/*
* Copyright 2002-2012 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.http.converter.json;
import java.io.IOException;
import java.lang.reflect.Type;
import java.nio.charset.Charset;
import java.util.List;
import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.GenericHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.util.Assert;
/**
* Implementation of {@link org.springframework.http.converter.HttpMessageConverter HttpMessageConverter}
* that can read and write JSON using <a href="http://jackson.codehaus.org/">Jackson 2's</a> {@link ObjectMapper}.
*
* <p>This converter can be used to bind to typed beans, or untyped {@link java.util.HashMap HashMap} instances.
*
* <p>By default, this converter supports {@code application/json}. This can be overridden by setting the
* {@link #setSupportedMediaTypes(List) supportedMediaTypes} property.
*
* @author Arjen Poutsma
* @author Keith Donald
* @since 3.1.2
* @see org.springframework.web.servlet.view.json.MappingJackson2JsonView
*/
public class MappingJackson2HttpMessageConverter extends AbstractHttpMessageConverter<Object>
implements GenericHttpMessageConverter<Object> {
public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
private ObjectMapper objectMapper = new ObjectMapper();
private boolean prefixJson = false;
private Boolean prettyPrint;
/**
* Construct a new {@code MappingJackson2HttpMessageConverter}.
*/
public MappingJackson2HttpMessageConverter() {
super(new MediaType("application", "json", DEFAULT_CHARSET), new MediaType("application", "*+json", DEFAULT_CHARSET));
}
/**
* Set the {@code ObjectMapper} for this view. If not set, a default
* {@link ObjectMapper#ObjectMapper() ObjectMapper} is used.
* <p>Setting a custom-configured {@code ObjectMapper} is one way to take further control of the JSON
* serialization process. For example, an extended {@link org.codehaus.jackson.map.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.
*/
public void setObjectMapper(ObjectMapper objectMapper) {
Assert.notNull(objectMapper, "ObjectMapper must not be null");
this.objectMapper = objectMapper;
configurePrettyPrint();
}
private void configurePrettyPrint() {
if (this.prettyPrint != null) {
this.objectMapper.configure(SerializationFeature.INDENT_OUTPUT, this.prettyPrint);
}
}
/**
* Return the underlying {@code ObjectMapper} for this view.
*/
public ObjectMapper getObjectMapper() {
return this.objectMapper;
}
/**
* Indicate whether the JSON output by this view should be prefixed with "{} &&". Default is false.
* <p>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.
*/
public void setPrefixJson(boolean prefixJson) {
this.prefixJson = prefixJson;
}
/**
* Whether to use the {@link DefaultPrettyPrinter} when writing JSON.
* This is a shortcut for setting up an {@code ObjectMapper} as follows:
* <pre>
* ObjectMapper mapper = new ObjectMapper();
* mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
* converter.setObjectMapper(mapper);
* </pre>
*/
public void setPrettyPrint(boolean prettyPrint) {
this.prettyPrint = prettyPrint;
configurePrettyPrint();
}
@Override
public boolean canRead(Class<?> clazz, MediaType mediaType) {
return canRead((Type) clazz, null, mediaType);
}
public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
JavaType javaType = getJavaType(type, contextClass);
return (this.objectMapper.canDeserialize(javaType) && canRead(mediaType));
}
@Override
public boolean canWrite(Class<?> clazz, MediaType mediaType) {
return (this.objectMapper.canSerialize(clazz) && canWrite(mediaType));
}
@Override
protected boolean supports(Class<?> clazz) {
// should not be called, since we override canRead/Write instead
throw new UnsupportedOperationException();
}
@Override
protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
throws IOException, HttpMessageNotReadableException {
JavaType javaType = getJavaType(clazz, null);
return readJavaType(javaType, inputMessage);
}
public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
throws IOException, HttpMessageNotReadableException {
JavaType javaType = getJavaType(type, contextClass);
return readJavaType(javaType, inputMessage);
}
private Object readJavaType(JavaType javaType, HttpInputMessage inputMessage) {
try {
return this.objectMapper.readValue(inputMessage.getBody(), javaType);
}
catch (IOException ex) {
throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
}
}
@Override
protected void writeInternal(Object object, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType());
JsonGenerator jsonGenerator =
this.objectMapper.getJsonFactory().createJsonGenerator(outputMessage.getBody(), encoding);
// A workaround for JsonGenerators not applying serialization features
// https://github.com/FasterXML/jackson-databind/issues/12
if (this.objectMapper.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
jsonGenerator.useDefaultPrettyPrinter();
}
try {
if (this.prefixJson) {
jsonGenerator.writeRaw("{} && ");
}
this.objectMapper.writeValue(jsonGenerator, object);
}
catch (JsonProcessingException ex) {
throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
}
}
/**
* Return the Jackson {@link JavaType} for the specified type and context class.
* <p>The default implementation returns {@link ObjectMapper#constructType(java.lang.reflect.Type)}
* or {@code ObjectMapper.getTypeFactory().constructType(type, contextClass)},
* but this can be overridden in subclasses, to allow for custom generic collection handling.
* For instance:
* <pre class="code">
* 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);
* }
* }
* </pre>
* @param type the type to return the java type for
* @param contextClass a context class for the target type, for example a class
* in which the target type appears in a method signature, can be {@code null}
* signature, can be {@code null}
* @return the java type
*/
protected JavaType getJavaType(Type type, Class<?> contextClass) {
return (contextClass != null) ?
this.objectMapper.getTypeFactory().constructType(type, contextClass) :
this.objectMapper.constructType(type);
}
/**
* Determine the JSON encoding to use for the given content type.
* @param contentType the media type as requested by the caller
* @return the JSON encoding to use (never <code>null</code>)
*/
protected JsonEncoding getJsonEncoding(MediaType contentType) {
if (contentType != null && contentType.getCharSet() != null) {
Charset charset = contentType.getCharSet();
for (JsonEncoding encoding : JsonEncoding.values()) {
if (charset.name().equals(encoding.getJavaName())) {
return encoding;
}
}
}
return JsonEncoding.UTF8;
}
}