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Modern server-side Java template engine for both web and standalone environments
/*
* =============================================================================
*
* Copyright (c) 2011-2016, The THYMELEAF team (http://www.thymeleaf.org)
*
* 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.thymeleaf.spring5.view.reactive;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import org.reactivestreams.Publisher;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.core.ReactiveAdapterRegistry;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferFactory;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.web.reactive.HandlerMapping;
import org.springframework.web.reactive.result.view.AbstractView;
import org.springframework.web.reactive.result.view.RequestContext;
import org.springframework.web.server.ServerWebExchange;
import org.thymeleaf.IEngineConfiguration;
import org.thymeleaf.context.IContext;
import org.thymeleaf.exceptions.TemplateProcessingException;
import org.thymeleaf.spring5.ISpringWebFluxTemplateEngine;
import org.thymeleaf.spring5.context.webflux.IReactiveDataDriverContextVariable;
import org.thymeleaf.spring5.context.webflux.ReactiveDataDriverContextVariable;
import org.thymeleaf.spring5.context.webflux.ReactiveLazyContextVariable;
import org.thymeleaf.spring5.context.webflux.SpringWebFluxExpressionContext;
import org.thymeleaf.spring5.context.webflux.SpringWebFluxThymeleafRequestContext;
import org.thymeleaf.spring5.expression.ThymeleafEvaluationContext;
import org.thymeleaf.spring5.naming.SpringContextVariableNames;
import org.thymeleaf.standard.expression.FragmentExpression;
import org.thymeleaf.standard.expression.IStandardExpressionParser;
import org.thymeleaf.standard.expression.StandardExpressionExecutionContext;
import org.thymeleaf.standard.expression.StandardExpressions;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
/**
*
* Base implementation of the Spring WebFlux {@link org.springframework.web.reactive.result.view.View}
* interface.
*
*
* Views represent a template being executed, after being resolved (and
* instantiated) by a {@link org.springframework.web.reactive.result.view.ViewResolver}.
*
*
* This is the default view implementation resolved by {@link ThymeleafReactiveViewResolver}.
*
*
* This view needs a {@link ISpringWebFluxTemplateEngine} for execution, and it will call its
* {@link ISpringWebFluxTemplateEngine#processStream(String, Set, IContext, DataBufferFactory, MediaType, Charset, int)}
* method to create the reactive data streams to be used for processing the template. See the documentation
* of this class to know more about the different operation modes available.
*
*
* @see ThymeleafReactiveViewResolver
* @see ISpringWebFluxTemplateEngine
* @see ReactiveDataDriverContextVariable
* @see IReactiveDataDriverContextVariable
*
* @author Daniel Fernández
*
* @since 3.0.3
*
*/
public class ThymeleafReactiveView extends AbstractView implements BeanNameAware {
protected static final Logger logger = LoggerFactory.getLogger(ThymeleafReactiveView.class);
public static final int DEFAULT_RESPONSE_CHUNK_SIZE_BYTES = Integer.MAX_VALUE;
private static final String WEBFLUX_CONVERSION_SERVICE_NAME = "webFluxConversionService";
private String beanName = null;
private ISpringWebFluxTemplateEngine templateEngine = null;
private String templateName = null;
private Locale locale = null;
private Map staticVariables = null;
// These two flags are meant to determine if these fields have been specifically set a
// value for this View object, so that we know that the ViewResolver should not be
// overriding them with its own view-resolution-wide values.
private boolean defaultCharsetSet = false;
private boolean supportedMediaTypesSet = false;
private Set markupSelectors = null;
// This will determine whether we will be throttling or not, and if so the maximum size of the chunks that will be
// produced by the throttled engine each time the back-pressure mechanism asks for a new "unit" (a new DataBuffer)
//
// The value established here is nullable (and null by default) because it will work as an override of the
// value established at the ThymeleafReactiveViewResolver for the same purpose.
