/*
* 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.freemarker;
import java.io.IOException;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Locale;
import java.util.Map;
import javax.servlet.GenericServlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import freemarker.core.ParseException;
import freemarker.ext.jsp.TaglibFactory;
import freemarker.ext.servlet.FreemarkerServlet;
import freemarker.ext.servlet.HttpRequestHashModel;
import freemarker.ext.servlet.HttpRequestParametersHashModel;
import freemarker.ext.servlet.HttpSessionHashModel;
import freemarker.ext.servlet.ServletContextHashModel;
import freemarker.template.Configuration;
import freemarker.template.ObjectWrapper;
import freemarker.template.Template;
import freemarker.template.TemplateException;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContextException;
import org.springframework.web.servlet.support.RequestContextUtils;
import org.springframework.web.servlet.view.AbstractTemplateView;
/**
* View using the FreeMarker template engine.
*
* <p>Exposes the following JavaBean properties:
* <ul>
* <li><b>url</b>: the location of the FreeMarker template to be wrapped,
* relative to the FreeMarker template context (directory).
* <li><b>encoding</b> (optional, default is determined by FreeMarker configuration):
* the encoding of the FreeMarker template file
* </ul>
*
* <p>Depends on a single {@link FreeMarkerConfig} object such as {@link FreeMarkerConfigurer}
* being accessible in the current web application context, with any bean name.
* Alternatively, you can set the FreeMarker {@link Configuration} object as bean property.
* See {@link #setConfiguration} for more details on the impacts of this approach.
*
* <p>Note: Spring's FreeMarker support requires FreeMarker 2.3 or higher.
*
* @author Darren Davison
* @author Juergen Hoeller
* @since 03.03.2004
* @see #setUrl
* @see #setExposeSpringMacroHelpers
* @see #setEncoding
* @see #setConfiguration
* @see FreeMarkerConfig
* @see FreeMarkerConfigurer
*/
public class FreeMarkerView extends AbstractTemplateView {
private String encoding;
private Configuration configuration;
private TaglibFactory taglibFactory;
private ServletContextHashModel servletContextHashModel;
/**
* Set the encoding of the FreeMarker template file. Default is determined
* by the FreeMarker Configuration: "ISO-8859-1" if not specified otherwise.
* <p>Specify the encoding in the FreeMarker Configuration rather than per
* template if all your templates share a common encoding.
*/
public void setEncoding(String encoding) {
this.encoding = encoding;
}
/**
* Return the encoding for the FreeMarker template.
*/
protected String getEncoding() {
return this.encoding;
}
/**
* Set the FreeMarker Configuration to be used by this view.
* If this is not set, the default lookup will occur: a single {@link FreeMarkerConfig}
* is expected in the current web application context, with any bean name.
* <strong>Note:</strong> using this method will cause a new instance of {@link TaglibFactory}
* to created for every single {@link FreeMarkerView} instance. This can be quite expensive
* in terms of memory and initial CPU usage. In production it is recommended that you use
* a {@link FreeMarkerConfig} which exposes a single shared {@link TaglibFactory}.
*/
public void setConfiguration(Configuration configuration) {
this.configuration = configuration;
}
/**
* Return the FreeMarker configuration used by this view.
*/
protected Configuration getConfiguration() {
return this.configuration;
}
/**
* Invoked on startup. Looks for a single FreeMarkerConfig bean to
* find the relevant Configuration for this factory.
* <p>Checks that the template for the default Locale can be found:
* FreeMarker will check non-Locale-specific templates if a
* locale-specific one is not found.
* @see freemarker.cache.TemplateCache#getTemplate
*/
protected void initApplicationContext() throws BeansException {
super.initApplicationContext();
if (getConfiguration() != null) {
this.taglibFactory = new TaglibFactory(getServletContext());
}
else {
FreeMarkerConfig config = autodetectConfiguration();
setConfiguration(config.getConfiguration());
this.taglibFactory = config.getTaglibFactory();
}
GenericServlet servlet = new GenericServletAdapter();
try {
servlet.init(new DelegatingServletConfig());
}
catch (ServletException ex) {
throw new BeanInitializationException("Initialization of GenericServlet adapter failed", ex);
}
this.servletContextHashModel = new ServletContextHashModel(servlet, getObjectWrapper());
checkTemplate();
}
/**
* Autodetect a {@link FreeMarkerConfig} object via the ApplicationContext.
