/*
* Copyright 2002-2016 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.reactive.result.view.freemarker;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.nio.charset.Charset;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Optional;
import freemarker.core.ParseException;
import freemarker.template.Configuration;
import freemarker.template.DefaultObjectWrapperBuilder;
import freemarker.template.ObjectWrapper;
import freemarker.template.SimpleHash;
import freemarker.template.Template;
import freemarker.template.Version;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContextException;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.http.MediaType;
import org.springframework.web.reactive.result.view.AbstractUrlBasedView;
import org.springframework.web.server.ServerWebExchange;
/**
* A {@code View} implementation that uses the FreeMarker template engine.
*
* <p>Depends on a single {@link FreeMarkerConfig} object such as
* {@link FreeMarkerConfigurer} being accessible in the application context.
* Alternatively set the FreeMarker configuration can be set directly on this
* class via {@link #setConfiguration}.
*
* <p>The {@link #setUrl(String) url} property is the location of the FreeMarker
* template relative to the FreeMarkerConfigurer's
* {@link FreeMarkerConfigurer#setTemplateLoaderPath templateLoaderPath}.
*
* <p>Note: Spring's FreeMarker support requires FreeMarker 2.3 or higher.
*
* @author Rossen Stoyanchev
* @since 5.0
*/
public class FreeMarkerView extends AbstractUrlBasedView {
private Configuration configuration;
private String encoding;
/**
* Set the FreeMarker Configuration to be used by this view.
* <p>Typically this property is not set directly. Instead a single
* {@link FreeMarkerConfig} is expected in the Spring application context
* which is used to obtain the FreeMarker configuration.
*/
public void setConfiguration(Configuration configuration) {
this.configuration = configuration;
}
/**
* Return the FreeMarker configuration used by this view.
*/
protected Configuration getConfiguration() {
return this.configuration;
}
/**
* Set the encoding of the FreeMarker template file.
* <p>By default {@link FreeMarkerConfigurer} sets the default encoding in
* the FreeMarker configuration to "UTF-8". It's recommended to 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;
}
@Override
public void afterPropertiesSet() throws Exception {
super.afterPropertiesSet();
if (getConfiguration() == null) {
FreeMarkerConfig config = autodetectConfiguration();
setConfiguration(config.getConfiguration());
}
}
/**
* 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 #setConfiguration
*/
protected FreeMarkerConfig autodetectConfiguration() throws BeansException {
try {
return 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);
}
}
/**
* 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.
*/
@Override
public boolean checkResourceExists(Locale locale) throws Exception {
try {
// Check that we can get the template, even if we might subsequently get it again.
getTemplate(locale);
return true;
}
catch (FileNotFoundException ex) {
if (logger.isDebugEnabled()) {
logger.debug("No FreeMarker view found for URL: " + getUrl());
}
return false;
}
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);
}
}
@Override
protected Mono<Void> renderInternal(Map<String, Object> renderAttributes, MediaType contentType,
ServerWebExchange exchange) {
// Expose all standard FreeMarker hash models.
SimpleHash freeMarkerModel = getTemplateModel(renderAttributes, exchange);
if (logger.isDebugEnabled()) {
logger.debug("Rendering FreeMarker template [" + getUrl() + "].");
}
List<Locale> locales = exchange.getRequest().getHeaders().getAcceptLanguageAsLocales();
Locale locale = locales.isEmpty() ? Locale.getDefault() : locales.get(0);
DataBuffer dataBuffer = exchange.getResponse().bufferFactory().allocateBuffer();
try {
Charset charset = getCharset(contentType).orElse(getDefaultCharset());
Writer writer = new OutputStreamWriter(dataBuffer.asOutputStream(), charset);
getTemplate(locale).process(freeMarkerModel, writer);
}
catch (IOException ex) {
String message = "Could not load FreeMarker template for URL [" + getUrl() + "]";
return Mono.error(new IllegalStateException(message, ex));
}
catch (Throwable ex) {
return Mono.error(ex);
}
return exchange.getResponse().writeWith(Flux.just(dataBuffer));
}
private Optional<Charset> getCharset(MediaType mediaType) {
return (mediaType != null ? Optional.ofNullable(mediaType.getCharset()) : Optional.empty());
}
/**
* Build a FreeMarker template model for the given model Map.
* <p>The default implementation builds a {@link SimpleHash}.
* @param model the model to use for rendering
* @param exchange current exchange
* @return the FreeMarker template model, as a {@link SimpleHash} or subclass thereof
*/
protected SimpleHash getTemplateModel(Map<String, Object> model, ServerWebExchange exchange) {
SimpleHash fmModel = new SimpleHash(getObjectWrapper());
fmModel.putAll(model);
return fmModel;
}
/**
* 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();
Version version = Configuration.DEFAULT_INCOMPATIBLE_IMPROVEMENTS;
return (ow != null ? ow : new DefaultObjectWrapperBuilder(version).build());
}
/**
* 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
*/
protected Template getTemplate(Locale locale) throws IOException {
return (getEncoding() != null ?
getConfiguration().getTemplate(getUrl(), locale, getEncoding()) :
getConfiguration().getTemplate(getUrl(), locale));
}
}