/*
* Copyright 2002-2012 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.xml;
import java.io.IOException;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.SortedSet;
import java.util.TreeSet;
import javax.xml.bind.JAXBException;
import javax.xml.bind.UnmarshalException;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.GenericHttpMessageConverter;
import org.springframework.http.converter.HttpMessageConversionException;
import org.springframework.http.converter.HttpMessageNotReadableException;
/**
* An {@code HttpMessageConverter} that can read XML collections using JAXB2.
*
* <p>This converter can read {@linkplain Collection collections} that contain classes
* annotated with {@link XmlRootElement} and {@link XmlType}. Note that this converter
* does not support writing.
*
* @author Arjen Poutsma
* @since 3.2
*/
public class Jaxb2CollectionHttpMessageConverter<T extends Collection>
extends AbstractJaxb2HttpMessageConverter<T> implements GenericHttpMessageConverter<T> {
private final XMLInputFactory inputFactory = createXmlInputFactory();
/**
* Always returns {@code false} since Jaxb2CollectionHttpMessageConverter
* required generic type information in order to read a Collection.
*/
@Override
public boolean canRead(Class<?> clazz, MediaType mediaType) {
return false;
}
/**
* {@inheritDoc}
* <p>Jaxb2CollectionHttpMessageConverter can read a generic
* {@link Collection} where the generic type is a JAXB type annotated with
* {@link XmlRootElement} or {@link XmlType}.
*/
public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
if (!(type instanceof ParameterizedType)) {
return false;
}
ParameterizedType parameterizedType = (ParameterizedType) type;
if (!(parameterizedType.getRawType() instanceof Class)) {
return false;
}
Class<?> rawType = (Class<?>) parameterizedType.getRawType();
if (!(Collection.class.isAssignableFrom(rawType))) {
return false;
}
if (parameterizedType.getActualTypeArguments().length != 1) {
return false;
}
Type typeArgument = parameterizedType.getActualTypeArguments()[0];
if (!(typeArgument instanceof Class)) {
return false;
}
Class<?> typeArgumentClass = (Class<?>) typeArgument;
return (typeArgumentClass.isAnnotationPresent(XmlRootElement.class) ||
typeArgumentClass.isAnnotationPresent(XmlType.class)) && canRead(mediaType);
}
/**
* Always returns {@code false} since Jaxb2CollectionHttpMessageConverter
* does not convert collections to XML.
*/
@Override
public boolean canWrite(Class<?> clazz, MediaType mediaType) {
return false;
}
@Override
protected boolean supports(Class<?> clazz) {
// should not be called, since we override canRead/Write
throw new UnsupportedOperationException();
}
@Override
protected T readFromSource(Class<? extends T> clazz, HttpHeaders headers, Source source) throws IOException {
// should not be called, since we return false for canRead(Class)
throw new UnsupportedOperationException();
}
public T read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
throws IOException, HttpMessageNotReadableException {
ParameterizedType parameterizedType = (ParameterizedType) type;
T result = createCollection((Class<?>) parameterizedType.getRawType());
Class<?> elementClass = (Class<?>) parameterizedType.getActualTypeArguments()[0];
try {
Unmarshaller unmarshaller = createUnmarshaller(elementClass);
XMLStreamReader streamReader = this.inputFactory.createXMLStreamReader(inputMessage.getBody());
int event = moveToFirstChildOfRootElement(streamReader);
while (event != XMLStreamReader.END_DOCUMENT) {
if (elementClass.isAnnotationPresent(XmlRootElement.class)) {
result.add(unmarshaller.unmarshal(streamReader));
}
else if (elementClass.isAnnotationPresent(XmlType.class)) {
result.add(unmarshaller.unmarshal(streamReader, elementClass).getValue());
}
else {
// should not happen, since we check in canRead(Type)
throw new HttpMessageConversionException("Could not unmarshal to [" + elementClass + "]");
}
event = moveToNextElement(streamReader);
}
return result;
}
catch (UnmarshalException ex) {
throw new HttpMessageNotReadableException("Could not unmarshal to [" + elementClass + "]: " + ex.getMessage(), ex);
}
catch (JAXBException ex) {
throw new HttpMessageConversionException("Could not instantiate JAXBContext: " + ex.getMessage(), ex);
}
catch (XMLStreamException ex) {
throw new HttpMessageConversionException(ex.getMessage(), ex);
}
}
/**
* Create a Collection of the given type, with the given initial capacity
* (if supported by the Collection type).
*
* @param collectionClass the type of Collection to instantiate
* @return the created Collection instance
*/
@SuppressWarnings("unchecked")
protected T createCollection(Class<?> collectionClass) {
if (!collectionClass.isInterface()) {
try {
return (T) collectionClass.newInstance();
}
catch (Exception ex) {
throw new IllegalArgumentException(
"Could not instantiate collection class [" +
collectionClass.getName() + "]: " + ex.getMessage());
}
}
else if (List.class.equals(collectionClass)) {
return (T) new ArrayList();
}
else if (SortedSet.class.equals(collectionClass)) {
return (T) new TreeSet();
}
else {
return (T) new LinkedHashSet();
}
}
private int moveToFirstChildOfRootElement(XMLStreamReader streamReader) throws XMLStreamException {
// root
int event = streamReader.next();
while (event != XMLStreamReader.START_ELEMENT) {
event = streamReader.next();
}
// first child
event = streamReader.next();
while ((event != XMLStreamReader.START_ELEMENT) && (event != XMLStreamReader.END_DOCUMENT)) {
event = streamReader.next();
}
return event;
}
private int moveToNextElement(XMLStreamReader streamReader) throws XMLStreamException {
int event = streamReader.getEventType();
while (event != XMLStreamReader.START_ELEMENT && event != XMLStreamReader.END_DOCUMENT) {
event = streamReader.next();
}
return event;
}
@Override
protected void writeToResult(T t, HttpHeaders headers, Result result) throws IOException {
throw new UnsupportedOperationException();
}
/**
* Create a {@code XMLInputFactory} that this converter will use to create {@link
* javax.xml.stream.XMLStreamReader} and {@link javax.xml.stream.XMLEventReader} objects.
* <p/> Can be overridden in subclasses, adding further initialization of the factory.
* The resulting factory is cached, so this method will only be called once.
*
* @return the created factory
*/
protected XMLInputFactory createXmlInputFactory() {
return XMLInputFactory.newInstance();
}
}