001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements. See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License. You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    
018    package org.apache.logging.log4j.core.config.plugins.processor;
019    
020    import java.io.IOException;
021    import java.io.OutputStream;
022    import java.util.ArrayList;
023    import java.util.Collection;
024    import java.util.Collections;
025    import java.util.Set;
026    import java.util.concurrent.ConcurrentMap;
027    
028    import javax.annotation.processing.AbstractProcessor;
029    import javax.annotation.processing.RoundEnvironment;
030    import javax.annotation.processing.SupportedAnnotationTypes;
031    import javax.lang.model.SourceVersion;
032    import javax.lang.model.element.Element;
033    import javax.lang.model.element.ElementVisitor;
034    import javax.lang.model.element.TypeElement;
035    import javax.lang.model.util.Elements;
036    import javax.lang.model.util.SimpleElementVisitor6;
037    import javax.tools.Diagnostic.Kind;
038    import javax.tools.FileObject;
039    import javax.tools.StandardLocation;
040    
041    import org.apache.logging.log4j.core.config.plugins.Plugin;
042    import org.apache.logging.log4j.core.config.plugins.PluginAliases;
043    import org.apache.logging.log4j.util.Strings;
044    
045    /**
046     * Annotation processor for pre-scanning Log4j 2 plugins.
047     */
048    @SupportedAnnotationTypes("org.apache.logging.log4j.core.config.plugins.*")
049    public class PluginProcessor extends AbstractProcessor {
050    
051        // TODO: this could be made more abstract to allow for compile-time and run-time plugin processing
052    
053        /**
054         * The location of the plugin cache data file. This file is written to by this processor, and read from by
055         * {@link org.apache.logging.log4j.core.config.plugins.util.PluginManager}.
056         */
057        public static final String PLUGIN_CACHE_FILE = "META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat";
058    
059        private final PluginCache pluginCache = new PluginCache();
060    
061        @Override
062        public SourceVersion getSupportedSourceVersion() {
063            return SourceVersion.latest();
064        }
065    
066        @Override
067        public boolean process(final Set<? extends TypeElement> annotations, final RoundEnvironment roundEnv) {
068            try {
069                final Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(Plugin.class);
070                if (elements.isEmpty()) {
071                    return false;
072                }
073                collectPlugins(elements);
074                writeCacheFile(elements.toArray(new Element[elements.size()]));
075                return true;
076            } catch (final IOException e) {
077                error(e.getMessage());
078                return false;
079            }
080        }
081    
082        private void error(final CharSequence message) {
083            processingEnv.getMessager().printMessage(Kind.ERROR, message);
084        }
085    
086        private void collectPlugins(final Iterable<? extends Element> elements) {
087            final Elements elementUtils = processingEnv.getElementUtils();
088            final ElementVisitor<PluginEntry, Plugin> pluginVisitor =
089                    new PluginElementVisitor(elementUtils);
090            final ElementVisitor<Collection<PluginEntry>, Plugin> pluginAliasesVisitor =
091                    new PluginAliasesElementVisitor(elementUtils);
092            for (final Element element : elements) {
093                final Plugin plugin = element.getAnnotation(Plugin.class);
094                final PluginEntry entry = element.accept(pluginVisitor, plugin);
095                final ConcurrentMap<String, PluginEntry> category = pluginCache.getCategory(entry.getCategory());
096                category.put(entry.getKey(), entry);
097                final Collection<PluginEntry> entries = element.accept(pluginAliasesVisitor, plugin);
098                for (final PluginEntry pluginEntry : entries) {
099                    category.put(pluginEntry.getKey(), pluginEntry);
100                }
101            }
102        }
103    
104        private void writeCacheFile(final Element... elements) throws IOException {
105            final FileObject fo = processingEnv.getFiler().createResource(StandardLocation.CLASS_OUTPUT,
106                Strings.EMPTY, PLUGIN_CACHE_FILE, elements);
107            final OutputStream out = fo.openOutputStream();
108            try {
109                pluginCache.writeCache(out);
110            } finally {
111                out.close();
112            }
113        }
114    
115        /**
116         * ElementVisitor to scan the Plugin annotation.
117         */
118        private static class PluginElementVisitor extends SimpleElementVisitor6<PluginEntry, Plugin> {
119    
120            private final Elements elements;
121    
122            private PluginElementVisitor(final Elements elements) {
123                this.elements = elements;
124            }
125    
126            @Override
127            public PluginEntry visitType(final TypeElement e, final Plugin plugin) {
128                if (plugin == null) {
129                    throw new NullPointerException("Plugin annotation is null.");
130                }
131                final PluginEntry entry = new PluginEntry();
132                entry.setKey(plugin.name().toLowerCase());
133                entry.setClassName(elements.getBinaryName(e).toString());
134                entry.setName(Plugin.EMPTY.equals(plugin.elementType()) ? plugin.name() : plugin.elementType());
135                entry.setPrintable(plugin.printObject());
136                entry.setDefer(plugin.deferChildren());
137                entry.setCategory(plugin.category());
138                return entry;
139            }
140        }
141    
142        /**
143         * ElementVisitor to scan the PluginAliases annotation.
144         */
145        private static class PluginAliasesElementVisitor extends SimpleElementVisitor6<Collection<PluginEntry>, Plugin> {
146    
147            private final Elements elements;
148    
149            private PluginAliasesElementVisitor(final Elements elements) {
150                super(Collections.<PluginEntry>emptyList());
151                this.elements = elements;
152            }
153    
154            @Override
155            public Collection<PluginEntry> visitType(final TypeElement e, final Plugin plugin) {
156                final PluginAliases aliases = e.getAnnotation(PluginAliases.class);
157                if (aliases == null) {
158                    return DEFAULT_VALUE;
159                }
160                final Collection<PluginEntry> entries = new ArrayList<PluginEntry>(aliases.value().length);
161                for (final String alias : aliases.value()) {
162                    final PluginEntry entry = new PluginEntry();
163                    entry.setKey(alias.toLowerCase());
164                    entry.setClassName(elements.getBinaryName(e).toString());
165                    entry.setName(Plugin.EMPTY.equals(plugin.elementType()) ? alias : plugin.elementType());
166                    entry.setPrintable(plugin.printObject());
167                    entry.setDefer(plugin.deferChildren());
168                    entry.setCategory(plugin.category());
169                    entries.add(entry);
170                }
171                return entries;
172            }
173        }
174    }