https://github.com/spring-projects/spring-framework: Spring Web (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2020 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
 *
 *      https://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.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.lang.reflect.Type;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.Collections;
import java.util.Map;
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.DefaultIndenter;
import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.fasterxml.jackson.databind.SerializationConfig;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.exc.InvalidDefinitionException;
import com.fasterxml.jackson.databind.ser.FilterProvider;

import org.springframework.core.GenericTypeResolver;
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.HttpMessageConversionException;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StreamUtils;
import org.springframework.util.TypeUtils;


Abstract base class for Jackson based and content type independent HttpMessageConverter implementations. 
Compatible with Jackson 2.9 to 2.12, as of Spring 5.3.

Author:Arjen Poutsma, Keith Donald, Rossen Stoyanchev, Juergen Hoeller, Sebastien Deleuze
See Also:
Since:4.1
/**
 * Abstract base class for Jackson based and content type independent
 * {@link HttpMessageConverter} implementations.
 *
 * <p>Compatible with Jackson 2.9 to 2.12, as of Spring 5.3.
 *
 * @author Arjen Poutsma
 * @author Keith Donald
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @author Sebastien Deleuze
 * @since 4.1
 * @see MappingJackson2HttpMessageConverter
 */
public abstract class AbstractJackson2HttpMessageConverter extends AbstractGenericHttpMessageConverter<Object> {

	private static final Map<String, JsonEncoding> ENCODINGS;

	static {
		ENCODINGS = CollectionUtils.newHashMap(JsonEncoding.values().length);
		for (JsonEncoding encoding : JsonEncoding.values()) {
			ENCODINGS.put(encoding.getJavaName(), encoding);
		}
		ENCODINGS.put("US-ASCII", JsonEncoding.UTF8);
	}


	
The default charset used by the converter.

/**
	 * The default charset used by the converter.
	 */
	@Nullable
	@Deprecated
	public static final Charset DEFAULT_CHARSET = null;


	protected ObjectMapper objectMapper;

	@Nullable
	private Boolean prettyPrint;

	@Nullable
	private PrettyPrinter ssePrettyPrinter;


	protected AbstractJackson2HttpMessageConverter(ObjectMapper objectMapper) {
		this.objectMapper = objectMapper;
		DefaultPrettyPrinter prettyPrinter = new DefaultPrettyPrinter();
		prettyPrinter.indentObjectsWith(new DefaultIndenter("  ", "\ndata:"));
		this.ssePrettyPrinter = prettyPrinter;
	}

	protected AbstractJackson2HttpMessageConverter(ObjectMapper objectMapper, MediaType supportedMediaType) {
		this(objectMapper);
		setSupportedMediaTypes(Collections.singletonList(supportedMediaType));
	}

	protected AbstractJackson2HttpMessageConverter(ObjectMapper objectMapper, MediaType... supportedMediaTypes) {
		this(objectMapper);
		setSupportedMediaTypes(Arrays.asList(supportedMediaTypes));
	}


	
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. 
/**
	 * 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 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 ObjectMapper for this view. 
/**
	 * Return the underlying {@code ObjectMapper} for this view.
	 */
	public ObjectMapper getObjectMapper() {
		return this.objectMapper;
	}

	
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);



/**
	 * Whether to use the {@link DefaultPrettyPrinter} when writing JSON.
	 * This is a shortcut for setting up an {@code ObjectMapper} as follows:
	 * <pre class="code">
	 * ObjectMapper mapper = new ObjectMapper();
	 * mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
	 * converter.setObjectMapper(mapper);
	 * </pre>
	 */
	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, @Nullable MediaType mediaType) {
		return canRead(clazz, null, mediaType);
	}

	@Override
	public boolean canRead(Type type, @Nullable Class<?> contextClass, @Nullable MediaType mediaType) {
		if (!canRead(mediaType)) {
			return false;
		}
		JavaType javaType = getJavaType(type, contextClass);
		AtomicReference<Throwable> causeRef = new AtomicReference<>();
		if (this.objectMapper.canDeserialize(javaType, causeRef)) {
			return true;
		}
		logWarningIfNecessary(javaType, causeRef.get());
		return false;
	}

