RDFXMLWriter.java

package com.mysema.rdfbean.model.io;

import java.io.IOException;
import java.io.Writer;
import java.util.Map;

import javax.annotation.Nullable;

import com.mysema.commons.l10n.support.LocaleUtil;
import com.mysema.rdfbean.model.LIT;
import com.mysema.rdfbean.model.RDF;
import com.mysema.rdfbean.model.RepositoryException;
import com.mysema.rdfbean.model.STMT;
import com.mysema.rdfbean.model.UID;

/**
 * @author tiwe
 * 
 */
public class RDFXMLWriter implements RDFWriter {

    private final Writer writer;

    private final Map<String, String> prefixes;

    @Nullable
    private STMT last;

    public RDFXMLWriter(Writer writer, Map<String, String> prefixes) {
        this.writer = writer;
        this.prefixes = prefixes;
    }

    @Override
    public void begin() {
        try {
            writer.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
            writer.append("<!DOCTYPE rdf:RDF [\n");
            for (Map.Entry<String, String> entry : prefixes.entrySet()) {
                writer.append("<!ENTITY " + entry.getValue() + " \"" + entry.getKey() + "\">\n");
            }
            writer.append("]>\n");

            writer.append("<rdf:RDF xmlns:rdf=\"&rdf;\"");
            for (Map.Entry<String, String> entry : prefixes.entrySet()) {
                if (!entry.getKey().equals(RDF.NS)) {
                    writer.append(" xmlns:" + entry.getValue() + "=\"&" + entry.getValue() + ";\"");
                }
            }
            writer.append(">\n");
        } catch (IOException e) {
            throw new RepositoryException(e);
        }
    }

    @Override
    public void end() {
        try {
            if (last != null) {
                writer.append("  </rdf:Description>\n");
            }
            writer.append("</rdf:RDF>\n");
            writer.flush();
        } catch (IOException e) {
            throw new RepositoryException(e);
        }
    }

    @Override
    public void handle(STMT stmt) {
        try {
            if (last == null || !last.getSubject().equals(stmt.getSubject())) {
                if (last != null) {
                    writer.append("  </rdf:Description>\n");
                }
                writer.append("  <rdf:Description");
                if (stmt.getSubject().isURI()) {
                    writer.append(" rdf:about=\"" + shorten(stmt.getSubject().asURI()) + "\">\n");
                } else {
                    writer.append(" rdf:nodeID=\"" + stmt.getSubject().getId() + "\">\n");
                }

            }
            String prefix = prefixes.get(stmt.getPredicate().ns());
            if (prefix == null) {
                prefix = "ns";
                writer.append("    <" + prefix + ":" + stmt.getPredicate().ln() + " xmlns:ns=\"" + stmt.getPredicate().ns() + "\"");
            } else {
                writer.append("    <" + prefix + ":" + stmt.getPredicate().ln());
            }
            if (stmt.getObject().isLiteral()) {
                LIT lit = stmt.getObject().asLiteral();
                if (lit.getLang() != null) {
                    writer.append(" xml:lang=\"" + LocaleUtil.toLang(lit.getLang()) + "\"");
                } else {
                    writer.append(" rdf:datatype=\"" + shorten(lit.getDatatype()) + "\"");
                }
                writer.append(">");
                appendEscaped(stmt.getObject().getValue());
                writer.append("</" + prefix + ":" + stmt.getPredicate().ln() + ">\n");
            } else if (stmt.getObject().isBNode()) {
                writer.append(" rdf:nodeID=\"" + stmt.getObject().getValue() + "\"/>\n");
            } else {
                writer.append(" rdf:resource=\"" + shorten(stmt.getObject().asURI()) + "\"/>\n");
            }
            last = stmt;
        } catch (IOException e) {
            throw new RepositoryException(e);
        }
    }

    private String shorten(UID uid) {
        if (prefixes.containsKey(uid.ns())) {
            return "&" + prefixes.get(uid.ns()) + ";" + uid.ln();
        } else {
            return uid.getId();
        }
    }

    private void appendEscaped(String val) throws IOException {
        for (int i = 0; i < val.length(); ++i) {
            char c = val.charAt(i);
            if (c == '&') {
                writer.write("&");
            } else if (c == '<') {
                writer.write("<");
            } else if (c == '>') {
                writer.write(">");
            } else if (c == '"') {
                writer.write(""");
            } else if (c == '\'') {
                writer.write("'");
            } else {
                writer.write(c);
            }
        }
    }

}