/*
* 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.Map;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.plugins.PluginManager;
import org.apache.logging.log4j.core.config.plugins.PluginType;
import org.apache.logging.log4j.status.StatusLogger;
/**
* The Interpolator is a StrLookup that acts as a proxy for all the other StrLookups.
*/
public class Interpolator implements StrLookup {
private static final Logger LOGGER = StatusLogger.getLogger();
/** Constant for the prefix separator. */
private static final char PREFIX_SEPARATOR = ':';
private final Map<String, StrLookup> lookups = new HashMap<String, StrLookup>();
private final StrLookup defaultLookup;
public Interpolator(final StrLookup defaultLookup) {
this.defaultLookup = defaultLookup == null ? new MapLookup(new HashMap<String, String>()) : defaultLookup;
final PluginManager manager = new PluginManager("Lookup");
manager.collectPlugins();
final Map<String, PluginType<?>> plugins = manager.getPlugins();
for (final Map.Entry<String, PluginType<?>> entry : plugins.entrySet()) {
@SuppressWarnings("unchecked")
final Class<? extends StrLookup> clazz = (Class<? extends StrLookup>) entry.getValue().getPluginClass();
try {
lookups.put(entry.getKey(), clazz.newInstance());
} 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.defaultLookup = new MapLookup(new HashMap<String, String>());
lookups.put("sys", new SystemPropertiesLookup());
lookups.put("env", new EnvironmentLookup());
lookups.put("jndi", new JndiLookup());
try {
if (Class.forName("javax.servlet.ServletContext") != null) {
lookups.put("web", new WebLookup());
}
} catch (ClassNotFoundException ex) {
LOGGER.debug("ServletContext not present - WebLookup not added");
} catch (Exception ex) {
LOGGER.error("Unable to locate ServletContext", ex);
}
}
/**
* 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 var the name of the variable whose value is to be looked up
* @return the value of this variable or <b>null</b> if it cannot be
* resolved
*/
@Override
public String lookup(final String var) {
return lookup(null, var);
}
/**
* 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 <b>null</b> 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);
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();
}
}