConverter() Construct a new MappingJackson2HttpMessageConverter.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	canRead(java.lang.Class<?> clazz, MediaType mediaType) This implementation checks if the given class is supported, and if the supported media types include the given media type.
boolean	canRead(java.lang.reflect.Type type, java.lang.Class<?> contextClass, MediaType mediaType) Indicates whether the given type can be read by this converter.
boolean	canWrite(java.lang.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 JavaType	getJavaType(java.lang.reflect.Type type, java.lang.Class<?> contextClass) Return the Jackson JavaType for the specified type and context class.
protected JsonEncoding	getJsonEncoding(MediaType contentType) Determine the JSON encoding to use for the given content type.
ObjectMapper	getObjectMapper() Return the underlying ObjectMapper for this view.
java.lang.Object	read(java.lang.reflect.Type type, java.lang.Class<?> contextClass, HttpInputMessage inputMessage) Read an object of the given type form the given input message, and returns it.
protected java.lang.Object	readInternal(java.lang.Class<?> clazz, HttpInputMessage inputMessage) Abstract template method that reads the actualy object.
void	setJsonPrefix(java.lang.String jsonPrefix) Specify a custom prefix to use for this view's JSON output.
void	setObjectMapper(ObjectMapper objectMapper) Set the ObjectMapper for this view.
void	setPrefixJson(boolean prefixJson) Indicate whether the JSON output by this view should be prefixed with "{} &&".
void	setPrettyPrint(boolean prettyPrint) Whether to use the DefaultPrettyPrinter when writing JSON.
protected boolean	supports(java.lang.Class<?> clazz) Indicates whether the given class is supported by this converter.
protected void	writeInternal(java.lang.Object object, HttpOutputMessage outputMessage) Abstract template method that writes the actual body.

Methods inherited from class org.springframework.http.converter.AbstractHttpMessageConverter

canRead, canWrite, getContentLength, getDefaultContentType, getSupportedMediaTypes, read, setSupportedMediaTypes, write

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, read, write

Field Detail

DEFAULT_CHARSET

public static final java.nio.charset.Charset DEFAULT_CHARSET

Constructor Detail

MappingJackson2HttpMessageConverter

public MappingJackson2HttpMessageConverter()

Construct a new MappingJackson2HttpMessageConverter.

Method Detail

setObjectMapper

public void setObjectMapper(ObjectMapper objectMapper)

Set the ObjectMapper for this view. If not set, a default ObjectMapper is used.

Setting a custom-configured ObjectMapper is one way to take further control of the JSON serialization process. For example, an extended SerializerFactory can be configured that provides custom serializers for specific types. The other option for refining the serialization process is to use Jackson's provided annotations on the types to be serialized, in which case a custom-configured ObjectMapper is unnecessary.

getObjectMapper

public ObjectMapper getObjectMapper()

Return the underlying ObjectMapper for this view.

setJsonPrefix

public void setJsonPrefix(java.lang.String jsonPrefix)

Specify a custom prefix to use for this view's JSON output. Default is none.

See Also:

setPrefixJson(boolean)

setPrefixJson

public void setPrefixJson(boolean prefixJson)

Indicate whether the JSON output by this view should be prefixed with "{} &&". Default is false.

Prefixing the JSON string in this manner is used to help prevent JSON Hijacking. The prefix renders the string syntactically invalid as a script so that it cannot be hijacked. This prefix does not affect the evaluation of JSON, but if JSON validation is performed on the string, the prefix would need to be ignored.

See Also:

setJsonPrefix(java.lang.String)

setPrettyPrint

public void setPrettyPrint(boolean prettyPrint)

Whether to use the DefaultPrettyPrinter when writing JSON. This is a shortcut for setting up an ObjectMapper as follows:

 ObjectMapper mapper = new ObjectMapper();
 mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
 converter.setObjectMapper(mapper);
 

canRead

public boolean canRead(java.lang.Class<?> clazz,
              MediaType mediaType)

Description copied from class: AbstractHttpMessageConverter

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<java.lang.Object>

Overrides:

canRead in class AbstractHttpMessageConverter<java.lang.Object>

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

public boolean canRead(java.lang.reflect.Type type,
              java.lang.Class<?> contextClass,
              MediaType mediaType)

Description copied from interface: GenericHttpMessageConverter

Indicates whether the given type can be read by this converter.

