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:

File Services

Time services

Weblogic events

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 are the different kinds of enterprise beans? - Different kind of enterrise beans are Stateless session bean, Stateful session bean, Entity bean, Message-driven bean.

What is Session Bean? - A session bean is a non-persistent object that implements some business logic running on the server. One way to think of a session object.

What is Entity Bean? - The entity bean is used to represent data in the database. It provides an object-oriented interface to

What are the methods of Entity Bean? - An entity bean consists of 4 groups of methods, create methods.

What is the difference between Container-Managed Persistent (CMP) bean and Bean-Managed Persistent(BMP) ? - Container-managed persistence (CMP) and bean-managed persistence (BMP). With CMP, the container manages the persistence of the entity bean.

What are the callback methods in Entity beans? - Callback methods allows the container to notify the bean of events in its life cycle. The callback methods are defined in the javax.ejb.EntityBean interface.

What is software architecture of EJB? - Session and Entity EJBs consist of 4 and 5 parts respectively, a remote interface.

Can Entity Beans have no create() methods? - Yes. In some cases the data is inserted NOT using Java application,.

What is bean managed transaction? - If a developer doesn’t want a Container to manage transactions, it’s possible to implement all database operations manually.

What are transaction attributes? - The transaction attribute specifies how the Container must manage transactions for a method when a client invokes the method via the enterprise bean’s home or.

What are transaction isolation levels in EJB? - Transaction_read_uncommitted, Transaction_read_committed, Transaction_repeatable_read.

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.

Components of JNDI - Naming Interface- The naming interface organizes information hierarchically and maps human-friendly names to addresses or objects that are machine-friendly. It allows access to named objects through multiple namespaces. Directory Interface - JNDI includes a directory service interface that provides access to directory objects, which can contain attributes, thereby providing attribute-based searching and schema support. Service Provider Interface - JNDI comes with the SPI, which supports the protocols provided by third parties.

What is the Max amount of information that can be saved in a Session Object? - As such there is no limit on the amount of information that can be saved in a Session Object. Only the RAM available on the server machine is the limitation. The only limit is the Session ID length(Identifier), which should not exceed more than 4K. If the data to be store is very huge, then it’s preferred to save it to a temporary file onto hard disk, rather than saving it in session. Internally if the amount of data being saved in Session exceeds the predefined limit, most of the servers write it to a temporary cache on Hard disk.

Must my bean-managed persistence mechanism use the WebLogic JTS driver? - BEA recommend that you use the TxDataSource for bean-managed persistence.

Do EJBs have to be homogeneously deployed across a cluster? Why? - Yes. Beginning with WebLogic Server version 6.0, EJBs must be homogeneously deployed across a cluster for the following reasons:

To keep clustering EJBs simple

To avoid cross server calls which results in more efficiency. If EJBs are not deployed on all servers, cross server calls are much more likely.

To ensure that every EJB is available locally

To ensure that all classes are loaded in an undeployable way

Every server must have access to each EJB’s classes so that it can be bound into the local JNDI tree. If only a subset of the servers deploys the bean, the other servers will have to load the bean’s classes in their respective system classpaths which makes it impossible to undeploy the beans.

Is an XSLT processor bundled in WebLogic Server? - Yes, an XSLT processor, based on Apache’s Xalan 2.0.1 processor, in WebLogic Server 6.1.

I plugged in a version of Apache Xalan that I downloaded from the Apache Web site, and now I get errors when I try to transform documents. What is the problem? - You must ensure that the version of Apache Xalan you download from the Apache Web site is compatible with Apache Xerces version 1.3.1. Because you cannot plug in a different version of Apache Xerces , the only version of Apache Xerces that is compatible with WebLogic Server 6.1 is 1.3.1. The built-in parser (based on version 1.3.1 of Apache Xerces) and transformer (based on version 2.0.1 of Apache Xalan) have been modified by BEA to be compatible with each other.

How do I increase WebLogic Server memory? - Increase the allocation of Java heap memory for WebLogic Server. (Set the minimum and the maximum to the same size.) Start WebLogic Server with the -ms32m option to increase the allocation, as in this example:

This allocates 32 megabytes of Java heap memory to WebLogic Server, which improves performance and allows WebLogic Server to handle more simultaneous connections. You can increase this value if necessary.

What causes Java.io exceptions in the log file of WebLogic Server? - You may see messages like these in the log file:

These messages occur when you are using servlets. A client initiates an HTTP request, and then performs a series of actions on the browser:

Click Stop or enter equivalent command or keystrokes

Click Refresh or enter equivalent command or keystrokes

Send a new HTTP request.

The messages indicate that WebLogic Server has detected and recovered from an interrupted HTTP request.

What is the function of T3 in WebLogic Server? - T3 provides a framework for WebLogic Server messages that support for enhancements. These enhancements include abbreviations and features, such as object replacement, that work in the context of WebLogic Server clusters and HTTP and other product tunneling. T3 predates Java Object Serialization and RMI, while closely tracking and leveraging these specifications. T3 is a superset of Java Object. Serialization or RMI; anything you can do in Java Object Serialization and RMI can be done over T3. T3 is mandated between WebLogic Servers and between programmatic clients and a WebLogic Server cluster. HTTP and IIOP are optional protocols that can be used to communicate between other processes and WebLogic Server. It depends on what you want to do. For example, when you want to communicate between a browser and WebLogic Server-use HTTP, or an ORB and WebLogic Server-IIOP.

What are the enhancements in EJB 2.0 specification with respect to Asynchronous communication? - EJB 2.0 mandates integration between JMS and EJB. We have specified the integration of Enterprise JavaBeans with the Java Message Service, and have introduced message-driven beans. A message-driven bean is a stateless component that is invoked by the container as a result of the arrival of a JMS message. The goal of the message-driven bean model is to make developing an enterprise bean that is asynchronously invoked to handle the processing of incoming JMS messages as simple as developing the same functionality in any other JMS MessageListener.

What are the enhancements in EJB 2.0 with respect to CMP? - EJB 2.0 extends CMP to include far more robust modeling capability, with support for declarative management of relationships between entity EJBs. Developers no longer need to re-establish relationships between the various beans that make up their application — the container will restore the connections automatically as beans are loaded, allowing bean developers to navigate between beans much as they would between any standard Java objects.
EJB 2.0 also introduces for the first time a portable query language, based on the abstract schema, not on the more complex database schema. This provides a database and vendor-independent way to find entity beans at run time, based on a wide variety of search criteria.