I'm trying to test out Spring Annotations to see how they work with some simple examples derived from the Spring 3.0 Source (in this case the "@Required" annotation specifically).
To start, I came up with a basic "Hello World" type example that doesn't use any annotations. This works as expected (i.e. prints "Hello Spring 3.0~!").
I then added a DAO
object field to the Spring3HelloWorld
class. My intention was to deliberately cause an exception to occur by annotating the setter for the DAO
with @Required
but then not setting it. However, I get a null pointer exception (since this.dao
is null) when I was expecting an exception based on not following the annotation "rules/requirements".
I thought I would have needed to set the DAO
object before calling any method from Spring3HelloWorld
, but apparently that's not the case. I assume I'm misunderstanding how @Required
works.
So basically how would I get the following to give me an error along the lines of "Hey you can't do that, you forgot to set DAO blah blah blah".
Spring3HelloWorldTest.java:
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;
public class Spring3HelloWorldTest {
public static void main(String[] args) {
XmlBeanFactory beanFactory = new XmlBeanFactory(new ClassPathResource ("SpringHelloWorld.xml"));
Spring3HelloWorld myBean = (Spring3HelloWorld) beanFactory.getBean("spring3HelloWorldBean");
myBean.sayHello();
}
}
Spring3HelloWorld.java:
import org.springframework.beans.factory.annotation.Required;
public class Spring3HelloWorld {
private DAO dao;
@Required
public void setDAO( DAO dao ){
this.dao = dao;
}
public void sayHello(){
System.out.println( "Hello Spring 3.0~!" );
//public field just for testing
this.dao.word = "BANANA!!!";
}
}
SpringHelloWorld.xml:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:annotation-config/>
<bean class="org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor"/>
<bean id="dao" class="src.DAO" ></bean>
<bean id="spring3HelloWorldBean" class="src.Spring3HelloWorld" ></bean>
</beans>