001 /* 002 * JBoss DNA (http://www.jboss.org/dna) 003 * See the COPYRIGHT.txt file distributed with this work for information 004 * regarding copyright ownership. Some portions may be licensed 005 * to Red Hat, Inc. under one or more contributor license agreements. 006 * See the AUTHORS.txt file in the distribution for a full listing of 007 * individual contributors. 008 * 009 * JBoss DNA is free software. Unless otherwise indicated, all code in JBoss DNA 010 * is licensed to you under the terms of the GNU Lesser General Public License as 011 * published by the Free Software Foundation; either version 2.1 of 012 * the License, or (at your option) any later version. 013 * 014 * JBoss DNA is distributed in the hope that it will be useful, 015 * but WITHOUT ANY WARRANTY; without even the implied warranty of 016 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 017 * Lesser General Public License for more details. 018 * 019 * You should have received a copy of the GNU Lesser General Public 020 * License along with this software; if not, write to the Free 021 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 022 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 023 */ 024 package org.jboss.dna.repository.sequencer; 025 026 import java.util.Set; 027 import net.jcip.annotations.ThreadSafe; 028 import org.jboss.dna.common.collection.Problems; 029 import org.jboss.dna.common.component.Component; 030 import org.jboss.dna.graph.Node; 031 import org.jboss.dna.graph.io.Destination; 032 import org.jboss.dna.graph.observe.Observer; 033 import org.jboss.dna.graph.observe.NetChangeObserver.NetChange; 034 import org.jboss.dna.repository.RepositoryLibrary; 035 import org.jboss.dna.repository.util.RepositoryNodePath; 036 037 /** 038 * The interface for a DNA sequencer, which sequences nodes and their content to extract additional information from the 039 * information. 040 * <p> 041 * Implementations must provide a no-argument constructor. 042 * </p> 043 * 044 * @author Randall Hauch 045 * @author John Verhaeg 046 */ 047 @ThreadSafe 048 public interface Sequencer extends Component<SequencerConfig> { 049 050 /** 051 * Execute the sequencing operation on the supplied node, which has recently been created or changed. The implementation of 052 * this method is responsible for modifying the appropriate nodes and {@link Destination#submit() saving} any changes made by 053 * this sequencer, and closing any other acquired resources, even in the case of exceptions. 054 * <p> 055 * The {@link SequencingService} determines the sequencers that should be executed by monitoring the changes to one or more 056 * workspaces (it registers an {@link Observer} with the {@link RepositoryLibrary}). Changes in those workspaces are 057 * aggregated for each transaction, and organized into {@link NetChange changes for each node}. The SequencingService then 058 * determines for each {@link NetChange set of changes to a node} the set of full paths to the properties that have changed 059 * and whether those paths {@link SequencerPathExpression#matcher(String) match} the sequencer's 060 * {@link SequencerConfig#getPathExpressions() path expressions}. Each path expression produces the path to the output node, 061 * and these output paths are accumulated and (with the original node that changed, the node change summary, and other 062 * information) supplied to the sequencer via this method. 063 * <p> 064 * It is possible that a sequencer is configured to apply to multiple properties on a node. So, in cases where multiple 065 * properties are changed on a single node (within a single repository transaction), the sequencer will only be executed once. 066 * Also, in such cases the sequencer's configuration may imply multiple output nodes, so it is left to the sequencer to define 067 * the behavior in such cases. 068 * </p> 069 * 070 * @param input the node that has recently been created or changed; never null 071 * @param sequencedPropertyName the name of the property that caused this sequencer to be executed; never null and never empty 072 * @param changes the immutable summary of changes that occurred on the <code>input</code> node within the transaction; never 073 * null 074 * @param outputPaths the paths to the nodes where the sequencing content should be placed; never null and never empty, but 075 * the set may contain paths for non-existent nodes or may reference the <code>input</code> node 076 * @param context the context in which this sequencer is executing; never null 077 * @param problems the interface used for recording problems; never null 078 * @throws SequencerException if there is an error in this sequencer 079 */ 080 void execute( Node input, 081 String sequencedPropertyName, 082 NetChange changes, 083 Set<RepositoryNodePath> outputPaths, 084 SequencerContext context, 085 Problems problems ) throws SequencerException; 086 087 }