Top 45+ EJBT Interview Questions and Answers
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45+ [REAL-TIME] EJBT Interview Questions and Answers

Last updated on 29th May 2024, Popular Course

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Rahul (EJB Developer )

Rahul, as an EJB Developer with three years of experience in the field, holds significant responsibilities within his role. His primary duty is to design, implement, and maintain Enterprise JavaBeans (EJB) components within Java Enterprise Edition (Java EE) applications.

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Enterprise JavaBeans (EJB) is a server-side component architecture for building distributed enterprise applications in Java. It simplifies the development of large-scale, mission-critical applications by providing a standardized way to build, package, deploy, and manage business components in a distributed environment. EJB components are managed by a container, which provides services such as lifecycle management, security, transaction management, concurrency control, and persistence.

1. What are Enterprise JavaBeans( EJBs)?

Ans:

Enterprise JavaBeans, or EJBs, are garçon- side factors that synopsize the business sense of an operation. They’re part of the Java EE( Enterprise Edition) platform, furnishing a standard way to develop scalable, distributed, and transactional Java operations. EJBs simplify the development process by handling enterprises similar to sales operation, security, and continuity, allowing inventors to concentrate on business sense.

2. What are the different types of EJBs and their differences?

Ans:

  • There are three types of EJBs: session sap, Entity sap, and Communication-driven sap. 
  • Session sap represents business sense and can be stateless or stateful, depending on whether it maintains a conversational state with the customer. 
  • Reality sap represents patient data stored in a database, and communication-driven sap handles asynchronous messaging. 
  • Each type serves different purposes in an enterprise operation.

3. What’s the difference between Stateful and Stateless Session sap?

Ans:

Stateful Session sap maintains a conversational state with the customer, conserving data between system calls within a specific customer session. In discrepancy, Stateless Session sap doesn’t preserve a customer-specific state, making it featherlight and scalable. Stateful session sap is suitable for scripts taking customer-specific data retention, while stateless session sap is preferred for high concurrency and stateless operations.

4. How does EJB handle deals?

Ans:

EJB provides declarative sale operations, allowing inventors to define transactional geste using reflections or deployment descriptors. Deals in EJB are managed by the vessel, ensuring ACID( Atomicity, thickness, insulation, continuity) parcels. Inventors can specify sale attributes similar to needed, REQUIRES_NEW, and MANDATORY to control transactional geste at the system position, furnishing inflexibility, and thickness in sale operation.

5.What is the differnt between session beans and entity beans?

Ans:

Aspect Session Beans Entity Beans
Lifecycle Session beans are typically short-lived and are created and destroyed by the EJB container as needed. Entity beans have longer lifecycles and may persist in the database beyond the scope of a single method invocation.
Purpose Used to encapsulate business logic and provide services to clients. Used to represent persistent data and provide CRUD operations for database entities.
State Management Stateless and stateful session beans may maintain conversational state between method invocations, but they do not represent persistent data. Entity beans represent persistent data and can maintain state between method invocations to reflect changes in the underlying database entities.
Usage Scenarios Used for implementing business logic, managing transactions, and coordinating services within an application. Used for mapping Java objects to database tables, performing CRUD operations, and managing persistent data within an application.

6. How do you handle security in EJB operations?

Ans:

EJB provides a comprehensive security model grounded on Java EE security reflections and declarative security settings. Inventors can secure EJB styles and coffers by annotating them with security constraints such as @RolesAllowed,@PermitAll, and @DenyAll. Also, EJB holders support integration with external authentication mechanisms such as LDAP, JAAS, or custom login modules, enabling authentication, authorization, and part-grounded access control in enterprise operations.

7. Explain the lifecycle of an Enterprise JavaBean( EJB).

Ans:

The lifecycle of an EJB consists of several stages: creation, system magic, and junking. During creation, the vessel instantiates the bean and injects dependencies. System incantation involves executing business sense within the bean. Eventually, junking occurs when the ship deallocates coffers, generally after the bean is no longer demanded, ensuring effective resource operation.

8. separate between original and remote interfaces in EJB.

Ans:

  • Local interfaces are used for intra-application communication within the same JVM, offering advanced performance and avoiding network outflow. 
  • Remote interfaces, on the other hand, grease inter-application communication across JVMs or physical machines, enabling distributed operations. 
  • Developers choose between them based on performance conditions and the need for distributed functionality.

9. How does EJB handle concurrency and thread safety?

Ans:

EJB holders manage concurrency through mechanisms like vessel-managed concurrency and bean pooling. Container-managed concurrency allows inventors to specify concurrency strategies similar to Singleton, Stateless, or Bean-Managed Concurrency. Also, EJBs ensure thread safety by providing access to participating coffers and managing access to bean cases, precluding race conditions, and ensuring data integrity.

