Creating a GraphViz graph in Java without any intermediate file

Question

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 gene…

Accepted Answer

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
```

Creating a GraphViz graph in Java without any intermediate file

Solution

Problem