Neo4j Result (in JSON format) to create D3 Tree Graph

Question

I am trying to represent a Hierarchy using a D3 Tree with some additional field details. Now I am not sure/dont know, how to get the required JSON for the D3 Tree graph; directly from the Java neo4j APIs. For some reason we are using Embedded Neo4j and Web-Service on top of Neo4j.

Seeking advice and sample Java code producing the following JSON format for the relationship:

A Sample Json and the D3 implementation is given below.

Domain Model:

(Switch)-[:CONNECTED_TO]->(Switch)

Using the JSON Format (See below) I want to generate a D3 Tree like below

var json = 
     {
  "name": "Start",
  "display" : "Entry",
  "parent": "null",
  "children": [
    {
      "name": "Swith-1",
      "display": "United States of America Entry Swith",
      "parent": "Start",
      "children": [
        {
          "name": "Swith-1.1",
      	  "display": "IL Entry Swith",
          "parent": "Swith-1",
           "children": [
				        {
				          "name": "Swith-1.1.1",
				      	  "display": "Chicago Entry Swith",
				          "parent": "Swith-1.1"
				        },
				        {
				          "name": "Swith-1.1.2",
				      	  "display": "Springfield Entry Swith",
				          "parent": "Swith-1.1"
				        }
				      ] 
        },
        {
          "name": "Swith-1.2",
      	  "display": "CA Entry Swith",
          "parent": "Swith-1"
        }
      ]
    },
    {
      "name": "Swith-2",
      "display": "External gateways",
      "parent": "Start"
    }
  ]
};

var width = 700;
var height = 650;
var maxLabel = 150;
var duration = 500;
var radius = 5;
    
var i = 0;
var root;

var tree = d3.layout.tree()
    .size([height, width]);

var diagonal = d3.svg.diagonal()
    .projection(function(d) { return [d.y, d.x]; });

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height)
        .append("g")
        .attr("transform", "translate(" + maxLabel + ",0)");

root = json;
root.x0 = height / 2;
root.y0 = 0;

root.children.forEach(collapse);

function update(source) 
{
    // Compute the new tree layout.
    var nodes = tree.nodes(root).reverse();
    var links = tree.links(nodes);

    // Normalize for fixed-depth.
    nodes.forEach(function(d) { d.y = d.depth * maxLabel; });

    // Update the nodes…
    var node = svg.selectAll("g.node")
        .data(nodes, function(d){ 
            return d.id || (d.id = ++i); 
        });

    // Enter any new nodes at the parent's previous position.
    var nodeEnter = node.enter()
        .append("g")
        .attr("class", "node")
        .attr("transform", function(d){ return "translate(" + source.y0 + "," + source.x0 + ")"; })
        .on("click", click);

    nodeEnter.append("circle")
        .attr("r", 0)
        .style("fill", function(d){ 
            return d._children ? "lightsteelblue" : "white"; 
        });

    nodeEnter.append("text")
        .attr("x", function(d){ 
            var spacing = computeRadius(d) + 5;
            return d.children || d._children ? -spacing : spacing; 
        })
        .attr("dy", "3")
        .attr("text-anchor", function(d){ return d.children || d._children ? "end" : "start"; })
        .text(function(d){ return d.name; })
        .style("fill-opacity", 0);

    // Transition nodes to their new position.
    var nodeUpdate = node.transition()
        .duration(duration)
        .attr("transform", function(d) { return "translate(" + d.y + "," + d.x + ")"; });

    nodeUpdate.select("circle")
        .attr("r", function(d){ return computeRadius(d); })
        .style("fill", function(d) { return d._children ? "lightsteelblue" : "#fff"; });

    nodeUpdate.select("text").style("fill-opacity", 1);

    // Transition exiting nodes to the parent's new position.
    var nodeExit = node.exit().transition()
        .duration(duration)
        .attr("transform", function(d) { return "translate(" + source.y + "," + source.x + ")"; })
        .remove();

    nodeExit.select("circle").attr("r", 0);
    nodeExit.select("text").style("fill-opacity", 0);

    // Update the links…
    var link = svg.selectAll("path.link")
        .data(links, function(d){ return d.target.id; });

    // Enter any new links at the parent's previous position.
    link.enter().insert("path", "g")
        .attr("class", "link")
        .attr("d", function(d){
            var o = {x: source.x0, y: source.y0};
            return diagonal({source: o, target: o});
        });

    // Transition links to their new position.
    link.transition()
        .duration(duration)
        .attr("d", diagonal);

    // Transition exiting nodes to the parent's new position.
    link.exit().transition()
        .duration(duration)
        .attr("d", function(d){
            var o = {x: source.x, y: source.y};
            return diagonal({source: o, target: o});
        })
        .remove();

