How to use velocity 1.7 with Spring

Question

I am using velocity 1.7 withe spring 3.1 framework for sending email. velocity is used for email templates.

Below is the configuration

<bean id="velocityEngine"
    class="org.springframework.ui.velocity.VelocityEngineFactoryBean">
    <property name="velocityProperties">
        <props>
            <prop key="resource.loader">class</prop>
            <prop key="class.resource.loader.class">
                org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader
            </prop>
        </props>
    </property>
</bean>

and below is my code

 @Component
 public class EmailUtils {

    @Autowired
    private static VelocityEngine velocityEngine;

    public static void sendMail(String subject, Map data, String template,
            String toName, String toAddress) {


        HtmlEmail email = new HtmlEmail();

        try {
            email.setHostName(hostName);
            email.setSmtpPort(smtpPort);
            email.setSubject(subject);

            System.out.println(template +" template");
            System.out.println(data +" data ");
            System.out.println(velocityEngine +" velocityEngine ");

            String message = VelocityEngineUtils.mergeTemplateIntoString(
                    velocityEngine, template, data);

            System.out.println(message +" message message ");

            email.setMsg(message);
            email.addTo(toAddress, toName);
            email.setFrom(fromAddress, fromName);
            email.send();
        } catch (EmailException e) {
            // TODO Auto-generated catch block

            e.printStackTrace();
        }
    }
}

When I run the application I get following error.

java.lang.NullPointerException
at org.springframework.ui.velocity.VelocityEngineUtils.mergeTemplate(VelocityEngineUtils.java:58)

as the velocity engine is null.

<?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:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
    http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">

<bean id="velocityEngine"
    class="org.springframework.ui.velocity.VelocityEngineFactoryBean">
    <property name="velocityProperties">
        <props>
            <prop key="resource.loader">class</prop>
            <prop key="class.resource.loader.class">
                org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader
            </prop>
        </props>
    </property>
</bean>

Please help me. Is there any other configuration that I need to do?

Answer 1

I had the same issue when using . I could have solved it in the following way:

@Configuration
public class ApplicationConfiguration {

    @Bean
    public VelocityEngine getVelocityEngine() throws VelocityException, IOException{
        VelocityEngineFactory factory = new VelocityEngineFactory();
        Properties props = new Properties();
        props.put("resource.loader", "class");
        props.put("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
        factory.setVelocityProperties(props);
        return factory.createVelocityEngine();      
    }
}

But instead - because I was using velocity templates for my views and had already declared a VelocityConfigurer, so I instead Autowired in my declaration of VelocityConfigurer and called getVelocityEngine() on that.

I did discover that, if it's being autowired into @Service-s or @Component-s and you've declared in a shared applicationContext.xml file, then the xml declaration had to be in that shared applicationContext.xml as well rather than the xxx-servlet.xml config.

I think this is because applicationContext.xml is shared amongst all servlets in the application, so it has to be fully processed before the xxx-servlet.xml files are.

Alternatively, you could enable spring bean factory debugging and see if it's having any issues instantiating it:

log4j.category.org.springframework.beans.factory=DEBUG

Answer 2

I think you cannot use @Autowired with a static field. You can work around this with a non-static setter:

@Autowired
public void setVelocityEngine(VelocityEngine ve) {
  EmailUtils.velocityEngine = ve;
}

or in another way but I would strongly recommend turning EmailUtils into a non-static bean. Spring handles non-static components much better (no ugly hacks needed), it will be possible to swap implementations and your code will stick to DI philosphy.