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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.Map;
26  import java.util.Objects;
27  import java.util.Set;
28  
29  import javax.annotation.processing.AbstractProcessor;
30  import javax.annotation.processing.RoundEnvironment;
31  import javax.annotation.processing.SupportedAnnotationTypes;
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  public class PluginProcessor extends AbstractProcessor {
51  
52      // TODO: this could be made more abstract to allow for compile-time and run-time plugin processing
53  
54      /**
55       * The location of the plugin cache data file. This file is written to by this processor, and read from by
56       * {@link org.apache.logging.log4j.core.config.plugins.util.PluginManager}.
57       */
58      public static final String PLUGIN_CACHE_FILE =
59              "META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat";
60  
61      private final PluginCache pluginCache = new PluginCache();
62  
63      @Override
64      public SourceVersion getSupportedSourceVersion() {
65          return SourceVersion.latest();
66      }
67  
68      @Override
69      public boolean process(final Set<? extends TypeElement> annotations, final RoundEnvironment roundEnv) {
70          try {
71              final Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(Plugin.class);
72              if (elements.isEmpty()) {
73                  return false;
74              }
75              collectPlugins(elements);
76              writeCacheFile(elements.toArray(new Element[elements.size()]));
77              return true;
78          } catch (final IOException e) {
79              error(e.getMessage());
80              return false;
81          }
82      }
83  
84      private void error(final CharSequence message) {
85          processingEnv.getMessager().printMessage(Kind.ERROR, message);
86      }
87  
88      private void collectPlugins(final Iterable<? extends Element> elements) {
89          final Elements elementUtils = processingEnv.getElementUtils();
90          final ElementVisitor<PluginEntry, Plugin> pluginVisitor = new PluginElementVisitor(elementUtils);
91          final ElementVisitor<Collection<PluginEntry>, Plugin> pluginAliasesVisitor = new PluginAliasesElementVisitor(
92                  elementUtils);
93          for (final Element element : elements) {
94              final Plugin plugin = element.getAnnotation(Plugin.class);
95              final PluginEntry entry = element.accept(pluginVisitor, plugin);
96              final Map<String, PluginEntry> category = pluginCache.getCategory(entry.getCategory());
97              category.put(entry.getKey(), entry);
98              final Collection<PluginEntry> entries = element.accept(pluginAliasesVisitor, plugin);
99              for (final PluginEntry pluginEntry : entries) {
100                 category.put(pluginEntry.getKey(), pluginEntry);
101             }
102         }
103     }
104 
105     private void writeCacheFile(final Element... elements) throws IOException {
106         final FileObject fo = processingEnv.getFiler().createResource(StandardLocation.CLASS_OUTPUT, Strings.EMPTY,
107                 PLUGIN_CACHE_FILE, elements);
108         try (final OutputStream out = fo.openOutputStream()) {
109             pluginCache.writeCache(out);
110         }
111     }
112 
113     /**
114      * ElementVisitor to scan the Plugin annotation.
115      */
116     private static class PluginElementVisitor extends SimpleElementVisitor6<PluginEntry, Plugin> {
117 
118         private final Elements elements;
119 
120         private PluginElementVisitor(final Elements elements) {
121             this.elements = elements;
122         }
123 
124         @Override
125         public PluginEntry visitType(final TypeElement e, final Plugin plugin) {
126             Objects.requireNonNull(plugin, "Plugin annotation is null.");
127             final PluginEntry entry = new PluginEntry();
128             entry.setKey(plugin.name().toLowerCase());
129             entry.setClassName(elements.getBinaryName(e).toString());
130             entry.setName(Plugin.EMPTY.equals(plugin.elementType()) ? plugin.name() : plugin.elementType());
131             entry.setPrintable(plugin.printObject());
132             entry.setDefer(plugin.deferChildren());
133             entry.setCategory(plugin.category());
134             return entry;
135         }
136     }
137 
138     /**
139      * ElementVisitor to scan the PluginAliases annotation.
140      */
141     private static class PluginAliasesElementVisitor extends SimpleElementVisitor6<Collection<PluginEntry>, Plugin> {
142 
143         private final Elements elements;
144 
145         private PluginAliasesElementVisitor(final Elements elements) {
146             super(Collections.<PluginEntry> emptyList());
147             this.elements = elements;
148         }
149 
150         @Override
151         public Collection<PluginEntry> visitType(final TypeElement e, final Plugin plugin) {
152             final PluginAliases aliases = e.getAnnotation(PluginAliases.class);
153             if (aliases == null) {
154                 return DEFAULT_VALUE;
155             }
156             final Collection<PluginEntry> entries = new ArrayList<>(aliases.value().length);
157             for (final String alias : aliases.value()) {
158                 final PluginEntry entry = new PluginEntry();
159                 entry.setKey(alias.toLowerCase());
160                 entry.setClassName(elements.getBinaryName(e).toString());
161                 entry.setName(Plugin.EMPTY.equals(plugin.elementType()) ? alias : plugin.elementType());
162                 entry.setPrintable(plugin.printObject());
163                 entry.setDefer(plugin.deferChildren());
164                 entry.setCategory(plugin.category());
165                 entries.add(entry);
166             }
167             return entries;
168         }
169     }
170 }