private Integer responseMaxChunkSizeBytes = null;
public ThymeleafReactiveView() {
super();
}
public String getMarkupSelector() {
return (this.markupSelectors == null || this.markupSelectors.size() == 0? null : this.markupSelectors.iterator().next());
}
public void setMarkupSelector(final String markupSelector) {
this.markupSelectors =
(markupSelector == null || markupSelector.trim().length() == 0? null : Collections.singleton(markupSelector.trim()));
}
// This flag is used from the ViewResolver in order to determine if it has to push its own
// configuration to the View (which it will do until the View has been specifically configured).
boolean isDefaultCharsetSet() {
return this.defaultCharsetSet;
}
// Implemented at AbstractView, but overridden here in order to set the flag
@Override
public void setDefaultCharset(final Charset defaultCharset) {
super.setDefaultCharset(defaultCharset);
this.defaultCharsetSet = true;
}
// This flag is used from the ViewResolver in order to determine if it has to push its own
// configuration to the View (which it will do until the View has been specifically configured).
boolean isSupportedMediaTypesSet() {
return this.supportedMediaTypesSet;
}
// Implemented at AbstractView, but overridden here in order to set the flag
@Override
public void setSupportedMediaTypes(final List supportedMediaTypes) {
super.setSupportedMediaTypes(supportedMediaTypes);
this.supportedMediaTypesSet = true;
}
public String getBeanName() {
return this.beanName;
}
public void setBeanName(final String beanName) {
this.beanName = beanName;
}
public String getTemplateName() {
return this.templateName;
}
public void setTemplateName(final String templateName) {
this.templateName = templateName;
}
protected Locale getLocale() {
return this.locale;
}
protected void setLocale(final Locale locale) {
this.locale = locale;
}
// Default is Integer.MAX_VALUE, which means no explicit limit (note there can still be a limit in
// the size of the chunks if execution is data driven, as output will be sent to the server after
// the processing of each data-driver buffer).
public int getResponseMaxChunkSizeBytes() {
return this.responseMaxChunkSizeBytes == null?
DEFAULT_RESPONSE_CHUNK_SIZE_BYTES : this.responseMaxChunkSizeBytes.intValue();
}
// We need this one at the ViewResolver to determine if a value has been set at all
Integer getNullableResponseMaxChunkSize() {
return this.responseMaxChunkSizeBytes;
}
public void setResponseMaxChunkSizeBytes(final int responseMaxBufferSizeBytes) {
this.responseMaxChunkSizeBytes = Integer.valueOf(responseMaxBufferSizeBytes);
}
protected ISpringWebFluxTemplateEngine getTemplateEngine() {
return this.templateEngine;
}
protected void setTemplateEngine(final ISpringWebFluxTemplateEngine templateEngine) {
this.templateEngine = templateEngine;
}
public Map getStaticVariables() {
if (this.staticVariables == null) {
return Collections.emptyMap();
}
return Collections.unmodifiableMap(this.staticVariables);
}
public void addStaticVariable(final String name, final Object value) {
if (this.staticVariables == null) {
this.staticVariables = new HashMap(3, 1.0f);
}
this.staticVariables.put(name, value);
}
public void setStaticVariables(final Map variables) {
if (variables != null) {
if (this.staticVariables == null) {
this.staticVariables = new HashMap(3, 1.0f);
}
this.staticVariables.putAll(variables);
}
}
@Override
protected Mono renderInternal(
final Map renderAttributes, final MediaType contentType, final ServerWebExchange exchange) {
return renderFragmentInternal(this.markupSelectors, renderAttributes, contentType, exchange);
}
protected Mono renderFragmentInternal(
final Set markupSelectorsToRender, final Map renderAttributes,
final MediaType contentType, final ServerWebExchange exchange) {
final String viewTemplateName = getTemplateName();
final ISpringWebFluxTemplateEngine viewTemplateEngine = getTemplateEngine();
if (viewTemplateName == null) {
return Mono.error(new IllegalArgumentException("Property 'templateName' is required"));
}
if (getLocale() == null) {
return Mono.error(new IllegalArgumentException("Property 'locale' is required"));
}
if (viewTemplateEngine == null) {
return Mono.error(new IllegalArgumentException("Property 'thymeleafTemplateEngine' is required"));
}
final ServerHttpResponse response = exchange.getResponse();
/*
* ----------------------------------------------------------------------------------------------------------
* GATHERING OF THE MERGED MODEL
* ----------------------------------------------------------------------------------------------------------
* - The merged model is the map that will be used for initialising the Thymelef IContext. This context will
* contain all the data accessible by the template during its execution.
