org.springframework.web.servlet.view.xml.MarshallingView Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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.web.servlet.view.xml;
import java.io.ByteArrayOutputStream;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.bind.JAXBElement;
import javax.xml.transform.stream.StreamResult;
import org.springframework.lang.Nullable;
import org.springframework.oxm.Marshaller;
import org.springframework.util.Assert;
import org.springframework.validation.BindingResult;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.view.AbstractView;
/**
* Spring-MVC {@link View} that allows for response context to be rendered as the result
* of marshalling by a {@link Marshaller}.
*
* The Object to be marshalled is supplied as a parameter in the model and then
* {@linkplain #locateToBeMarshalled(Map) detected} during response rendering. Users can
* either specify a specific entry in the model via the {@link #setModelKey(String) sourceKey}
* property or have Spring locate the Source object.
*
* @author Arjen Poutsma
* @author Juergen Hoeller
* @since 3.0
*/
public class MarshallingView extends AbstractView {
/**
* Default content type. Overridable as bean property.
*/
public static final String DEFAULT_CONTENT_TYPE = "application/xml";
@Nullable
private Marshaller marshaller;
@Nullable
private String modelKey;
/**
* Construct a new {@code MarshallingView} with no {@link Marshaller} set.
* The marshaller must be set after construction by invoking {@link #setMarshaller}.
*/
public MarshallingView() {
setContentType(DEFAULT_CONTENT_TYPE);
setExposePathVariables(false);
}
/**
* Constructs a new {@code MarshallingView} with the given {@link Marshaller} set.
*/
public MarshallingView(Marshaller marshaller) {
this();
Assert.notNull(marshaller, "Marshaller must not be null");
this.marshaller = marshaller;
}
/**
* Set the {@link Marshaller} to be used by this view.
*/
public void setMarshaller(Marshaller marshaller) {
this.marshaller = marshaller;
}
/**
* Set the name of the model key that represents the object to be marshalled.
* If not specified, the model map will be searched for a supported value type.
* @see Marshaller#supports(Class)
*/
public void setModelKey(String modelKey) {
this.modelKey = modelKey;
}
@Override
protected void initApplicationContext() {
Assert.notNull(this.marshaller, "Property 'marshaller' is required");
}
@Override
protected void renderMergedOutputModel(Map model, HttpServletRequest request,
HttpServletResponse response) throws Exception {
Object toBeMarshalled = locateToBeMarshalled(model);
if (toBeMarshalled == null) {
throw new IllegalStateException("Unable to locate object to be marshalled in model: " + model);
}
Assert.state(this.marshaller != null, "No Marshaller set");
ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);
this.marshaller.marshal(toBeMarshalled, new StreamResult(baos));
setResponseContentType(request, response);
response.setContentLength(baos.size());
baos.writeTo(response.getOutputStream());
}
/**
* Locate the object to be marshalled.
* The default implementation first attempts to look under the configured
* {@linkplain #setModelKey(String) model key}, if any, before attempting to
* locate an object of {@linkplain Marshaller#supports(Class) supported type}.
* @param model the model Map
* @return the Object to be marshalled (or {@code null} if none found)
* @throws IllegalStateException if the model object specified by the
* {@linkplain #setModelKey(String) model key} is not supported by the marshaller
* @see #setModelKey(String)
*/
@Nullable
protected Object locateToBeMarshalled(Map model) throws IllegalStateException {
if (this.modelKey != null) {
Object value = model.get(this.modelKey);
if (value == null) {
throw new IllegalStateException("Model contains no object with key [" + this.modelKey + "]");
}
if (!isEligibleForMarshalling(this.modelKey, value)) {
throw new IllegalStateException("Model object [" + value + "] retrieved via key [" +
this.modelKey + "] is not supported by the Marshaller");
}
return value;
}
for (Map.Entry entry : model.entrySet()) {
Object value = entry.getValue();
if (value != null && (model.size() == 1 || !(value instanceof BindingResult)) &&
isEligibleForMarshalling(entry.getKey(), value)) {
return value;
}
}
return null;
}
/**
* Check whether the given value from the current view's model is eligible
* for marshalling through the configured {@link Marshaller}.
* The default implementation calls {@link Marshaller#supports(Class)},
* unwrapping a given {@link JAXBElement} first if applicable.
* @param modelKey the value's key in the model (never {@code null})
* @param value the value to check (never {@code null})
* @return whether the given value is to be considered as eligible
* @see Marshaller#supports(Class)
*/
protected boolean isEligibleForMarshalling(String modelKey, Object value) {
Assert.state(this.marshaller != null, "No Marshaller set");
Class classToCheck = value.getClass();
if (value instanceof JAXBElement) {
classToCheck = ((JAXBElement) value).getDeclaredType();
}
return this.marshaller.supports(classToCheck);
}
}