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The Apache Log4j Implementation
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache license, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the license for the specific language governing permissions and
* limitations under the license.
*/
package org.apache.logging.log4j.core.lookup;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.ConfigurationAware;
import org.apache.logging.log4j.core.config.plugins.util.PluginManager;
import org.apache.logging.log4j.core.config.plugins.util.PluginType;
import org.apache.logging.log4j.core.util.Loader;
import org.apache.logging.log4j.core.util.ReflectionUtil;
import org.apache.logging.log4j.status.StatusLogger;
/**
* Proxies all the other {@link StrLookup}s.
*/
public class Interpolator extends AbstractConfigurationAwareLookup {
private static final Logger LOGGER = StatusLogger.getLogger();
/** Constant for the prefix separator. */
private static final char PREFIX_SEPARATOR = ':';
private final Map lookups = new HashMap<>();
private final StrLookup defaultLookup;
public Interpolator(final StrLookup defaultLookup) {
this(defaultLookup, null);
}
/**
* Constructs an Interpolator using a given StrLookup and a list of packages to find Lookup plugins in.
*
* @param defaultLookup the default StrLookup to use as a fallback
* @param pluginPackages a list of packages to scan for Lookup plugins
* @since 2.1
*/
public Interpolator(final StrLookup defaultLookup, final List pluginPackages) {
this.defaultLookup = defaultLookup == null ? new MapLookup(new HashMap()) : defaultLookup;
final PluginManager manager = new PluginManager(CATEGORY);
manager.collectPlugins(pluginPackages);
final Map> plugins = manager.getPlugins();
for (final Map.Entry> entry : plugins.entrySet()) {
try {
final Class clazz = entry.getValue().getPluginClass().asSubclass(StrLookup.class);
lookups.put(entry.getKey(), ReflectionUtil.instantiate(clazz));
} catch (final Exception ex) {
LOGGER.error("Unable to create Lookup for {}", entry.getKey(), ex);
}
}
}
/**
* Create the default Interpolator using only Lookups that work without an event.
*/
public Interpolator() {
this((Map) null);
}
/**
* Creates the Interpolator using only Lookups that work without an event and initial properties.
*/
public Interpolator(final Map properties) {
this.defaultLookup = new MapLookup(properties == null ? new HashMap() : properties);
// TODO: this ought to use the PluginManager
lookups.put("log4j", new Log4jLookup());
lookups.put("sys", new SystemPropertiesLookup());
lookups.put("env", new EnvironmentLookup());
lookups.put("main", MainMapLookup.MAIN_SINGLETON);
lookups.put("marker", new MarkerLookup());
lookups.put("java", new JavaLookup());
// JNDI
try {
// [LOG4J2-703] We might be on Android
lookups.put("jndi",
Loader.newCheckedInstanceOf("org.apache.logging.log4j.core.lookup.JndiLookup", StrLookup.class));
} catch (final Throwable e) {
// java.lang.VerifyError: org/apache/logging/log4j/core/lookup/JndiLookup
LOGGER.warn(
"JNDI lookup class is not available because this JRE does not support JNDI. JNDI string lookups will not be available, continuing configuration.",
e);
}
// JMX input args
try {
// We might be on Android
lookups.put("jvmrunargs",
Loader.newCheckedInstanceOf("org.apache.logging.log4j.core.lookup.JmxRuntimeInputArgumentsLookup", StrLookup.class));
} catch (final Throwable e) {
// java.lang.VerifyError: org/apache/logging/log4j/core/lookup/JmxRuntimeInputArgumentsLookup
LOGGER.warn(
"JMX runtime input lookup class is not available because this JRE does not support JMX. JMX lookups will not be available, continuing configuration.",
e);
}
lookups.put("date", new DateLookup());
lookups.put("ctx", new ContextMapLookup());
if (Loader.isClassAvailable("javax.servlet.ServletContext")) {
try {
lookups.put("web",
Loader.newCheckedInstanceOf("org.apache.logging.log4j.web.WebLookup", StrLookup.class));
} catch (final Exception ignored) {
LOGGER.info("Log4j appears to be running in a Servlet environment, but there's no log4j-web module " +
"available. If you want better web container support, please add the log4j-web JAR to your " +
"web archive or server lib directory.");
}
} else {
LOGGER.debug("Not in a ServletContext environment, thus not loading WebLookup plugin.");
}
}
/**
* Resolves the specified variable. This implementation will try to extract
* a variable prefix from the given variable name (the first colon (':') is
* used as prefix separator). It then passes the name of the variable with
* the prefix stripped to the lookup object registered for this prefix. If
* no prefix can be found or if the associated lookup object cannot resolve
* this variable, the default lookup object will be used.
*
* @param event The current LogEvent or null.
* @param var the name of the variable whose value is to be looked up
* @return the value of this variable or null if it cannot be
* resolved
*/
@Override
public String lookup(final LogEvent event, String var) {
if (var == null) {
return null;
}
final int prefixPos = var.indexOf(PREFIX_SEPARATOR);
if (prefixPos >= 0) {
final String prefix = var.substring(0, prefixPos);
final String name = var.substring(prefixPos + 1);
final StrLookup lookup = lookups.get(prefix);
if (lookup instanceof ConfigurationAware) {
((ConfigurationAware) lookup).setConfiguration(configuration);
}
String value = null;
if (lookup != null) {
value = event == null ? lookup.lookup(name) : lookup.lookup(event, name);
}
if (value != null) {
return value;
}
var = var.substring(prefixPos + 1);
}
if (defaultLookup != null) {
return event == null ? defaultLookup.lookup(var) : defaultLookup.lookup(event, var);
}
return null;
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
for (final String name : lookups.keySet()) {
if (sb.length() == 0) {
sb.append('{');
} else {
sb.append(", ");
}
sb.append(name);
}
if (sb.length() > 0) {
sb.append('}');
}
return sb.toString();
}
}