10. What’s the part of deals in EJB?

Ans:

Deals in EJB ensure data integrity and thickness by grouping multiple operations into a single tiny unit of work. EJB holders manage deals, furnishing declarative sale operations through reflections or deployment descriptors. Inventors can specify sale attributes like needed or REQUIRES_NEW to define transactional geste, ensuring ACID parcels and robust error handling in enterprise operations.

11. Explain the difference between vessel- managed deals( CMT) and bean- managed deals( BMT) in EJB.

Ans:

  • Container-managed deals( CMT) delegate sale control to the EJB vessel, which automatically manages sale boundaries and resource investiture. 
  • In contrast, bean-managed deals( BMT) require the inventor to explicitly manage sale discrimination and resource investiture within the EJB styles using the UserTransaction API. 
  • CMT is simpler to apply and suitable for most scripts, while BMT offers more fine-granulated control over sale geste.

12. What’s the purpose of activation and passivation in EJB?

Ans:

Activation and passivation are mechanisms used to manage the lifecycle of stateful session sap( SFSBs) to conserve garçon coffers. Activation involves restoring a passivated bean case from the secondary storehouse into memory when it’s demanded, while passivation involves reissuing the bean’s state and storing it in the secondary storehouse when the bean isn’t in use to free up memory. This ensures practical resource application and scalability in operations with numerous concurrent users.

13. How does EJB support asynchronous processing?

Ans:

EJB provides support for asynchronous processing through communication-driven sap( MDBs), which consume dispatches asynchronously from communication ranges or motifs. MDBs allow operations to uncouple the sender and receiver of dispatches, enabling scalable and approximately coupled infrastructures. By using JMS( Java Message Service), EJB operations can handle background tasks, event-driven processing, and communication-ground communication efficiently.

14. What are the advantages of using EJB in enterprise operations?

Ans:

  • EJB offers several advantages, including declarative sale operation, security enforcement, and scalability. 
  • It simplifies the development of distributed operations by furnishing erected-in support for distributed factors and handling common structure enterprises such as concurrency, continuity, and messaging. 
  • Also, EJB’s integration with Java EE technologies like JPA( Java Persistence API) and JMS streamlines development and promotes modular, justifiable infrastructures.

15. How does EJB handle continuity?

Ans:

EJB handles continuity through the Java continuity API( JPA), which allows realities to be counterplotted to database tables and managed by the EJB vessel. Reality sap in EJB represents patient data, and inventors can use reflections to define object-relational mappings, connections, and deals. EJB holders manage the lifecycle of reality sap, ensuring transparent continuity and furnishing features like lazy loading, hiding, and auspicious locking for effective database relations.

16. Explain the role of interceptors in EJB.

Ans:

Interceptors in EJB provide a medium for cross-cutting enterprises, similar to logging, security, and performance monitoring, to be applied to EJB styles. They allow inventors to modularize and synopsize standard functionality, promoting reusability and maintainability. Interceptors can be configured declaratively using reflections or XML deployment descriptors, furnishing a flexible and non-intrusive way to enhance the geste of EJB factors.

17. What’s the difference between a session bean and a reality bean in EJB?

Ans:

  • Session sap represents business sense and is frequently used to perform operations on behalf of a customer, while reality sap represents patient data stored in a database. 
  • Session sap doesn’t have a patient identity and is generally short-lived, while reality sap has a patient identity and represents data stored in a database. 
  • Session sap is stateful or stateless, whereas reality sap is used to model data realities with the patient state.

18. How does EJB support sales operations across multiple SAP?

Ans:

EJB provides support for distributed sale operations through the Java Transaction API( JTA). When multiple saps share in a sale, the EJB vessel coordinates their conduct and ensures that the sale is infinitesimal, harmonious, insulated, and durable( ACID). Inventors can use declarative sale attributes to specify the transactional geste of individual saps, ensuring data integrity and thickness across the distributed operation.

19. What are the benefits of using vessel-managed continuity( CMP) in EJB?

Ans:

Container-managed continuity( CMP) simplifies the development of EJBs by delegating the responsibility of managing reality bean continuity to the EJB vessel. With CMP, inventors only need to define the reality bean’s patient fields and connections, and the ship handles database relations, including SQL generation, hiding, and sale operation. CMP reduces the quantum of boilerplate law needed for database access, improves productivity, and promotes thickness in database relations across the operation.

20. How does EJB handle security authentication and authorization?

Ans:

EJB provides a robust security model for authentication and authorization using Java EE security mechanisms. Authentication verifies users’ identities, and EJB supports various authentication mechanisms similar to Drive, FORM, and customer—CERT. Authorization controls access to EJB styles and coffers grounded on the places assigned to users, which can be defined using reflections or deployment descriptors. EJB holders apply security constraints, ensuring that only authorized users can pierce defended coffers.