    // Stash the old positions for transition.
    nodes.forEach(function(d){
        d.x0 = d.x;
        d.y0 = d.y;
    });
}

function computeRadius(d)
{
    if(d.children || d._children) return radius + (radius * nbEndNodes(d) / 10);
    else return radius;
}

function nbEndNodes(n)
{
    nb = 0;    
    if(n.children){
        n.children.forEach(function(c){ 
            nb += nbEndNodes(c); 
        });
    }
    else if(n._children){
        n._children.forEach(function(c){ 
            nb += nbEndNodes(c); 
        });
    }
    else nb++;
    
    return nb;
}

function click(d)
{
    if (d.children){
        d._children = d.children;
        d.children = null;
    } 
    else{
        d.children = d._children;
        d._children = null;
    }
    update(d);
}

function collapse(d){
    if (d.children){
        d._children = d.children;
        d._children.forEach(collapse);
        d.children = null;
    }
}

update(root);

html{
    font: 10px sans-serif;
}

svg{
    border: 1px solid silver;
}

.node{
    cursor: pointer;
}

.node circle{
    stroke: steelblue;
    stroke-width: 1.5px;
}

.link{
    fill: none;
    stroke: lightgray;
    stroke-width: 1.5px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>
<div id=tree></div>

Answer 1

Finally I am able to get it. Pasting here the raw code. It definitely requires cleanup though:

Main Logic....

@GET
@javax.ws.rs.Path("/getTree/{name}/")
@Produces({ "application/json" })
public Response getTree(@PathParam("name") final String name, @Context final GraphDatabaseService db)
        throws IOException {

    System.out.println(" Attribute Name To SearchByName: " + name);

    HashMap<Long, TreeNode> treeNodeMap = new HashMap<Long, TreeNode>();

    TreeNode rootNode = null;

    String attrubute = "name";

    try (Transaction tx = db.beginTx()) {
        final Node swtch = db.findNode(Labels.Switch, attrubute, name);
        if (swtch != null) {
            TraversalDescription td = db.traversalDescription().depthFirst()
                    .expand(PathExpanders.forTypeAndDirection(RelationshipTypes.CONNECTED_TO, Direction.OUTGOING));

            for (Path directoryPath : td.traverse(swtch)) 
            {
                Iterable<Relationship> connectedTos = directoryPath.endNode().getRelationships(Direction.OUTGOING,RelationshipTypes.CONNECTED_TO);

                if (connectedTos != null) 
                {
                    for(Relationship connectedTo : connectedTos)
                    {
                        //For the Current Relationship
                        //get the start node as parent
                        Node parentNode = connectedTo.getStartNode();
                        Long parentNodeId = parentNode.getId();
                        TreeNode parentTreeNode = treeNodeMap.get(parentNodeId);

                        if(parentTreeNode == null)
                        {
                            ////Populate the Parent Details
                            parentTreeNode = new TreeNode(parentNode.getProperty("name", "NoName").toString());
                            if(rootNode == null)
                                rootNode = parentTreeNode;
                            //Add to the linear HashMap for subsequent searches
                            treeNodeMap.put(parentNodeId, parentTreeNode);
                        }

                        //For the Current Relationship get the end node Children
                        Node childNode = connectedTo.getEndNode();
                        Long childNodeId = childNode.getId();
                        TreeNode childTreeNode = treeNodeMap.get(childNodeId);

                        if(childTreeNode == null)
                        {
                            childTreeNode = new TreeNode(childNode.getProperty("name", "NoName").toString());
                            treeNodeMap.put(childNodeId, childTreeNode);
                            parentTreeNode.setChildren(childTreeNode);
                        }
                    }
            }
        }
        tx.success();
    }
    }
    /*
     System.out.println("JSON: " + objectMapper.writeValueAsString(rootNode));
     System.out.println("LinearHashMap: " + objectMapper.writeValueAsString(treeNodeMap ));
     */

    return Response.ok().entity(objectMapper.writeValueAsString(rootNode)).build();

}

Answer 2

I have done something similar in node.js, should be similar in Java because the CIPHER query syntax is the same.

An example of the end result: http://visualize-terms.herokuapp.com/terms/6

For getting the nodes and the links, see my sourcecode:
https://github.com/paradite/Graphpedia/blob/master/models/term.js

Particularly Term.prototype.getOutgoingAndOthers and Term.get (which uses the neo4j npm package, but you have access to the source code)

The cipher for getting the outgoing links for a node is:

//Construct neo4j raw query
var query = [
    'MATCH (term:Term), (other:Term)',
    'OPTIONAL MATCH (term) -[relall]-> (other)',
    'WHERE ID(term) = {termId}',
    'RETURN other, COUNT(relall), type(relall)',
    // COUNT(rel) is a hack for 1 or 0, 1 indicates there is an outgoing relationship.
].join('\n')

For parsing them into d3.js objects for use in tree layout, see:
https://github.com/paradite/Graphpedia/blob/master/routes/terms.js#L108
See exports.show function.