Freemarker template example with Spring expressions

greeting-template.ftl

<@spel expression="We say '{@greetingBean.printGreeting(name)}'"/> from Freemarker

pom.xml

<dependency>
	<groupId>org.freemarker</groupId>
	<artifactId>freemarker</artifactId>
	<version>2.3.19</version>
</dependency>
<dependency>
	<groupId>javax.servlet</groupId>
	<artifactId>servlet-api</artifactId>
	<version>2.5</version>
	<scope>provided</scope>
</dependency>		
<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-webmvc</artifactId>
	<version>3.1.2.RELEASE</version>
</dependency>
<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-test</artifactId>
	<version>3.1.2.RELEASE</version>
	<scope>test</scope>
</dependency>
<dependency>
	<groupId>com.adaptiweb.utils</groupId>
	<artifactId>spel-evaluator</artifactId>
	<version>1.5-SNAPSHOT</version>
</dependency>
<dependency>
	<groupId>junit</groupId>
	<artifactId>junit</artifactId>
	<version>4.8.2</version>
	<scope>test</scope>
</dependency>

SpelFreemarkerTemplateDirective.java

public class SpelFreemarkerTemplateDirective implements TemplateDirectiveModel {
	SpelEvaluator spelEvaluator;
	
	@Required
	public void setSpelEvaluator(SpelEvaluator spelEvaluator) {
		this.spelEvaluator = spelEvaluator;
	}
	
	@Override
	public void execute(Environment env, @SuppressWarnings("rawtypes") Map params, TemplateModel[] loopVars,
			TemplateDirectiveBody body) throws TemplateException, IOException {

		@SuppressWarnings("unchecked")
		String spelResult = spelEvaluator
				// set all freemarker variables as root object - map
				.setRootObject(new FreemarkerVariables(env, env.getKnownVariableNames()))
				// resolve expression either from parameter or from body
				.setExpression(resolveSpelExpression(params, body))
				.evaluate(String.class);
		env.getOut().write(spelResult);
		
		spelEvaluator.dispose();
	}
	
	private String resolveSpelExpression(Map<String, Object> params, TemplateDirectiveBody body) throws TemplateException, IOException {
		if (params.containsKey("expression")) {
			TemplateModel expressionModel = (TemplateModel) params.get("expression");
			return (String) DeepUnwrap.permissiveUnwrap(expressionModel);
		} else { // expression in body
			StringWriter expressionWriter = new StringWriter();
			body.render(expressionWriter);
			return expressionWriter.toString();
		}
	}
	
	static class FreemarkerVariables implements Map<String, Object> {
		final Environment env;
		final Set<String> variableNames;

		FreemarkerVariables(Environment env, Set<String> variableNames) {
			this.env = env;
			this.variableNames = variableNames;
		}

		@Override
		public int size() {
			return variableNames.size();
		}
		@Override
		public boolean isEmpty() {
			return variableNames.isEmpty();
		}
		@Override
		public boolean containsKey(Object key) {
			return variableNames.contains(key);
		}
		@Override
		public Object get(Object key) {
			try {
				TemplateModel model = env.getVariable((String) key);
				return DeepUnwrap.permissiveUnwrap(model);
			} catch (TemplateModelException e) {
				return null;
			}
		}
		@Override
		public Set<String> keySet() {
			return variableNames;
		}

		@Override public boolean containsValue(Object value) { throw new RuntimeException("Unsupported operation"); }
		@Override public Object put(String key, Object value) { throw new RuntimeException("Unsupported operation"); }
		@Override public Object remove(Object key) { throw new RuntimeException("Unsupported operation"); }
		@Override public void putAll(Map<? extends String, ? extends Object> m) { throw new RuntimeException("Unsupported operation"); }
		@Override public void clear() { throw new RuntimeException("Unsupported operation"); }
		@Override public Collection<Object> values() { throw new RuntimeException("Unsupported operation"); }
		@Override public Set<java.util.Map.Entry<String, Object>> entrySet() { throw new RuntimeException("Unsupported operation"); }
	}
}

SpelFreemarkerTest-context.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <!-- FreeMarker configuration -->
    <bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer"
        p:configuration-ref="freemarkerConfiguration"/>
 
    <bean id="freemarkerConfiguration" class="org.springframework.ui.freemarker.FreeMarkerConfigurationFactoryBean"
            p:templateLoaderPath="/" p:preferFileSystemAccess="false">
        <property name="freemarkerVariables">
            <map>
                <entry key="spel" value-ref="spelDirective"/>
            </map>
        </property>
    </bean>

	<bean id="spelDirective" class="com.adaptiweb.blog.example.SpelFreemarkerTemplateDirective"
		p:spelEvaluator-ref="spelEvaluator"/>

	<bean id="spelEvaluator" class="com.adaptiweb.utils.spel.SpelEvaluatorFactoryBean"
		p:useBeanResolver="true" p:useBeanAccessor="true" p:useMapAccessor="true"
		p:templatePrefix="{" p:templateSuffix="}"/>

	<bean id="greetingBean" class="com.adaptiweb.blog.example.SpelFreemarkerTest.GreetingBean"
		p:greeting="Hello"/>

</beans>

SpelFreemarkerTest.java

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration
public class SpelFreemarkerTest {
	@Autowired GreetingBean greetingBean;
	@Autowired Configuration freemarkerConfig;
	
	@Test
	public void testFreemarkerSpel() throws IOException, TemplateException {
		Map<String, String> model = new HashMap<String, String>();
		model.put("name", "Felix");
		Template template = freemarkerConfig.getTemplate("greeting-template.ftl");
		String output = FreeMarkerTemplateUtils.processTemplateIntoString(template, model);
		System.out.println(output);
		String expected = "We say '" + greetingBean.printGreeting(model.get("name")) + "' from Freemarker";
		assertEquals(expected, output);
	}
	
	public static class GreetingBean {
		private String greeting;
		
		@Required
		public void setGreeting(String greeting) {
			this.greeting = greeting;
		}		
		public String printGreeting(String name) {
			return greeting + " " + name;
		}
	}
}