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Neo4j Spatial

Neo4j Spatial is a library facilitating the import, storage and querying of spatial data in the [Neo4j open source graph database](http://neo4j.org/).

Open Street Map

Some key features include:

  • Utilities for importing from ESRI Shapefile as well as Open Street Map files

  • Support for all the common geometry types

  • An RTree index for fast searches on geometries

  • Support for topology operations during the search (contains, within, intersects, covers, disjoint, etc.)

  • The possibility to enable spatial operations on any graph of data, regardless of the way the spatial data is stored, as long as an adapter is provided to map from the graph to the geometries.

  • Ability to split a single layer or dataset into multiple sub-layers or views with pre-configured filters

Index and Querying

The current index is an RTree index, but it has been developed in an extensible way allowing for other indices to be added if necessary. The spatial queries implemented are:

  • Contain

  • Cover

  • Covered By

  • Cross

  • Disjoint

  • Intersect

  • Intersect Window

  • Overlap

  • Touch

  • Within

  • Within Distance

Building

The simplest way to build Neo4j Spatial is by using maven. Just clone the git repository and run

mvn install

This will download all dependencies, compiled the library, run the tests and install the artifact in your local repository.

Layers and GeometryEncoders

The primary type that defines a collection of geometries is the Layer. A layer contains an index for querying. In addition a Layer can be an EditableLayer if it is possible to add and modify geometries in the layer. The next most important interface is the GeometryEncoder.

The DefaultLayer is the standard layer, making use of the WKBGeometryEncoder for storing all geometry types as byte[] properties of one node per geometry instance.

The OSMLayer is a special layer supporting Open Street Map and storing the OSM model as a single fully connected graph. The set of Geometries provided by this layer includes Points, LineStrings and Polygons, and as such cannot be exported to Shapefile format, since that format only allows a single Geometry per layer. However, OMSLayer extends DynamicLayer, which allow it to provide any number of sub-layers, each with a specific geometry type and in addition based on a OSM tag filter. For example you can have a layer providing all cycle paths as LineStrings, or a layer providing all lakes as Polygons. Underneath these are all still backed by the same fully connected graph, but exposed dynamically as apparently separate geometry layers.

Examples

Importing a shapefile

Spatial data is divided in Layers and indexed by a RTree.

GraphDatabaseService database = new EmbeddedGraphDatabase(storeDir);
	try {
		ShapefileImporter importer = new ShapefileImporter(database);
	    importer.importFile("roads.shp", "layer_roads");
	} finally {
		database.shutdown();
	}

Importing an Open Street Map file

This is more complex because the current OSMImporter class runs in two phases, the first requiring a batch-inserter on the database. The is ongoing work to allow for a non-batch-inserter on the entire process, and possibly when you have read this that will already be available. Refer to the unit tests in classes TestDynamicLayers and TestOSMImport for the latest code for importing OSM data. At the time of writing the following worked:

	OSMImporter importer = new OSMImporter("sweden");

	BatchInserter batchInserter = new BatchInserterImpl(dir, config);
	importer.importFile(batchInserter, "sweden.osm", false);
	batchInserter.shutdown();

    GraphDatabaseService db = new EmbeddedGraphDatabase(dir);
	importer.reIndex(db, 10000);
	db.shutdown();

Executing a spatial query

	GraphDatabaseService database = new EmbeddedGraphDatabase(storeDir);
	try {
    	SpatialDatabaseService spatialService = new SpatialDatabaseService(database);
        Layer layer = spatialService.getLayer("layer_roads");
        SpatialIndexReader spatialIndex = layer.getIndex();

        Search searchQuery = new SearchIntersectWindow(new Envelope(xmin, xmax, ymin, ymax));
        spatialIndex.executeSearch(searchQuery);
   	    List<SpatialDatabaseRecord> results = searchQuery.getResults();
	} finally {
		database.shutdown();
	}

Refer to the test code in the LayerTest and the SpatialTest classes for more examples of query code. Also review the classes in the org.neo4j.gis.spatial.query package for the full range or search queries currently implemented.

Neo4j Spatial Geoserver Plugin

Important
Tested with: GeoServer 2.1.1

Building

mvn clean install

Deployment into Geoserver

  • unzip the target/xxxx-server-plugin.zip and the Neo4j libraries from your Neo4j download under NEO4J_HOME/lib into $GEOSERVER_HOME/webapps/geoserver/WEB-INF/lib

  • restart geoserver

  • configure a new workspace

  • configure a new datasource neo4j in your workspace. Point the "The directory path of the Neo4j database:" parameter to the relative (form the GeoServer working dir) or aboslute path to a Neo4j Spatial database with layers (see Neo4j Spatial)

  • in Layers, do "Add new resource" and choose your Neo4j datastore to see the exisitng Neo4j Spatial layers and add them.