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    21. Explain the difference between a singleton session bean and a stateless session bean.

    Ans:

    • Singleton session sap has only one case per operation and is participated among all guests, making them suitable for managing operation-wide coffers and participating data. 
    • In discrepancy, stateless session sap doesn’t maintain a conversational state with guests and is created and destroyed for each customer request, making them featherlight and scalable. 
    • Singleton sap is generally used for hiding, resource pooling, and managing operation-wide state, while stateless sap is used for transactional business sense.

    22. How does EJB handle exceptions and error running?

    Ans:

    EJB provides a robust exception-handling medium to manage crimes and faults within enterprise operations. Inventors can use the pass-catch-eventually construct to handle exceptions within EJB styles and propagate exceptions to the customer or vessel as demanded. EJB holders block system-position exceptions and restate them into operation-specific exceptions, allowing inventors to handle crimes constantly across the operation.

    23. What are the advantages of using EJB over traditional JavaBeans?

    Ans:

    EJB offers several advantages over traditional JavaBeans, including erected-in support for distributed computing, declarative sale operation, and vessel-managed services similar to security and concurrency. EJB’s element-grounded armature promotes modularity and scalability, allowing inventors to concentrate on business sense while the vessel handles structured enterprises. Also, EJB provides standardized APIs and interoperability with other Java EE technologies, easing the development of robust enterprise operations.

    24. How does EJB handle concurrency issues in multi-threaded surroundings?

    Ans:

    • EJB holders manage concurrency by controlling access to bean cases and furnishing thread-safe prosecution surroundings for EJB styles. 
    • Containers use mechanisms like bean pooling and vessel-managed concurrency to ensure that multiple guests can safely pierce EJBs coincidently without encountering race conditions or data corruption. 
    • Inventors can also configure concurrency settings and locking strategies to optimize performance and resource application in multi-threaded surroundings.

    25. What are the different types of EJB deals and their characteristics?

    Ans:

    EJB deals can be classified into vessel-managed deals( CMT) and bean-managed deals( BMT). In vessel-managed deals, the EJB vessel automatically manages sale boundaries and resource investiture, simplifying sale operations for inventors. Bean-managed deals, on the other hand, bear inventors to explicitly manage sale discrimination and resource investiture within EJB styles using the UserTransaction API, furnishing further fine-granulated control over sale geste.

    26. How does EJB handle distributed communication between factors?

    Ans:

    EJB facilitates distributed communication between factors using remote system incantation( RMI) or web services. Remote interfaces allow EJB factors to be penetrated even from guests running in different JVMs or physical machines, enabling distributed operations. EJB holders manage the serialization and deserialization of system parameters and return values, as well as sale propagation and security enforcement, ensuring interoperability and trustability in distributed communication.

    27. What’s the purpose of the EJB vessel?

    Ans:

    • The EJB vessel provides a runtime terrain for executing Enterprise JavaBeans 
    • within a Java EE operation garçon. It manages the lifecycle of EJB factors, including externalization, reliance injection, and resource pooling. 
    • The vessel also provides services similar to sale operation, security enforcement, and concurrency control, ensuring the dependable and effective prosecution of EJBs in enterprise operations.

    28. How does EJB handle asynchronous processing and messaging?

    Ans:

    EJB supports asynchronous processing and messaging through communication-driven sap( MDBs), which consume dispatches from JMS( Java Message Service) destinations similar to ranges or motifs. MDBs allow EJB operations to reuse dispatches asynchronously, divorcing the sender and receiver of dispatches and enabling scalable and responsive infrastructures. EJB holders manage the lifecycle and concurrency of MDB cases, ensuring effective communication processing and fault forbearance in enterprise operations.

    29. What’s the role of interceptors in EJB, and how are they used?

    Ans:

    Interceptors in EJB provide a medium for cross-cutting enterprises, similar to logging, security, and performance monitoring, to be applied to EJB styles. Interceptors are configured using reflections or XML descriptors and are invoked ahead and after the prosecution of target EJB styles. They allow inventors to modularize and synopsize standard functionality, promoting reusability and maintainability in enterprise operations.

    30. What are the stylish practices for designing and developing EJB operations?

    Ans:

    Some stylish practices for designing and developing EJB operations include keeping EJBs featherlight and concentrated on business sense, minimizing dependencies between factors, and using applicable sale operation strategies. It’s also essential to optimize resource operation by configuring bean pooling and vessel-managed concurrency settings. Also, inventors should follow rendering conventions, use design patterns where applicable, and conduct thorough testing to ensure the trustability and scalability of EJB operations.