* - The base of the merged model is the ModelMap created by the Controller, but there are some additional
* things
* ----------------------------------------------------------------------------------------------------------
*/
final Map mergedModel = new HashMap<>(30);
// First of all, set all the static variables into the mergedModel
final Map templateStaticVariables = getStaticVariables();
if (templateStaticVariables != null) {
mergedModel.putAll(templateStaticVariables);
}
// Add path variables to merged model (if there are any)
final Map pathVars =
(Map) exchange.getAttributes().get(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE);
if (pathVars != null) {
mergedModel.putAll(pathVars);
}
// Simply dump all the renderAttributes (model coming from the controller) into the merged model
if (renderAttributes != null) {
mergedModel.putAll(renderAttributes);
}
final ApplicationContext applicationContext = getApplicationContext();
// Initialize RequestContext (reactive version) and add it to the model as another attribute,
// so that it can be retrieved from elsewhere.
final RequestContext requestContext = new RequestContext(exchange, mergedModel, applicationContext);
final SpringWebFluxThymeleafRequestContext thymeleafRequestContext =
new SpringWebFluxThymeleafRequestContext(requestContext, exchange);
mergedModel.put(SpringContextVariableNames.SPRING_REQUEST_CONTEXT, requestContext);
// Add the Thymeleaf RequestContext wrapper that we will be using in this dialect (the bare RequestContext
// stays in the context to for compatibility with other dialects)
mergedModel.put(SpringContextVariableNames.THYMELEAF_REQUEST_CONTEXT, thymeleafRequestContext);
// Expose Thymeleaf's own evaluation context as a model variable
//
// Note Spring's EvaluationContexts are NOT THREAD-SAFE (in exchange for SpelExpressions being thread-safe).
// That's why we need to create a new EvaluationContext for each request / template execution, even if it is
// quite expensive to create because of requiring the initialization of several ConcurrentHashMaps.
final ConversionService conversionService =
applicationContext.containsBean(WEBFLUX_CONVERSION_SERVICE_NAME)?
(ConversionService)applicationContext.getBean(WEBFLUX_CONVERSION_SERVICE_NAME): null;
final ThymeleafEvaluationContext evaluationContext =
new ThymeleafEvaluationContext(applicationContext, conversionService);
mergedModel.put(ThymeleafEvaluationContext.THYMELEAF_EVALUATION_CONTEXT_CONTEXT_VARIABLE_NAME, evaluationContext);
// Initialize those model attributes that might be instances of ReactiveLazyContextVariable and therefore
// need to be set the ReactiveAdapterRegistry.
initializeApplicationAwareModel(applicationContext, mergedModel);
/*
* ----------------------------------------------------------------------------------------------------------
* INSTANTIATION OF THE CONTEXT
* ----------------------------------------------------------------------------------------------------------
* - Once the model has been merged, we can create the Thymeleaf context object itself.
* - The reason it is an ExpressionContext and not a Context is that before executing the template itself,
* we might need to use it for computing the markup selectors (if "template :: selector" was specified).
* - The reason it is not a WebExpressionContext is that this class is linked to the Servlet API, which
* might not be present in a Spring WebFlux environment.
