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/*
 * Copyright 2002-2015 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.concurrent.atomic.AtomicReference;

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.PrettyPrinter;
import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.ser.FilterProvider;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractGenericHttpMessageConverter;
import org.springframework.http.converter.GenericHttpMessageConverter;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.TypeUtils;

/**
 * Abstract base class for Jackson based and content type independent
 * {@link HttpMessageConverter} implementations.
 *
 * 

Compatible with Jackson 2.1 and higher. * * @author Arjen Poutsma * @author Keith Donald * @author Rossen Stoyanchev * @author Juergen Hoeller * @author Sebastien Deleuze * @since 4.1 */ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGenericHttpMessageConverter implements GenericHttpMessageConverter { public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8"); // Check for Jackson 2.3's overloaded canDeserialize/canSerialize variants with cause reference private static final boolean jackson23Available = ClassUtils.hasMethod(ObjectMapper.class, "canDeserialize", JavaType.class, AtomicReference.class); // Check for Jackson 2.6+ for support of generic type aware serialization of polymorphic collections private static final boolean jackson26Available = ClassUtils.hasMethod(ObjectMapper.class, "setDefaultPrettyPrinter", PrettyPrinter.class); protected ObjectMapper objectMapper; private Boolean prettyPrint; protected AbstractJackson2HttpMessageConverter(ObjectMapper objectMapper) { this.objectMapper = objectMapper; } protected AbstractJackson2HttpMessageConverter(ObjectMapper objectMapper, MediaType supportedMediaType) { super(supportedMediaType); this.objectMapper = objectMapper; } protected AbstractJackson2HttpMessageConverter(ObjectMapper objectMapper, MediaType... supportedMediaTypes) { super(supportedMediaTypes); this.objectMapper = objectMapper; } /** * Set the {@code ObjectMapper} for this view. * If not set, a default {@link ObjectMapper#ObjectMapper() ObjectMapper} is used. *

Setting a custom-configured {@code ObjectMapper} is one way to take further * control of the JSON serialization process. For example, an extended * {@link com.fasterxml.jackson.databind.ser.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(); } /** * Return the underlying {@code ObjectMapper} for this view. */ public ObjectMapper getObjectMapper() { return this.objectMapper; } /** * Whether to use the {@link DefaultPrettyPrinter} when writing JSON. * This is a shortcut for setting up an {@code ObjectMapper} as follows: *

	 * ObjectMapper mapper = new ObjectMapper();
	 * mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
	 * converter.setObjectMapper(mapper);
	 * 
*/ public void setPrettyPrint(boolean prettyPrint) { this.prettyPrint = prettyPrint; configurePrettyPrint(); } private void configurePrettyPrint() { if (this.prettyPrint != null) { this.objectMapper.configure(SerializationFeature.INDENT_OUTPUT, this.prettyPrint); } } @Override public boolean canRead(Class clazz, MediaType mediaType) { return canRead(clazz, null, mediaType); } @Override public boolean canRead(Type type, Class contextClass, MediaType mediaType) { JavaType javaType = getJavaType(type, contextClass); if (!jackson23Available || !logger.isWarnEnabled()) { return (this.objectMapper.canDeserialize(javaType) && canRead(mediaType)); } AtomicReference causeRef = new AtomicReference(); if (this.objectMapper.canDeserialize(javaType, causeRef) && canRead(mediaType)) { return true; } Throwable cause = causeRef.get(); if (cause != null) { String msg = "Failed to evaluate deserialization for type " + javaType; if (logger.isDebugEnabled()) { logger.warn(msg, cause); } else { logger.warn(msg + ": " + cause); } } return false; } @Override public boolean canWrite(Class clazz, MediaType mediaType) { if (!jackson23Available || !logger.isWarnEnabled()) { return (this.objectMapper.canSerialize(clazz) && canWrite(mediaType)); } AtomicReference causeRef = new AtomicReference(); if (this.objectMapper.canSerialize(clazz, causeRef) && canWrite(mediaType)) { return true; } Throwable cause = causeRef.get(); if (cause != null) { String msg = "Failed to evaluate serialization for type [" + clazz + "]"; if (logger.isDebugEnabled()) { logger.warn(msg, cause); } else { logger.warn(msg + ": " + cause); } } return false; } @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); } @Override public Object read(Type type, Class contextClass, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException { JavaType javaType = getJavaType(type, contextClass); return readJavaType(javaType, inputMessage); } @SuppressWarnings("deprecation") private Object readJavaType(JavaType javaType, HttpInputMessage inputMessage) { try { if (inputMessage instanceof MappingJacksonInputMessage) { Class deserializationView = ((MappingJacksonInputMessage) inputMessage).getDeserializationView(); if (deserializationView != null) { return this.objectMapper.readerWithView(deserializationView).withType(javaType). readValue(inputMessage.getBody()); } } return this.objectMapper.readValue(inputMessage.getBody(), javaType); } catch (IOException ex) { throw new HttpMessageNotReadableException("Could not read document: " + ex.getMessage(), ex); } } @Override @SuppressWarnings("deprecation") protected void writeInternal(Object object, Type type, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException { JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType()); JsonGenerator generator = this.objectMapper.getFactory().createGenerator(outputMessage.getBody(), encoding); try { writePrefix(generator, object); Class serializationView = null; FilterProvider filters = null; Object value = object; JavaType javaType = null; if (object instanceof MappingJacksonValue) { MappingJacksonValue container = (MappingJacksonValue) object; value = container.getValue(); serializationView = container.getSerializationView(); filters = container.getFilters(); } if (jackson26Available && type != null && value != null && TypeUtils.isAssignable(type, value.getClass())) { javaType = getJavaType(type, null); } ObjectWriter objectWriter; if (serializationView != null) { objectWriter = this.objectMapper.writerWithView(serializationView); } else if (filters != null) { objectWriter = this.objectMapper.writer(filters); } else { objectWriter = this.objectMapper.writer(); } if (javaType != null) { objectWriter = objectWriter.withType(javaType); } objectWriter.writeValue(generator, value); writeSuffix(generator, object); generator.flush(); } catch (JsonProcessingException ex) { throw new HttpMessageNotWritableException("Could not write content: " + ex.getMessage(), ex); } } /** * Write a prefix before the main content. * @param generator the generator to use for writing content. * @param object the object to write to the output message. */ protected void writePrefix(JsonGenerator generator, Object object) throws IOException { } /** * Write a suffix after the main content. * @param generator the generator to use for writing content. * @param object the object to write to the output message. */ protected void writeSuffix(JsonGenerator generator, Object object) throws IOException { } /** * Return the Jackson {@link JavaType} for the specified type and context class. *

The default implementation returns {@code typeFactory.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);
	 *   }
	 * }
	 * 
* @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 this.objectMapper.getTypeFactory().constructType(type, contextClass); } /** * 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}) */ 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; } @Override protected MediaType getDefaultContentType(Object object) throws IOException { if (object instanceof MappingJacksonValue) { object = ((MappingJacksonValue) object).getValue(); } return super.getDefaultContentType(object); } @Override protected Long getContentLength(Object object, MediaType contentType) throws IOException { if (object instanceof MappingJacksonValue) { object = ((MappingJacksonValue) object).getValue(); } return super.getContentLength(object, contentType); } }