121.What is the use of “Destination” in JMS? How many types of “Destinations” are available in JMS?
- A destination is a lightweight object that is stored in JNDI.
- It is the target on a JMS server for sending or receiving messages.
- The JMS destination types are:
122.Explain about “Queue Destinations”?
In JMS point-to-point messaging, note the following:
- Clients communicate with a queue destination.
- Messages are distributed to consumers in a serial fashion (first in, first out).
- Each message is delivered only to a single consumer.
123.Explain about “Topic Destinations”?
In JMS publish/subscribe messaging, the following is true:
- Clients communicate with a topic destination.
- Messages are broadcast to all subscribers.
- A message can be saved until at least one subscriber has consumed it (“durable”).
124.Explain about Threshold and Quotas in JMS?
- A threshold and a quota can be set for the server and destination objects.
- A quota is a limit defined for the JMS-administered objects; it includes the following values:
- The maximum number of bytes that can be stored
- The maximum number of messages that can be stored
- A threshold is a limit that triggers message paging, flow control, and logged warnings, using:
- Upper and lower values for the number of bytes
- Upper and lower values for the number of messages
125.Difference between “Durable Subscribers and Subscriptions”?
- Durable subscribers register durable subscriptions for guaranteed message delivery even if the subscribers are inactive.
- A subscriber is considered active if the Java object that represents it exists.
- By default, subscribers are nondurable.
- Administrators configure:
- Where the messages are persisted
- Persistent connection factories and destinations
126.What is “Persistent Messaging”? When to Use it?
- Persistent messaging permits messages in memory to be written out to a persistent store.
- Configure persistent messaging if:
- Development requires durable subscriptions (use durable subscribers in the application)
- You require that in-progress messages persist across server restarts
127.How will you Configuring a Durable Subscription in Weblogic?
- To configure durable subscriptions, an administrator must:
- Create and configure a JMS store
- Configure connection factories or destinations as persistent
- Associate the JMS store with the JMS server
- The JMS store can be configured to use either:
- A file store
- A JDBC store (a connection pool)
128.How a Durable Subscription Works?
- If a subscriber client is active, messages are delivered normally.
- When the client becomes active again, its ID is used to retrieve and redeliver messages.
129.What Node manager can do in Weblogic server?
You can use Node Manager to:
- Start, shut down, and restart an Administration Server
- Start, shut down, suspend, and restart Managed Servers
- Automatically restart the Administration and Managed Servers on failure
- Monitor servers and collect log data