	@Override
	public boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType) {
		if (!canWrite(mediaType)) {
			return false;
		}
		if (mediaType != null && mediaType.getCharset() != null) {
			Charset charset = mediaType.getCharset();
			if (!ENCODINGS.containsKey(charset.name())) {
				return false;
			}
		}
		AtomicReference<Throwable> causeRef = new AtomicReference<>();
		if (this.objectMapper.canSerialize(clazz, causeRef)) {
			return true;
		}
		logWarningIfNecessary(clazz, causeRef.get());
		return false;
	}

	
Determine whether to log the given exception coming from a canDeserialize.canDeserialize / canSerialize.canSerialize check. 
Params:
  • type – the class that Jackson tested for (de-)serializability
  • cause – the Jackson-thrown exception to evaluate (typically a JsonMappingException)
Since:4.3
/**
	 * Determine whether to log the given exception coming from a
	 * {@link ObjectMapper#canDeserialize} / {@link ObjectMapper#canSerialize} check.
	 * @param type the class that Jackson tested for (de-)serializability
	 * @param cause the Jackson-thrown exception to evaluate
	 * (typically a {@link JsonMappingException})
	 * @since 4.3
	 */
	protected void logWarningIfNecessary(Type type, @Nullable Throwable cause) {
		if (cause == null) {
			return;
		}

		// Do not log warning for serializer not found (note: different message wording on Jackson 2.9)
		boolean debugLevel = (cause instanceof JsonMappingException && cause.getMessage().startsWith("Cannot find"));

		if (debugLevel ? logger.isDebugEnabled() : logger.isWarnEnabled()) {
			String msg = "Failed to evaluate Jackson " + (type instanceof JavaType ? "de" : "") +
					"serialization for type [" + type + "]";
			if (debugLevel) {
				logger.debug(msg, cause);
			}
			else if (logger.isDebugEnabled()) {
				logger.warn(msg, cause);
			}
			else {
				logger.warn(msg + ": " + cause);
			}
		}
	}

	@Override
	public Object read(Type type, @Nullable Class<?> contextClass, HttpInputMessage inputMessage)
			throws IOException, HttpMessageNotReadableException {

		JavaType javaType = getJavaType(type, contextClass);
		return readJavaType(javaType, inputMessage);
	}

	@Override
	protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
			throws IOException, HttpMessageNotReadableException {

		JavaType javaType = getJavaType(clazz, null);
		return readJavaType(javaType, inputMessage);
	}

	private Object readJavaType(JavaType javaType, HttpInputMessage inputMessage) throws IOException {
		MediaType contentType = inputMessage.getHeaders().getContentType();
		Charset charset = getCharset(contentType);

		boolean isUnicode = ENCODINGS.containsKey(charset.name());
		try {
			if (inputMessage instanceof MappingJacksonInputMessage) {
				Class<?> deserializationView = ((MappingJacksonInputMessage) inputMessage).getDeserializationView();
				if (deserializationView != null) {
					ObjectReader objectReader = this.objectMapper.readerWithView(deserializationView).forType(javaType);
					if (isUnicode) {
						return objectReader.readValue(inputMessage.getBody());
					}
					else {
						Reader reader = new InputStreamReader(inputMessage.getBody(), charset);
						return objectReader.readValue(reader);
					}
				}
			}
			if (isUnicode) {
				return this.objectMapper.readValue(inputMessage.getBody(), javaType);
			}
			else {
				Reader reader = new InputStreamReader(inputMessage.getBody(), charset);
				return this.objectMapper.readValue(reader, javaType);
			}
		}
		catch (InvalidDefinitionException ex) {
			throw new HttpMessageConversionException("Type definition error: " + ex.getType(), ex);
		}
		catch (JsonProcessingException ex) {
			throw new HttpMessageNotReadableException("JSON parse error: " + ex.getOriginalMessage(), ex, inputMessage);
		}
	}

	
Determine the charset to use for JSON input.

