FreeMarker: Working with Map

‘list’ directive can be used to access the elements of a map.

 

Syntax1

<#list map?keys as key>

    ${key} = ${map[key]}

</#list>

 

Syntax2

<#list map as key, value>

    ${key} = ${value}

</#list>

 

Step 1: Define template file.

countryCapitals.ftl

Approach 1
-------------
<#list countries?keys as key> 
    ${key} = ${countries[key]} 
</#list> 

Approach 2
-----------
<#list countries as key, value> 
    ${key} = ${value} 
</#list>

Step 2: Define ‘FreeMarkerUtil’ class that takes a model object 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 ‘CountryCapitalsPopulator’ class.

 

CountryCapitalsPopulator.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 CountryCapitalsPopulator {
	public static void main(String args[]) throws Exception {

		Map<String, String> countriesMap = new HashMap<>();
		countriesMap.put("India", "New Delhi");
		countriesMap.put("Nepal", "Khatmandu");
		countriesMap.put("Italy", "Vienna");
		
		Map<String, Object> modelObject = new HashMap<> ();
		modelObject.put("countries", countriesMap);
		
		StringWriter stringWriter = FreeMarkerUtil.mergeModelAndTemplate(modelObject, "countryCapitals.ftl");
		System.out.println(stringWriter.toString().trim());

	}
}

Output

Approach 1
-------------
    Italy = Vienna 
    Nepal = Khatmandu 
    India = New Delhi 

Approach 2
-----------
    Italy = Vienna 
    Nepal = Khatmandu 
    India = New Delhi

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