src/main/java/freemarker/template/utility/NormalizeNewlines.java

/*
 * Copyright (c) 2003 The Visigoth Software Society. All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Visigoth Software Society (http://www.visigoths.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the
 *    project contributors may be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact visigoths@visigoths.org.
 *
 * 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
 *    nor may "FreeMarker" or "Visigoth" appear in their names
 *    without prior written permission of the Visigoth Software Society.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Visigoth Software Society. For more
 * information on the Visigoth Software Society, please see
 * http://www.visigoths.org/
 */

package freemarker.template.utility;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Map;

import freemarker.template.TemplateTransformModel;

/**
 * <p>Transformer that supports FreeMarker legacy behavior: all newlines appearing
 * within the transformed area will be transformed into the platform's default
 * newline. Unlike the old behavior, however, newlines generated by the data
 * model are also converted. Legacy behavior was to leave newlines in the
 * data model unaltered.</p>
 *
 * <p>Usage:<br />
 * From java:</p>
 * <pre>
 * SimpleHash root = new SimpleHash();
 *
 * root.put( "normalizeNewlines", new freemarker.template.utility.NormalizeNewlines() );
 *
 * ...
 * </pre>
 *
 * <p>From your FreeMarker template:</p>
 * <pre>
 * &lt;transform normalizeNewlines&gt;
 *   &lt;html&gt;
 *   &lt;head&gt;
 *   ...
 *   &lt;p&gt;This template has all newlines normalized to the current platform's
 *   default.&lt;/p&gt;
 *   ...
 *   &lt;/body&gt;
 *   &lt;/html&gt;
 * &lt;/transform&gt;
 * </pre>
 */
public class NormalizeNewlines implements TemplateTransformModel {

    public Writer getWriter(final Writer out,
                            final Map args)
    {
        final StringBuffer buf = new StringBuffer();
        return new Writer() {
            public void write(char cbuf[], int off, int len) {
                buf.append(cbuf, off, len);
            }

            public void flush() throws IOException {
                out.flush();
            }

            public void close() throws IOException {
                StringReader sr = new StringReader(buf.toString());
                StringWriter sw = new StringWriter();
                transform(sr, sw);
                out.write(sw.toString());
            }
        };
    }

    /**
     * Performs newline normalization on FreeMarker output.
     *
     * @param in the input to be transformed
     * @param out the destination of the transformation
     */
    public void transform(Reader in, Writer out) throws IOException
    {
        BufferedReader br = (in instanceof BufferedReader)
                            ? (BufferedReader) in
                            : new BufferedReader(in);
        PrintWriter pw = (out instanceof PrintWriter)
                         ? (PrintWriter) out
                         : new PrintWriter(out);
        String line = br.readLine();
        if (line != null) {
            if ( line.length() > 0 ) {
                pw.println(line);
            }
        }
        while ((line = br.readLine()) != null) {
            pw.println(line);
        }
    }
}