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Weblogic Interview Questions
- 1) How does a server know when another server is unavailable?
- 2) How can I set deployment order for applications?
- 3) How do stubs work in a WebLogic Server cluster?
- 4) Is an XSLT processor bundled in WebLogic Server?
- 5) What is the function of T3 in WebLogic Server?
- 6) Can I start a Managed Server if the Administration Server is unavailable?
- 7) What happens if remove( ) is never invoked on a session bean?
- 8) What does isIdentical() method return in case of different type of beans?
- 9) What is the Java Authentication and Authorization Service (JAAS) 1.0?
- 10) Why would a client application use JTA transactions?
- 11) What is the difference between creating a distributed application using RMI and using a EJB architecture?
- 12) List Components of JNDI?
- 13) What causes Java.io exceptions in the log file of WebLogic Server?
- 14) Which types of JDBC databases does WebLogic JMS support?
- 15) What is the difference between JNDI lookup(), list(), listBindings(), and search()?
- 16) What are the enhancements in EJB 2.0 specification with respect to Asynchronous communication?
- 17) Do EJBs have to be homogeneously deployed across a cluster? Why?
- 18) What technologies are included in J2EE?
- 19) What happens when a failure occurs and the stub cannot connect to a WebLogic Server instance?
- 20) How should you type cast a remote object? Why?
- 21) Can the bean class implement the EJBObject class directly? If not why?
- 22) How do clients handle DNS requests to failed servers?
- 23) How many WebLogic Servers can I have on a multi-cpu machine?
- 24) What are the special design care that must be taken when you work with local interfaces?
- 25) Can you briefly describe local interfaces?
Below are the list of Best Weblogic Interview Questions and Answers
WebLogic Server monitors socket errors to check the availability of a server instance. As an example, if server instance A1 has associate degree open socket to server instance B1, and also the socket unexpectedly closes, server A1 assumes that server B1 is offline.
You can set the deployment order of a Startup class, follow the instructions in Configure startup classes.
Clients that are connected to a WebLogic Server cluster obtain a replica-aware stub for the object. This stub contains the load balancing logic for distributing the load among its host servers. The stub also contains the list of available server instances that host implementations of the object.
Yes! An XSLT processor is bundled in WebLogic Server.
T3 is the protocol which is a standardized rule used to transport information between WebLogic servers and other types of Java programs. WebLogic keeps track of every Java virtual machine connected to the application and creates a single T3 connection to carry traffic to the Java virtual machine.
Yes! We start a Managed Server if the Administration Server is unavailable.
If remove( ) is never invoked then the bean may be kept in cache till either the session times out/session out, in which case the bean is removed or when there is a requirement for memory in which case the data is cached and the bean is sent to free pool.
The isIdentical() method returns 0 (zero) in case of different type of beans.
The full form of JAAS is Java Authentication and Authorization Service. It is a set of application program interfaces (APIs) that can determine the identity of a user or computer attempting to run Java code. It ensures that the entity has the right to execute the functions requested. Logically, authentication precedes authorization.
JTA stands for Java Transaction API that allows applications to perform distributed transactions. it also performs transactions that access and update data on two or more networked computer resources. A client application uses JTA transactions because It allows us to start, commit, and rollback transactions in a resource-agnostic way. The true power of JTA lies in its ability to manage multiple resources (i.e. databases, messaging services) in a single transaction
11) What is the difference between creating a distributed application using RMI and using a EJB architecture?
The difference between creating a distributed application using RMI and using an EJB architecture is as follows:
|S. N.||JavaTM RMI technology||Enterprise JavaBeansTM technology|
|1||You can use Java RMI technology to enable communication between Java objects on different virtual machines and different physical machines.||Enterprise JavaBeansTM (EJBTM) technology is part of the Java 2 Platform, Enterprise Edition.|
|2||You can use Java RMI technology without its IIOP option leverages its strengths of code portability, security, and garbage collection.||Enterprise JavaBeans components use the Java RMI/Java IDL technology for their distributed object model. It also uses the Java Transaction Service (JTS) for its distributed transaction model.|
Some of the Components of JNDI are:
- JNDI Names and Resources.
- J2EE Naming Services.
- Naming References and Binding Information.
Broken pipe causes Java.io exceptions in the log file of WebLogic Server.
WebLogic JMS supports Oracle JDBC databases.
The differences among JNDI lookup(), list(), listBindings(), and search() are as follows.
|JNDI lookup()||JNDI list()||JNDI listBindings()||JNDI search()|
|lookup() is used to find the specified object in the given context. i.e., it looks for a single, specific object and either find it in the current context or it fails.||list() is used for enumeration of the NameClassPair of all of the objects in the current context. 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 whose object is it. td>||listBindings() is a listing of all of the objects in the current context with an object's name, a reference to the object itself, and its class name. It's used to return an enumeration of the Bindings of all of the objects in the current context.||search() used to return an enumeration of all of the objects matching a given set of search criteria. It can search across multiple contexts. It can return the attributes of the objects that you desire. etc. It's the most complex and powerful but is also the most expensive.|
EJB 2.0 mandates integration between JMS and EJB. It is specified as the integration of Enterprise JavaBeans with the Java Message Service and has introduced message-driven beans that are a stateless component also invoked by the container as a result of a JMS arrival message. The goal of the message-driven bean model is developing an enterprise bean.