    31. How does EJB handle resource operation and pooling?

    Ans:

    • EJB holders manage resource pooling to optimize resource operation and facilitate performance in enterprise operations. 
    • Coffers similar to database connections, JMS connections, and thread pools are pooled and participated among EJB cases, reducing the outflow of creating and destroying coffers for each customer request. 
    • Inventors can configure resource pooling settings to control the maximum number of pooled coffers, idle downtime, and other parameters, ensuring practical resource application and scalability in EJB operations.

    32. Explain the conception of bean pooling in EJB and its benefits.

    Ans:

    Bean pooling in EJB involves recycling and reusing bean cases to serve customer requests, enhancing performance and scalability. The vessel manages a pool of bean cases and assigns them to guests as demanded, reducing the outflow of creating and destroying sap for each request. Bean pooling conserves memory and CPU coffers, improves response time, and promotes practical resource application in EJB operations, particularly in high-concurrency surroundings.

    33. What’s the difference between original and global JNDI lookups in EJB?

    Ans:

    Original JNDI lookups are used to detect EJB factors within the same operation or module, furnishing fast and effective access to original coffers. Global JNDI lookups, on the other hand, are used to detect EJB factors across different operations or modules stationed in the same Java EE terrain. Global lookups involve fresh outflow and network communication compared to original lookups, making them suitable for penetrating remote coffers.

    34. What’s a singleton session bean?

    Ans:

    • A singleton session bean in EJB is a type of session bean where only one case exists per operation, serving all guests. 
    • It’s generally used for managing operation-wide coffers, hiding, or maintaining a participating state. 
    • The singleton bean case is created when the operation starts and is destroyed when the operation shuts down, making it suitable for scripts taking centralized control or collaboration.

    35. What’s JMS?

    Ans:

    JMS( Java Message Service) is an API provided by Java for asynchronous messaging between operations or factors. It standardizes how Java operations shoot, admit, and process dispatches, enabling dependable communication in distributed systems. JMS supports both point-to-point ( PTP) and publish-subscribe ( cantina/ Sub) messaging models, easing scalable and approximately coupled infrastructures.

    36. What are the advantages of JMS?

    Ans:

    • JMS offers several advantages, including asynchronous communication, trustability, and scalability. 
    • By divorcing communication directors and consumers, JMS enables systems to handle high communication outturn and respond to events in real- time. 
    • It also provides features like communication acknowledgment, continuity, and communication pickers, ensuring communication delivery and easing fault forbearance in distributed operations.

    37. What’s the PTP model?

    Ans:

    PTP(point-to-point) is a messaging model in JMS where dispatches are transferred from a single patron to a single consumer. It involves a line-grounded communication pattern, where dispatches are stored in a line until they’re consumed by a receiver. PTP ensures dependable communication delivery and supports point-to-point communication between factors without the need for direct commerce.

    38. What’s a cantinal Sub model?

    Ans:

    Cantina/ Sub( Publish/ Subscribe) is a messaging model in JMS where dispatches are published by directors and entered by multiple subscribers. It involves a content-grounded communication pattern, where dispatches are published to content and delivered to all subscribed consumers asynchronously. Cantina/ Sub facilitates event-driven infrastructures, allowing factors to reply to events and updates in real-time.

    39. What’s MDB?

    Ans:

    • MDB(Message-Driven Bean) is a type of enterprise bean in EJB that processes dispatches asynchronously from JMS destinations similar to ranges or motifs. 
    • MDBs allow EJB operations to uncouple communication directors and consumers, enabling scalable and approximately coupled infrastructures. 
    • They handle communication processing sense and can be configured to hear specific destinations for communication consumption.

    40. What’s Entity Bean?

    Ans:

    An Entity Bean in EJB is a type of enterprise bean that represents patient data stored in a database. It maps to a row in a database table and provides object-acquainted access to database realities. Reality sap manages the lifecycle and continuity of data, supporting operations like producing, reading, updating, and canceling ( smut). They’re generally used to model business realities and manage data integrity in enterprise operations.

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    41. What’s Session Facade?

    Ans:

    Session Facade is a design pattern used in EJB to give a simplified interface to pierce complex business sense. It encapsulates multiple EJBs behind a single facade interface, allowing guests to interact with the system through a unified interface. Session Facade promotes modularity, improves performance, and enhances maintainability by polarizing business sense and minimizing remote system conjurations

    42. List some crucial actors in continuity API

    Ans:

    • crucial actors in continuity API include realities, reality directors, continuity units, and query languages like JPQL( Java Persistence Query Language). 
    • Realities represent patient data, while reality directors manage the lifecycle and continuity of realities. 
    • Continuity units define the configuration and metadata for continuity operations, and JPQL enables inventors to query realities using object-acquainted syntax.

    43. List down the way for the demonstration of the EJP continuity medium.

    Ans:

    Demonstrating EJB continuity involves defining reality classes annotated with JPA reflections, configuring continuity unit inpersistence.xml, creating a reality director plant, carrying reality director case, and performing CRUD operations using reality director styles. Eventually, the operation is planted in an operation garçon and tested for continuity functionality.

