Add Mustache support for Spring WebFlux apps

This commit moves the existing Spring MVC Mustache support to its own
`servlet` package and adds a new one under `reactive` for the WebFlux
web applications.

New `MustacheView` and `MustacheViewResolver` types resolve and render
Mustache views for WebFlux applications.

Since this templating engine is now supported by two flavors of Spring
web apps, the `spring-boot-starter-mustache` does not depend anymore on
the `spring-boot-starter-web` one: it's up to the developer to add the
relevant starter `web` or `webflux` to their application.

Fixes spring-projectsgh-8648

Author: bclozel

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mobile/DeviceDelegatingViewResolverAutoConfiguration.java

@@ -28,7 +28,7 @@
 import org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration;
 import org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration;
 import org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration;
-import org.springframework.boot.autoconfigure.mustache.web.MustacheViewResolver;
+import org.springframework.boot.autoconfigure.mustache.servlet.MustacheViewResolver;
 import org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/MustacheAutoConfiguration.java

@@ -30,7 +30,7 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
-import org.springframework.boot.autoconfigure.mustache.web.MustacheViewResolver;
+import org.springframework.boot.autoconfigure.mustache.servlet.MustacheViewResolver;
 import org.springframework.boot.autoconfigure.template.TemplateLocation;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.ApplicationContext;
@@ -43,6 +43,7 @@
  * {@link EnableAutoConfiguration Auto-configuration} for Mustache.
  *
  * @author Dave Syer
+ * @author Brian Clozel
  * @since 1.2.2
  */
 @Configuration
@@ -123,4 +124,34 @@ public MustacheViewResolver mustacheViewResolver(Compiler mustacheCompiler) {
 
 	}
 
+	@Configuration
+	@ConditionalOnWebApplication(type = Type.REACTIVE)
+	protected static class MustacheReactiveWebConfiguration {
+
+		private final MustacheProperties mustache;
+
+		protected MustacheReactiveWebConfiguration(MustacheProperties mustache) {
+			this.mustache = mustache;
+		}
+
+		@Bean
+		@ConditionalOnMissingBean(org.springframework.boot.autoconfigure
+				.mustache.reactive.MustacheViewResolver.class)
+		public org.springframework.boot.autoconfigure
+				.mustache.reactive.MustacheViewResolver mustacheViewResolver(Compiler mustacheCompiler) {
+			org.springframework.boot.autoconfigure
+					.mustache.reactive.MustacheViewResolver resolver
+					= new org.springframework.boot.autoconfigure
+					.mustache.reactive.MustacheViewResolver(mustacheCompiler);
+			resolver.setPrefix(this.mustache.getPrefix());
+			resolver.setSuffix(this.mustache.getSuffix());
+			resolver.setViewNames(this.mustache.getViewNames());
+			resolver.setRequestContextAttribute(this.mustache.getRequestContextAttribute());
+			resolver.setCharset(this.mustache.getCharsetName());
+			resolver.setOrder(Ordered.LOWEST_PRECEDENCE - 10);
+			return resolver;
+		}
+
+	}
+
 }

