Dynamic Routing key on RabbitListener Annotation - spring

Question

I need to create a queue linked to Direct Exchange for every user who has logged in to the application. The basement routing will be 'user_' + userId.
That is, every time I receive a message through the user management queue that a user is logged on. Instantiate a bean with scope 'prototype' that contains a method annotated with RabbitListener to declare its queue. To this bean, I passed the userId to be able to configure the name of the queue and routingKey. But I can not access this instance variable in the Spel expression due to a circular reference error.
Here I put the bean with which declares the queue:
#Component("usersHandler")
#Scope(value = "prototype")
public class UsersHandler {
private static Logger logger = LoggerFactory.getLogger(UsersHandler.class);
private Long userId;
public UsersHandler(Long userId) {
this.userId = userId;
}
public Long getUserId() {
return userId;
}
public void setUserId(Long userId) {
this.userId = userId;
}
#RabbitListener(bindings
= #QueueBinding(
value = #Queue(
value = "#{'queue_'.concat(usersHandler.userId)}",
durable = "false",
autoDelete = "true",
arguments = {
#Argument(
name = "x-message-ttl",
value = "#{rabbitCustomProperties.directExchange.queueArguments['x-message-ttl']}",
type = "java.lang.Integer"
)
,
#Argument(
name = "x-expires",
value = "#{rabbitCustomProperties.directExchange.queueArguments['x-expires']}",
type = "java.lang.Integer"
)
,
#Argument(
name = "x-dead-letter-exchange",
value = "#{rabbitCustomProperties.directExchange.queueArguments['x-dead-letter-exchange']}",
type = "java.lang.String"
)
}
),
exchange = #Exchange(
value = "#{rabbitCustomProperties.directExchange.name}",
type = ExchangeTypes.DIRECT,
durable = "#{rabbitCustomProperties.directExchange.durable}",
autoDelete = "#{rabbitCustomProperties.directExchange.autoDelete}",
arguments = {
#Argument(
name = "alternate-exchange",
value = "#{rabbitCustomProperties.directExchange.arguments['alternate-exchange']}",
type = "java.lang.String"
)
}
),
key = "#{'user_'.concat(usersHandler.userId)}")
)
public void handleMessage(#Payload Notification notification) {
logger.info("Notification Received : " + notification);
}
}
This is the other bean in charge of creating as many UserHandler as users have logged in:
#Component("adminHandler")
public class AdminHandler implements UsersManadgementVisitor {
#Autowired
private ApplicationContext appCtx;
private Map<Long, UsersHandler> handlers = new HashMap<Long, UsersHandler>();
private static Logger logger = LoggerFactory.getLogger(AdminHandler.class);
#RabbitListener(queues="#{rabbitCustomProperties.adminExchange.queues['users'].name}")
public void handleMessage(#Payload UsersManadgementMessage message) {
logger.info("Message -> " + message);
message.getType().accept(this, message.getId());
}
#Override
public void visitUserConnected(Long idUser) {
logger.info("Declare new queue for user: " + idUser );
UsersHandler userHandler = appCtx.getBean(UsersHandler.class, idUser);
handlers.put(idUser, userHandler);
}
#Override
public void visitUserDisconnected(Long idUser) {
logger.info("Remove queue for user: " + idUser );
handlers.remove(idUser);
}
}
My question is this:
How can I make the variable userId available in the evaluation context of the SpEL expressions?

Answer 1

You could use a ThreadLocal and the T operator...
#SpringBootApplication
public class So43717710Application {
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(So43717710Application.class, args);
UserHolder.setUser("someUser");
context.getBean(Listener.class);
UserHolder.clearUser();
context.getBean(RabbitTemplate.class).convertAndSend("foo", "user_someUser", "bar");
Thread.sleep(5000);
context.close();
}
#Bean
#Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public Listener listener() {
return new Listener();
}
public static class Listener {
#RabbitListener(bindings = #QueueBinding(value = #Queue("#{'queue_' + T(com.example.UserHolder).getUser()}"),
exchange = #Exchange(value = "foo"),
key = "#{'user_' + T(com.example.UserHolder).getUser()}"))
public void listen(String in) {
System.out.println(in);
}
}
}
public class UserHolder {
private static final ThreadLocal<String> user = new ThreadLocal<String>();
public static void setUser(String userId) {
user.set(userId);
}
public static String getUser() {
return user.get();
}
public static void clearUser() {
user.remove();
}
}
If the ThreadLocal is in a #Bean you can use a bean reference...
#SpringBootApplication
public class So43717710Application {
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(So43717710Application.class, args);
UserHolder.setUser("someUser");
context.getBean(Listener.class);
UserHolder.clearUser();
context.getBean(RabbitTemplate.class).convertAndSend("foo", "user_someUser", "bar");
Thread.sleep(5000);
context.close();
}
#Bean
public UserHolder holder() {
return new UserHolder();
}
#Bean
#Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public Listener listener() {
return new Listener();
}
public static class Listener {
#RabbitListener(bindings = #QueueBinding(value = #Queue("#{'queue_' + #holder.user}"),
exchange = #Exchange(value = "foo"),
key = "#{'user_' + #holder.user}"))
public void listen(String in) {
System.out.println(in);
}
}
}