    44. Name the attributes of Java. ejb.Stateful.

    Ans:

    The attributes of Java. ejb.Stateful reflection includes name, description, mapped name, and activationConfig. The name trait specifies the logical name of the session bean, while the description provides a textual description of the session bean. mappedName allows inventors to specify the JNDI name under which the session bean will be bound, and activationConfig is used to configure activation parcels for communication-driven sap.

    45. Mention the three situations for applying interceptor styles.

    Ans:

    • Interceptor styles in EJB can be applied in three situations: class position, system position, and lifecycle message position. 
    • Class-position interceptors apply to all styles of the bean class, system-position interceptors apply to specific styles and lifecycle message interceptors apply to bean lifecycle events similar to initialization and destruction. 
    • This inflexibility allows inventors to apply across enterprises at different granularities.

    46. Mention the Java types that can be counter-plotted using the@Lob reflection.

    Ans:

    The@Lob reflection in JPA( Java Persistence API) can be used to collude large objects to database columns. Java types that can be counter-plotted using @Lob include String, byte(), and Java.sql.Clob, and java.sql.Blob.@Lob reflection allows investors to store and recoup large double or character data types similar to textbooks, images, or lines in the database, furnishing inflexibility and effectiveness in handling large data objects.

    47. Name the ACID parcels of a sale.

    Ans:

    The ACID parcels of a sale are Atomicity, thickness, insulation, and continuity. Atomicity ensures that a sale is either completely completed or wholly abandoned, maintaining data integrity. Thickness guarantees that the database remains in a valid state before and after the sale. Insulation ensures that deals are executed singly without hindrance from other deals. Continuity ensures that married deals persist in the event of system failures.

    48. Explain the armature of EJB.

    Ans:

    • The armature of EJB( Enterprise JavaBeans) consists of factors similar to Session 
    • sap, Entity sap, and Communication-Driven sap, which synopsize business sense, manage patient data, and handle asynchronous messaging independently. 
    • These factors run within an EJB vessel, which provides services similar to lifecycle operation, reliance injection, and sale operation. 
    • EJBs interact with guests through original or remote interfaces, enabling distributed and scalable enterprise operations.

    49. What’s a remote customer view?

    Ans:

    A remote customer view in EJB allows guests to pierce enterprise sap from remote JVMs or physical machines over a network. Remote guests use remainders and configurations to communicate with the EJB vessel, invoking styles on remote interfaces. This enables distributed communication between guests and EJB factors, easing the development of distributed operations across different systems.

    50. What’s the Original customer view?

    Ans:

    Original customer view in EJB enables guests to pierce enterprise sap within the same JVM or operation garçon without the outflow of remote communication. Original guests use in-memory system conjurations to interact with EJB factors, furnishing advanced performance and effectiveness compared to remote conjurations. Original customer view is suitable for intra-application communication and is frequently used to optimize performance in clustered surroundings.

    51. What Is a Deployment Descriptor?

    Ans:

    • A deployment descriptor in EJB is an XML train that contains configuration information about EJB modules and factors. 
    • It provides metadata similar to EJB names, interfaces, sale attributes, security settings, and resource references, allowing the EJB vessel to emplace and manage EJBs effectively. 
    • Deployment descriptors are used to customize the geste of EJB factors and configure their runtime terrain within the operation garçon.

    52. What’s meant by Lazy Loading?

    Ans:

    Lazy loading is a fashion used in ORM( Object- Relational Mapping) fabrics like  JPA to postpone the loading of associated realities or collections until they’re explicitly penetrated. This optimizes performance by costing only the needed data from the database when demanded, reducing gratuitous database queries and minimizing memory operation. Lazy loading is generally used to facilitate the effectiveness of costing complex object graphs with hierarchical connections in enterprise operations.

    53. What’s meant by EJB Ql?

    Ans:

    EJB QL( Enterprise JavaBeans Query Language) is a query language used to perform database queries on reality sap in EJB operations. It’s analogous to SQL but is object-aware and designed specifically for querying reality sap and its connections. EJB QL enables inventors to express complex database queries using reality bean attributes and connections, easing data reclamation and manipulation in EJB operations.

    54. Explain the generalities of connection pooling features of EJB Container.

    Ans:

    • The EJB vessel tools use connection pooling to optimize resource operation and facilitate performance in EJB operations. 
    • It manages a pool of database connections that can be shared among multiple EJB cases, reducing the outflow of establishing and tearing down connections for each customer request. 
    • Connection pooling features include configuring connection pool size, idle downtime, and maximum delay time, ensuring practical resource application and scalability.