Testing in GeoServer trunk

  • check out the geoserver source

svn co https://svn.codehaus.org/geoserver/trunk geoserver-trunk
  • build the source

cd geoserver-trunk
mvn clean install
cd src/web/app
mvn jetty:run
    <profile>
      <id>neo4j</id>
      <dependencies>
        <dependency>
          <groupId>org.neo4j</groupId>
          <artifactId>neo4j-spatial</artifactId>
          <version>0.9-SNAPSHOT</version>
        </dependency>
      </dependencies>
    </profile>
  • start the GeoServer webapp again with the added neo4j profile

cd $GEOSERVER_SRC/src/web/app
mvn jetty:run -Pneo4j

Using Neo4j Spatial with uDig

For more info head over to [Neo4j Wiki on uDig](http://wiki.neo4j.org/content/Neo4j_Spatial_in_uDig)

Using the Neo4j Spatial Server plugin

Neo4j Spatial is also packaged as a ZIP file that can be unzipped into the Neo4j Server /plugin directory. After restarting the server, you should be able to do things liek the following REST calls (here illustrated using curl)

    #install the plugin
    cp $NEO4J_SPATIAL_HOME/target/neo4j-spatial-XXXX-server-plugin.zip $NEO4J_HOME/plugins
    cd unzip neo4j-spatial-XXXX-server-plugin.zip -d $NEO4J_HOME/plugins

    #start the server
    $NEO4J_HOME/bin/neo4j start

    curl http://localhost:7474/db/data/

    {
      "relationship_index" : "http://localhost:7474/db/data/index/relationship",
      "node" : "http://localhost:7474/db/data/node",
      "relationship_types" : "http://localhost:7474/db/data/relationship/types",
      "extensions_info" : "http://localhost:7474/db/data/ext",
      "node_index" : "http://localhost:7474/db/data/index/node",
      "reference_node" : "http://localhost:7474/db/data/node/0",
      "extensions" : {
      "SpatialPlugin" : {
          "addSimplePointLayer" : "http://localhost:7474/db/data/ext/SpatialPlugin/graphdb/addSimplePointLayer",
          "addNodeToLayer" : "http://localhost:7474/db/data/ext/SpatialPlugin/graphdb/addNodeToLayer"
        }
      }
    }

    curl -d "layer=test" http://localhost:7474/db/data/ext/SpatialPlugin/graphdb/addSimplePointLayer

    Creating new layer 'test' unless it already exists
    [ {
      "outgoing_relationships" : "http://localhost:7474/db/data/node/2/relationships/out",
      "data" : {
        "layer_class" : "org.neo4j.gis.spatial.EditableLayerImpl",
        "layer" : "test",
        "geomencoder" : "org.neo4j.gis.spatial.encoders.SimplePointEncoder",
        "ctime" : 1304444390349
      },
      "traverse" : "http://localhost:7474/db/data/node/2/traverse/{returnType}",
      "all_typed_relationships" : "http://localhost:7474/db/data/node/2/relationships/all/{-list|&|types}",
      "property" : "http://localhost:7474/db/data/node/2/properties/{key}",
      "self" : "http://localhost:7474/db/data/node/2",
      "properties" : "http://localhost:7474/db/data/node/2/properties",
      "outgoing_typed_relationships" : "http://localhost:7474/db/data/node/2/relationships/out/{-list|&|types}",
      "incoming_relationships" : "http://localhost:7474/db/data/node/2/relationships/in",
      "extensions" : {
      },
      "create_relationship" : "http://localhost:7474/db/data/node/2/relationships",
      "all_relationships" : "http://localhost:7474/db/data/node/2/relationships/all",
      "incoming_typed_relationships" : "http://localhost:7474/db/data/node/2/relationships/in/{-list|&|types}"
    } ]

Building Neo4j spatial

    git clone https://github.com/neo4j/spatial.git
    cd spatial
    mvn clean package

Integration-Testing the Neo4j-Spatial Server Plugin

    source ./setenv.sh
    rake

or

    mvn integration-test -Dcucumber.installGems=true -Pqa-test

Using Neo4j spatial in your Java project with Maven

Add the following dependency to your project’s pom.xml:

        <dependency>
            <groupId>org.neo4j</groupId>
            <artifactId>neo4j-spatial</artifactId>
            <version>0.9-SNAPSHOT</version>
        </dependency>

Note: neo4j-spatial has a mandatory dependency on GremlinGroovyPipeline from the com.tinkerpop.gremlin.groovy package. The dependency in neo4j is type provided, so when using neo4j-spatial in your own Java project, make sure to add the following dependency to your pom.xml, too.

        <dependency>
            <groupId>com.tinkerpop.gremlin</groupId>
            <artifactId>gremlin-groovy</artifactId>
            <version>1.4</version>
            <type>jar</type>
            <exclusions>
        <!-- Sail support not needed -->
                <exclusion>
                    <groupId>com.tinkerpop.blueprints</groupId>
                    <artifactId>blueprints-sail-graph</artifactId>
                </exclusion>
        <!-- Maven support in groovy not needed -->
                <exclusion>
                    <groupId>org.codehaus.groovy.maven</groupId>
                    <artifactId>gmaven-plugin</artifactId>
                </exclusion>
        <!-- "readline" not needed - we only expose gremlin through webadmin -->
                <exclusion>
                    <groupId>jline</groupId>
                    <artifactId>jline</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

If the dependency is omitted, neo4j-spatial will probably throw an exception like this:

java.lang.NoClassDefFoundError: com/tinkerpop/gremlin/groovy/GremlinGroovyPipeline
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
at org.neo4j.gis.spatial.indexprovider.LayerNodeIndex.query(LayerNodeIndex.java:237)
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