View Javadoc
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  package org.apache.logging.log4j.core.appender.rewrite;
18  
19  import java.util.concurrent.ConcurrentHashMap;
20  import java.util.concurrent.ConcurrentMap;
21  
22  import org.apache.logging.log4j.core.Appender;
23  import org.apache.logging.log4j.core.Filter;
24  import org.apache.logging.log4j.core.LogEvent;
25  import org.apache.logging.log4j.core.appender.AbstractAppender;
26  import org.apache.logging.log4j.core.config.AppenderControl;
27  import org.apache.logging.log4j.core.config.AppenderRef;
28  import org.apache.logging.log4j.core.config.Configuration;
29  import org.apache.logging.log4j.core.config.plugins.Plugin;
30  import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
31  import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
32  import org.apache.logging.log4j.core.config.plugins.PluginElement;
33  import org.apache.logging.log4j.core.config.plugins.PluginFactory;
34  import org.apache.logging.log4j.core.util.Booleans;
35  
36  /**
37   * This Appender allows the logging event to be manipulated before it is processed by other Appenders.
38   */
39  @Plugin(name = "Rewrite", category = "Core", elementType = "appender", printObject = true)
40  public final class RewriteAppender extends AbstractAppender {
41      
42      private static final long serialVersionUID = 1L;
43  
44      private final Configuration config;
45      private final ConcurrentMap<String, AppenderControl> appenders = new ConcurrentHashMap<String, AppenderControl>();
46      private final RewritePolicy rewritePolicy;
47      private final AppenderRef[] appenderRefs;
48  
49      private RewriteAppender(final String name, final Filter filter, final boolean ignoreExceptions,
50                              final AppenderRef[] appenderRefs, final RewritePolicy rewritePolicy,
51                              final Configuration config) {
52          super(name, filter, null, ignoreExceptions);
53          this.config = config;
54          this.rewritePolicy = rewritePolicy;
55          this.appenderRefs = appenderRefs;
56      }
57  
58      @Override
59      public void start() {
60          for (final AppenderRef ref : appenderRefs) {
61              final String name = ref.getRef();
62              final Appender appender = config.getAppender(name);
63              if (appender != null) {
64                  final Filter filter = appender instanceof AbstractAppender ?
65                      ((AbstractAppender) appender).getFilter() : null;
66                  appenders.put(name, new AppenderControl(appender, ref.getLevel(), filter));
67              } else {
68                  LOGGER.error("Appender " + ref + " cannot be located. Reference ignored");
69              }
70          }
71          super.start();
72      }
73  
74      @Override
75      public void stop() {
76          super.stop();
77      }
78  
79      /**
80       * Modify the event and pass to the subordinate Appenders.
81       * @param event The LogEvent.
82       */
83      @Override
84      public void append(LogEvent event) {
85          if (rewritePolicy != null) {
86              event = rewritePolicy.rewrite(event);
87          }
88          for (final AppenderControl control : appenders.values()) {
89              control.callAppender(event);
90          }
91      }
92  
93      /**
94       * Create a RewriteAppender.
95       * @param name The name of the Appender.
96       * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
97       *               they are propagated to the caller.
98       * @param appenderRefs An array of Appender names to call.
99       * @param config The Configuration.
100      * @param rewritePolicy The policy to use to modify the event.
101      * @param filter A Filter to filter events.
102      * @return The created RewriteAppender.
103      */
104     @PluginFactory
105     public static RewriteAppender createAppender(
106             @PluginAttribute("name") final String name,
107             @PluginAttribute("ignoreExceptions") final String ignore,
108             @PluginElement("AppenderRef") final AppenderRef[] appenderRefs,
109             @PluginConfiguration final Configuration config,
110             @PluginElement("RewritePolicy") final RewritePolicy rewritePolicy,
111             @PluginElement("Filter") final Filter filter) {
112 
113         final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
114         if (name == null) {
115             LOGGER.error("No name provided for RewriteAppender");
116             return null;
117         }
118         if (appenderRefs == null) {
119             LOGGER.error("No appender references defined for RewriteAppender");
120             return null;
121         }
122         return new RewriteAppender(name, filter, ignoreExceptions, appenderRefs, rewritePolicy, config);
123     }
124 }