FreeMarker: Concatenate lists or sequences

Using ‘+’ operator, you can concatenate lists or sequences.

 

Example

<#list ["Ram", "Rahim", "Joel"] + ["Krishna", "Abdul", "Chella"] + ["Sailu", "Mary"] as userName>

- ${userName}

</#list>

 

Find the below working application.

 

Step 1: Define listConcatenation.ftl file under src/main/resources/templates folder.

 

listConcatenation.ftl

<#list ["Ram", "Rahim", "Joel"] + ["Krishna", "Abdul", "Chella"] + ["Sailu", "Mary"] as userName>
- ${userName}
</#list>

Step 2: Define ‘FreeMarkerUtil’ class that takes model class and template file as input and merge them.

 

FreeMarkerUtil.java

package com.sample.app.util;

import java.io.StringWriter;
import java.util.Locale;

import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateExceptionHandler;

public class FreeMarkerUtil {

	private static final Configuration FREE_MARKER_CONFIGURATION = new Configuration(Configuration.VERSION_2_3_30);

	static {
		FREE_MARKER_CONFIGURATION.setClassForTemplateLoading(FreeMarkerUtil.class, "/templates/");
		FREE_MARKER_CONFIGURATION.setDefaultEncoding("UTF-8");
		FREE_MARKER_CONFIGURATION.setLocale(Locale.US);
		FREE_MARKER_CONFIGURATION.setTemplateExceptionHandler(TemplateExceptionHandler.RETHROW_HANDLER);
		FREE_MARKER_CONFIGURATION.setFallbackOnNullLoopVariable(false);
	}

	public static StringWriter mergeModelAndTemplate(Object modelObject, String ftlFile) throws Exception {
		StringWriter stringWriter = new StringWriter();

		Template template = FREE_MARKER_CONFIGURATION.getTemplate(ftlFile);

		template.process(modelObject, stringWriter);

		return stringWriter;
	}

}

Step 3: Define ListConcatenationPopulator.

 

ListConcatenationPopulator.java

package com.sample.app;

import java.io.StringWriter;
import java.util.HashMap;
import java.util.Map;

import com.sample.app.util.FreeMarkerUtil;

public class ListConcatenationPopulator {
	public static void main(String args[]) throws Exception {

		Map<String, Object> modelObject = new HashMap<String, Object>();

		StringWriter stringWriter = FreeMarkerUtil.mergeModelAndTemplate(modelObject, "listConcatenation.ftl");
		System.out.println(stringWriter.toString().trim());

	}
}

Output

- Ram

- Rahim

- Joel

- Krishna

- Abdul

- Chella

- Sailu

- Mary

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