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/reactive/MustacheView.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2012-2017 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.boot.autoconfigure.mustache.reactive;
+
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.io.Reader;
+import java.io.Writer;
+import java.nio.charset.Charset;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Optional;
+
+import com.samskivert.mustache.Mustache;
+import com.samskivert.mustache.Template;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.http.MediaType;
+import org.springframework.web.reactive.result.view.AbstractUrlBasedView;
+import org.springframework.web.reactive.result.view.View;
+import org.springframework.web.server.ServerWebExchange;
+
+/**
+ * Spring WebFlux {@link View} using the Mustache template engine.
+ *
+ * @author Brian Clozel
+ * @since 2.0.0
+ */
+public class MustacheView extends AbstractUrlBasedView {
+
+	private Mustache.Compiler compiler;
+
+	private String charset;
+
+	/**
+	 * Set the JMustache compiler to be used by this view.
+	 * <p>Typically this property is not set directly. Instead a single
+	 * {@link Mustache.Compiler} is expected in the Spring application context
+	 * which is used to compile Mustache templates.
+	 * @param compiler the Mustache compiler
+	 */
+	public void setCompiler(Mustache.Compiler compiler) {
+		this.compiler = compiler;
+	}
+
+	/**
+	 * Set the charset used for reading Mustache template files.
+	 * @param charset the charset to use for reading template files
+	 */
+	public void setCharset(String charset) {
+		this.charset = charset;
+	}
+
+	@Override
+	public boolean checkResourceExists(Locale locale) throws Exception {
+		return resolveResource() != null;
+	}
+
+	private Resource resolveResource() {
+		Resource resource = getApplicationContext().getResource(getUrl());
+		if (resource == null || !resource.exists()) {
+			return null;
+		}
+		return resource;
+	}
+
+	@Override
+	protected Mono<Void> renderInternal(Map<String, Object> model,
+			MediaType contentType, ServerWebExchange exchange) {
+		Resource resource = resolveResource();
+		if (resource == null) {
+			return Mono.error(new IllegalStateException("Could not find Mustache template with URL ["
+					+ getUrl() + "]"));
+		}
+		DataBuffer dataBuffer = exchange.getResponse().bufferFactory().allocateBuffer();
+		try (Reader reader = getReader(resource)) {
+			Template template = this.compiler.compile(reader);
+			Charset charset = getCharset(contentType).orElse(getDefaultCharset());
+			try (Writer writer = new OutputStreamWriter(dataBuffer.asOutputStream(), charset)) {
+				template.execute(model, writer);
+				writer.flush();
+			}
+		}
+		catch (Throwable exc) {
+			return Mono.error(exc);
+		}
+		return exchange.getResponse().writeWith(Flux.just(dataBuffer));
+	}
+
+	private Reader getReader(Resource resource) throws IOException {
+		if (this.charset != null) {
+			return new InputStreamReader(resource.getInputStream(), this.charset);
+		}
+		return new InputStreamReader(resource.getInputStream());
+	}
+
+	private Optional<Charset> getCharset(MediaType mediaType) {
+		return (mediaType != null ? Optional.ofNullable(mediaType.getCharset()) : Optional.empty());
+	}
+}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/reactive/MustacheViewResolver.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2012-2017 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.boot.autoconfigure.mustache.reactive;
+
+import com.samskivert.mustache.Mustache;
+
+import org.springframework.web.reactive.result.view.AbstractUrlBasedView;
+import org.springframework.web.reactive.result.view.UrlBasedViewResolver;
+import org.springframework.web.reactive.result.view.ViewResolver;
+
+/**
+ * Spring WebFlux {@link ViewResolver} for Mustache.
+ *
+ * @author Brian Clozel
+ * @since 2.0.0
+ */
+public class MustacheViewResolver extends UrlBasedViewResolver {
+
+	private final Mustache.Compiler compiler;
+
+	private String charset;
+
+	/**
+	 * Create a {@code MustacheViewResolver} backed by a default
+	 * instance of a {@link Mustache.Compiler}.
+	 */
+	public MustacheViewResolver() {
+		this.compiler = Mustache.compiler();
+		setViewClass(requiredViewClass());
+	}
+
+	/**
+	 * Create a {@code MustacheViewResolver} backed by a custom
+	 * instance of a {@link Mustache.Compiler}.
+	 * @param compiler the Mustache compiler used to compile templates
+	 */
+	public MustacheViewResolver(Mustache.Compiler compiler) {
+		this.compiler = compiler;
+		setViewClass(requiredViewClass());
+	}
+
+	/**
+	 * Set the charset.
+	 * @param charset the charset
+	 */
+	public void setCharset(String charset) {
+		this.charset = charset;
+	}
+
+	@Override
+	protected Class<?> requiredViewClass() {
+		return MustacheView.class;
+	}
+
+	@Override
+	protected AbstractUrlBasedView createUrlBasedView(String viewName) {
+		MustacheView view = (MustacheView) super.createUrlBasedView(viewName);
+		view.setCompiler(this.compiler);
+		view.setCharset(this.charset);
+		return view;
+	}
+
+}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/reactive/package-info.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2012-2017 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.
+ */
+
+/**
+ * Auto-configuration for Mustache with Spring WebFlux.
+ */
+package org.springframework.boot.autoconfigure.mustache.reactive;

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/web/MustacheView.java renamed to spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/servlet/MustacheView.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.boot.autoconfigure.mustache.web;
+package org.springframework.boot.autoconfigure.mustache.servlet;
 
 import java.util.Map;
 

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/web/MustacheViewResolver.java renamed to spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/servlet/MustacheViewResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.boot.autoconfigure.mustache.web;
+package org.springframework.boot.autoconfigure.mustache.servlet;
 
 import java.io.IOException;
 import java.io.InputStreamReader;

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/web/package-info.java renamed to spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/servlet/package-info.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -17,4 +17,4 @@
 /**
  * Auto-configuration for Mustache with Spring MVC.
  */
-package org.springframework.boot.autoconfigure.mustache.web;
+package org.springframework.boot.autoconfigure.mustache.servlet;

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mobile/DeviceDelegatingViewResolverAutoConfigurationTests.java

@@ -34,7 +34,7 @@
 import org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration;
 import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
 import org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration;
-import org.springframework.boot.autoconfigure.mustache.web.MustacheViewResolver;
+import org.springframework.boot.autoconfigure.mustache.servlet.MustacheViewResolver;
 import org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration;
 import org.springframework.boot.test.util.EnvironmentTestUtils;