javascript - Save and Load jsPlumb flowchart including exact anchors and connections

Question

This is the jsFiddle of the flowchart editor I am building.

This is an example of what can be easily created with "Add Decision" + "Add Task", connecting and moving the elements.

Now for the hard part: I want to be able to save and load the exact flowchart. For this I got started based with a similar thread here at Stackoverflow.

For this I added the "Save" and "Load" buttons that export/import the flowchart to/from JSON (shown in a textform in the jsFiddle after save - same textform can be used for loading).

The save function:

function saveFlowchart(){
            var nodes = []
            $(".node").each(function (idx, elem) {
            var $elem = $(elem);
            var endpoints = jsPlumb.getEndpoints($elem.attr('id'));
            console.log('endpoints of '+$elem.attr('id'));
            console.log(endpoints);
                nodes.push({
                    blockId: $elem.attr('id'),
                    nodetype: $elem.attr('data-nodetype'),
                    positionX: parseInt($elem.css("left"), 10),
                    positionY: parseInt($elem.css("top"), 10)
                });
            });
            var connections = [];
            $.each(jsPlumb.getConnections(), function (idx, connection) {
                connections.push({
                    connectionId: connection.id,
                    pageSourceId: connection.sourceId,
                    pageTargetId: connection.targetId
                });
            });

            var flowChart = {};
            flowChart.nodes = nodes;
            flowChart.connections = connections;
            flowChart.numberOfElements = numberOfElements;

            var flowChartJson = JSON.stringify(flowChart);
            //console.log(flowChartJson);

            $('#jsonOutput').val(flowChartJson);
        }

The resulting JSON of the example above:

{"nodes":[{"blockId":"startpoint","nodetype":"startpoint","positionX":273,"positionY":8},{"blockId":"endpoint","nodetype":"endpoint","positionX":310,"positionY":385},{"blockId":"taskcontainer1","nodetype":"task","positionX":381,"positionY":208},{"blockId":"decisioncontainer2","nodetype":"decision","positionX":261,"positionY":103}],"connections":[{"connectionId":"con_18","pageSourceId":"decisioncontainer2","pageTargetId":"taskcontainer1"},{"connectionId":"con_25","pageSourceId":"taskcontainer1","pageTargetId":"endpoint"},{"connectionId":"con_32","pageSourceId":"decisioncontainer2","pageTargetId":"endpoint"},{"connectionId":"con_46","pageSourceId":"startpoint","pageTargetId":"decisioncontainer2"}],"numberOfElements":2}

With that I am able to save the position of the elements as well as part of the information of the connections. Here the load function:

function loadFlowchart(){
            var flowChartJson = $('#jsonOutput').val();
            var flowChart = JSON.parse(flowChartJson);
            var nodes = flowChart.nodes;
            $.each(nodes, function( index, elem ) {
                if(elem.nodetype === 'startpoint'){
                    repositionElement('startpoint', elem.positionX, elem.positionY);
                }else if(elem.nodetype === 'endpoint'){
                    repositionElement('endpoint', elem.positionX, elem.positionY);
                }else if(elem.nodetype === 'task'){
                    var id = addTask(elem.blockId);
                    repositionElement(id, elem.positionX, elem.positionY);
                }else if(elem.nodetype === 'decision'){
                    var id = addDecision(elem.blockId);
                    repositionElement(id, elem.positionX, elem.positionY);
                }else{

                }
            });

            var connections = flowChart.connections;
            $.each(connections, function( index, elem ) {
                 var connection1 = jsPlumb.connect({
                    source: elem.pageSourceId,
                    target: elem.pageTargetId,
                    anchors: ["BottomCenter", [0.75, 0, 0, -1]]

                });
            });

            numberOfElements = flowChart.numberOfElements;
        }

However, the exact position of the anchors and connections are lost. Same example again, the result after deleting the elements and then loading the exported JSON:

This comes not as a big surprise as I have not yet stored the information. But I am stuck at this point.

My question is: which information regarding the anchors/connectors position do I need to store for the whole flowchart design and how I can extract it from (& load into it again) jsPlumb?

Answer 1

See this JSFiddle for a solution.

You need to save the anchor details as follows. This conforms to the Anchor representation defined here. Note the double nesting to avoid the JQuery auto-flatten on the map.

    $.each(jsPlumb.getConnections(), function (idx, connection) {
      connections.push({
      connectionId: connection.id,
      pageSourceId: connection.sourceId,
      pageTargetId: connection.targetId,
      anchors: $.map(connection.endpoints, function(endpoint) {

        return [[endpoint.anchor.x, 
        endpoint.anchor.y, 
        endpoint.anchor.orientation[0], 
        endpoint.anchor.orientation[1],
        endpoint.anchor.offsets[0],
        endpoint.anchor.offsets[1]]];

      })
    });
  });

...and load them, as follows:

    $.each(connections, function( index, elem ) {
     var connection1 = jsPlumb.connect({
      source: elem.pageSourceId,
      target: elem.pageTargetId,
      anchors: elem.anchors
    });

  });

Note that this solution does not preserve end-point details including the shape and type of end-points. It only preserves the anchor details, as you requested.