By default this is either the charset from the input MediaType or otherwise falling back on UTF-8. Can be overridden in subclasses. 
Params:
  • contentType – the content type of the HTTP input message
Returns:the charset to use
Since:5.1.18
/**
	 * Determine the charset to use for JSON input.
	 * <p>By default this is either the charset from the input {@code MediaType}
	 * or otherwise falling back on {@code UTF-8}. Can be overridden in subclasses.
	 * @param contentType the content type of the HTTP input message
	 * @return the charset to use
	 * @since 5.1.18
	 */
	protected Charset getCharset(@Nullable MediaType contentType) {
		if (contentType != null && contentType.getCharset() != null) {
			return contentType.getCharset();
		}
		else {
			return StandardCharsets.UTF_8;
		}
	}

	@Override
	protected void writeInternal(Object object, @Nullable Type type, HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException {

		MediaType contentType = outputMessage.getHeaders().getContentType();
		JsonEncoding encoding = getJsonEncoding(contentType);

		OutputStream outputStream = StreamUtils.nonClosing(outputMessage.getBody());
		try (JsonGenerator generator = this.objectMapper.getFactory().createGenerator(outputStream, encoding)) {
			writePrefix(generator, object);

			Object value = object;
			Class<?> serializationView = null;
			FilterProvider filters = null;
			JavaType javaType = null;

			if (object instanceof MappingJacksonValue) {
				MappingJacksonValue container = (MappingJacksonValue) object;
				value = container.getValue();
				serializationView = container.getSerializationView();
				filters = container.getFilters();
			}
			if (type != null && TypeUtils.isAssignable(type, value.getClass())) {
				javaType = getJavaType(type, null);
			}

			ObjectWriter objectWriter = (serializationView != null ?
					this.objectMapper.writerWithView(serializationView) : this.objectMapper.writer());
			if (filters != null) {
				objectWriter = objectWriter.with(filters);
			}
			if (javaType != null && javaType.isContainerType()) {
				objectWriter = objectWriter.forType(javaType);
			}
			SerializationConfig config = objectWriter.getConfig();
			if (contentType != null && contentType.isCompatibleWith(MediaType.TEXT_EVENT_STREAM) &&
					config.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
				objectWriter = objectWriter.with(this.ssePrettyPrinter);
			}
			objectWriter.writeValue(generator, value);

			writeSuffix(generator, object);
			generator.flush();
		}
		catch (InvalidDefinitionException ex) {
			throw new HttpMessageConversionException("Type definition error: " + ex.getType(), ex);
		}
		catch (JsonProcessingException ex) {
			throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getOriginalMessage(), ex);
		}
	}

	
Write a prefix before the main content.

Params:
  • generator – the generator to use for writing content.
  • object – the object to write to the output message.
/**
	 * 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.

Params:
  • generator – the generator to use for writing content.
  • object – the object to write to the output message.
/**
	 * 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 JavaType for the specified type and context class. 
Params:
  • type – the generic type to return the Jackson JavaType 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)
Returns:the Jackson JavaType
/**
	 * Return the Jackson {@link JavaType} for the specified type and context class.
	 * @param type the generic type to return the Jackson JavaType 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})
	 * @return the Jackson JavaType
	 */
	protected JavaType getJavaType(Type type, @Nullable Class<?> contextClass) {
		return this.objectMapper.constructType(GenericTypeResolver.resolveType(type, contextClass));
	}

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

Params:
  • contentType – the media type as requested by the caller
Returns:the JSON encoding to use (never null)
/**
	 * 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(@Nullable MediaType contentType) {
		if (contentType != null && contentType.getCharset() != null) {
			Charset charset = contentType.getCharset();
			JsonEncoding encoding = ENCODINGS.get(charset.name());
			if (encoding != null) {
				return encoding;
			}
		}
		return JsonEncoding.UTF8;
	}

	@Override
	@Nullable
	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, @Nullable MediaType contentType) throws IOException {
		if (object instanceof MappingJacksonValue) {
			object = ((MappingJacksonValue) object).getValue();
		}
		return super.getContentLength(object, contentType);
	}

}