https://freemarker.apache.org/: FreeMarker is a "template engine"; a generic tool to generate text output based on templates. (Apache Software Foundation) 
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 * Licensed to the Apache Software Foundation (ASF) under one
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 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 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;


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.


Usage:

From java:


SimpleHash root = new SimpleHash();
root.put( "normalizeNewlines", new freemarker.template.utility.NormalizeNewlines() );
...



From your FreeMarker template:


<transform normalizeNewlines>
  <html>
  <head>
  ...
  <p>This template has all newlines normalized to the current platform's
  default.</p>
  ...
  </body>
  </html>
</transform>



/**
 * <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 StringBuilder buf = new StringBuilder();
        return new Writer() {
            @Override
            public void write(char cbuf[], int off, int len) {
                buf.append(cbuf, off, len);
            }

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

            @Override
            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.

Params:
  • in – the input to be transformed
  • out – the destination of the transformation
/**
     * 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);
        }
    }
}