-
Notifications
You must be signed in to change notification settings - Fork 2.3k
/
CalculateShortestPath.java
138 lines (127 loc) · 4.74 KB
/
CalculateShortestPath.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
/*
* 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 java.io.File;
import org.neo4j.graphalgo.GraphAlgoFactory;
import org.neo4j.graphalgo.PathFinder;
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.RelationshipType;
import org.neo4j.graphdb.Transaction;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;
import org.neo4j.graphdb.index.Index;
import org.neo4j.graphdb.traversal.Paths;
public class CalculateShortestPath
{
private static final String DB_PATH = "target/neo4j-shortest-path";
private static final String NAME_KEY = "name";
private static RelationshipType KNOWS = RelationshipType.withName( "KNOWS" );
private static GraphDatabaseService graphDb;
private static Index<Node> indexService;
public static void main( final String[] args )
{
deleteFileOrDirectory( new File( DB_PATH ) );
graphDb = new GraphDatabaseFactory().newEmbeddedDatabase( DB_PATH );
registerShutdownHook();
try ( Transaction tx = graphDb.beginTx() )
{
indexService = graphDb.index().forNodes( "nodes" );
/*
* (Neo) --> (Trinity)
* \ ^
* v /
* (Morpheus) --> (Cypher)
* \ |
* v v
* (Agent Smith)
*/
createChain( "Neo", "Trinity" );
createChain( "Neo", "Morpheus", "Trinity" );
createChain( "Morpheus", "Cypher", "Agent Smith" );
createChain( "Morpheus", "Agent Smith" );
tx.success();
}
try ( Transaction tx = graphDb.beginTx() )
{
// So let's find the shortest path between Neo and Agent Smith
Node neo = getOrCreateNode( "Neo" );
Node agentSmith = getOrCreateNode( "Agent Smith" );
// START SNIPPET: shortestPathUsage
PathFinder<Path> finder = GraphAlgoFactory.shortestPath(
PathExpanders.forTypeAndDirection( KNOWS, Direction.BOTH ), 4 );
Path foundPath = finder.findSinglePath( neo, agentSmith );
System.out.println( "Path from Neo to Agent Smith: "
+ Paths.simplePathToString( foundPath, NAME_KEY ) );
// END SNIPPET: shortestPathUsage
}
System.out.println( "Shutting down database ..." );
graphDb.shutdown();
}
private static void createChain( String... names )
{
for ( int i = 0; i < names.length - 1; i++ )
{
Node firstNode = getOrCreateNode( names[i] );
Node secondNode = getOrCreateNode( names[i + 1] );
firstNode.createRelationshipTo( secondNode, KNOWS );
}
}
private static Node getOrCreateNode( String name )
{
Node node = indexService.get( NAME_KEY, name ).getSingle();
if ( node == null )
{
node = graphDb.createNode();
node.setProperty( NAME_KEY, name );
indexService.add( node, NAME_KEY, name );
}
return node;
}
private static void registerShutdownHook()
{
// Registers a shutdown hook for the Neo4j instance so that it
// shuts down nicely when the VM exits (even if you "Ctrl-C" the
// running example before it's completed)
Runtime.getRuntime().addShutdownHook( new Thread()
{
@Override
public void run()
{
graphDb.shutdown();
}
} );
}
private static void deleteFileOrDirectory( File file )
{
if ( file.exists() )
{
if ( file.isDirectory() )
{
for ( File child : file.listFiles() )
{
deleteFileOrDirectory( child );
}
}
file.delete();
}
}
}