abstractxsltview.java

spring api 源代码

/*
 * 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.BufferedOutputStream;
import java.io.IOException;
import java.net.URL;
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.TransformerException;
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.Node;

import org.springframework.context.ApplicationContextException;
import org.springframework.core.io.Resource;
import org.springframework.util.Assert;
import org.springframework.util.xml.SimpleTransformErrorListener;
import org.springframework.web.servlet.view.AbstractView;
import org.springframework.web.util.NestedServletException;

/**
 * Convenient superclass for views rendered using an XSLT stylesheet.
 * 
 * <p>Subclasses typically must provide the {@link Source} to transform
 * by overriding {@link #createXsltSource}. Subclasses do not need to
 * concern themselves with XSLT other than providing a valid stylesheet location.
 *
 * <p>Properties:
 * <ul>
 * <li>{@link #setStylesheetLocation(org.springframework.core.io.Resource) stylesheetLocation}:
 * a {@link Resource} pointing to the XSLT stylesheet
 * <li>{@link #setRoot(String) root}: the name of the root element; defaults to {@link #DEFAULT_ROOT "DocRoot"}
 * <li>{@link #setUriResolver(javax.xml.transform.URIResolver) uriResolver}:
 * the {@link URIResolver} to be used in the transform
 * <li>{@link #setErrorListener(javax.xml.transform.ErrorListener) errorListener} (optional):
 * the {@link ErrorListener} implementation instance for custom handling of warnings and errors during TransformerFactory operations
 * <li>{@link #setIndent(boolean) indent} (optional): whether additional whitespace
 * may be added when outputting the result; defaults to <code>true</code>
 * <li>{@link #setCache(boolean) cache} (optional): are templates to be cached; debug setting only; defaults to <code>true</code> 
 * </ul>
 *
 * <p>Note that setting {@link #setCache(boolean) "cache"} to <code>false</code>
 * will cause the template objects to be reloaded for each rendering. This is
 * useful during development, but will seriously affect performance in production
 * and is not thread-safe.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Darren Davison
 */
public abstract class AbstractXsltView extends AbstractView {

	/** The default content type if no stylesheet specified */
	public static final String XML_CONTENT_TYPE = "text/xml;charset=ISO-8859-1";

	/** The default document root name */
	public static final String DEFAULT_ROOT = "DocRoot";


	private boolean customContentTypeSet = false;

	private Class transformerFactoryClass;

	private Resource stylesheetLocation;

	private String root = DEFAULT_ROOT;

	private boolean useSingleModelNameAsRoot = true;

	private URIResolver uriResolver;

	private ErrorListener errorListener = new SimpleTransformErrorListener(logger);

	private boolean indent = true;

	private Properties outputProperties;

	private boolean cache = true;

	private TransformerFactory transformerFactory;

	private volatile Templates cachedTemplates;


	/**
	 * This constructor sets the content type to "text/xml;charset=ISO-8859-1"
	 * by default. This will be switched to the standard web view default
	 * "text/html;charset=ISO-8859-1" if a stylesheet location has been specified.
	 * <p>A specific content type can be configured via the
	 * {@link #setContentType "contentType"} bean property.
	 */
	protected AbstractXsltView() {
		super.setContentType(XML_CONTENT_TYPE);
	}


	public void setContentType(String contentType) {
		super.setContentType(contentType);
		this.customContentTypeSet = true;
	}

	/**
	 * 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 location of the XSLT stylesheet.
	 * <p>If the {@link TransformerFactory} used by this instance has already
	 * been initialized then invoking this setter will result in the
	 * {@link TransformerFactory#newTemplates(javax.xml.transform.Source) attendant templates}
	 * being re-cached.
	 * @param stylesheetLocation the location of the XSLT stylesheet
	 * @see org.springframework.context.ApplicationContext#getResource
	 */
	public void setStylesheetLocation(Resource stylesheetLocation) {
		this.stylesheetLocation = stylesheetLocation;
		// Re-cache templates if transformer factory already initialized.
		resetCachedTemplates();
	}

	/**
	 * Return the location of the XSLT stylesheet, if any.
	 */
	protected Resource getStylesheetLocation() {
		return this.stylesheetLocation;
	}

	/**
	 * The document root element name. Default is {@link #DEFAULT_ROOT "DocRoot"}.
	 * <p>Only used if we're not passed a single {@link Node} as the model.
	 * @param root the document root element name
	 * @see #DEFAULT_ROOT
	 */
	public void setRoot(String root) {
		this.root = root;
	}

	/**
	 * Set whether to use the name of a given single model object as the
	 * document root element name.
	 * <p>Default is <code>true</code> : If you pass in a model with a single object
	 * named "myElement", then the document root will be named "myElement"
	 * as well. Set this flag to <code>false</code> if you want to pass in a single
	 * model object while still using the root element name configured
	 * through the {@link #setRoot(String) "root" property}.
	 * @param useSingleModelNameAsRoot <code>true</code> if the name of a given single
	 * model object is to be used as the document root element name
	 * @see #setRoot
	 */
	public void setUseSingleModelNameAsRoot(boolean useSingleModelNameAsRoot) {
		this.useSingleModelNameAsRoot = useSingleModelNameAsRoot;
	}

	/**
	 * Set the URIResolver used in the transform.
	 * <p>The URIResolver handles calls to the XSLT <code>document()</code> 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;
	}

	/**
	 * Set whether the XSLT transformer may add additional whitespace when
	 * outputting the result tree.
	 * <p>Default is <code>true</code> (on); set this to <code>false</code> (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;
	}

	/**
	 * Set whether to activate the template cache for this view.
	 * <p>Default is <code>true</code>. Turn this off to refresh
	 * the Templates object on every access, e.g. during development.
	 * @see #resetCachedTemplates()
	 */
	public void setCache(boolean cache) {
		this.cache = cache;
	}

	/**
	 * Reset the cached Templates object, if any.
	 * <p>The Templates object will subsequently be rebuilt on next
	 * {@link #getTemplates() access}, if caching is enabled.
	 * @see #setCache
	 */
	public final void resetCachedTemplates() {
		this.cachedTemplates = null;
	}


	/**
	 * Here we load our template, as we need the
	 * {@link org.springframework.context.ApplicationContext} to do it.
	 */
	protected final void initApplicationContext() throws ApplicationContextException {
		this.transformerFactory = newTransformerFactory(this.transformerFactoryClass);
		this.transformerFactory.setErrorListener(this.errorListener);
		if (this.uriResolver != null) {
			this.transformerFactory.setURIResolver(this.uriResolver);
		}
		if (getStylesheetLocation() != null && !this.customContentTypeSet) {
			// Use "text/html" as default (instead of "text/xml") if a stylesheet
			// has been configured but no custom content type has been set.
			super.setContentType(DEFAULT_CONTENT_TYPE);
		}
		try {
			getTemplates();
		}
		catch (TransformerConfigurationException ex) {
			throw new ApplicationContextException("Cannot load stylesheet for XSLT view '" + getBeanName() + "'", ex);
		}
	}

	/**
	 * 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
	 * @throws TransformerFactoryConfigurationError in case of instantiation failure
	 * @see #setTransformerFactoryClass
	 * @see #getTransformerFactory()
	 */
	protected TransformerFactory newTransformerFactory(Class transformerFactoryClass) {
		if (transformerFactoryClass != null) {
			try {