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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  package org.apache.logging.log4j.core.lookup;
18  
19  import java.util.HashMap;
20  import java.util.Map;
21  
22  import org.apache.logging.log4j.Logger;
23  import org.apache.logging.log4j.core.LogEvent;
24  import org.apache.logging.log4j.core.config.plugins.util.PluginManager;
25  import org.apache.logging.log4j.core.config.plugins.util.PluginType;
26  import org.apache.logging.log4j.core.util.Loader;
27  import org.apache.logging.log4j.status.StatusLogger;
28  
29  /**
30   * The Interpolator is a StrLookup that acts as a proxy for all the other StrLookups.
31   */
32  public class Interpolator implements StrLookup {
33  
34      private static final Logger LOGGER = StatusLogger.getLogger();
35  
36      /** Constant for the prefix separator. */
37      private static final char PREFIX_SEPARATOR = ':';
38  
39      private final Map<String, StrLookup> lookups = new HashMap<String, StrLookup>();
40  
41      private final StrLookup defaultLookup;
42  
43      public Interpolator(final StrLookup defaultLookup) {
44          this.defaultLookup = defaultLookup == null ? new MapLookup(new HashMap<String, String>()) : defaultLookup;
45          final PluginManager manager = new PluginManager("Lookup");
46          manager.collectPlugins();
47          final Map<String, PluginType<?>> plugins = manager.getPlugins();
48  
49          for (final Map.Entry<String, PluginType<?>> entry : plugins.entrySet()) {
50              @SuppressWarnings("unchecked")
51              final Class<? extends StrLookup> clazz = (Class<? extends StrLookup>) entry.getValue().getPluginClass();
52              try {
53                  lookups.put(entry.getKey(), clazz.getConstructor().newInstance());
54              } catch (final Exception ex) {
55                  LOGGER.error("Unable to create Lookup for {}", entry.getKey(), ex);
56              }
57          }
58      }
59  
60      /**
61       * Create the default Interpolator using only Lookups that work without an event.
62       */
63      public Interpolator() {
64          this((Map<String, String>) null);
65      }
66  
67      /**
68       * Create the dInterpolator using only Lookups that work without an event and initial properties.
69       */
70      public Interpolator(final Map<String, String> properties) {
71          this.defaultLookup = new MapLookup(properties == null ? new HashMap<String, String>() : properties);
72          // TODO: this ought to use the PluginManager
73          lookups.put("sys", new SystemPropertiesLookup());
74          lookups.put("env", new EnvironmentLookup());
75          try {
76              // [LOG4J2-703] We might be on Android
77              lookups.put("jndi", (StrLookup) Class.forName("org.apache.logging.log4j.core.lookup.JndiLookup")
78                      .newInstance());
79          } catch (Throwable e) {
80              // java.lang.VerifyError: org/apache/logging/log4j/core/lookup/JndiLookup
81              LOGGER.warn(
82                      "JNDI lookup class is not available because this JRE does not support JNDI. JNDI string lookups will not be available, continuing configuration.",
83                      e);
84          }
85          lookups.put("date", new DateLookup());
86          lookups.put("ctx", new ContextMapLookup());
87          if (Loader.isClassAvailable("javax.servlet.ServletContext")) {
88              try {
89                  lookups.put("web",
90                      Loader.newCheckedInstanceOf("org.apache.logging.log4j.web.WebLookup", StrLookup.class));
91              } catch (final Exception ignored) {
92                  LOGGER.info("Log4j appears to be running in a Servlet environment, but there's no log4j-web module " +
93                      "available. If you want better web container support, please add the log4j-web JAR to your " +
94                      "web archive or server lib directory.");
95              }
96          } else {
97              LOGGER.debug("Not in a ServletContext environment, thus not loading WebLookup plugin.");
98          }
99      }
100 
101      /**
102      * Resolves the specified variable. This implementation will try to extract
103      * a variable prefix from the given variable name (the first colon (':') is
104      * used as prefix separator). It then passes the name of the variable with
105      * the prefix stripped to the lookup object registered for this prefix. If
106      * no prefix can be found or if the associated lookup object cannot resolve
107      * this variable, the default lookup object will be used.
108      *
109      * @param var the name of the variable whose value is to be looked up
110      * @return the value of this variable or <b>null</b> if it cannot be
111      * resolved
112      */
113     @Override
114     public String lookup(final String var) {
115         return lookup(null, var);
116     }
117 
118     /**
119      * Resolves the specified variable. This implementation will try to extract
120      * a variable prefix from the given variable name (the first colon (':') is
121      * used as prefix separator). It then passes the name of the variable with
122      * the prefix stripped to the lookup object registered for this prefix. If
123      * no prefix can be found or if the associated lookup object cannot resolve
124      * this variable, the default lookup object will be used.
125      *
126      * @param event The current LogEvent or null.
127      * @param var the name of the variable whose value is to be looked up
128      * @return the value of this variable or <b>null</b> if it cannot be
129      * resolved
130      */
131     @Override
132     public String lookup(final LogEvent event, String var) {
133         if (var == null) {
134             return null;
135         }
136 
137         final int prefixPos = var.indexOf(PREFIX_SEPARATOR);
138         if (prefixPos >= 0) {
139             final String prefix = var.substring(0, prefixPos);
140             final String name = var.substring(prefixPos + 1);
141             final StrLookup lookup = lookups.get(prefix);
142             String value = null;
143             if (lookup != null) {
144                 value = event == null ? lookup.lookup(name) : lookup.lookup(event, name);
145             }
146 
147             if (value != null) {
148                 return value;
149             }
150             var = var.substring(prefixPos + 1);
151         }
152         if (defaultLookup != null) {
153             return event == null ? defaultLookup.lookup(var) : defaultLookup.lookup(event, var);
154         }
155         return null;
156     }
157 
158     @Override
159     public String toString() {
160         final StringBuilder sb = new StringBuilder();
161         for (final String name : lookups.keySet()) {
162             if (sb.length() == 0) {
163                 sb.append('{');
164             } else {
165                 sb.append(", ");
166             }
167 
168             sb.append(name);
169         }
170         if (sb.length() > 0) {
171             sb.append('}');
172         }
173         return sb.toString();
174     }
175 }