StormTopology to graphviz dot format

Visualization.java

package com.radius.kafkastorm;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.Map;

import backtype.storm.generated.Bolt;
import backtype.storm.generated.ComponentObject;
import backtype.storm.generated.GlobalStreamId;
import backtype.storm.generated.Grouping;
import backtype.storm.generated.SpoutSpec;
import backtype.storm.generated.StormTopology;

/**
 * Returns a <tt>graphviz</tt> compatible string representing the provided
 * {@linkplain backtype.storm.generated.StormTopology}.
 * It is accurate as of 
 * <a href="https://github.com/apache/storm/tree/v0.9.2-incubating">0.9.2-incubating</a>.
 * This is the transliteration of <a href="https://github.com/schleyfox/storm-test/blob/master/src/clj/storm/test/visualization.clj"
 * >visualization.clj</a>.
 */
public class Visualization
{
    public static final String[] COLORS = new String[] {
            "red", "orange", "yellow", "green", "blue", "indigo", "violet"
    };

    public static String topologyToDot(StormTopology topo) {
        final Map<String, SpoutSpec> spouts = topo.get_spouts();
        final Map<String, Bolt> bolts = topo.get_bolts();
        return String.format("digraph Topology {%n" +
                        "%s" +
                        "%s" +
                        "%s" +
                        "%n" +
                        "}%n",
                labelSpouts(spouts),
                labelBolts(bolts),
                drawConnections(bolts));
    }

    private static String labelSpouts(final Map<String, SpoutSpec> spouts) {
        final StringBuilder sb = new StringBuilder();
        for (final String id : spouts.keySet()) {
            final SpoutSpec spout = spouts.get(id);
            sb.append(String.format(
                    " \"%s\" [%s,shape=box];%n",
                    id, labelNode(id, spout)));
        }
        return sb.toString();
    }
    private static String labelBolts(final Map<String, Bolt> bolts) {
        final StringBuilder sb = new StringBuilder();
        for (final String id : bolts.keySet()) {
            final Bolt bolt = bolts.get(id);
            sb.append(String.format(
                    " \"%s\" [%s];%n",
                    id, labelNode(id, bolt)));
        }
        return sb.toString();
    }

    private static String labelNode(String id, Bolt b) {
        return labelNode(id, b.get_bolt_object());
    }

    private static String labelNode(String id, SpoutSpec s) {
        return labelNode(id, s.get_spout_object());
    }

    private static String labelNode(String id, ComponentObject co) {
        final byte[] java_bytes = co.get_serialized_java();
        assert null != java_bytes;
        final Object javaO;
        try {
            javaO = new ObjectInputStream(new ByteArrayInputStream(java_bytes)).readObject();
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace(System.err);
            throw new RuntimeException(e);
        }
        return String.format("label=\"%s (%s)\"", id,
                null == javaO ? "NULL": javaO.getClass().getName()
                        .replaceAll(".*\\.([^\\.]+)", "$1"));
    }

    private static String drawConnections(final Map<String, Bolt> bolts) {
        final StringBuilder sb = new StringBuilder();
        for (final String id : bolts.keySet()) {
            final Bolt bolt = bolts.get(id);
            final Map<GlobalStreamId, Grouping> inputs = bolt.get_common().get_inputs();
            for (final GlobalStreamId from : inputs.keySet()) {
                final Grouping grouping = inputs.get(from);
                final String fromId = from.get_componentId();
                final String streamId = from.get_streamId();
                sb.append(String.format(" \"%s\" -> \"%s\" [%s%s];%n",
                        fromId, id,
                        "default".equals(streamId)
                                ? ""
                                : String.format(
                                "color=%s,",
                                COLORS[new java.util.Random().nextInt(COLORS.length)]),
                        labelConnection(streamId, grouping)));
            }
        }
        return sb.toString();
    }

    private static String labelConnection(String streamId, Grouping grouping) {
        final String fieldName = grouping.getSetField().getFieldName();
        final String groupingStr;
        if ("fields".equals(fieldName)) {
            groupingStr = String.valueOf(grouping.get_fields());
        } else {
            groupingStr = fieldName;
        }
        final String streamName = "default".equals(streamId)
                ? ""
                : String.format(" \\\"%s\\\"", streamId);
        return String.format("label=\"%s%s\"",
                groupingStr.replaceAll("\"", "\\\""), streamName);
    }
}