/
PathFindingDocTest.java
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/
PathFindingDocTest.java
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/**
* Licensed to Neo Technology under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Neo Technology 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.neo4j.examples;
import static org.junit.Assert.assertEquals;
import java.io.File;
import java.util.Iterator;
import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;
import org.neo4j.graphalgo.CommonEvaluators;
import org.neo4j.graphalgo.EstimateEvaluator;
import org.neo4j.graphalgo.GraphAlgoFactory;
import org.neo4j.graphalgo.PathFinder;
import org.neo4j.graphalgo.WeightedPath;
import org.neo4j.graphdb.Direction;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Path;
import org.neo4j.graphdb.PathExpanders;
import org.neo4j.graphdb.PropertyContainer;
import org.neo4j.graphdb.Relationship;
import org.neo4j.graphdb.RelationshipType;
import org.neo4j.graphdb.Transaction;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;
import org.neo4j.test.TargetDirectory;
public class PathFindingDocTest
{
private static GraphDatabaseService graphDb;
private Transaction tx;
private static enum ExampleTypes implements RelationshipType
{
MY_TYPE
}
@BeforeClass
public static void startDb()
{
String storeDir = TargetDirectory.forTest( PathFindingDocTest.class ).makeGraphDbDir().getAbsolutePath();
deleteFileOrDirectory( new File( storeDir ) );
graphDb = new GraphDatabaseFactory().newEmbeddedDatabase( storeDir );
}
@Before
public void doBefore()
{
tx = graphDb.beginTx();
}
@After
public void doAfter()
{
tx.success();
tx.close();
}
@AfterClass
public static void shutdownDb()
{
try
{
if ( graphDb != null ) graphDb.shutdown();
}
finally
{
graphDb = null;
}
}
@Test
public void shortestPathExample()
{
// START SNIPPET: shortestPathUsage
Node startNode = graphDb.createNode();
Node middleNode1 = graphDb.createNode();
Node middleNode2 = graphDb.createNode();
Node middleNode3 = graphDb.createNode();
Node endNode = graphDb.createNode();
createRelationshipsBetween( startNode, middleNode1, endNode );
createRelationshipsBetween( startNode, middleNode2, middleNode3, endNode );
// Will find the shortest path between startNode and endNode via
// "MY_TYPE" relationships (in OUTGOING direction), like f.ex:
//
// (startNode)-->(middleNode1)-->(endNode)
//
PathFinder<Path> finder = GraphAlgoFactory.shortestPath(
PathExpanders.forTypeAndDirection( ExampleTypes.MY_TYPE, Direction.OUTGOING ), 15 );
Iterable<Path> paths = finder.findAllPaths( startNode, endNode );
// END SNIPPET: shortestPathUsage
Path path = paths.iterator().next();
assertEquals( 2, path.length() );
assertEquals( startNode, path.startNode() );
assertEquals( endNode, path.endNode() );
Iterator<Node> iterator = path.nodes().iterator();
iterator.next();
assertEquals( middleNode1, iterator.next() );
}
private void createRelationshipsBetween( final Node... nodes )
{
for ( int i = 0; i < nodes.length - 1; i++ )
{
nodes[i].createRelationshipTo( nodes[i+1], ExampleTypes.MY_TYPE );
}
}
@Test
public void dijkstraUsage()
{
Node node1 = graphDb.createNode();
Node node2 = graphDb.createNode();
Relationship rel = node1.createRelationshipTo( node2, ExampleTypes.MY_TYPE );
rel.setProperty( "cost", 1d );
findCheapestPathWithDijkstra( node1, node2 );
}
public WeightedPath findCheapestPathWithDijkstra( final Node nodeA, final Node nodeB )
{
// START SNIPPET: dijkstraUsage
PathFinder<WeightedPath> finder = GraphAlgoFactory.dijkstra(
PathExpanders.forTypeAndDirection( ExampleTypes.MY_TYPE, Direction.BOTH ), "cost" );
WeightedPath path = finder.findSinglePath( nodeA, nodeB );
// Get the weight for the found path
path.weight();
// END SNIPPET: dijkstraUsage
return path;
}
private Node createNode( final Object... properties )
{
return setProperties( graphDb.createNode(), properties );
}
private <T extends PropertyContainer> T setProperties( final T entity, final Object[] properties )
{
for ( int i = 0; i < properties.length; i++ )
{
String key = properties[i++].toString();
Object value = properties[i];
entity.setProperty( key, value );
}
return entity;
}
private Relationship createRelationship( final Node start, final Node end,
final Object... properties )
{
return setProperties( start.createRelationshipTo( end, ExampleTypes.MY_TYPE ),
properties );
}
@SuppressWarnings( "unused" )
@Test
public void astarExample()
{
// START SNIPPET: astarUsage
Node nodeA = createNode( "name", "A", "x", 0d, "y", 0d );
Node nodeB = createNode( "name", "B", "x", 7d, "y", 0d );
Node nodeC = createNode( "name", "C", "x", 2d, "y", 1d );
Relationship relAB = createRelationship( nodeA, nodeC, "length", 2d );
Relationship relBC = createRelationship( nodeC, nodeB, "length", 3d );
Relationship relAC = createRelationship( nodeA, nodeB, "length", 10d );
EstimateEvaluator<Double> estimateEvaluator = new EstimateEvaluator<Double>()
{
@Override
public Double getCost( final Node node, final Node goal )
{
double dx = (Double) node.getProperty( "x" ) - (Double) goal.getProperty( "x" );
double dy = (Double) node.getProperty( "y" ) - (Double) goal.getProperty( "y" );
double result = Math.sqrt( Math.pow( dx, 2 ) + Math.pow( dy, 2 ) );
return result;
}
};
PathFinder<WeightedPath> astar = GraphAlgoFactory.aStar(
PathExpanders.allTypesAndDirections(),
CommonEvaluators.doubleCostEvaluator( "length" ), estimateEvaluator );
WeightedPath path = astar.findSinglePath( nodeA, nodeB );
// END SNIPPET: astarUsage
}
public static void deleteFileOrDirectory( File file )
{
if ( !file.exists() )
{
return;
}
if ( file.isDirectory() )
{
for ( File child : file.listFiles() )
{
deleteFileOrDirectory( child );
}
}
else
{
file.delete();
}
}
}