RNDCS Core Java Campus Interview Question Answer

What is the need for Clustering?

To scale the application so that it is highly available and has high throughput.

What are the benefits of Clustering and workload management?

They are
1. It balances client processing requests, allowing incoming work requests to be distributed according to a configured Workload Management selection policy.
2. It provides fail over capability by redirecting client requests to a running server when one or more servers are unavailable. This improves the availability of applications and administrative services.
3. It enables systems to be scaled up to serve a higher client load than provided by the basic configuration. With server groups and clones additional instances of servers can easily be added to the configuration.
4. It enables servers to be transparently maintained and upgraded while applications remain available for users.
5. It centralizes administration of application servers and other objects.

What are the types of Scaling?

There are two types of scaling: Vertical Scaling and Horizontal Scaling.

What is Vertical Scaling?

When multiple server clones of an application server are defined on the same physical m/c, it is called Vertical Scaling. The objective is to use the processing power of that m/c more efficiently.

What is Horizontal Scaling?

When Clones of an application server are defined on multiple physical m/c, it is called Horizontal Scaling. The objective is to use more than one less powerful m/c more efficiently.

What is a Server Group?

A server group is a template of an Application Server(and its contents) i.e, it is a logical representation of the application server. It has the same structure and attributes as the real Application Server, but it is not associated with any node, and does not correspond to any real server process running on any node.

What is a Clone?

The copies of a server group are called Clones. But unlike a Server Group Clones are associated with a node and are real server process running in that node.

What is Ripple Effect?

The process of propagating the changes in the properties of a server group during runtime to all the associated clones is called Ripple Effect.

What level of Load Balancing is possible with EJBs?

The workload management service provides load balancing for the following types of enterprise beans: Homes of entity or session beans, Instances of entity beans, Instances of stateless session beans.

What is the basic requirement for in-memory replication in Weblogic?

The data in session should consist only of Serialized objects. Only setAttribute function should be used to set objects in session.

How JDBC services can be used in clustered environment?

Identical DataSource has to be created in each clustered server instances and configure to use different connection pools.

What are the services that should not be used in a Clustered Environment?

Non-clustered services:

   1. File Services

   2. Time services

   3. Weblogic events

   4. Weblogic Workspaces (In WebLogic 5.1)

Mention some tools to cluster Web Servers?

Web Servers can be clustered using Edge Server or DNS.

What is in-memory replication?

The process by which the contents in the memory of one physical m/c are replicated in all the m/c in the cluster is called in-memory replication.

Difference Between Abstraction and Encapsulation

Abstraction is removing some distinctions between objects, so as to show their commonalities. Encapsulation is hiding the details of the implementation of an object so that there are no external dependencies on the particular implementation.

What is the difference between URL instance and URLConnection instance?

A URL instance represents the location of a resource, and a URLConnection instance represents a link for accessing or communicating with the resource at the location.

What are the two important TCP Socket classes?

Socket and ServerSocket. ServerSocket is used for normal two-way socket communication. Socket class allows us to read and write through the sockets. getInputStream() and getOutputStream() are the two methods available in Socket class.

What technologies are included in J2EE? -

The primary technologies in J2EE are: Enterprise JavaBeansTM (EJBsTM), JavaServer PagesTM (JSPsTM), Java Servlets, the Java Naming and Directory InterfaceTM (JNDITM), the Java Transaction API (JTA), CORBA, and the JDBCTM data access API.

What is the Java Authentication and Authorization Service (JAAS) 1.0?

The Java Authentication and Authorization Service (JAAS) provides a way for a J2EE application to authenticate and authorize a specific user or group of users to run it. JAAS is a Java programing language version of the standard Pluggable Authentication Module (PAM) framework that extends the Java 2 platform security architecture to support user-based authorization.

What’s the difference between JNDI lookup(), list(), listBindings(), and search()?

lookup() attempts to find the specified object in the given context. I.e., it looks for a single, specific object and either finds it in the current context or it fails. list() attempts to return an enumeration of all of the NameClassPair’s of all of the objects in the current context. I.e., it’s a listing of all of the objects in the current context but only returns the object’s name and the name of the class to which the object belongs. listBindings() attempts to return an enumeration of the Binding’s of all of the objects in the current context. I.e., it’s a listing of all of the objects in the current context with the object’s name, its class name, and a reference to the object itself. search() attempts to return an enumeration of all of the objects matching a given set of search criteria. It can search across multiple contexts (or not). It can return whatever attributes of the objects that you desire. It’s by far the most complex and powerful of these options but is also the most expensive.