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Spring Framework example source code file (XsltView.java)

This example Spring Framework source code file (XsltView.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

applicationcontextexception, dom, exception, httpservletresponse, io, ioexception, request, response, servlet, source, source, streamsource, streamsource, string, string, templates, transformer, transformer, transformerfactory, util

The Spring Framework XsltView.java source code

/*
 * Copyright 2002-2007 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.web.servlet.view.xslt;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.transform.ErrorListener;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Templates;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerFactoryConfigurationError;
import javax.xml.transform.URIResolver;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.w3c.dom.Document;
import org.w3c.dom.Node;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContextException;
import org.springframework.core.io.Resource;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
import org.springframework.util.xml.SimpleTransformErrorListener;
import org.springframework.web.servlet.view.AbstractUrlBasedView;
import org.springframework.web.util.WebUtils;

/**
 * XSLT-driven View that allows for response context to be rendered as the
 * result of an XSLT transformation.
 *
 * <p>The XSLT Source object is supplied as a parameter in the model and then
 * {@link #locateSource detected} during response rendering. Users can either specify
 * a specific entry in the model via the {@link #setSourceKey sourceKey} property or
 * have Spring locate the Source object. This class also provides basic conversion
 * of objects into Source implementations. See {@link #getSourceTypes() here}
 * for more details.
 *
 * <p>All model parameters are passed to the XSLT Transformer as parameters.
 * In addition the user can configure {@link #setOutputProperties output properties}
 * to be passed to the Transformer.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 2.0
 */
public class XsltView extends AbstractUrlBasedView {

	private Class transformerFactoryClass;

	private String sourceKey;

	private URIResolver uriResolver;

	private ErrorListener errorListener = new SimpleTransformErrorListener(logger);

	private boolean indent = true;

	private Properties outputProperties;

	private boolean cacheTemplates = true;

	private TransformerFactory transformerFactory;

	private Templates cachedTemplates;


	/**
	 * Specify the XSLT TransformerFactory class to use.
	 * <p>The default constructor of the specified class will be called
	 * to build the TransformerFactory for this view.
	 */
	public void setTransformerFactoryClass(Class transformerFactoryClass) {
		Assert.isAssignable(TransformerFactory.class, transformerFactoryClass);
		this.transformerFactoryClass = transformerFactoryClass;
	}

	/**
	 * Set the name of the model attribute that represents the XSLT Source.
	 * If not specified, the model map will be searched for a matching value type.
	 * <p>The following source types are supported out of the box:
	 * {@link Source}, {@link Document}, {@link Node}, {@link Reader},
	 * {@link InputStream} and {@link Resource}.
	 * @see #getSourceTypes
	 * @see #convertSource
	 */
	public void setSourceKey(String sourceKey) {
		this.sourceKey = sourceKey;
	}

	/**
	 * Set the URIResolver used in the transform.
	 * <p>The URIResolver handles calls to the XSLT document() function.
	 */
	public void setUriResolver(URIResolver uriResolver) {
		this.uriResolver = uriResolver;
	}

	/**
	 * Set an implementation of the {@link javax.xml.transform.ErrorListener}
	 * interface for custom handling of transformation errors and warnings.
	 * <p>If not set, a default
	 * {@link org.springframework.util.xml.SimpleTransformErrorListener} is
	 * used that simply logs warnings using the logger instance of the view class,
	 * and rethrows errors to discontinue the XML transformation.
	 * @see org.springframework.util.xml.SimpleTransformErrorListener
	 */
	public void setErrorListener(ErrorListener errorListener) {
		this.errorListener = (errorListener != null ? errorListener : new SimpleTransformErrorListener(logger));
	}

	/**
	 * Set whether the XSLT transformer may add additional whitespace when
	 * outputting the result tree.
	 * <p>Default is true (on); set this to false (off)
	 * to not specify an "indent" key, leaving the choice up to the stylesheet.
	 * @see javax.xml.transform.OutputKeys#INDENT
	 */
	public void setIndent(boolean indent) {
		this.indent = indent;
	}

