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/*
* Copyright 2002-2023 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.messaging.converter;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;
import java.lang.reflect.Type;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import org.springframework.lang.Nullable;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;
import org.springframework.util.ClassUtils;
import org.springframework.util.MimeType;
/**
* Common base class for plain JSON converters, for example, Gson and JSON-B.
*
* @author Juergen Hoeller
* @since 5.3
* @see GsonMessageConverter
* @see JsonbMessageConverter
* @see #fromJson(Reader, Type)
* @see #fromJson(String, Type)
* @see #toJson(Object, Type)
* @see #toJson(Object, Type, Writer)
*/
public abstract class AbstractJsonMessageConverter extends AbstractMessageConverter {
private static final Charset DEFAULT_CHARSET = StandardCharsets.UTF_8;
protected AbstractJsonMessageConverter() {
super(new MimeType("application", "json"));
}
@Override
protected boolean supports(Class clazz) {
return true;
}
@Override
@Nullable
protected Object convertFromInternal(Message message, Class targetClass, @Nullable Object conversionHint) {
try {
Type resolvedType = getResolvedType(targetClass, conversionHint);
Object payload = message.getPayload();
if (ClassUtils.isAssignableValue(targetClass, payload)) {
return payload;
}
else if (payload instanceof byte[] bytes) {
return fromJson(getReader(bytes, message.getHeaders()), resolvedType);
}
else {
// Assuming a text-based source payload
return fromJson(payload.toString(), resolvedType);
}
}
catch (Exception ex) {
throw new MessageConversionException(message, "Could not read JSON: " + ex.getMessage(), ex);
}
}
@Override
@Nullable
protected Object convertToInternal(Object payload, @Nullable MessageHeaders headers, @Nullable Object conversionHint) {
try {
Type resolvedType = getResolvedType(payload.getClass(), conversionHint);
if (byte[].class == getSerializedPayloadClass()) {
ByteArrayOutputStream out = new ByteArrayOutputStream(1024);
Writer writer = getWriter(out, headers);
toJson(payload, resolvedType, writer);
writer.flush();
return out.toByteArray();
}
else {
// Assuming a text-based target payload
return toJson(payload, resolvedType);
}
}
catch (Exception ex) {
throw new MessageConversionException("Could not write JSON: " + ex.getMessage(), ex);
}
}
private Reader getReader(byte[] payload, @Nullable MessageHeaders headers) {
InputStream in = new ByteArrayInputStream(payload);
return new InputStreamReader(in, getCharsetToUse(headers));
}
private Writer getWriter(ByteArrayOutputStream out, @Nullable MessageHeaders headers) {
return new OutputStreamWriter(out, getCharsetToUse(headers));
}
private Charset getCharsetToUse(@Nullable MessageHeaders headers) {
MimeType mimeType = getMimeType(headers);
return (mimeType != null && mimeType.getCharset() != null ? mimeType.getCharset() : DEFAULT_CHARSET);
}
protected abstract Object fromJson(Reader reader, Type resolvedType);
protected abstract Object fromJson(String payload, Type resolvedType);
protected abstract void toJson(Object payload, Type resolvedType, Writer writer);
protected abstract String toJson(Object payload, Type resolvedType);
}