/**
* 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.solr.util.plugin;
import java.util.ArrayList;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.solr.common.ResourceLoader;
import org.apache.solr.common.SolrException;
import org.apache.solr.common.SolrException.ErrorCode;
import org.apache.solr.common.util.DOMUtil;
import org.apache.solr.core.SolrConfig;
import org.apache.solr.core.SolrResourceLoader;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
/**
* An abstract super class that manages standard solr-style plugin configuration.
*
* @version $Id: AbstractPluginLoader.java 945886 2010-05-18 21:07:28Z hossman $
* @since solr 1.3
*/
public abstract class AbstractPluginLoader<T>
{
public static Logger log = LoggerFactory.getLogger(AbstractPluginLoader.class);
private final String type;
private final boolean preRegister;
private final boolean requireName;
/**
* @param type is the 'type' name included in error messages.
* @param preRegister if true, this will first register all Plugins, then it will initialize them.
*/
public AbstractPluginLoader( String type, boolean preRegister, boolean requireName )
{
this.type = type;
this.preRegister = preRegister;
this.requireName = requireName;
}
public AbstractPluginLoader( String type )
{
this( type, false, true );
}
/**
* Where to look for classes
*/
protected String[] getDefaultPackages()
{
return new String[]{};
}
/**
* Create a plugin from an XML configuration. Plugins are defined using:
* <plugin name="name1" class="solr.ClassName">
* ...
* </plugin>
*
* @param name - The registered name. In the above example: "name1"
* @param className - class name for requested plugin. In the above example: "solr.ClassName"
* @param node - the XML node defining this plugin
*/
@SuppressWarnings("unchecked")
protected T create( ResourceLoader loader, String name, String className, Node node ) throws Exception
{
return (T) loader.newInstance( className, getDefaultPackages() );
}
/**
* Register a plugin with a given name.
* @return The plugin previously registered to this name, or null
*/
abstract protected T register( String name, T plugin ) throws Exception;
/**
* Initialize the plugin.
*
* @param plugin - the plugin to initialize
* @param node - the XML node defining this plugin
*/
abstract protected void init( T plugin, Node node ) throws Exception;
/**
* Given a NodeList from XML in the form:
*
* <plugins>
* <plugin name="name1" class="solr.ClassName" >
* ...
* </plugin>
* <plugin name="name2" class="solr.ClassName" >
* ...
* </plugin>
* </plugins>
*
* This will initialize and register each plugin from the list. A class will
* be generated for each class name and registered to the given name.
*
* If 'preRegister' is true, each plugin will be registered *before* it is initialized
* This may be useful for implementations that need to inspect other registered
* plugins at startup.
*
* One (and only one) plugin may declare itself to be the 'default' plugin using:
* <plugin name="name2" class="solr.ClassName" default="true">
* If a default element is defined, it will be returned from this function.
*
*/
public T load( ResourceLoader loader, NodeList nodes )
{
List<PluginInitInfo> info = new ArrayList<PluginInitInfo>();
T defaultPlugin = null;
if (nodes !=null ) {
for (int i=0; i<nodes.getLength(); i++) {
Node node = nodes.item(i);
// In a production environment, we can tolerate an error in some request handlers,
// still load the others, and have a working system.
try {
String name = DOMUtil.getAttr(node,"name", requireName?type:null);
String className = DOMUtil.getAttr(node,"class", type);
String defaultStr = DOMUtil.getAttr(node,"default", null );
T plugin = create(loader, name, className, node );
log.info("created " + ((name != null) ? name : "") + ": " + plugin.getClass().getName());
// Either initialize now or wait till everything has been registered
if( preRegister ) {
info.add( new PluginInitInfo( plugin, node ) );
}
else {
init( plugin, node );
}
T old = register( name, plugin );
if( old != null && !( name == null && !requireName ) ) {
throw new SolrException( ErrorCode.SERVER_ERROR,
"Multiple "+type+" registered to the same name: "+name+" ignoring: "+old );
}
if( defaultStr != null && Boolean.parseBoolean( defaultStr ) ) {
if( defaultPlugin != null ) {
throw new SolrException( ErrorCode.SERVER_ERROR,
"Multiple default "+type+" plugins: "+defaultPlugin + " AND " + name );
}
defaultPlugin = plugin;
}
}
catch (Exception ex) {
SolrException e = new SolrException
(ErrorCode.SERVER_ERROR,
"Plugin init failure for " + type + ":" + ex.getMessage(), ex);
SolrConfig.severeErrors.add( e );
SolrException.logOnce(log,null,e);
throw e;
}
}
}
// If everything needs to be registered *first*, this will initialize later
for( PluginInitInfo pinfo : info ) {
try {
init( pinfo.plugin, pinfo.node );
}
catch( Exception ex ) {
SolrException e = new SolrException
(ErrorCode.SERVER_ERROR, "Plugin Initializing failure for " + type, ex);
SolrConfig.severeErrors.add( e );
SolrException.logOnce(log,null,e);
throw e;
}
}
return defaultPlugin;
}
/**
* Given a NodeList from XML in the form:
*
* <plugin name="name1" class="solr.ClassName" > ... </plugin>
*
* This will initialize and register a single plugin. A class will be
* generated for the plugin and registered to the given name.
*
* If 'preRegister' is true, the plugin will be registered *before* it is
* initialized This may be useful for implementations that need to inspect
* other registered plugins at startup.
*
* The created class for the plugin will be returned from this function.
*
*/
public T loadSingle(ResourceLoader loader, Node node) {
List<PluginInitInfo> info = new ArrayList<PluginInitInfo>();
T plugin = null;
try {
String name = DOMUtil.getAttr(node, "name", requireName ? type : null);
String className = DOMUtil.getAttr(node, "class", type);
plugin = create(loader, name, className, node);
log.info("created " + name + ": " + plugin.getClass().getName());
// Either initialize now or wait till everything has been registered
if (preRegister) {
info.add(new PluginInitInfo(plugin, node));
} else {
init(plugin, node);
}
T old = register(name, plugin);
if (old != null && !(name == null && !requireName)) {
throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
"Multiple " + type + " registered to the same name: " + name
+ " ignoring: " + old);
}
} catch (Exception ex) {
SolrException e = new SolrException
(ErrorCode.SERVER_ERROR, "Plugin init failure for " + type, ex);
SolrConfig.severeErrors.add( e );
SolrException.logOnce(log,null,e);
throw e;
}
// If everything needs to be registered *first*, this will initialize later
for (PluginInitInfo pinfo : info) {
try {
init(pinfo.plugin, pinfo.node);
} catch (Exception ex) {
SolrException e = new SolrException
(ErrorCode.SERVER_ERROR, "Plugin init failure for " + type, ex);
SolrConfig.severeErrors.add( e );
SolrException.logOnce(log,null,e);
throw e;
}
}
return plugin;
}
/**
* Internal class to hold onto initialization info so that it can be initialized
* after it is registered.
*/
private class PluginInitInfo
{
final T plugin;
final Node node;
PluginInitInfo( T plugin, Node node )
{
this.plugin = plugin;
this.node = node;
}
}
}