Specified by:

canRead in interface GenericHttpMessageConverter<java.lang.Object>

Parameters:

type - the type to test for readability

contextClass - a context class for the target type, for example a class in which the target type appears in a method signature, can be null

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

canWrite

public boolean canWrite(java.lang.Class<?> clazz,
               MediaType mediaType)

Description copied from class: AbstractHttpMessageConverter

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<java.lang.Object>

Overrides:

canWrite in class AbstractHttpMessageConverter<java.lang.Object>

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

supports

protected boolean supports(java.lang.Class<?> clazz)

Description copied from class: AbstractHttpMessageConverter

Indicates whether the given class is supported by this converter.

Specified by:

supports in class AbstractHttpMessageConverter<java.lang.Object>

Parameters:

clazz - the class to test for support

Returns:

true if supported; false otherwise

readInternal

protected java.lang.Object readInternal(java.lang.Class<?> clazz,
                            HttpInputMessage inputMessage)
                                 throws java.io.IOException,
                                        HttpMessageNotReadableException

Description copied from class: AbstractHttpMessageConverter

Abstract template method that reads the actualy object. Invoked from AbstractHttpMessageConverter.read(java.lang.Class<? extends T>, org.springframework.http.HttpInputMessage).

Specified by:

readInternal in class AbstractHttpMessageConverter<java.lang.Object>

Parameters:

clazz - the type of object to return

inputMessage - the HTTP input message to read from

Returns:

the converted object

Throws:

java.io.IOException - in case of I/O errors

HttpMessageNotReadableException - in case of conversion errors

read

public java.lang.Object read(java.lang.reflect.Type type,
                    java.lang.Class<?> contextClass,
                    HttpInputMessage inputMessage)
                      throws java.io.IOException,
                             HttpMessageNotReadableException

Description copied from interface: GenericHttpMessageConverter

Read an object of the given type form the given input message, and returns it.

Specified by:

read in interface GenericHttpMessageConverter<java.lang.Object>

Parameters:

type - 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.

contextClass - a context class for the target type, for example a class in which the target type appears in a method signature, can be null

inputMessage - the HTTP input message to read from

Returns:

the converted object

Throws:

java.io.IOException - in case of I/O errors

HttpMessageNotReadableException - in case of conversion errors

writeInternal

protected void writeInternal(java.lang.Object object,
                 HttpOutputMessage outputMessage)
                      throws java.io.IOException,
                             HttpMessageNotWritableException

Description copied from class: AbstractHttpMessageConverter

Abstract template method that writes the actual body. Invoked from AbstractHttpMessageConverter.write(T, org.springframework.http.MediaType, org.springframework.http.HttpOutputMessage).

Specified by:

writeInternal in class AbstractHttpMessageConverter<java.lang.Object>

Parameters:

object - the object to write to the output message

outputMessage - the message to write to

Throws:

java.io.IOException - in case of I/O errors

HttpMessageNotWritableException - in case of conversion errors

getJavaType

protected JavaType getJavaType(java.lang.reflect.Type type,
                   java.lang.Class<?> contextClass)

Return the Jackson JavaType for the specified type and context class.

The default implementation returns ObjectMapper.constructType(java.lang.reflect.Type) or ObjectMapper.getTypeFactory().constructType(type, contextClass), but this can be overridden in subclasses, to allow for custom generic collection handling. For instance:

 protected JavaType getJavaType(Type type) {
   if (type instanceof Class && List.class.isAssignableFrom((Class)type)) {
     return TypeFactory.collectionType(ArrayList.class, MyBean.class);
   } else {
     return super.getJavaType(type);
   }
 }
 

Parameters:

type - the type to return the java type for

contextClass - a context class for the target type, for example a class in which the target type appears in a method signature, can be null signature, can be null

Returns:

the java type

getJsonEncoding

protected JsonEncoding getJsonEncoding(MediaType contentType)

Determine the JSON encoding to use for the given content type.

Parameters:

contentType - the media type as requested by the caller

Returns:

the JSON encoding to use (never null)