GraphStream : JSON output

Convert2JSON.java

import java.io.InputStreamReader;
import java.io.IOException;
import java.io.PrintStream;

import java.lang.reflect.Array;
import java.util.Map;

import org.graphstream.graph.Graph;
import org.graphstream.graph.Node;
import org.graphstream.graph.Edge;
import org.graphstream.graph.implementations.AdjacencyListGraph;
import org.graphstream.stream.file.FileSourceDGS;

public class Convert2JSON {
  public static void main(String... args) {
    FileSourceDGS dgs = new FileSourceDGS();
    Graph g = new AdjacencyListGraph("dgs2json");

    dgs.addSink(g);

    try {
      if (args.length > 0) {
        dgs.readAll(ConvertData.class.getResourceAsStream(args[0]));
      }
      else {
        dgs.readAll(new InputStreamReader(System.in));
      }
    } catch(IOException e) {
      e.printStackTrace();
      System.exit(1);
    }

    dgs.removeSink(g);

    PrintStream out = null;

    if (args.length > 1) {
      try {
        out = new PrintStream(args[1]);
      } catch(IOException e) {
        e.printStackTrace();
        System.exit(1);
      }
    }
    else {
      out = System.out;
    }

    outputJSON(out, g);
  }

  public static String getAttributes(Element e) {
    StringBuilder buffer = new StringBuilder("{");
    String sep = "";

    for (String key: e.getAttributeKeySet()) {
      buffer.append(sep).append("\"" + key + "\":");
      getAttributeValue(buffer, e.getAttribute(key));
      sep = ",";
    }

    return buffer.append("}").toString();
  }

  public static void getAttributeValue(StringBuilder buffer, Object o) {
    if (o == null) {
      buffer.append("\"\"");
    }
    else if (o instanceof Number || o instanceof Boolean) {
      buffer.append(o.toString());
    }
    else if (o.getClass().isArray()) {
      buffer.append("[");

      for (int i = 0; i < Array.getLength(o); i++) {
        buffer.append(i > 0 ? "," : "");
        getAttributeValue(buffer, Array.get(o, i));
      }

      buffer.append("]");
    }
    else if (o instanceof Map<?,?>) {
      Map<?,?> m = (Map<?,?>) o;
      String sep = "";

      buffer.append("{");

      for (Object key: m.keySet()) {
        buffer
          .append(sep)
          .append('"')
          .append(key.toString())
          .append("\":");

        getAttributeValue(buffer, m.get(key));
        sep = ",";
      }

      buffer.append("}");
    }
    else {
      buffer.append('"').append(o.toString()).append('"');
    }
  }

  public static void outputJSON(PrintStream out, Graph g) {
    out.printf("{");

    out.printf("\"nodes\": [");
    for (int i=0; i<g.getNodeCount(); i++) {
      Node n = g.getNode(i);
      out.printf("%s{\"id\": \"%s\", \"attributes\":\"%s\"}",
        i > 0 ? ", " : "",
        n.getId(),
        getAttributes(s));
    }
    out.printf("],");

    out.printf("\"links\": [");
    for (int i=0; i<g.getEdgeCount(); i++) {
      Edge e = g.getEdge(i);
      String cls = e.hasAttribute("ui.class") ? (String) e.getAttribute("ui.class") : "normal";

      out.printf("%s{\"id\": \"%s\", \"source\":%d, \"target\":%d, \"attributes\":\"%s\"}",
        i > 0 ? ", " : "",
        e.getId(),
        e.getSourceNode().getIndex(),
        e.getTargetNode().getIndex(),
        getAttributes(e));
    }
    out.printf("]");

    out.printf("}");
  }
}