xử lý template với Freemarker trong java

Chào các bạn, trong quá trình tìm hiểu mình có bắt gặp thư viện xử lý template hay,
Feemarker. Viết thử demo cái
package net.net;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Map;

import freemarker.template.Configuration;
import freemarker.template.DefaultObjectWrapper;
import freemarker.template.Template;
import freemarker.template.TemplateException;

public class Main {

public static final String DATA_PARAMETER = "data";

public Map parameters = new HashMap();

/**
* This exception handler is lenient when values are undefined. In that case nothing is printed or
* returned.
*/
public String getlabel() {
return "Demo Label";
}

public String getRootMenuOptions() {
return "Demo!";
}

public Configuration getNewConfiguration() {
final Configuration cfg = new Configuration();
cfg.setObjectWrapper(new DefaultObjectWrapper());

return cfg;
}

public String readFileAsString(File file) throws java.io.IOException {
byte[] buffer = new byte[(int) file.length()];
FileInputStream f = new FileInputStream(file);
f.read(buffer);
return new String(buffer);
}

public String readTemplateSourceFromClasspath(String path) {
try {

final File file = new File(path);
return readFileAsString(file);
} catch (Exception e) {
throw new IllegalArgumentException(e);
}
}

public String generate() throws TemplateException {
if (getData() != null) {
parameters.put(DATA_PARAMETER, getData());
}

try {

Template tpl = new freemarker.template.Template("template", new StringReader(
readTemplateSourceFromClasspath("C:/Users/pc/workspace/Demo/src/net/net/demo.ftl")),
getNewConfiguration());
return processTemplate(tpl, parameters);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}

}

public String processTemplate(freemarker.template.Template templateImplementation,
Map data) {
try {
final StringWriter output = new StringWriter();

templateImplementation.process(data, output);
return output.toString();
} catch (IOException e) {
throw new IllegalStateException(e);
} catch (TemplateException e) {
// System.out.println("khong ton tai : " + e.toString());
return null;
}
}

public Object getData() {
return this;
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Main demo = new Main();
// System.out.println("ga gag ");
try {
System.out.println("ket qua demo : " + demo.generate());
} catch (TemplateException e) {
// TODO Auto-generated catch block
// System.out.println("thu phat da " + e.toString());
}
}

}

- File demo.ftl: ${data.label},${data.rootMenuOptions}

Va ket qua la :
ket qua demo : title: Demo Label,Demo!