Yes, EJBs have to be homogeneously deployed across a cluster. The reason behind, EJBs must be homogeneously deployed across a cluster are as follows:
- It keeps clustering EJBs simple
- It ensures every EJB is available locally
- It improves performance by avoiding cross-server calls
- It ensures all classes are loaded in an undeployable way. Every server must have access to each EJB’s classes so You can say that it can be bound into the local JNDI tree
The primary technologies in the J2EE platform are as follows:
- JDBC data access API
- Java Transaction API (JTA)
- Java Message Service (JMS)
- J2EE Deployment API
- J2EE Management Model
- J2EE Connector Architecture
- JavaServer Pages, Java Servlets
- Enterprise JavaBeans components
- Java API for XML Registries (JAXR)
- Java Management Extensions (JMX)
- Java API for XML-Based RPC (JAX-RPC)
- J2EE Authorization Contract for Containers
- Java Naming and Directory Interface (JNDI)
When a failure happens and also the stub removes the unsuccessful server instance from its list, the stub cannot connect with a WebLogic Server instance. If there aren't any servers in its list, the stub uses DNS once more to go looking for a running server additionally acquire a current list of running instances, and also the stub periodically refreshes its list of accessible server instances within the cluster. It permits the stub to require advantage of the new servers.
You can typecast a remote object with the help of typecasting operators as it reduces the efforts and unnecessary additional lines of codes to declare variables according to their respective type.
The bean class can implement the EJBObject class optionally therefore the bean class can not be implemented the EJBObject class directly.
If a server fails then DNS continues to send requests to the unavailable machine that can waste bandwidth. This problem occurs only during startup for a Java client application. WebLogic Server caches the DNS entries and removes the unavailable ones, to prevent the client from accessing a failed server again it avoids unnecessary DNS requests with browser-based clients, It uses third-party load-balancer products such as Resonate, BigIP, Alteon, and LocalDirector that products mask multiple DNS addresses as a single address. It also provides more sophisticated load-balancing options than round-robin and keeps track of failed servers to avoid routing unnecessary requests.
Multiple WebLogic Servers can be on a multi-CPU machine. You can have many possible configurations that have no built-in limit for the number of server instances. It can also reside in a cluster. Large Multi-processor servers like Sun Microsystems and Inc. Sun Enterprise 10000 can host multiple clusters.
There is no special design care that must be taken when you work with local interfaces.
Yes, The local interface is a standard Java interface that does not inherit from RMI. An enterprise bean uses the local interface to expose its methods to other beans to reside within the same container.
The enhancements in EJB 2.0 with respect to CMP is as follows:
- Local interfaces, which improve the efficiency of intracontainer entity relationships
- Container-managed relationships, in which the container manages object relationships between entity beans
- Changes to EJB QL, a query language for portable EJB finder methods
- Enhancements to the interfaces of Message-Driven Beans (MDBs), as well as to the home interfaces of remote entity beans.
You must provide the credentials of a user who is permitted to start and stop servers for the domain to start and stop WebLogic Server instances. User Credentials to Start and Stop Servers are described below: If you specify the Username and password on the command line. The server instance Uses them and does not prompt you for either credential. If you specify the Username and password in the boot. properties.
The server instance Uses them and does not prompt you for either credential. If you specify Username but no password on the command line The server instance Uses the username from the command line and Prompts you for the password twice. If you specify Password but no username on the command line. The server instance Prompts you for the username and Ignores the password from the command line and prompts you for the password twice
You can set the classpath to follow these steps:
Step 1: Select Start -> Control Panel -> System -> Advanced -> Environment Variables -> System Variables -> CLASSPATH.
Step 2: Select New. Step 4: Specify name and path Click on OK
The two important TCP Socket classes are as follows:
1. Socket Class: This class provides enriched methods and properties for network communications that allow both synchronous and asynchronous data transfer.
2. Server Socket Class: This class is used to implement server sockets that are used to respond to requests received over the network
You can increase WebLogic Server memory by Changing the JVM Heap Size with the help of the following steps:
Step 1: Expand your WebLogic domain (for example, PeopleSoft) and click Environment, then Servers.
Step 2: Select the managed server you intend to modify.
Step 3: Select the Configuration tab and the Server Start sub-tab.
Step 4: Update the Arguments field.
Step 5: Click Save.
Passive learning is a method of learning or instruction where learners receive information from the instructor, internalize it, and receive no feedback from the instructor". They can quietly absorb information and knowledge without typically engaging with the information received or the learning experience.
The max amount of information that can be saved in a Session Object is 80 KB.
When a new instance joins the cluster, The WebLogic Server cluster broadcasts the availability of a new server instance. Cluster-aware stubs also periodically update the list of available server instances.
A URL instance is used to represent the location of a resource whereas A URL connection instance is used to represent a link for accessing and communicating with the resource at the location.
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