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    package org.apache.logging.log4j.core.lookup;
018    
019    import java.util.HashMap;
020    import java.util.Map;
021    
022    import org.apache.logging.log4j.Logger;
023    import org.apache.logging.log4j.core.LogEvent;
024    import org.apache.logging.log4j.core.config.plugins.util.PluginManager;
025    import org.apache.logging.log4j.core.config.plugins.util.PluginType;
026    import org.apache.logging.log4j.core.util.Loader;
027    import org.apache.logging.log4j.status.StatusLogger;
028    
029    /**
030     * Proxies all the other StrLookups.
031     */
032    public class Interpolator implements StrLookup {
033    
034        private static final Logger LOGGER = StatusLogger.getLogger();
035    
036        /** Constant for the prefix separator. */
037        private static final char PREFIX_SEPARATOR = ':';
038    
039        private final Map<String, StrLookup> lookups = new HashMap<String, StrLookup>();
040    
041        private final StrLookup defaultLookup;
042    
043        public Interpolator(final StrLookup defaultLookup) {
044            this.defaultLookup = defaultLookup == null ? new MapLookup(new HashMap<String, String>()) : defaultLookup;
045            final PluginManager manager = new PluginManager("Lookup");
046            manager.collectPlugins();
047            final Map<String, PluginType<?>> plugins = manager.getPlugins();
048    
049            for (final Map.Entry<String, PluginType<?>> entry : plugins.entrySet()) {
050                @SuppressWarnings("unchecked")
051                final Class<? extends StrLookup> clazz = (Class<? extends StrLookup>) entry.getValue().getPluginClass();
052                try {
053                    lookups.put(entry.getKey(), clazz.getConstructor().newInstance());
054                } catch (final Exception ex) {
055                    LOGGER.error("Unable to create Lookup for {}", entry.getKey(), ex);
056                }
057            }
058        }
059    
060        /**
061         * Create the default Interpolator using only Lookups that work without an event.
062         */
063        public Interpolator() {
064            this((Map<String, String>) null);
065        }
066    
067        /**
068         * Create the dInterpolator using only Lookups that work without an event and initial properties.
069         */
070        public Interpolator(final Map<String, String> properties) {
071            this.defaultLookup = new MapLookup(properties == null ? new HashMap<String, String>() : properties);
072            // TODO: this ought to use the PluginManager
073            lookups.put("sys", new SystemPropertiesLookup());
074            lookups.put("env", new EnvironmentLookup());
075            try {
076                // [LOG4J2-703] We might be on Android
077                lookups.put("jndi",
078                    Loader.newCheckedInstanceOf("org.apache.logging.log4j.core.lookup.JndiLookup", StrLookup.class));
079            } catch (Throwable e) {
080                // java.lang.VerifyError: org/apache/logging/log4j/core/lookup/JndiLookup
081                LOGGER.warn(
082                        "JNDI lookup class is not available because this JRE does not support JNDI. JNDI string lookups will not be available, continuing configuration.",
083                        e);
084            }
085            lookups.put("date", new DateLookup());
086            lookups.put("ctx", new ContextMapLookup());
087            if (Loader.isClassAvailable("javax.servlet.ServletContext")) {
088                try {
089                    lookups.put("web",
090                        Loader.newCheckedInstanceOf("org.apache.logging.log4j.web.WebLookup", StrLookup.class));
091                } catch (final Exception ignored) {
092                    LOGGER.info("Log4j appears to be running in a Servlet environment, but there's no log4j-web module " +
093                        "available. If you want better web container support, please add the log4j-web JAR to your " +
094                        "web archive or server lib directory.");
095                }
096            } else {
097                LOGGER.debug("Not in a ServletContext environment, thus not loading WebLookup plugin.");
098            }
099        }
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    }