org.jgrapht.nio.json.JSONImporter Maven / Gradle / Ivy
/*
* (C) Copyright 2019-2021, by Dimitrios Michail and Contributors.
*
* JGraphT : a free Java graph-theory library
*
* See the CONTRIBUTORS.md file distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the
* GNU Lesser General Public License v2.1 or later
* which is available at
* http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html.
*
* SPDX-License-Identifier: EPL-2.0 OR LGPL-2.1-or-later
*/
package org.jgrapht.nio.json;
import java.io.Reader;
import java.util.HashMap;
import java.util.Map;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;
import org.jgrapht.Graph;
import org.jgrapht.GraphType;
import org.jgrapht.alg.util.Pair;
import org.jgrapht.alg.util.Triple;
import org.jgrapht.nio.Attribute;
import org.jgrapht.nio.BaseEventDrivenImporter;
import org.jgrapht.nio.DefaultAttribute;
import org.jgrapht.nio.GraphImporter;
import org.jgrapht.nio.ImportException;
/**
* Imports a graph from a JSON file.
*
* Below is a small example of a graph in JSON format.
*
*
* {
* "nodes": [
* { "id": "1" },
* { "id": "2", "label": "Node 2 label" },
* { "id": "3" }
* ],
* "edges": [
* { "source": "1", "target": "2", "weight": 2.0, "label": "Edge between 1 and 2" },
* { "source": "2", "target": "3", "weight": 3.0, "label": "Edge between 2 and 3" }
* ]
* }
*
*
*
* In case the graph is weighted then the importer also reads edge weights. Otherwise edge weights
* are ignored. The importer also supports reading additional string attributes such as label or
* custom user attributes.
*
*
* The parser completely ignores elements from the input that are not related to vertices or edges
* of the graph. Moreover, complicated nested structures which are inside vertices or edges are
* simply returned as a whole. For example, in the following graph
*
*
* {
* "nodes": [
* { "id": "1" },
* { "id": "2" }
* ],
* "edges": [
* { "source": "1", "target": "2", "points": { "x": 1.0, "y": 2.0 } }
* ]
* }
*
*
* the points attribute of the edge is returned as a string containing {"x":1.0,"y":2.0}. The same
* is done for arrays or any other arbitrary nested structure.
*
*
* 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 {@link #setVertexFactory(Function)}. The factory method is responsible to create a new
* graph vertex given the vertex identifier read from file. Additionally this importer also supports
* creating vertices with {@link #setVertexWithAttributesFactory(BiFunction)}. This factory method
* is responsible for creating a new graph vertex given the vertex identifier read from file
* together with all available attributes of the vertex at the location of the file where the vertex
* is first defined.
*
*
* The default behavior of the importer is to use the graph edge supplier in order to create edges.
* The user can also bypass edge creation by providing a custom edge factory method using
* {@link #setEdgeWithAttributesFactory(Function)}. The factory method is responsible to create a
* new graph edge given all available attributes of the edge at the location of the file where the
* edge is first defined.
*
* @param the vertex type
* @param the edge type
*
* @author Dimitrios Michail
*/
public class JSONImporter
extends
BaseEventDrivenImporter
implements
GraphImporter
{
/**
* Default key used for vertex ID.
*/
public static final String DEFAULT_VERTEX_ID_KEY = "ID";
private Function vertexFactory;
private BiFunction, V> vertexWithAttributesFactory;
private Function, E> edgeWithAttributesFactory;
/**
* Construct a new importer
*/
public JSONImporter()
{
super();
}
/**
* Import a graph.
*
*
* The provided graph must be able to support the features of the graph that is read. For
* example if the file contains self-loops then the graph provided must also support self-loops.
* The same for multiple edges.
*
*
* If the provided graph is a weighted graph, the importer also reads edge weights. Otherwise
* edge weights are ignored.
*
* @param graph the output graph
* @param input the input reader
* @throws ImportException in case an error occurs, such as I/O or parse error
*/
@Override
public void importGraph(Graph graph, Reader input)
{
final boolean verticesOutOfOrder = vertexWithAttributesFactory == null;
final boolean edgesOutOfOrder = edgeWithAttributesFactory == null;
JSONEventDrivenImporter genericImporter =
new JSONEventDrivenImporter(verticesOutOfOrder, edgesOutOfOrder);
Consumers consumers = new Consumers(graph);
if (vertexWithAttributesFactory != null) {
genericImporter.addVertexWithAttributesConsumer(consumers.vertexWithAttributesConsumer);
} else {
genericImporter.addVertexConsumer(consumers.vertexConsumer);
}
genericImporter.addVertexAttributeConsumer(consumers.vertexAttributeConsumer);
if (edgeWithAttributesFactory != null) {
genericImporter.addEdgeWithAttributesConsumer(consumers.edgeWithAttributesConsumer);
} else {
genericImporter.addEdgeConsumer(consumers.edgeConsumer);
}
genericImporter.addEdgeAttributeConsumer(consumers.edgeAttributeConsumer);
genericImporter.importInput(input);
}
/**
* Get the user custom vertex factory. This is null by default and the graph supplier is used
* instead.