	/**
	 * Set arbitrary transformer output properties to be applied to the stylesheet.
	 * <p>Any values specified here will override defaults that this view sets
	 * programmatically.
	 * @see javax.xml.transform.Transformer#setOutputProperty
	 */
	public void setOutputProperties(Properties outputProperties) {
		this.outputProperties = outputProperties;
	}

	/**
	 * Turn on/off the caching of the XSLT {@link Templates} instance.
	 * <p>The default value is "true". Only set this to "false" in development,
	 * where caching does not seriously impact performance.
	 */
	public void setCacheTemplates(boolean cacheTemplates) {
		this.cacheTemplates = cacheTemplates;
	}


	/**
	 * Initialize this XsltView's TransformerFactory.
	 */
	protected void initApplicationContext() throws BeansException {
		this.transformerFactory = newTransformerFactory(this.transformerFactoryClass);
		this.transformerFactory.setErrorListener(this.errorListener);
		if (this.uriResolver != null) {
			this.transformerFactory.setURIResolver(this.uriResolver);
		}
		if (this.cacheTemplates) {
			this.cachedTemplates = loadTemplates();
		}
	}

	/**
	 * Instantiate a new TransformerFactory for this view.
	 * <p>The default implementation simply calls
	 * {@link javax.xml.transform.TransformerFactory#newInstance()}.
	 * If a {@link #setTransformerFactoryClass "transformerFactoryClass"}
	 * has been specified explicitly, the default constructor of the
	 * specified class will be called instead.
	 * <p>Can be overridden in subclasses.
	 * @param transformerFactoryClass the specified factory class (if any)
	 * @return the new TransactionFactory instance
	 * @see #setTransformerFactoryClass
	 * @see #getTransformerFactory()
	 */
	protected TransformerFactory newTransformerFactory(Class transformerFactoryClass) {
		if (transformerFactoryClass != null) {
			try {
				return (TransformerFactory) transformerFactoryClass.newInstance();
			}
			catch (Exception ex) {
				throw new TransformerFactoryConfigurationError(ex, "Could not instantiate TransformerFactory");
			}
		}
		else {
			return TransformerFactory.newInstance();
		}
	}

	/**
	 * Return the TransformerFactory that this XsltView uses.
	 * @return the TransformerFactory (never <code>null)
	 */
	protected final TransformerFactory getTransformerFactory() {
		return this.transformerFactory;
	}


	protected void renderMergedOutputModel(Map model, HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		Templates templates = this.cachedTemplates;
		if (templates == null) {
			templates = loadTemplates();
		}

		Transformer transformer = createTransformer(templates);
		configureTransformer(model, response, transformer);
		configureResponse(model, response, transformer);
		Source source = null;
		try {
			source = locateSource(model);
			if (source == null) {
				throw new IllegalArgumentException("Unable to locate Source object in model: " + model);
			}
			transformer.transform(source, createResult(response));
		}
		finally {
			closeSourceIfNecessary(source);
		}
	}

	/**
	 * Create the XSLT {@link Result} used to render the result of the transformation.
	 * <p>The default implementation creates a {@link StreamResult} wrapping the supplied
	 * HttpServletResponse's {@link HttpServletResponse#getOutputStream() OutputStream}.
	 * @param response current HTTP response
	 * @return the XSLT Result to use
	 * @throws Exception if the Result cannot be built
	 */
	protected Result createResult(HttpServletResponse response) throws Exception {
		return new StreamResult(response.getOutputStream());
	}

	/**
	 * <p>Locate the {@link Source} object in the supplied model,
	 * converting objects as required.
	 * The default implementation first attempts to look under the configured
	 * {@link #setSourceKey source key}, if any, before attempting to locate
	 * an object of {@link #getSourceTypes() supported type}.
	 * @param model the merged model Map
	 * @return the XSLT Source object (or <code>null if none found)
	 * @throws Exception if an error occured during locating the source
	 * @see #setSourceKey
	 * @see #convertSource
	 */
	protected Source locateSource(Map model) throws Exception {
		if (this.sourceKey != null) {
			return convertSource(model.get(this.sourceKey));
		}
		Object source = CollectionUtils.findValueOfType(model.values(), getSourceTypes());
		return (source != null ? convertSource(source) : null);
	}

