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     * The Interpolator is a StrLookup that acts as a proxy for 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                lookups.put("jndi", new JndiLookup());
077            } catch (Throwable e) {
078                // [LOG4J2-703] We might be on Android
079                // java.lang.VerifyError: org/apache/logging/log4j/core/lookup/JndiLookup
080                LOGGER.warn(
081                        "JNDI lookup class is not available because this JRE does not support JNDI. JNDI string lookups will not be available, continuing configuration.",
082                        e);
083            }
084            lookups.put("date", new DateLookup());
085            lookups.put("ctx", new ContextMapLookup());
086            if (Loader.isClassAvailable("javax.servlet.ServletContext")) {
087                try {
088                    lookups.put("web",
089                        Loader.newCheckedInstanceOf("org.apache.logging.log4j.web.WebLookup", StrLookup.class));
090                } catch (final Exception ignored) {
091                    LOGGER.info("Log4j appears to be running in a Servlet environment, but there's no log4j-web module " +
092                        "available. If you want better web container support, please add the log4j-web JAR to your " +
093                        "web archive or server lib directory.");
094                }
095            } else {
096                LOGGER.debug("Not in a ServletContext environment, thus not loading WebLookup plugin.");
097            }
098        }
099    
100         /**
101         * Resolves the specified variable. This implementation will try to extract
102         * a variable prefix from the given variable name (the first colon (':') is
103         * used as prefix separator). It then passes the name of the variable with
104         * the prefix stripped to the lookup object registered for this prefix. If
105         * no prefix can be found or if the associated lookup object cannot resolve
106         * this variable, the default lookup object will be used.
107         *
108         * @param var the name of the variable whose value is to be looked up
109         * @return the value of this variable or <b>null</b> if it cannot be
110         * resolved
111         */
112        @Override
113        public String lookup(final String var) {
114            return lookup(null, var);
115        }
116    
117        /**
118         * Resolves the specified variable. This implementation will try to extract
119         * a variable prefix from the given variable name (the first colon (':') is
120         * used as prefix separator). It then passes the name of the variable with
121         * the prefix stripped to the lookup object registered for this prefix. If
122         * no prefix can be found or if the associated lookup object cannot resolve
123         * this variable, the default lookup object will be used.
124         *
125         * @param event The current LogEvent or null.
126         * @param var the name of the variable whose value is to be looked up
127         * @return the value of this variable or <b>null</b> if it cannot be
128         * resolved
129         */
130        @Override
131        public String lookup(final LogEvent event, String var) {
132            if (var == null) {
133                return null;
134            }
135    
136            final int prefixPos = var.indexOf(PREFIX_SEPARATOR);
137            if (prefixPos >= 0) {
138                final String prefix = var.substring(0, prefixPos);
139                final String name = var.substring(prefixPos + 1);
140                final StrLookup lookup = lookups.get(prefix);
141                String value = null;
142                if (lookup != null) {
143                    value = event == null ? lookup.lookup(name) : lookup.lookup(event, name);
144                }
145    
146                if (value != null) {
147                    return value;
148                }
149                var = var.substring(prefixPos + 1);
150            }
151            if (defaultLookup != null) {
152                return event == null ? defaultLookup.lookup(var) : defaultLookup.lookup(event, var);
153            }
154            return null;
155        }
156    
157        @Override
158        public String toString() {
159            final StringBuilder sb = new StringBuilder();
160            for (final String name : lookups.keySet()) {
161                if (sb.length() == 0) {
162                    sb.append('{');
163                } else {
164                    sb.append(", ");
165                }
166    
167                sb.append(name);
168            }
169            if (sb.length() > 0) {
170                sb.append('}');
171            }
172            return sb.toString();
173        }
174    }