Java tutorial
/* * 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}. * * <p>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<String, Object> 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. * <p>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<String, Object> 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<String, Object> 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}. * <p>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); } }