	/**
	 * Return the array of {@link Class Classes} that are supported when converting to an
	 * XSLT {@link Source}.
	 * <p>Currently supports {@link Source}, {@link Document}, {@link Node},
	 * {@link Reader}, {@link InputStream} and {@link Resource}.
	 * @return the supported source types
	 */
	protected Class[] getSourceTypes() {
		return new Class[] {Source.class, Document.class, Node.class, Reader.class, InputStream.class, Resource.class};
	}

	/**
	 * Convert the supplied {@link Object} into an XSLT {@link Source} if the
	 * {@link Object} type is {@link #getSourceTypes() supported}.
	 * @param source the original source object
	 * @return the adapted XSLT Source
	 * @throws IllegalArgumentException if the given Object is not of a supported type
	 */
	protected Source convertSource(Object source) throws Exception {
		if (source instanceof Source) {
			return (Source) source;
		}
		else if (source instanceof Document) {
			return new DOMSource(((Document) source).getDocumentElement());
		}
		else if (source instanceof Node) {
			return new DOMSource((Node) source);
		}
		else if (source instanceof Reader) {
			return new StreamSource((Reader) source);
		}
		else if (source instanceof InputStream) {
			return new StreamSource((InputStream) source);
		}
		else if (source instanceof Resource) {
			return new StreamSource(((Resource) source).getInputStream());
		}
		else {
			throw new IllegalArgumentException("Value '" + source + "' cannot be converted to XSLT Source");
		}
	}

	/**
	 * Configure the supplied {@link Transformer} instance.
	 * <p>The default implementation copies parameters from the model into the
	 * Transformer's {@link Transformer#setParameter parameter set}.
	 * This implementation also copies the {@link #setOutputProperties output properties}
	 * into the {@link Transformer} {@link Transformer#setOutputProperty output properties}.
	 * Indentation properties are set as well.
	 * @param model merged output Map (never <code>null)
	 * @param response current HTTP response
	 * @param transformer the target transformer
	 * @see #copyModelParameters(Map, Transformer)
	 * @see #copyOutputProperties(Transformer)
	 * @see #configureIndentation(Transformer)
	 */
	protected void configureTransformer(Map model, HttpServletResponse response, Transformer transformer) {
		copyModelParameters(model, transformer);
		copyOutputProperties(transformer);
		configureIndentation(transformer);
	}

	/**
	 * Configure the indentation settings for the supplied {@link Transformer}.
	 * @param transformer the target transformer
	 * @throws IllegalArgumentException if the supplied {@link Transformer} is <code>null
	 * @see TransformerUtils#enableIndenting(javax.xml.transform.Transformer) 
	 * @see TransformerUtils#disableIndenting(javax.xml.transform.Transformer)
	 */
	protected final void configureIndentation(Transformer transformer) {
		if (this.indent) {
			TransformerUtils.enableIndenting(transformer);
		}
		else {
			TransformerUtils.disableIndenting(transformer);
		}
	}

	/**
	 * Copy the configured output {@link Properties}, if any, into the
	 * {@link Transformer#setOutputProperty output property set} of the supplied
	 * {@link Transformer}.
	 * @param transformer the target transformer
	 */
	protected final void copyOutputProperties(Transformer transformer) {
		if (this.outputProperties != null) {
			Enumeration en = this.outputProperties.propertyNames();
			while (en.hasMoreElements()) {
				String name = (String) en.nextElement();
				transformer.setOutputProperty(name, this.outputProperties.getProperty(name));
			}
		}
	}

	/**
	 * Copy all entries from the supplied Map into the
	 * {@link Transformer#setParameter(String, Object) parameter set}
	 * of the supplied {@link Transformer}.
	 * @param model merged output Map (never <code>null)
	 * @param transformer the target transformer
	 */
	protected final void copyModelParameters(Map model, Transformer transformer) {
		copyMapEntriesToTransformerParameters(model, transformer);
	}

