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Prefuse is a set of software tools for creating rich interactive data visualizations in the Java programming language.
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/**
 * Copyright (c) 2004-2006 Regents of the University of California.
 * See "license-prefuse.txt" for licensing terms.
 */
package prefuse.data.io;

import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;

import prefuse.data.Edge;
import prefuse.data.Graph;
import prefuse.data.Node;
import prefuse.data.Schema;
import prefuse.util.io.XMLWriter;

/**
 * GraphWriter instance that writes a graph file formatted using the
 * GraphML file format. GraphML is an XML format supporting graph
 * structure and typed data schemas for both nodes and edges. For more
 * information about the format, please see the
 * GraphML home page.
 * 
 * The GraphML spec only supports the data types int,
 * long, float, double,
 * boolean, and string. An exception will
 * be thrown if a data type outside these allowed types is
 * encountered.
 * 
 * @author jeffrey heer
 */
public class GraphMLWriter extends AbstractGraphWriter {

    /**
     * String tokens used in the GraphML format.
     */
    public interface Tokens extends GraphMLReader.Tokens  {
        public static final String GRAPHML = "graphml";
        
        public static final String GRAPHML_HEADER =
            "\n\n";
    }
    
    /**
     * Map containing legal data types and their names in the GraphML spec
     */
    public static final java.util.Map TYPES; 
    static {
        HashMap types = new HashMap();
        types.put(int.class, Tokens.INT);
        types.put(long.class, Tokens.LONG);
        types.put(float.class, Tokens.FLOAT);
        types.put(double.class, Tokens.DOUBLE);
        types.put(boolean.class, Tokens.BOOLEAN);
        types.put(String.class, Tokens.STRING);
        TYPES = Collections.unmodifiableMap(types);
    }
    
    /**
     * @see prefuse.data.io.GraphWriter#writeGraph(prefuse.data.Graph, java.io.OutputStream)
     */
    public void writeGraph(Graph graph, OutputStream os) throws DataIOException
    {
        // first, check the schemas to ensure GraphML compatibility
        Schema ns = graph.getNodeTable().getSchema();
        Schema es = graph.getEdgeTable().getSchema();
        checkGraphMLSchema(ns);
        checkGraphMLSchema(es);
        
        XMLWriter xml = new XMLWriter(new PrintWriter(os));
        xml.begin(Tokens.GRAPHML_HEADER, 2);
        
        xml.comment("prefuse GraphML Writer | "
                + new Date(System.currentTimeMillis()));
        
        // print the graph schema
        printSchema(xml, Tokens.NODE, ns, null);
        printSchema(xml, Tokens.EDGE, es, new String[] {
            graph.getEdgeSourceField(), graph.getEdgeTargetField()
        });
        xml.println();
        
        // print graph contents
        xml.start(Tokens.GRAPH, Tokens.EDGEDEF,
            graph.isDirected() ? Tokens.DIRECTED : Tokens.UNDIRECTED);
        
        // print the nodes
        xml.comment("nodes");
        Iterator nodes = graph.nodes();
        while ( nodes.hasNext() ) {
            Node n = (Node)nodes.next();
            
            if ( ns.getColumnCount() > 0 ) {
                xml.start(Tokens.NODE, Tokens.ID, String.valueOf(n.getRow()));
                for ( int i=0; i 2 ) {
                xml.start(Tokens.EDGE, attr, vals, 3);
                for ( int i=0; i\n");
    }
    
    /**
     * Print a table schema to a GraphML file
     * @param xml the XMLWriter to write to
     * @param group the data group (node or edge) for the schema
     * @param s the schema
     */
    private void printSchema(XMLWriter xml, String group, Schema s,
                             String[] ignore)
    {
        String[] attr = new String[] {Tokens.ID, Tokens.FOR,
                Tokens.ATTRNAME, Tokens.ATTRTYPE };
        String[] vals = new String[4];

OUTER:
        for ( int i=0; iint,
     * long, float, double,
     * boolean, and string.
     * @param s the Schema to check
     */
    public static void checkGraphMLSchema(Schema s) throws DataIOException {
        for ( int i=0; i