* ----------------------------------------------------------------------------------------------------------
*/
final IEngineConfiguration configuration = viewTemplateEngine.getConfiguration();
final SpringWebFluxExpressionContext context =
new SpringWebFluxExpressionContext(configuration, exchange, getLocale(), mergedModel);
/*
* ----------------------------------------------------------------------------------------------------------
* COMPUTATION OF (OPTIONAL) MARKUP SELECTORS
* ----------------------------------------------------------------------------------------------------------
* - If view name has been specified with a template selector (in order to execute only a fragment of
* the template) like "template :: selector", we will extract it and compute it.
* ----------------------------------------------------------------------------------------------------------
*/
final String templateName;
final Set markupSelectors;
if (!viewTemplateName.contains("::")) {
// No fragment specified at the template name
templateName = viewTemplateName;
markupSelectors = null;
} else {
// Template name contains a fragment name, so we should parse it as such
final IStandardExpressionParser parser = StandardExpressions.getExpressionParser(configuration);
final FragmentExpression fragmentExpression;
try {
// By parsing it as a standard expression, we might profit from the expression cache
fragmentExpression = (FragmentExpression) parser.parseExpression(context, "~{" + viewTemplateName + "}");
} catch (final TemplateProcessingException e) {
return Mono.error(
new IllegalArgumentException("Invalid template name specification: '" + viewTemplateName + "'"));
}
final FragmentExpression.ExecutedFragmentExpression fragment =
FragmentExpression.createExecutedFragmentExpression(context, fragmentExpression, StandardExpressionExecutionContext.NORMAL);
templateName = FragmentExpression.resolveTemplateName(fragment);
markupSelectors = FragmentExpression.resolveFragments(fragment);
final Map nameFragmentParameters = fragment.getFragmentParameters();
if (nameFragmentParameters != null) {
if (fragment.hasSyntheticParameters()) {
// We cannot allow synthetic parameters because there is no way to specify them at the template
// engine execution!
return Mono.error(new IllegalArgumentException(
"Parameters in a view specification must be named (non-synthetic): '" + viewTemplateName + "'"));
}
context.setVariables(nameFragmentParameters);
}
}
final Set processMarkupSelectors;
if (markupSelectors != null && markupSelectors.size() > 0) {
if (markupSelectorsToRender != null && markupSelectorsToRender.size() > 0) {
return Mono.error(new IllegalArgumentException(
"A markup selector has been specified (" + Arrays.asList(markupSelectors) + ") for a view " +
"that was already being executed as a fragment (" + Arrays.asList(markupSelectorsToRender) + "). " +
"Only one fragment selection is allowed."));
}
processMarkupSelectors = markupSelectors;
} else {
if (markupSelectorsToRender != null && markupSelectorsToRender.size() > 0) {
processMarkupSelectors = markupSelectorsToRender;
} else {
processMarkupSelectors = null;
}
}
/*
* ----------------------------------------------------------------------------------------------------------
* COMPUTATION OF TEMPLATE PROCESSING PARAMETERS AND HTTP HEADERS
* ----------------------------------------------------------------------------------------------------------
* - At this point we will compute the final values of the different parameters needed for processing the
* template (locale, encoding, buffer sizes, etc.)
* ----------------------------------------------------------------------------------------------------------
*/
final int templateResponseMaxChunkSizeBytes = getResponseMaxChunkSizeBytes();
final HttpHeaders responseHeaders = exchange.getResponse().getHeaders();
final Locale templateLocale = getLocale();
if (templateLocale != null) {
responseHeaders.setContentLanguage(templateLocale);
}
// Get the charset from the selected content type (or use default)
final Charset charset = getCharset(contentType).orElse(getDefaultCharset());
/*
* ----------------------------------------------------------------------------------------------------------
* SET (AND RETURN) THE TEMPLATE PROCESSING Flux OBJECTS
* ----------------------------------------------------------------------------------------------------------
* - There are three possible processing mode, for each of which a Publisher will be created in a
* different way:
*
* 1. FULL: Output buffers not limited (templateResponseMaxChunkSizeBytes == Integer.MAX_VALUE) and
* no data-driven execution (no context variable of type Publisher driving the template engine
* execution): In this case Thymeleaf will be executed unthrottled, in full mode, writing output
* to a single DataBuffer instanced before execution, and which will be passed to the output channels
* in a single onNext(buffer) call (immediately followed by onComplete()).