    55. What’s meant by deals and various styles to manage it?

    Ans:

    Deals in EJB represent a series of operations that must succeed or fail, ensuring data integrity and thickness. EJB provides various styles to manage deals, including declarative sale operations using reflections or deployment descriptors, programmatic sale operations using the UserTransaction API, and vessel-managed sale discrimination. These styles allow inventors to specify transactional geste and ensure ACID parcels in EJB operations.

    56. What does ACID mean in the environment of sales operation?

    Ans:

    ACID stands for Atomicity, thickness, insulation, and continuity, which are the abecedarian parcels of a sale in database operation systems. Atomicity ensures that all operations in a sale are completed successfully or none are executed at all. Thickness guarantees that the database remains in a valid state before and after the sale. Insulation ensures that deals are executed singly without hindrance from other deals. Continuity ensures that married deals persist in the event of system failures.

    57. What’s Callback in EJB?

    Ans:

    • Callbacks in EJB are styles defined in enterprise bean classes that the vessel invokes in response to specific lifecycle events. 
    • These events include bean initialization, destruction, activation, and passivation. 
    • Callback styles allow inventors to hook into the lifecycle of EJB factors and perform custom initialization, remittal, or business sense. 
    • Examples of message styles include@PostConstruct and@PreDestroy reflections for lifecycle initialization and remittal.

    58. Is it possible to have threading in an EJB operation

    Ans:

    Yes, it’s possible to have threading in an EJB operation, but it must be managed precisely to ensure compliance with the EJB specification. EJB holders give mechanisms for managing concurrency and thread safety, similar to vessel-managed concurrency and bean pooling. Developers should avoid directly spawning vestments within EJB factors and instead calculate on the vessel-managed mechanisms to handle concurrency, ensuring the stability and trustability of the operation.

    59. What’s the procedure and creation of Stateless EJB?

    Ans:

    To produce a Stateless EJB, you define a Java class annotated with @Stateless, apply business sense within its styles, and embed it within an EJB vessel. Stateless EJBs don’t maintain a conversational state with guests, making them featherlight and scalable for handling stateless operations. Guests pierce Stateless EJBs through original or remote interfaces, allowing them to bring styles to the bean case.

    60. What are the called reflections for reality sap?

    Ans:

    Message reflections for reality sap include@PrePersist, @PostPersist, @PreUpdate, @PostUpdate, @PreRemove, and@PostRemove. These reflections define message styles that the vessel invokes during the lifecycle of reality sap, similar to ahead and after persisting, streamlining, or removing realities from the database. Callback styles allow inventors to execute custom sense at specific lifecycle events of reality sap.

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    61. What’s the difference between SessionContext and EntityContext?

    Ans:

    • SessionContext is used in session sap to give access to the runtime terrain and EJB services, similar to the sales operation and security environment. 
    • EntityContext, on the other hand, is used in reality sap to give access to the reality’s environment and lifecycle styles, similar to carrying a reference to the reality’s primary key and penetrating the associated reality manage.

    62. Is Decorator a Design Pattern in Ejb?

    Ans:

    Yes, Decorator is a design pattern generally used in EJB to stoutly extend the geste of enterprise sap without modifying their law. Decorator sap wraps around being EJBs, adding fresh functionality or interdicting system conjurations. This pattern promotes modularity, reusability, and maintainability by allowing inventors to add or remove functionalities stoutly at runtime.

    63. separate observance, Jar, and War lines?

    Ans:

    Observance ( Enterprise Archive) lines contain multiple Java EE modules, including EJBs, servlets, and libraries, packaged together for deployment to an operation garçon. Jar( Java Archive) lines are used to package Java classes and libraries, generally used for EJB modules or mileage libraries. War( Web Library) files package web factors similar to servlets, JSPs, and HTML lines for deployment to a web garçon.

    64. separate an interface and an Abstract.

    Ans:

    • An interface in Java defines a contract for classes to apply, specifying system autographs without system executions. 
    • An abstract class may contain both abstract styles( styles without perpetration) and concrete styles( styles with perpetration). 
    • While interfaces give complete abstraction, abstract classes can contain both abstract and concrete styles, allowing for partial perpetration and law exercise.

    65. What’s the purpose of the specific system created in the EJB2?x world?

    Ans:

    In EJB2.x, the specific system was used to gain the primary key of a recently created reality bean case after persisting it to the database. It was generally used in reality sap to recoup the primary crucial value generated by the database, allowing guests to gain a reference to the recently created reality for further operations. Still, in EJB3.x and later performances, the specific system is no longer used, replaced by further streamlined mechanisms similar to automatic primary crucial generation.

    66. What’s the purpose of the idea in EJB3.0?

    Ans:

    In EJB3.0, the primary purpose of the idea was to simplify the development of enterprise operations by introducing reflections and reducing the quantum of boilerplate law needed. It aimed to streamline the development process, ameliorate inventor productivity, and promote a more featherlight and POJO- grounded programming model compared to former performances of EJB.