	/**
	 * Configure the supplied {@link HttpServletResponse}.
	 * <p>The default implementation of this method sets the
	 * {@link HttpServletResponse#setContentType content type} and
	 * {@link HttpServletResponse#setCharacterEncoding encoding}
	 * from the "media-type" and "encoding" output properties
	 * specified in the {@link Transformer}.
	 * @param model merged output Map (never <code>null)
	 * @param response current HTTP response
	 * @param transformer the target transformer
	 */
	protected void configureResponse(Map model, HttpServletResponse response, Transformer transformer) {
		String contentType = getContentType();
		String mediaType = transformer.getOutputProperty(OutputKeys.MEDIA_TYPE);
		String encoding = transformer.getOutputProperty(OutputKeys.ENCODING);
		if (StringUtils.hasText(mediaType)) {
			contentType = mediaType;
		}
		if (StringUtils.hasText(encoding)) {
			// Only apply encoding if content type is specified but does not contain charset clause already.
			if (contentType != null && contentType.toLowerCase().indexOf(WebUtils.CONTENT_TYPE_CHARSET_PREFIX) == -1) {
				contentType = contentType + WebUtils.CONTENT_TYPE_CHARSET_PREFIX + encoding;
			}
		}
		response.setContentType(contentType);
	}

	/**
	 * Load the {@link Templates} instance for the stylesheet at the configured location.
	 */
	private Templates loadTemplates() throws ApplicationContextException {
		Source stylesheetSource = getStylesheetSource();
		try {
			Templates templates = this.transformerFactory.newTemplates(stylesheetSource);
			if (logger.isDebugEnabled()) {
				logger.debug("Loading templates '" + templates + "'");
			}
			return templates;
		}
		catch (TransformerConfigurationException ex) {
			throw new ApplicationContextException("Can't load stylesheet from '" + getUrl() + "'", ex);
		}
		finally {
			closeSourceIfNecessary(stylesheetSource);
		}
	}

	/**
	 * Create the {@link Transformer} instance used to prefer the XSLT transformation.
	 * <p>The default implementation simply calls {@link Templates#newTransformer()}, and
	 * configures the {@link Transformer} with the custom {@link URIResolver} if specified.
	 * @param templates the XSLT Templates instance to create a Transformer for
	 * @return the Transformer object
	 * @throws TransformerConfigurationException in case of creation failure
	 */
	protected Transformer createTransformer(Templates templates) throws TransformerConfigurationException {
		Transformer transformer = templates.newTransformer();
		if (this.uriResolver != null) {
			transformer.setURIResolver(this.uriResolver);
		}
		return transformer;
	}

	/**
	 * Get the XSLT {@link Source} for the XSLT template under the {@link #setUrl configured URL}.
	 * @return the Source object
	 */
	protected Source getStylesheetSource() {
		String url = getUrl();
		if (logger.isDebugEnabled()) {
			logger.debug("Loading XSLT stylesheet from '" + url + "'");
		}
		try {
			Resource stylesheetResource = getApplicationContext().getResource(url);
			String systemId = url.substring(0, url.lastIndexOf('/') + 1);
			return new StreamSource(stylesheetResource.getInputStream(), systemId);
		}
		catch (IOException ex) {
			throw new ApplicationContextException("Can't load XSLT stylesheet from '" + url + "'", ex);
		}
	}

	/**
	 * Copy all {@link Map.Entry entries} from the supplied {@link Map} into the
	 * {@link Transformer#setParameter(String, Object) parameter set} of the supplied
	 * {@link Transformer}.
	 */
	private void copyMapEntriesToTransformerParameters(Map map, Transformer transformer) {
		for (Iterator iterator = map.entrySet().iterator(); iterator.hasNext();) {
			Map.Entry entry = (Map.Entry) iterator.next();
			transformer.setParameter(ObjectUtils.nullSafeToString(entry.getKey()), entry.getValue());
		}
	}

	/**
	 * Close the underlying resource managed by the supplied {@link Source} if applicable.
	 * <p>Only works for {@link StreamSource StreamSources}.
	 * @param source the XSLT Source to close (may be <code>null)
	 */
	private void closeSourceIfNecessary(Source source) {
		if (source instanceof StreamSource) {
			StreamSource streamSource = (StreamSource) source;
			if (streamSource.getReader() != null) {
				try {
					streamSource.getReader().close();
				}
				catch (IOException ex) {
				}
			}
			if (streamSource.getInputStream() != null) {
				try {
					streamSource.getInputStream().close();
				}
				catch (IOException ex) {
				}
			}
		}
	}

}

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