net.ontopia.xml.CanonicalPrinter.java Source code

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Here is the source code for net.ontopia.xml.CanonicalPrinter.java

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/*
 * #!
 * Ontopia Engine
 * #-
 * Copyright (C) 2001 - 2013 The Ontopia Project
 * #-
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * !#
 */

package net.ontopia.xml;

import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import net.ontopia.utils.OntopiaRuntimeException;
import org.apache.commons.lang3.StringUtils;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;

/**
 * INTERNAL: SAX document handler that prints canonical XML. Note that
 * this does not support all of http://www.w3.org/TR/xml-c14n, only
 * what is needed for Canonical XTM.
 */
public class CanonicalPrinter implements ContentHandler {
    protected PrintWriter writer;
    private final boolean closeWRiter;

    /**
     * Creates a CanonicalPrinter that writes to the given OutputStream.
     * The encoding used is always utf-8.
     */
    public CanonicalPrinter(OutputStream stream, boolean closeWRiter) {
        try {
            this.writer = new PrintWriter(new OutputStreamWriter(stream, "utf-8"));
        } catch (UnsupportedEncodingException use) {
            throw new OntopiaRuntimeException(use);
        }
        this.closeWRiter = closeWRiter;
    }

    /**
     * Creates a CanonicalPrinter that writes to the given Writer.
     */
    public CanonicalPrinter(Writer writer, boolean closeWRiter) {
        this.writer = new PrintWriter(writer);
        this.closeWRiter = closeWRiter;
    }

    // Document events

    @Override
    public void startDocument() {
        // no-op
    }

    @Override
    public void startElement(String uri, String localName, String name, Attributes atts) {
        // first: sort attributes
        String[] attNames = new String[atts.getLength()];
        for (int i = 0; i < atts.getLength(); i++) {
            attNames[i] = atts.getQName(i);
        }
        java.util.Arrays.sort(attNames);

        // then write it out in sorted order
        writer.print("<" + name);
        for (int i = 0; i < attNames.length; i++)
            writer.print(" " + attNames[i] + "=\"" + escape(atts.getValue(attNames[i])) + "\"");
        writer.print(">");
    }

    @Override
    public void endElement(String uri, String localName, String name) {
        writer.print("</" + name + ">");
    }

    @Override
    public void characters(char ch[], int start, int length) {
        StringBuilder content = new StringBuilder();
        for (int i = start; i < start + length; i++) {
            switch (ch[i]) {
            case '&':
                content.append("&amp;");
                break;
            case '<':
                content.append("&lt;");
                break;
            case '>':
                content.append("&gt;");
                break;
            case 13: /* that is, \u000D */
                content.append("&#xD;");
                break;
            default:
                content.append(ch[i]);
            }
        }
        writer.print(content.toString());
    }

    @Override
    public void ignorableWhitespace(char ch[], int start, int length) {
        writer.write(ch, start, length);
    }

    @Override
    public void processingInstruction(String target, String data) {
        writer.print("<?" + target + " " + data + "?>\n");
    }

    @Override
    public void endDocument() {
        writer.flush();
        if (closeWRiter) {
            writer.close();
        }
    }

    @Override
    public void setDocumentLocator(Locator locator) {
        // no-op
    }

    // --- Internal methods

    public String escape(String attrval) {
        return StringUtils.replace(StringUtils.replace(StringUtils.replace(attrval, "&", "&amp;"), "<", "&lt;"),
                "\"", "&quot;");
    }

    @Override
    public void startPrefixMapping(String prefix, String uri) throws SAXException {
        // no-op
    }

    @Override
    public void endPrefixMapping(String prefix) throws SAXException {
        // no-op
    }

    @Override
    public void skippedEntity(String name) throws SAXException {
        // no-op
    }
}