001/*
002 * Copyright 2012-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.boot.web.reactive.result.view;
018
019import java.io.IOException;
020import java.io.InputStreamReader;
021import java.io.OutputStreamWriter;
022import java.io.Reader;
023import java.io.Writer;
024import java.nio.charset.Charset;
025import java.util.Locale;
026import java.util.Map;
027import java.util.Optional;
028
029import com.samskivert.mustache.Mustache.Compiler;
030import com.samskivert.mustache.Template;
031import reactor.core.publisher.Flux;
032import reactor.core.publisher.Mono;
033
034import org.springframework.core.io.Resource;
035import org.springframework.core.io.buffer.DataBuffer;
036import org.springframework.core.io.buffer.DataBufferUtils;
037import org.springframework.http.MediaType;
038import org.springframework.web.reactive.result.view.AbstractUrlBasedView;
039import org.springframework.web.reactive.result.view.View;
040import org.springframework.web.server.ServerWebExchange;
041
042/**
043 * Spring WebFlux {@link View} using the Mustache template engine.
044 *
045 * @author Brian Clozel
046 * @since 2.0.0
047 */
048public class MustacheView extends AbstractUrlBasedView {
049
050        private Compiler compiler;
051
052        private String charset;
053
054        /**
055         * Set the JMustache compiler to be used by this view. Typically this property is not
056         * set directly. Instead a single {@link Compiler} is expected in the Spring
057         * application context which is used to compile Mustache templates.
058         * @param compiler the Mustache compiler
059         */
060        public void setCompiler(Compiler compiler) {
061                this.compiler = compiler;
062        }
063
064        /**
065         * Set the charset used for reading Mustache template files.
066         * @param charset the charset to use for reading template files
067         */
068        public void setCharset(String charset) {
069                this.charset = charset;
070        }
071
072        @Override
073        public boolean checkResourceExists(Locale locale) throws Exception {
074                return resolveResource() != null;
075        }
076
077        @Override
078        protected Mono<Void> renderInternal(Map<String, Object> model, MediaType contentType,
079                        ServerWebExchange exchange) {
080                Resource resource = resolveResource();
081                if (resource == null) {
082                        return Mono.error(new IllegalStateException(
083                                        "Could not find Mustache template with URL [" + getUrl() + "]"));
084                }
085                DataBuffer dataBuffer = exchange.getResponse().bufferFactory().allocateBuffer();
086                try (Reader reader = getReader(resource)) {
087                        Template template = this.compiler.compile(reader);
088                        Charset charset = getCharset(contentType).orElse(getDefaultCharset());
089                        try (Writer writer = new OutputStreamWriter(dataBuffer.asOutputStream(),
090                                        charset)) {
091                                template.execute(model, writer);
092                                writer.flush();
093                        }
094                }
095                catch (Exception ex) {
096                        DataBufferUtils.release(dataBuffer);
097                        return Mono.error(ex);
098                }
099                return exchange.getResponse().writeWith(Flux.just(dataBuffer));
100        }
101
102        private Resource resolveResource() {
103                Resource resource = getApplicationContext().getResource(getUrl());
104                if (resource == null || !resource.exists()) {
105                        return null;
106                }
107                return resource;
108        }
109
110        private Reader getReader(Resource resource) throws IOException {
111                if (this.charset != null) {
112                        return new InputStreamReader(resource.getInputStream(), this.charset);
113                }
114                return new InputStreamReader(resource.getInputStream());
115        }
116
117        private Optional<Charset> getCharset(MediaType mediaType) {
118                return Optional.ofNullable((mediaType != null) ? mediaType.getCharset() : null);
119        }
120
121}