/*
* Copyright 2002-2010 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.nio.charset.Charset;
import java.util.List;
import org.codehaus.jackson.JsonEncoding;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.type.TypeFactory;
import org.codehaus.jackson.type.JavaType;
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.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'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
* @since 3.0
* @see org.springframework.web.servlet.view.json.MappingJacksonJsonView
*/
public class MappingJacksonHttpMessageConverter extends AbstractHttpMessageConverter<Object> {
public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
private ObjectMapper objectMapper = new ObjectMapper();
private boolean prefixJson = false;
/**
* Construct a new {@code BindingJacksonHttpMessageConverter}.
*/
public MappingJacksonHttpMessageConverter() {
super(new MediaType("application", "json", DEFAULT_CHARSET));
}
/**
* Sets 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;
}
/**
* Indicates 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;
}
@Override
public boolean canRead(Class<?> clazz, MediaType mediaType) {
JavaType javaType = getJavaType(clazz);
return this.objectMapper.canDeserialize(javaType) && canRead(mediaType);
}
/**
* Returns the Jackson {@link JavaType} for the specific class.
*
* <p>Default implementation returns {@link TypeFactory#type(java.lang.reflect.Type)}, but this can be overridden
* in subclasses, to allow for custom generic collection handling. For instance:
* <pre class="code">
* protected JavaType getJavaType(Class<?> clazz) {
* if (List.class.isAssignableFrom(clazz)) {
* return TypeFactory.collectionType(ArrayList.class, MyBean.class);
* } else {
* return super.getJavaType(clazz);
* }
* }
* </pre>
*
* @param clazz the class to return the java type for
* @return the java type
*/
protected JavaType getJavaType(Class<?> clazz) {
return TypeFactory.type(clazz);
}
@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);
try {
return this.objectMapper.readValue(inputMessage.getBody(), javaType);
}
catch (JsonParseException ex) {
throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
}
}
@Override
protected void writeInternal(Object o, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
JsonEncoding encoding = getEncoding(outputMessage.getHeaders().getContentType());
JsonGenerator jsonGenerator =
this.objectMapper.getJsonFactory().createJsonGenerator(outputMessage.getBody(), encoding);
try {
if (this.prefixJson) {
jsonGenerator.writeRaw("{} && ");
}
this.objectMapper.writeValue(jsonGenerator, o);
}
catch (JsonGenerationException ex) {
throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
}
}
private JsonEncoding getEncoding(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;
}
}
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