    67. What’s the purpose of creating a public system?

    Ans:

    • Creating a public system allows other classes or factors to penetrate and bring the functionality reprised within the system. 
    • Public styles define the interface of a class or element, furnishing a way for external law to interact with and use its capabilities. 
    • They promote encapsulation, modularity, and law exercises in object-acquainted programming.

    68. What are the names of the two styles that serve as lifecycle calls in the singleton beam?

    Ans:

    The two styles that serve as lifecycle calls in the singleton bean are@PostConstruct and@PreDestroy. These styles are invoked by the EJB vessel during the lifecycle of the singleton bean, allowing inventors to perform initialization and remittal tasks ahead and after the bean’s actuality.

    69. What’s the access modifier of these two styles?

    Ans:

    The access modifier of the@PostConstruct and@PreDestroy styles is generally public. This allows the EJB vessel to bring these styles during the lifecycle of the singleton bean. The vessel can pierce and execute these styles as part of its life cycle operation liabilities.

    70. What’s the purpose of the pre-destroy reflection?

    Ans:

    The PreDestroy reflection is used in EJB to designate a system that will be invoked by the vessel before the singleton bean case is destroyed or removed from service. It allows inventors to perform remittal tasks or release coffers held by the bean case, ensuring proper arrestment and resource operation in operation.

    71. What are the three types of sap in the EJB world?

    Ans:

    In the EJB world, there are three types of sap: session sap, reality sap, and  communication-driven sap. Session sap represents business sense or processes within the operation, reality sap manages patient data, and communication-driven sap handles asynchronous messaging and event-driven processing.

    72. What are the three types of state maps in the EJB world?

    Ans:

    • The three types of state maps in the EJB world are Stateful, Stateless, and Singleton. 
    • Stateful session sap maintains a conversational state with guests, retaining state across multiple system conjurations. 
    • Stateless session sap doesn’t maintain a conversational state and is created and destroyed for each customer request. 
    • Singleton session sap has only one case per operation and is participated among all guests.

    73. What was the issue with the picking convention used in the EJB2?x world?

    Ans:

    The issue with the picking convention used in the EJB2.x world was that it needed inventors to cleave to a complex and circumlocutory picking convention for reality sap, home interfaces, and remote interfaces. This convention involved prefixing interfaces with” Home” and” Remote,” leading to long and clumsy interface names, which made the codebase less readable and justifiable. The complexity of the picking convention hindered the development process and contributed to law bloat.

    74. What’s the purpose of mounding multiple reflections?

    Ans:

    Mounding multiple reflections allows inventors to apply multiple metadata attributes or configurations to a single program element, similar to a class or system. This approach promotes modularity, inflexibility, and law readability by combining different functionalities or settings in a terse and declarative manner. Piled reflections streamline development and configuration, enhancing law association and maintainability.

    75. How do business rules fit into an n- n-subcaste armature?

    Ans:

    • In an n—n-subcaste armature, business rules are generally reprised within the business sense subcaste( also known as the service subcaste or sphere subcaste). 
    • This subcaste implements the core business sense and regulations that govern the operation’s geste. 
    • By polarizing business rules in the business sense subcaste, the armature promotes separation of enterprises, modularity, and maintainability, allowing changes to business rules without affecting other layers.

    76. What are design-by-contract technologies?

    Ans:

    Design-by-contract technologies are programming paradigms that apply formal contracts between factors or modules within a software system. These contracts specify preconditions, postconditions, and invariants that factors must satisfy when interacting with each other. Design-by-contract promotes robustness, trustability, and law correctness by explicitly defining the anticipated geste and liabilities of software factors.

    77. What’s a business object?

    Ans:

    A business object is an abstract representation of real-world realities or generalities within a business sphere. It encapsulates both data and gestures related to specific business realities, such as guests, products, or orders. Business objects generally model business processes, rules, and workflows, serving as the foundation for enforcing business sense and functionality in software operations.

    78. How does Java SAP help businesses handle and execute business sense and rules?

    Ans:

    Java SAP takes an element-grounded approach to enforcing and executing business 

    sense and rules in Java operations. By recapitulating business sense within Java SAP, inventors can produce applicable, modular factors that represent specific business functions or processes. By modularizing and recapitulating business sense, Java SAP greases the separation of enterprises, promotes law exercise, and enhances maintainability.

    79. What’s the difference between a stateful, reality, and communication-driven EJB?

    Ans:

    • Stateful session sap maintains a conversational state with guests across multiple 
    • system conjurations, suitable for scripts taking customer affinity. 
    • Reality sap represents patient data stored in a database and manages data continuity and connections. 
    • Communication-driven sap processes asynchronous dispatches from messaging systems like JMS, easing event-driven infrastructures and scalable messaging results.

