If there are multi CDI @Obsevers methods defined, in the former CDI, there is no way to ensure they are executed in a certain order.
In CDI 2.0, this gap is filled by @Priority.
Let's create a simple example to demonstrate it.
Create a bean to fire a CDI Event.
@ViewScoped
@Named("eventBean")
public class EventBean implements Serializable {
private static final Logger LOG = Logger.getLogger(EventBean.class.getName());
@Inject
Event<Message> event;
private String message;
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public void fireEvent() {
LOG.log(Level.INFO, "fire event async...");
event.fire(new Message(this.message));
}
}
The event payload Message.
public class Message implements Serializable {
private String content;
Message() {
}
Message(String content) {
this.content = content;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
@Override
public int hashCode() {
int hash = 7;
hash = 79 * hash + Objects.hashCode(this.content);
return hash;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
final Message other = (Message) obj;
if (!Objects.equals(this.content, other.content)) {
return false;
}
return true;
}
@Override
public String toString() {
return "Message{" + "content=" + content + '}';
}
}
Observes the events.
@ApplicationScoped
public class EventHandler implements Serializable {
public static final Logger LOG = Logger.getLogger(EventHandler.class.getName());
public void onMessage(@Observes @Priority(value = 1) Message message) {
LOG.log(Level.INFO, "observes event with @Priority(value = 1):{0}", message);
}
public void onAnotherMessage(@Observes @Priority(value = 2) Message message) {
LOG.log(Level.INFO, "observes event @Priority(value = 2):{0}", message);
}
}
Run this application on Glassfish, open browser and navigate to .
Input some message in the input box, you will see the similar info in IDE console.
Info: observes event with @Priority(value = 1):Message{content=hello CDI event}
Info: observes event @Priority(value = 2):Message{content=hello CDI event}
