@zenbeni has answered this question but I wanna tell you about my implementation, it's hard to make spouts/bolts as spring beans. But to use other spring spring beans inside your spouts/bolts you could declare a global variable & in your execute method check whtether variable is null or not. If it's null you have to get bean from application context. Create a class which contains a method to initialize beans if it's not initialized already. Look ApplicationContextAware interface for more information(Spring bean reuse).
Example Code:
Bolt Class:
public class Class1 implements IRichBolt{
Class2 class2Object;
public void prepare() {
if (class2Object== null) {
class2Object= (Class2) Util
.initializeContext("class2");
}
}
}
Util Class for initializing Beans if not initialized already:
public class Util{
public static Object initializeContext(String beanName) {
Object bean = null;
try {
synchronized (Util.class) {
if (ApplicationContextUtil.getAppContext() == null) {
ApplicationContext appContext = new ClassPathXmlApplicationContext("beans.xml");
bean = ApplicationContextUtil.getAppContext().getBean(
beanName);
} else {
bean = ApplicationContextUtil.getAppContext().getBean(
beanName);
}
}
} catch (Exception e) {
e.printStackTrace();
}
return bean;
}
}
Listener for Application Context Change:
@Component
public class ApplicationContextUtil implements ApplicationContextAware {
private static ApplicationContext appContext;
public void setApplicationContext(ApplicationContext applicationContext)
throws BeansException {
appContext = applicationContext;
}
public static ApplicationContext getAppContext() {
return appContext;
}
}
Note: Each Worker will initialize spring context because it's running in different JVM.
UPDATE
If you want to use a spring bean class in which you have some values previously assigned try this,
Note: Passing the current class to Bolt's constructor
Class (Topology Creation Class) which is already contains values:
public class StormTopologyClass implements ITopologyBuilder, Serializable {
public Map<String, String> attributes = new HashMap<String, String>();
TopologyBuilder builder=new TopologyBuilder();
builder.setBolt("Class1",new Class1(this));
builder.createTopology();
}
Bolt by using single argument constructor:
public class Class1 implements IRichBolt{
StormTopologyClass topology;
public Class1 (StormTopologyClass topology) {
this.topology = topology;
}
}
Now you could use attributes variable & it's values in bolt class.
