org.springframework.boot.autoconfigure.http.HttpMessageConverters Maven / Gradle / Ivy
/*
* Copyright 2012-2020 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.boot.autoconfigure.http;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter;
import org.springframework.http.converter.xml.AbstractXmlHttpMessageConverter;
import org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter;
import org.springframework.util.ClassUtils;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
/**
* Bean used to manage the {@link HttpMessageConverter}s used in a Spring Boot
* application. Provides a convenient way to add and merge additional
* {@link HttpMessageConverter}s to a web application.
*
* An instance of this bean can be registered with specific
* {@link #HttpMessageConverters(HttpMessageConverter...) additional converters} if
* needed, otherwise default converters will be used.
*
* NOTE: The default converters used are the same as standard Spring MVC (see
* {@link WebMvcConfigurationSupport}) with some slight re-ordering to put XML converters
* at the back of the list.
*
* @author Dave Syer
* @author Phillip Webb
* @author Andy Wilkinson
* @since 2.0.0
* @see #HttpMessageConverters(HttpMessageConverter...)
* @see #HttpMessageConverters(Collection)
* @see #getConverters()
*/
public class HttpMessageConverters implements Iterable> {
private static final List> NON_REPLACING_CONVERTERS;
static {
List> nonReplacingConverters = new ArrayList<>();
addClassIfExists(nonReplacingConverters,
"org.springframework.hateoas.server.mvc.TypeConstrainedMappingJackson2HttpMessageConverter");
NON_REPLACING_CONVERTERS = Collections.unmodifiableList(nonReplacingConverters);
}
private final List> converters;
/**
* Create a new {@link HttpMessageConverters} instance with the specified additional
* converters.
* @param additionalConverters additional converters to be added. Items are added just
* before any default converter of the same type (or at the front of the list if no
* default converter is found). The {@link #postProcessConverters(List)} method can be
* used for further converter manipulation.
*/
public HttpMessageConverters(HttpMessageConverter... additionalConverters) {
this(Arrays.asList(additionalConverters));
}
/**
* Create a new {@link HttpMessageConverters} instance with the specified additional
* converters.
* @param additionalConverters additional converters to be added. Items are added just
* before any default converter of the same type (or at the front of the list if no
* default converter is found). The {@link #postProcessConverters(List)} method can be
* used for further converter manipulation.
*/
public HttpMessageConverters(Collection> additionalConverters) {
this(true, additionalConverters);
}
/**
* Create a new {@link HttpMessageConverters} instance with the specified converters.
* @param addDefaultConverters if default converters should be added
* @param converters converters to be added. Items are added just before any default
* converter of the same type (or at the front of the list if no default converter is
* found). The {@link #postProcessConverters(List)} method can be used for further
* converter manipulation.
*/
public HttpMessageConverters(boolean addDefaultConverters, Collection> converters) {
List> combined = getCombinedConverters(converters,
addDefaultConverters ? getDefaultConverters() : Collections.emptyList());
combined = postProcessConverters(combined);
this.converters = Collections.unmodifiableList(combined);
}
private List> getCombinedConverters(Collection> converters,
List> defaultConverters) {
List> combined = new ArrayList<>();
List> processing = new ArrayList<>(converters);
for (HttpMessageConverter defaultConverter : defaultConverters) {
Iterator> iterator = processing.iterator();
while (iterator.hasNext()) {
HttpMessageConverter candidate = iterator.next();
if (isReplacement(defaultConverter, candidate)) {
combined.add(candidate);
iterator.remove();
}
}
combined.add(defaultConverter);
if (defaultConverter instanceof AllEncompassingFormHttpMessageConverter) {
configurePartConverters((AllEncompassingFormHttpMessageConverter) defaultConverter, converters);
}
}
combined.addAll(0, processing);
return combined;
}
private boolean isReplacement(HttpMessageConverter defaultConverter, HttpMessageConverter candidate) {
for (Class nonReplacingConverter : NON_REPLACING_CONVERTERS) {
if (nonReplacingConverter.isInstance(candidate)) {
return false;
}
}
return ClassUtils.isAssignableValue(defaultConverter.getClass(), candidate);
}
private void configurePartConverters(AllEncompassingFormHttpMessageConverter formConverter,
Collection> converters) {
List> partConverters = formConverter.getPartConverters();
List> combinedConverters = getCombinedConverters(converters, partConverters);
combinedConverters = postProcessPartConverters(combinedConverters);
formConverter.setPartConverters(combinedConverters);
}
/**
* Method that can be used to post-process the {@link HttpMessageConverter} list
* before it is used.
* @param converters a mutable list of the converters that will be used.
* @return the final converts list to use
*/
protected List> postProcessConverters(List> converters) {
return converters;
}
/**
* Method that can be used to post-process the {@link HttpMessageConverter} list
* before it is used to configure the part converters of
* {@link AllEncompassingFormHttpMessageConverter}.
* @param converters a mutable list of the converters that will be used.
* @return the final converts list to use
* @since 1.3.0
*/
protected List> postProcessPartConverters(List> converters) {
return converters;
}
private List> getDefaultConverters() {
List> converters = new ArrayList<>();
if (ClassUtils.isPresent("org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport",
null)) {
converters.addAll(new WebMvcConfigurationSupport() {
public List> defaultMessageConverters() {
return super.getMessageConverters();
}
}.defaultMessageConverters());
}
else {
converters.addAll(new RestTemplate().getMessageConverters());
}
reorderXmlConvertersToEnd(converters);
return converters;
}
private void reorderXmlConvertersToEnd(List> converters) {
List> xml = new ArrayList<>();
for (Iterator> iterator = converters.iterator(); iterator.hasNext();) {
HttpMessageConverter converter = iterator.next();
if ((converter instanceof AbstractXmlHttpMessageConverter)
|| (converter instanceof MappingJackson2XmlHttpMessageConverter)) {
xml.add(converter);
iterator.remove();
}
}
converters.addAll(xml);
}
@Override
public Iterator> iterator() {
return getConverters().iterator();
}
/**
* Return an immutable list of the converters in the order that they will be
* registered.
* @return the converters
*/
public List> getConverters() {
return this.converters;
}
private static void addClassIfExists(List> list, String className) {
try {
list.add(Class.forName(className));
}
catch (ClassNotFoundException | NoClassDefFoundError ex) {
// Ignore
}
}
}