    80. What’s an element-grounded development armature?

    Ans:

    Elementelement-grounded development armature is an approach to software development that emphasizes the creation of applicable, tone-contained software factors. These factors synopsize specific functionality or services and can be assembled and integrated to make complex systems. Element-grounded development promotes modularity, reusability, and maintainability by enabling inventors to concentrate on structure and composing independent, interoperable factors.

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    81. Why is it necessary to use J2EE garçon with servlet and EJBs together?

    Ans:

    Using a J2EE garçon with servlets and EJBs together allows for the development of robust, scalable, and enterprise-grade operations. Servlets handle web requests and responses, while EJBs provide business sense and sales operations. The J2EE garçon provides the runtime terrain and services such as security, concurrency control, and resource operation, ensuring dependable and effective prosecution of servlets and EJBs in a distributed terrain.

    82. What are the problems caused by loading native law?

    Ans:

    • Loading native law into a Java operation can introduce platform dependencies, security pitfalls, and performance issues. 
    • Native law may not be movable across different platforms, leading to comity issues. 
    • It also bypasses Java’s memory operation and security features, potentially exposing the operation to memory leaks or security vulnerabilities. 
    • Also, native law can degrade operation performance due to a lack of optimization and integration with Java runtime surroundings.

    83. State the difference between CMP and BMP.

    Ans:

    CMP( Container- Managed continuity) and BMP( Bean- Managed continuity) are two approaches to managing continuity in EJB. CMP relies on the EJB vessel to handle database relations transparently using metadata and reflections, reducing inventor trouble and promoting thickness. In discrepancy, BMP requires inventors to apply continuity sense manually within reality sap, offering further control over database operations but taking further law and conservation.

    84. What are the different types of enforcement that are present in EJB?

    Ans:

    EJB provides several types of enforcement mechanisms, including declarative security enforcement, transactional enforcement, and concurrency control enforcement. Declarative security enforcement allows inventors to specify security constraints using reflections or deployment descriptors. Transactional enforcement ensures ACID parcels for transactional styles using sale attributes. Concurrency control enforcement manages concurrent access to EJB cases using vessel-managed concurrency settings.

    85. What are the different types of enforcement that are present in EJB?

    Ans:

    • EJB provides several types of enforcement mechanisms, including declarative security enforcement, transactional enforcement, and concurrency control enforcement. 
    • Declarative security enforcement allows inventors to specify security constraints using reflections or deployment descriptors. 
    • Transactional enforcement ensures ACID parcels for transactional styles using sale attributes. 
    • Concurrency control enforcement manages concurrent access to EJB cases using vessel-managed concurrency settings.

    86. What’s in-memory replication?

    Ans:

    In-memory replication is a method used in distributed systems to replicate data across multiple bumps or waiters’ memory. It improves fault forbearance, vacuity, and performance by maintaining spare clones of data in memory. In-memory replication systems frequently use methods similar to data synchronization, thickness protocols, and distributed hiding to ensure data thickness and trustability across replicated bumps. This approach enhances system scalability and adaptability to knot failures or network partitions.

    87. What happens if spread() is invoked on a session bean?

    Ans:

    Still, if spread () is Norway invoked on a session bean, the vessel will ultimately reclaim the bean case through scrap collection. Still, without explicitly calling spread(), the vessel can not release associated coffers or perform any remittal tasks defined in the bean’ s@PreDestroy system. This may lead to resource leaks or hamstrung resource applications, especially if the session bean holds onto precious coffers like database connections.

    88. What’s EJB QL?

    Ans:

    • EJB QL( Enterprise JavaBeans Query Language) is a query language used to 
    • perform database queries on reality sap in EJB operations. 
    • It’s analogous to SQL but is object-aware and designed specifically for querying reality sap and its connections. 
    • EJB QL enables inventors to express complex database queries using reality bean attributes and connections, easing data reclamation and manipulation in EJB operations.

    89. How does EJB Invocation happen?

    Ans:

    EJB incantation generally involves a customer making a system call on an original or remote interface of an EJB element. The EJB vessel intercepts the system call, performs any necessary sale operation, security checks, and reliance injection, and also delegates the system prosecution to the target EJB case. After the system prosecution is completed, the vessel returns the result to the customer, handling any exceptions or transactional rollbacks as demanded.

    90. How can I call one EJB from inside of another EJB?

    Ans:

    To call one EJB from inside another EJB, you can fit a reference to the target EJB  using reliance injection. You can use reflections like @EJB or @Inject to fit the reference to the target EJB’s interface into the calling EJB. Once fitted, you can bring styles on the fitted EJB reference, just like calling original styles, allowing flawless integration and collaboration between different EJB factors within the operation.

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