*
* @return the user custom vertex factory
*/
public Function getVertexFactory()
{
return 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.
*
* @param vertexFactory a vertex factory
*/
public void setVertexFactory(Function vertexFactory)
{
this.vertexFactory = vertexFactory;
}
/**
* Set the user custom vertex factory with attributes. 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 input.
* The method is called with parameter the vertex identifier from the input and a set of
* attributes and should return the actual graph vertex to add to the graph. Note that the set
* of attributes might not be complete, as only attributes available at the first vertex
* definition are collected.
*
* @param vertexWithAttributesFactory a vertex factory with attributes
*/
public void setVertexWithAttributesFactory(
BiFunction, V> vertexWithAttributesFactory)
{
this.vertexWithAttributesFactory = vertexWithAttributesFactory;
}
/**
* Get the user custom edges factory with attributes. This is null by default and the graph
* supplier is used instead.
*
* @return the user custom edge factory with attributes.
*/
public Function, E> getEdgeWithAttributesFactory()
{
return edgeWithAttributesFactory;
}
/**
* Set the user custom edge factory with attributes. The default behavior is being null in which
* case the graph edge supplier is used.
*
* If supplied the edge factory is called every time a new edge is encountered in the input. The
* method is called with parameter the set of attributes and should return the actual graph edge
* to add to the graph. Note that the set of attributes might not be complete, as only
* attributes available at the first edge definition are collected.
*
* @param edgeWithAttributesFactory an edge factory with attributes
*/
public void setEdgeWithAttributesFactory(
Function, E> edgeWithAttributesFactory)
{
this.edgeWithAttributesFactory = edgeWithAttributesFactory;
}
private class Consumers
{
private Graph graph;
private GraphType graphType;
private Map map;
private Triple lastTriple;
private E lastEdge;
public Consumers(Graph graph)
{
this.graph = graph;
this.graphType = graph.getType();
this.map = new HashMap<>();
}
public final Consumer vertexConsumer = (t) -> {
if (map.containsKey(t)) {
throw new ImportException("Node " + t + " already exists");
}
V v;
if (vertexFactory != null) {
v = vertexFactory.apply(t);
graph.addVertex(v);
} else {
v = graph.addVertex();
}
map.put(t, v);
notifyVertex(v);
notifyVertexAttribute(v, DEFAULT_VERTEX_ID_KEY, DefaultAttribute.createAttribute(t));
};
public final BiConsumer> vertexWithAttributesConsumer =
(t, attrs) -> {
if (map.containsKey(t)) {
throw new ImportException("Node " + t + " already exists");
}
V v;
if (vertexWithAttributesFactory != null) {
v = vertexWithAttributesFactory.apply(t, attrs);
graph.addVertex(v);
} else {
v = graph.addVertex();
}
map.put(t, v);
// notify with all collected attributes
attrs.put(DEFAULT_VERTEX_ID_KEY, DefaultAttribute.createAttribute(t));
notifyVertexWithAttributes(v, attrs);
};
public final BiConsumer, Attribute> vertexAttributeConsumer =
(p, a) -> {
String vertex = p.getFirst();
if (!map.containsKey(vertex)) {
throw new ImportException("Node " + vertex + " does not exist");
}
notifyVertexAttribute(map.get(vertex), p.getSecond(), a);
};
public final Consumer> edgeConsumer = (t) -> {
String source = t.getFirst();
V from = map.get(source);
if (from == null) {
throw new ImportException("Node " + source + " does not exist");
}
String target = t.getSecond();
V to = map.get(target);
if (to == null) {
throw new ImportException("Node " + target + " does not exist");
}
E e = graph.addEdge(from, to);
if (graphType.isWeighted() && t.getThird() != null) {
graph.setEdgeWeight(e, t.getThird());
}
notifyEdge(e);
lastTriple = t;
lastEdge = e;
};
public final BiConsumer,
Map> edgeWithAttributesConsumer = (t, attrs) -> {
String source = t.getFirst();
V from = map.get(source);
if (from == null) {
throw new ImportException("Node " + source + " does not exist");
}
String target = t.getSecond();
V to = map.get(target);
if (to == null) {
throw new ImportException("Node " + target + " does not exist");
}
E e;
if (edgeWithAttributesFactory != null) {
e = edgeWithAttributesFactory.apply(attrs);
graph.addEdge(from, to, e);
} else {
e = graph.addEdge(from, to);
}
notifyEdgeWithAttributes(e, attrs);
lastTriple = t;
lastEdge = e;
};
public final BiConsumer, String>,
Attribute> edgeAttributeConsumer = (p, a) -> {
Triple t = p.getFirst();
if (t == lastTriple) {
notifyEdgeAttribute(lastEdge, p.getSecond(), a);
}
};
}
}