Module org.jgrapht.io
Package org.jgrapht.nio.graphml

Class SimpleGraphMLImporter<V,E>

java.lang.Object
org.jgrapht.nio.BaseEventDrivenImporter<V,E>
org.jgrapht.nio.graphml.SimpleGraphMLImporter<V,E>
Type Parameters:
V - the graph vertex type
E - the graph edge type
All Implemented Interfaces:
GraphImporter<V,E>
public class SimpleGraphMLImporter<V,E> extends BaseEventDrivenImporter<V,E> implements GraphImporter<V,E>
Imports a graph from a GraphML data source.

This is a simple implementation with supports only a limited set of features of the GraphML specification. For a more rigorous parser use GraphMLImporter. This version is oriented towards parsing speed.

The importer uses the graph suppliers (Graph.getVertexSupplier() and Graph.getEdgeSupplier()) in order to create new vertices and edges. Moreover, it notifies lazily and completely out-of-order for any additional vertex, edge or graph attributes in the input file. Users can register consumers for vertex, edge and graph attributes after construction of the importer. Finally, default attribute values are completely ignored.

For a description of the format see http://en.wikipedia.org/wiki/ GraphML or the GraphML Primer.

Below is small example of a graph in GraphML format. 

 
 <?xml version="1.0" encoding="UTF-8"?>
 <graphml xmlns="http://graphml.graphdrawing.org/xmlns"  
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns 
     http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
   <key id="d0" for="node" attr.name="color" attr.type="string" />
   <key id="d1" for="edge" attr.name="weight" attr.type="double"/>
   <graph id="G" edgedefault="undirected">
     <node id="n0">
       <data key="d0">green</data>
     </node>
     <node id="n1">
       <data key="d0">black</data>
     </node>     
     <node id="n2">
       <data key="d0">blue</data>
     </node>
     <node id="n3">
       <data key="d0">red</data>
     </node>
     <node id="n4">
       <data key="d0">white</data>
     </node>
     <node id="n5">
       <data key="d0">turquoise</data>
     </node>
     <edge id="e0" source="n0" target="n2">
       <data key="d1">1.0</data>
     </edge>
     <edge id="e1" source="n0" target="n1">
       <data key="d1">1.0</data>
     </edge>
     <edge id="e2" source="n1" target="n3">
       <data key="d1">2.0</data>
     </edge>
     <edge id="e3" source="n3" target="n2"/>
     <edge id="e4" source="n2" target="n4"/>
     <edge id="e5" source="n3" target="n5"/>
     <edge id="e6" source="n5" target="n4">
       <data key="d1">1.1</data>
     </edge>
   </graph>
 </graphml>

The importer reads the input into a graph which is provided by the user. In case the graph is weighted and the corresponding edge key with attr.name="weight" is defined, the importer also reads edge weights. Otherwise edge weights are ignored. To test whether the graph is weighted, method Graph.getType() can be used.

The provided graph object, where the imported graph will be stored, must be able to support the features of the graph that is read. For example if the GraphML file contains self-loops then the graph provided must also support self-loops. The same for multiple edges. Moreover, the parser completely ignores the attribute "edgedefault" which denotes whether an edge is directed or not. Whether edges are directed or not depends on the underlying implementation of the user provided graph object.

The importer by default validates the input using the 1.0 GraphML Schema. The user can (not recommended) disable the validation by calling setSchemaValidation(boolean).

The graph vertices and edges are build using the corresponding graph suppliers. The id of the vertices in the original dot file are reported as a vertex attribute named "ID". Thus, in case vertices in the dot file also contain an "ID" attribute, such an attribute will be reported multiple times.

The default behavior of the importer is to use the graph vertex supplier in order to create vertices. The user can also bypass vertex creation by providing a custom vertex factory method using setVertexFactory(Function). The factory method is responsible to create a new graph vertex given the vertex identifier read from file.

Author:
Dimitrios Michail

  • Field Details

    • DEFAULT_VERTEX_ID_KEY

      public static final String DEFAULT_VERTEX_ID_KEY
      Default key used for vertex ID.
      See Also:

  • Constructor Details

    • SimpleGraphMLImporter

      public SimpleGraphMLImporter()
      Constructs a new importer.

  • Method Details

    • getEdgeWeightAttributeName

      public String getEdgeWeightAttributeName()
      Get the attribute name for edge weights
      Returns:
      the attribute name

    • setEdgeWeightAttributeName

      public void setEdgeWeightAttributeName(String edgeWeightAttributeName)
      Set the attribute name to use for edge weights.
      Parameters:
      edgeWeightAttributeName - the attribute name

    • isSchemaValidation

      public boolean isSchemaValidation()
      Whether the importer validates the input
      Returns:
      true if the importer validates the input

    • setSchemaValidation

      public void setSchemaValidation(boolean schemaValidation)
      Set whether the importer should validate the input
      Parameters:
      schemaValidation - value for schema validation

    • getVertexFactory

      public Function<String,V> getVertexFactory()
      Get the user custom vertex factory. This is null by default and the graph supplier is used instead.
      Returns:
      the user custom vertex factory

    • setVertexFactory

      public void setVertexFactory(Function<String,V> vertexFactory)
      Set the user custom vertex factory. The default behavior is being null in which case the graph vertex supplier is used. If supplied the vertex factory is called every time a new vertex is encountered in the file. The method is called with parameter the vertex identifier from the file and should return the actual graph vertex to add to the graph.
      Parameters:
      vertexFactory - a vertex factory

    • importGraph

      public void importGraph(Graph<V,E> graph, Reader input)
      Import a graph.

      The provided graph must be able to support the features of the graph that is read. For example if the GraphML file contains self-loops then the graph provided must also support self-loops. The same for multiple edges.

      Specified by:
      importGraph in interface GraphImporter<V,E>
      Parameters:
      graph - the output graph
      input - the input reader
      Throws:
      ImportException - in case an error occurs, such as I/O or parse error