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.List;
021    import java.util.Map;
022    
023    import org.apache.logging.log4j.Logger;
024    import org.apache.logging.log4j.core.LogEvent;
025    import org.apache.logging.log4j.core.config.plugins.util.PluginManager;
026    import org.apache.logging.log4j.core.config.plugins.util.PluginType;
027    import org.apache.logging.log4j.core.util.Loader;
028    import org.apache.logging.log4j.core.util.ReflectionUtil;
029    import org.apache.logging.log4j.status.StatusLogger;
030    
031    /**
032     * Proxies all the other {@link StrLookup}s.
033     */
034    public class Interpolator extends AbstractLookup {
035    
036        private static final Logger LOGGER = StatusLogger.getLogger();
037    
038        /** Constant for the prefix separator. */
039        private static final char PREFIX_SEPARATOR = ':';
040    
041        private final Map<String, StrLookup> lookups = new HashMap<String, StrLookup>();
042    
043        private final StrLookup defaultLookup;
044    
045        public Interpolator(final StrLookup defaultLookup) {
046            this(defaultLookup, null);
047        }
048    
049        /**
050         * Constructs an Interpolator using a given StrLookup and a list of packages to find Lookup plugins in.
051         *
052         * @param defaultLookup  the default StrLookup to use as a fallback
053         * @param pluginPackages a list of packages to scan for Lookup plugins
054         * @since 2.1
055         */
056        public Interpolator(final StrLookup defaultLookup, final List<String> pluginPackages) {
057            this.defaultLookup = defaultLookup == null ? new MapLookup(new HashMap<String, String>()) : defaultLookup;
058            final PluginManager manager = new PluginManager(CATEGORY);
059            manager.collectPlugins(pluginPackages);
060            final Map<String, PluginType<?>> plugins = manager.getPlugins();
061    
062            for (final Map.Entry<String, PluginType<?>> entry : plugins.entrySet()) {
063                try {
064                    final Class<? extends StrLookup> clazz = entry.getValue().getPluginClass().asSubclass(StrLookup.class);
065                    lookups.put(entry.getKey(), ReflectionUtil.instantiate(clazz));
066                } catch (final Exception ex) {
067                    LOGGER.error("Unable to create Lookup for {}", entry.getKey(), ex);
068                }
069            }
070        }
071    
072        /**
073         * Create the default Interpolator using only Lookups that work without an event.
074         */
075        public Interpolator() {
076            this((Map<String, String>) null);
077        }
078    
079        /**
080         * Creates the Interpolator using only Lookups that work without an event and initial properties.
081         */
082        public Interpolator(final Map<String, String> properties) {
083            this.defaultLookup = new MapLookup(properties == null ? new HashMap<String, String>() : properties);
084            // TODO: this ought to use the PluginManager
085            lookups.put("sys", new SystemPropertiesLookup());
086            lookups.put("env", new EnvironmentLookup());
087            lookups.put("main", MapLookup.MAIN_SINGLETON);
088            lookups.put("java", new JavaLookup());
089            // JNDI
090            try {
091                // [LOG4J2-703] We might be on Android
092                lookups.put("jndi",
093                    Loader.newCheckedInstanceOf("org.apache.logging.log4j.core.lookup.JndiLookup", StrLookup.class));
094            } catch (final Throwable e) {
095                // java.lang.VerifyError: org/apache/logging/log4j/core/lookup/JndiLookup
096                LOGGER.warn(
097                        "JNDI lookup class is not available because this JRE does not support JNDI. JNDI string lookups will not be available, continuing configuration.",
098                        e);
099            }
100            // JMX input args
101            try {
102                // We might be on Android
103                lookups.put("jvmrunargs",
104                    Loader.newCheckedInstanceOf("org.apache.logging.log4j.core.lookup.JmxRuntimeInputArgumentsLookup", StrLookup.class));
105            } catch (final Throwable e) {
106                // java.lang.VerifyError: org/apache/logging/log4j/core/lookup/JmxRuntimeInputArgumentsLookup
107                LOGGER.warn(
108                        "JMX runtime input lookup class is not available because this JRE does not support JMX. JMX lookups will not be available, continuing configuration.",
109                        e);
110            }
111            lookups.put("date", new DateLookup());
112            lookups.put("ctx", new ContextMapLookup());
113            if (Loader.isClassAvailable("javax.servlet.ServletContext")) {
114                try {
115                    lookups.put("web",
116                        Loader.newCheckedInstanceOf("org.apache.logging.log4j.web.WebLookup", StrLookup.class));
117                } catch (final Exception ignored) {
118                    LOGGER.info("Log4j appears to be running in a Servlet environment, but there's no log4j-web module " +
119                        "available. If you want better web container support, please add the log4j-web JAR to your " +
120                        "web archive or server lib directory.");
121                }
122            } else {
123                LOGGER.debug("Not in a ServletContext environment, thus not loading WebLookup plugin.");
124            }
125        }
126    
127        /**
128         * Resolves the specified variable. This implementation will try to extract
129         * a variable prefix from the given variable name (the first colon (':') is
130         * used as prefix separator). It then passes the name of the variable with
131         * the prefix stripped to the lookup object registered for this prefix. If
132         * no prefix can be found or if the associated lookup object cannot resolve
133         * this variable, the default lookup object will be used.
134         *
135         * @param event The current LogEvent or null.
136         * @param var the name of the variable whose value is to be looked up
137         * @return the value of this variable or <b>null</b> if it cannot be
138         * resolved
139         */
140        @Override
141        public String lookup(final LogEvent event, String var) {
142            if (var == null) {
143                return null;
144            }
145    
146            final int prefixPos = var.indexOf(PREFIX_SEPARATOR);
147            if (prefixPos >= 0) {
148                final String prefix = var.substring(0, prefixPos);
149                final String name = var.substring(prefixPos + 1);
150                final StrLookup lookup = lookups.get(prefix);
151                String value = null;
152                if (lookup != null) {
153                    value = event == null ? lookup.lookup(name) : lookup.lookup(event, name);
154                }
155    
156                if (value != null) {
157                    return value;
158                }
159                var = var.substring(prefixPos + 1);
160            }
161            if (defaultLookup != null) {
162                return event == null ? defaultLookup.lookup(var) : defaultLookup.lookup(event, var);
163            }
164            return null;
165        }
166    
167        @Override
168        public String toString() {
169            final StringBuilder sb = new StringBuilder();
170            for (final String name : lookups.keySet()) {
171                if (sb.length() == 0) {
172                    sb.append('{');
173                } else {
174                    sb.append(", ");
175                }
176    
177                sb.append(name);
178            }
179            if (sb.length() > 0) {
180                sb.append('}');
181            }
182            return sb.toString();
183        }
184    }