* @return the Configuration instance to use for FreeMarkerViews
* @throws BeansException if no Configuration instance could be found
* @see #getApplicationContext
* @see #setConfiguration
*/
protected FreeMarkerConfig autodetectConfiguration() throws BeansException {
try {
return (FreeMarkerConfig) BeanFactoryUtils.beanOfTypeIncludingAncestors(
getApplicationContext(), FreeMarkerConfig.class, true, false);
}
catch (NoSuchBeanDefinitionException ex) {
throw new ApplicationContextException(
"Must define a single FreeMarkerConfig bean in this web application context " +
"(may be inherited): FreeMarkerConfigurer is the usual implementation. " +
"This bean may be given any name.", ex);
}
}
/**
* Return the configured FreeMarker {@link ObjectWrapper}, or the
* {@link ObjectWrapper#DEFAULT_WRAPPER default wrapper} if none specified.
* @see freemarker.template.Configuration#getObjectWrapper()
*/
protected ObjectWrapper getObjectWrapper() {
ObjectWrapper ow = getConfiguration().getObjectWrapper();
return (ow != null ? ow : ObjectWrapper.DEFAULT_WRAPPER);
}
/**
* Check that the FreeMarker template used for this view exists and is valid.
* <p>Can be overridden to customize the behavior, for example in case of
* multiple templates to be rendered into a single view.
* @throws ApplicationContextException if the template cannot be found or is invalid
*/
protected void checkTemplate() throws ApplicationContextException {
try {
// Check that we can get the template, even if we might subsequently get it again.
getTemplate(getConfiguration().getLocale());
}
catch (ParseException ex) {
throw new ApplicationContextException(
"Failed to parse FreeMarker template for URL [" + getUrl() + "]", ex);
}
catch (IOException ex) {
throw new ApplicationContextException(
"Could not load FreeMarker template for URL [" + getUrl() + "]", ex);
}
}
/**
* Process the model map by merging it with the FreeMarker template.
* Output is directed to the servlet response.
* <p>This method can be overridden if custom behavior is needed.
*/
protected void renderMergedTemplateModel(
Map model, HttpServletRequest request, HttpServletResponse response) throws Exception {
exposeHelpers(model, request);
doRender(model, request, response);
}
/**
* Expose helpers unique to each rendering operation. This is necessary so that
* different rendering operations can't overwrite each other's formats etc.
* <p>Called by <code>renderMergedTemplateModel</code>. The default implementation
* is empty. This method can be overridden to add custom helpers to the model.
* @param model The model that will be passed to the template at merge time
* @param request current HTTP request
* @throws Exception if there's a fatal error while we're adding information to the context
* @see #renderMergedTemplateModel
*/
protected void exposeHelpers(Map model, HttpServletRequest request) throws Exception {
}
/**
* Render the FreeMarker view to the given response, using the given model
* map which contains the complete template model to use.
* <p>The default implementation renders the template specified by the "url"
* bean property, retrieved via <code>getTemplate</code>. It delegates to the
* <code>processTemplate</code> method to merge the template instance with
* the given template model.
* <p>Adds the standard Freemarker hash models to the model: request parameters,
* request, session and application (ServletContext), as well as the JSP tag
* library hash model.
* <p>Can be overridden to customize the behavior, for example to render
* multiple templates into a single view.
