Neo4j Export to Graphviz

GraphvizFunction.java

package myapp;

import java.util.HashSet;
import java.util.Set;

import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Relationship;
import org.neo4j.procedure.Description;
import org.neo4j.procedure.Name;
import org.neo4j.procedure.UserAggregationFunction;
import org.neo4j.procedure.UserAggregationResult;
import org.neo4j.procedure.UserAggregationUpdate;

public class GraphvizFunction {
    @UserAggregationFunction
    @Description("myapp.exportGraphviz(nodes, rels) - draws specified nodes and relationships with Graphviz")
    public NodesRelsAggregator exportGraphviz() {
        return new NodesRelsAggregator();
    }

    public static class NodesRelsAggregator {
        private Set<Node> nodes = new HashSet<>();
        private Set<Relationship> relationships = new HashSet<>();

        @UserAggregationUpdate
        public void exportGraphviz(@Name("node") Node node, @Name("relationship") Relationship rel) {
            nodes.add(node);
            relationships.add(rel);
        }

        @UserAggregationResult
        public String result() {
            return MyGraphvizWriter.getGraphvizForNodesAndRels(nodes, relationships);
        }
    }
}

MyGraphvizWriter.java

package myapp;

import java.io.ByteArrayOutputStream;
import java.nio.charset.Charset;
import java.util.Set;

import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Relationship;
import org.neo4j.visualization.graphviz.GraphvizWriter;
import org.neo4j.walk.Visitor;
import org.neo4j.walk.Walker;

public class MyGraphvizWriter {
    
    public static String getGraphvizForNodesAndRels(Set<Node> nodes, Set<Relationship> relationships) {
        try {
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            GraphvizWriter writer = new GraphvizWriter();
            writer.emit(out, getWalkerForNodesAndRels(nodes, relationships));
            return out.toString(Charset.defaultCharset());
        } catch (Exception e) {e.printStackTrace();}
        return null;
    }
    
    private static Walker getWalkerForNodesAndRels(Set<Node> nodes, Set<Relationship> relationships) {
        return new Walker() {
            @Override
            public <R, E extends Throwable> R accept(Visitor<R,E> visitor) throws E {
                for (Node node : nodes) {
                    visitor.visitNode(node);
                }
                for (Relationship relationship : relationships) {
                    visitor.visitRelationship(relationship);
                }
                return visitor.done();
            }
        };
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>mygroup</groupId>
	<artifactId>Neo4jGraphvizPlugin</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	
	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.neo4j</groupId>
			<artifactId>neo4j</artifactId>
			<version>5.22.0</version>
			<scope>provided</scope>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<source>17</source>
					<target>17</target>
				</configuration>
			</plugin>
			<plugin>
				<artifactId>maven-shade-plugin</artifactId>
				<executions>
					<execution>
						<phase>package</phase>
						<goals>
							<goal>shade</goal>
						</goals>
					</execution>
				</executions>
			</plugin>
		</plugins>
	</build>
</project>