CODEWITHSUNDEEP
javagraphviz
Kaijiro
Kaijiro

Reputation: 339

Creating a GraphViz graph in Java without any intermediate file

I would like to use GraphViz to generate some graphs in my program. There is just a problem : I don't want to generate any temporary file.

Here is what I got from here :

public class GraphBuilder{
    /* Some code generating a DOT formatted String representing my graph */

    /* Generation the graph using the plain format */
    Runtime runtime = Runtime.getRuntime();
    Process p = null;
    try {
        p = runtime.exec("neato -Tplain c:\\users\\tristan\\desktop\\test1");
    } catch (IOException e) {
        System.err.println(e.getMessage());
    }

    BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
    StringBuilder builder = new StringBuilder();
    String line = null;
    try{
        while ( (line = br.readLine()) != null) {
           builder.append(line);
           builder.append(System.getProperty("line.separator"));
        }
    } catch(IOException e){

    }
    String result = builder.toString();
    System.out.println(result);

Ok so, from now, my program is reading a file but I want the neato program to read my String that had been generated earlier by the program.

How should I do ?

Thanks in advance !

Upvotes: 3

Views: 2145

Answers (2)

anony_std
anony_std

Reputation: 29

You can use GraphvizV8Engine() for this purpose. This will not create the temp files create by cmdLineEngine.

Graphviz.useEngine(new GraphvizV8Engine());

This will initialize javascript to display your graph.

2022-11-29 15:01:57.628  INFO 19208 --- [nio-8080-exec-2] g.n.graphviz.engine.V8JavascriptEngine   : Starting V8 runtime...
2022-11-29 15:01:58.383  INFO 19208 --- [nio-8080-exec-2] g.n.graphviz.engine.V8JavascriptEngine   : Started V8 runtime. Initializing javascript...
2022-11-29 15:01:58.386  INFO 19208 --- [nio-8080-exec-2] g.n.graphviz.engine.V8JavascriptEngine   : Initialized javascript.
2022-11-29 15:02:02.709  INFO 19208 --- [nio-8080-exec-2] g.n.graphviz.engine.V8JavascriptEngine   : Starting V8 runtime...
2022-11-29 15:02:02.774  INFO 19208 --- [nio-8080-exec-2] g.n.graphviz.engine.V8JavascriptEngine   : Started V8 runtime. Initializing javascript...
2022-11-29 15:02:02.775  INFO 19208 --- [nio-8080-exec-2] g.n.graphviz.engine.V8JavascriptEngine   : Initialized javascript.

Upvotes: 0

slim
slim

Reputation: 41213

Something like:

// Create the process
Process process = new ProcessBuilder("neato", "-Tplain").start();

// Write to process's stdin
OutputStream osToProcess = process.getOutputStream();
PrintWriter pwToProcess = new PrintWriter(osToProcess);
pwToProcess.write("graph G { node1 -- node2; }"); // for example
pwToProcess.close();

// Read from process's stdout
InputStream isFromProcess = process.getInputStream();
BufferedReader brFromProcess = new BufferedReader(isFromProcess);
// do whatever you want with the reader, then...
brFromProcess.close();

// optionally...
process.waitFor();

I omitted exception handling from this example code -- you'll need to put it in to meet your requirements. It may be sufficient to wrap the whole thing in a try/catch block - it depends what you need.

I validated that neato reads/writes stdin/stdout at the command line:

$ echo 'graph G { n1 -- n2; }' | neato -Tplain
graph 1 1.3667 1.2872
node n1 0.375 0.25 0.75 0.5 n1 solid ellipse black lightgrey
node n2 0.99169 1.0372 0.75 0.5 n2 solid ellipse black lightgrey
edge n1 n2 4 0.55007 0.47348 0.63268 0.57893 0.7311 0.70457 0.81404 0.81044 solid black
stop

Upvotes: 5

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