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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.logging.log4j.core.config.plugins.processor;
19  
20  import java.io.IOException;
21  import java.io.OutputStream;
22  import java.util.ArrayList;
23  import java.util.Collection;
24  import java.util.Collections;
25  import java.util.Set;
26  import java.util.concurrent.ConcurrentMap;
27  
28  import javax.annotation.processing.AbstractProcessor;
29  import javax.annotation.processing.RoundEnvironment;
30  import javax.annotation.processing.SupportedAnnotationTypes;
31  import javax.annotation.processing.SupportedSourceVersion;
32  import javax.lang.model.SourceVersion;
33  import javax.lang.model.element.Element;
34  import javax.lang.model.element.ElementVisitor;
35  import javax.lang.model.element.TypeElement;
36  import javax.lang.model.util.Elements;
37  import javax.lang.model.util.SimpleElementVisitor6;
38  import javax.tools.Diagnostic.Kind;
39  import javax.tools.FileObject;
40  import javax.tools.StandardLocation;
41  
42  import org.apache.logging.log4j.core.config.plugins.Plugin;
43  import org.apache.logging.log4j.core.config.plugins.PluginAliases;
44  import org.apache.logging.log4j.util.Strings;
45  
46  /**
47   * Annotation processor for pre-scanning Log4j 2 plugins.
48   */
49  @SupportedAnnotationTypes("org.apache.logging.log4j.core.config.plugins.*")
50  @SupportedSourceVersion(SourceVersion.RELEASE_6)
51  public class PluginProcessor extends AbstractProcessor {
52  
53      // TODO: this could be made more abstract to allow for compile-time and run-time plugin processing
54  
55      /**
56       * The location of the plugin cache data file. This file is written to by this processor, and read from by
57       * {@link org.apache.logging.log4j.core.config.plugins.util.PluginManager}.
58       */
59      public static final String PLUGIN_CACHE_FILE = "META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat";
60  
61      private final PluginCache pluginCache = new PluginCache();
62  
63      @Override
64      public boolean process(final Set<? extends TypeElement> annotations, final RoundEnvironment roundEnv) {
65          try {
66              final Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(Plugin.class);
67              if (elements.isEmpty()) {
68                  return false;
69              }
70              collectPlugins(elements);
71              writeCacheFile(elements.toArray(new Element[elements.size()]));
72              return true;
73          } catch (final IOException e) {
74              error(e.getMessage());
75              return false;
76          }
77      }
78  
79      private void error(final CharSequence message) {
80          processingEnv.getMessager().printMessage(Kind.ERROR, message);
81      }
82  
83      private void collectPlugins(final Iterable<? extends Element> elements) {
84          final Elements elementUtils = processingEnv.getElementUtils();
85          final ElementVisitor<PluginEntry, Plugin> pluginVisitor =
86                  new PluginElementVisitor(elementUtils);
87          final ElementVisitor<Collection<PluginEntry>, Plugin> pluginAliasesVisitor =
88                  new PluginAliasesElementVisitor(elementUtils);
89          for (final Element element : elements) {
90              final Plugin plugin = element.getAnnotation(Plugin.class);
91              final PluginEntry entry = element.accept(pluginVisitor, plugin);
92              final ConcurrentMap<String, PluginEntry> category = pluginCache.getCategory(entry.getCategory());
93              category.put(entry.getKey(), entry);
94              final Collection<PluginEntry> entries = element.accept(pluginAliasesVisitor, plugin);
95              for (final PluginEntry pluginEntry : entries) {
96                  category.put(pluginEntry.getKey(), pluginEntry);
97              }
98          }
99      }
100 
101     private void writeCacheFile(final Element... elements) throws IOException {
102         final FileObject fo = processingEnv.getFiler().createResource(StandardLocation.CLASS_OUTPUT,
103             Strings.EMPTY, PLUGIN_CACHE_FILE, elements);
104         final OutputStream out = fo.openOutputStream();
105         try {
106             pluginCache.writeCache(out);
107         } finally {
108             out.close();
109         }
110     }
111 
112     /**
113      * ElementVisitor to scan the Plugin annotation.
114      */
115     private static class PluginElementVisitor extends SimpleElementVisitor6<PluginEntry, Plugin> {
116 
117         private final Elements elements;
118 
119         private PluginElementVisitor(final Elements elements) {
120             this.elements = elements;
121         }
122 
123         @Override
124         public PluginEntry visitType(final TypeElement e, final Plugin plugin) {
125             if (plugin == null) {
126                 throw new NullPointerException("Plugin annotation is null.");
127             }
128             final PluginEntry entry = new PluginEntry();
129             entry.setKey(plugin.name().toLowerCase());
130             entry.setClassName(elements.getBinaryName(e).toString());
131             entry.setName(Plugin.EMPTY.equals(plugin.elementType()) ? plugin.name() : plugin.elementType());
132             entry.setPrintable(plugin.printObject());
133             entry.setDefer(plugin.deferChildren());
134             entry.setCategory(plugin.category());
135             return entry;
136         }
137     }
138 
139     /**
140      * ElementVisitor to scan the PluginAliases annotation.
141      */
142     private static class PluginAliasesElementVisitor extends SimpleElementVisitor6<Collection<PluginEntry>, Plugin> {
143 
144         private final Elements elements;
145 
146         private PluginAliasesElementVisitor(final Elements elements) {
147             super(Collections.<PluginEntry>emptyList());
148             this.elements = elements;
149         }
150 
151         @Override
152         public Collection<PluginEntry> visitType(final TypeElement e, final Plugin plugin) {
153             final PluginAliases aliases = e.getAnnotation(PluginAliases.class);
154             if (aliases == null) {
155                 return DEFAULT_VALUE;
156             }
157             final Collection<PluginEntry> entries = new ArrayList<PluginEntry>(aliases.value().length);
158             for (final String alias : aliases.value()) {
159                 final PluginEntry entry = new PluginEntry();
160                 entry.setKey(alias.toLowerCase());
161                 entry.setClassName(elements.getBinaryName(e).toString());
162                 entry.setName(Plugin.EMPTY.equals(plugin.elementType()) ? alias : plugin.elementType());
163                 entry.setPrintable(plugin.printObject());
164                 entry.setDefer(plugin.deferChildren());
165                 entry.setCategory(plugin.category());
166                 entries.add(entry);
167             }
168             return entries;
169         }
170     }
171 }