*
* 2. CHUNKED: Output buffers limited in size (responseMaxChunkSizeBytes) but no data-driven
* execution (no Publisher driving engine execution). All model attributes are expected to be fully
* resolved before engine execution (except those implementing Thymeleaf's ILazyContextVariable
* interface, including its reactive implementation ReactiveLazyContextVariable) and the Thymeleaf
* engine will execute in throttled mode, performing a full-stop each time the buffer reaches the
* specified size, sending it to the output channels with onNext(buffer) and then waiting until
* these output channels make the engine resume its work with a new request(n) call. This
* execution mode will request an output flush from the server after producing each buffer.
*
* 3. DATA-DRIVEN: one of the model attributes is a Publisher wrapped inside an implementation
* of the IReactiveDataDriverContextVariable interface. In this case, the Thymeleaf engine will
* execute as a response to onNext(List) events triggered by this Publisher. The
* "bufferSizeElements" specified at the model attribute will define the amount of elements
* produced by this Publisher that will be buffered into a List before triggering the template
* engine each time (which is why Thymeleaf will react on onNext(List) and not onNext(X)). Thymeleaf
* will expect to find a "th:each" iteration on the data-driven variable inside the processed template,
* and will be executed in throttled mode for the published elements, sending the resulting DataBuffer
* (or DataBuffers) to the output channels via onNext(buffer) and stopping until a new onNext(List)
* event is triggered. When execution is data-driven, a limit in size can be optionally specified for
* the output buffers (responseMaxChunkSizeBytes) which will make Thymeleaf never send
* to the output channels a buffer bigger than that (thus splitting the output generated for a List
* of published elements into several buffers if required) and also will make Thymeleaf request
* an output flush from the server after producing each buffer.
* ----------------------------------------------------------------------------------------------------------
*/
final Publisher stream =
viewTemplateEngine.processStream(
templateName, processMarkupSelectors, context, response.bufferFactory(), contentType, charset,
templateResponseMaxChunkSizeBytes); // FULL/DATADRIVEN if MAX_VALUE, CHUNKED/DATADRIVEN if other
if (templateResponseMaxChunkSizeBytes == Integer.MAX_VALUE) {
// No size limit for output chunks has been set, so we will let the
// server apply its standard behaviour ("writeWith").
return response.writeWith(stream);
}
// A limit for output chunks has been set, so we will use "writeAndFlushWith" in order to make
// sure that output is flushed after each buffer.
return response.writeAndFlushWith(Flux.from(stream).window(1));
}
private static Optional getCharset(final MediaType mediaType) {
return mediaType != null ? Optional.ofNullable(mediaType.getCharset()) : Optional.empty();
}
private static void initializeApplicationAwareModel(
final ApplicationContext applicationContext, final Map model) {
final ReactiveAdapterRegistry reactiveAdapterRegistry;
try {
reactiveAdapterRegistry = applicationContext.getBean(ReactiveAdapterRegistry.class);
} catch (final NoSuchBeanDefinitionException ignored) {
// No registry, but note that we can live without it (though limited to Flux and Mono)
return;
}
for (final Object value : model.values()) {
if (value instanceof ReactiveLazyContextVariable) {
((ReactiveLazyContextVariable)value).setReactiveAdapterRegistry(reactiveAdapterRegistry);
} else if (value instanceof ReactiveDataDriverContextVariable) {
((ReactiveDataDriverContextVariable)value).setReactiveAdapterRegistry(reactiveAdapterRegistry);
}
}
}
}
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