* @param model the template model to use for rendering
* @param request current HTTP request
* @param response current servlet response
* @throws IOException if the template file could not be retrieved
* @throws Exception if rendering failed
* @see #setUrl
* @see org.springframework.web.servlet.support.RequestContextUtils#getLocale
* @see #getTemplate(java.util.Locale)
* @see #processTemplate
* @see freemarker.ext.servlet.FreemarkerServlet
*/
protected void doRender(Map model, HttpServletRequest request, HttpServletResponse response) throws Exception {
// Expose model to JSP tags (as request attributes).
exposeModelAsRequestAttributes(model, request);
// Expose all standard FreeMarker hash models.
model.put(FreemarkerServlet.KEY_JSP_TAGLIBS, this.taglibFactory);
model.put(FreemarkerServlet.KEY_APPLICATION, this.servletContextHashModel);
model.put(FreemarkerServlet.KEY_SESSION, buildSessionModel(request, response));
model.put(FreemarkerServlet.KEY_REQUEST, new HttpRequestHashModel(request, response, getObjectWrapper()));
model.put(FreemarkerServlet.KEY_REQUEST_PARAMETERS, new HttpRequestParametersHashModel(request));
if (logger.isDebugEnabled()) {
logger.debug("Rendering FreeMarker template [" + getUrl() + "] in FreeMarkerView '" + getBeanName() + "'");
}
// Grab the locale-specific version of the template.
Locale locale = RequestContextUtils.getLocale(request);
processTemplate(getTemplate(locale), model, response);
}
/**
* Build a FreeMarker {@link HttpSessionHashModel} for the given request,
* detecting whether a session already exists and reacting accordingly.
* @param request current HTTP request
* @param response current servlet response
* @return the FreeMarker HttpSessionHashModel
*/
private HttpSessionHashModel buildSessionModel(HttpServletRequest request, HttpServletResponse response) {
HttpSession session = request.getSession(false);
if (session != null) {
return new HttpSessionHashModel(session, getObjectWrapper());
}
else {
return new HttpSessionHashModel(null, request, response, getObjectWrapper());
}
}
/**
* Retrieve the FreeMarker template for the given locale,
* to be rendering by this view.
* <p>By default, the template specified by the "url" bean property
* will be retrieved.
* @param locale the current locale
* @return the FreeMarker template to render
* @throws IOException if the template file could not be retrieved
* @see #setUrl
* @see #getTemplate(String, java.util.Locale)
*/
protected Template getTemplate(Locale locale) throws IOException {
return getTemplate(getUrl(), locale);
}
/**
* Retrieve the FreeMarker template specified by the given name,
* using the encoding specified by the "encoding" bean property.
* <p>Can be called by subclasses to retrieve a specific template,
* for example to render multiple templates into a single view.
* @param name the file name of the desired template
* @param locale the current locale
* @return the FreeMarker template
* @throws IOException if the template file could not be retrieved
*/
protected Template getTemplate(String name, Locale locale) throws IOException {
return (getEncoding() != null ?
getConfiguration().getTemplate(name, locale, getEncoding()) :
getConfiguration().getTemplate(name, locale));
}
/**
* Process the FreeMarker template to the servlet response.
* <p>Can be overridden to customize the behavior.
* @param template the template to process
* @param model the model for the template
* @param response servlet response (use this to get the OutputStream or Writer)
* @throws IOException if the template file could not be retrieved
* @throws TemplateException if thrown by FreeMarker
* @see freemarker.template.Template#process(Object, java.io.Writer)
*/
protected void processTemplate(Template template, Map model, HttpServletResponse response)
throws IOException, TemplateException {
template.process(model, response.getWriter());
}
/**
* Simple adapter class that extends {@link GenericServlet}.
* Needed for JSP access in FreeMarker.
*/
private static class GenericServletAdapter extends GenericServlet {
public void service(ServletRequest servletRequest, ServletResponse servletResponse) {
// no-op
}
}
/**
* Internal implementation of the {@link ServletConfig} interface,
* to be passed to the servlet adapter.
*/
private class DelegatingServletConfig implements ServletConfig {
public String getServletName() {
return FreeMarkerView.this.getBeanName();
}
public ServletContext getServletContext() {
return FreeMarkerView.this.getServletContext();
}
public String getInitParameter(String paramName) {
return null;
}
public Enumeration getInitParameterNames() {
return Collections.enumeration(Collections.EMPTY_SET);
}
}
}