What are J2EE Patterns?

  • A set of design patterns for software development using the C++ programming language
  • A set of design patterns for software development using the Java programming language
  • A set of design patterns for software development using the Python programming language
  • A set of design patterns for software development using the Ruby programming language
J2EE Patterns are a set of design patterns for software development using the Java programming language. These patterns provide solutions to common problems that arise in J2EE-based software development, such as implementing security, managing transactions, and integrating with other systems.

What is Interpreter pattern?

  • A design pattern that converts a request into a standalone object, allowing the client to parametrize objects with different requests, queue a request, or log requests
  • A design pattern that creates objects by cloning existing objects, rather than creating new instances from scratch
  • A design pattern that implements a specialized language, allowing the client to express complex operations in a simplified manner
  • A design pattern that uses shared objects to support large numbers of similar objects efficiently
Interpreter pattern is a design pattern that implements a specialized language, allowing the client to express complex operations in a simplified manner. The pattern involves creating an interpreter class that evaluates expressions in the language, and performs the operations specified by the expressions. This pattern can be useful in situations where you want to allow the client to specify complex operations in a concise and easily understandable manner.

What is the difference between the Front Controller and Intercepting Filter patterns?

  • Front Controller pattern acts as a single entry point for all incoming requests, while the Intercepting Filter pattern is used to filter requests before they are processed by the target resource.
  • Front Controller pattern handles incoming requests and dispatches them to the appropriate handlers, while the Intercepting Filter pattern is used to filter incoming requests and modify them before they reach the target.
  • Front Controller pattern is used for request processing in a centralized manner, while the Intercepting Filter pattern is used for request processing in a more modular and flexible manner.
  • Front Controller pattern provides a centralized request handling mechanism that dispatches requests to individual handlers based on the request URL. Intercepting Filter pattern provides a way to intercept requests, manipulate request data and modify responses before they are sent to the target resource.
The Front Controller pattern provides a centralized request handling mechanism, while the Intercepting Filter pattern provides a way to intercept and modify incoming requests before they are processed by the target resource.

What are some reasons to use Repository Pattern?

  • To abstract data access and encapsulate underlying data storage
  • To allow for code reuse
  • To increase security by limiting direct access to the data storage
  • To manage the complexity of a software system
Repository Pattern is used to abstract data access and encapsulate the underlying data storage, making it easier to change data storage solutions without affecting the rest of the application. It also helps to manage the complexity of a software system by providing a clear separation of concerns between the data access logic and the business logic.

What is the difference between the Transfer Object and Data Access Object patterns?

  • Transfer Object is a client-side pattern, while Data Access Object is a server-side pattern.
  • Transfer Object is a simple object used to pass data between layers, while Data Access Object is used to perform CRUD operations on a database.
  • Transfer Object is used to manage the lifecycle of objects, while Data Access Object is used to encapsulate complex business logic.
  • Transfer Object is used to perform CRUD operations on a database, while Data Access Object is a simple object used to pass data between layers.
The Transfer Object pattern involves a simple object used to pass data between layers, while the Data Access Object pattern involves an object used to perform CRUD operations on a database.

Explain usage of Service Locator Pattern

  • The Service Locator pattern is used to access a centralized registry of service objects, so that client objects can access the services directly.
  • The Service Locator pattern is used to access a centralized registry of service objects, so that client objects do not have to depend on the concrete implementations of the services.
  • The Service Locator pattern is used to create a centralized registry of service objects, so that client objects can access the services indirectly.
  • The Service Locator pattern is used to maintain a centralized registry of service objects, so that client objects can access the services through a locator object.
The Service Locator pattern is used to maintain a centralized registry of service objects, and provides a single point of access for clients to access the services through a locator object.

What is Decorator pattern?

  • A design pattern that allows objects to be decorated with additional responsibilities, dynamically, at runtime
  • A design pattern that creates objects by cloning existing objects, rather than creating new instances from scratch
  • A design pattern that filters a set of objects based on certain criteria and returns a subset of those objects
  • A design pattern that separates an object's implementation from its interface, allowing the two to vary independently
Decorator pattern is a design pattern that allows objects to be decorated with additional responsibilities, dynamically, at runtime. The pattern involves creating a decorator class that wraps the original object, adding the new responsibilities to the original object's behavior. This pattern can be useful in situations where you want to add or remove responsibilities from objects dynamically, without affecting the behavior of the original objects.

What are the main categories of Design Patterns?

  • Behavioral, Management, and Maintenance
  • Creational, Structural, and Behavioral
  • Presentational, Container, and Behavioral
  • Structural, Logical, and Physical
Design Patterns are usually categorized into three types: Creational, Structural, and Behavioral. Creational patterns deal with object creation mechanisms, trying to create objects in a manner suitable to the situation. Structural patterns deal with object composition, creating relationships between objects to form larger structures. Behavioral patterns focus on communication between objects, what goes on between objects and how they operate together.

Can we use CQRS without Event Sourcing?

  • No, CQRS and Event Sourcing are tightly coupled and cannot be used separately.
  • No, CQRS requires Event Sourcing to function properly.
  • Yes, CQRS and Event Sourcing are separate patterns and can be used independently of each other. CQRS can be used without Event Sourcing, but Event Sourcing can provide benefits in terms of versioning and auditing.
  • Yes, but the benefits of CQRS will not be fully realized without Event Sourcing.
CQRS and Event Sourcing are separate patterns and can be used independently of each other. However, using Event Sourcing with CQRS can provide benefits in terms of versioning and auditing.

What are the difference between a Static class and a Singleton class?

  • A Static class can have instance methods and properties, while a Singleton class can only have static methods and properties.
  • A Static class can have multiple instances, while a Singleton class can have only one instance.
  • A Static class does not maintain state, while a Singleton class maintains state for a single instance.
  • A Static class is a class that cannot be instantiated, while a Singleton class can be instantiated only once.
A Static class is a class that cannot be instantiated and can only have static members. It is a sealed class, which means it cannot be inherited. A Singleton class is a design pattern that ensures a class has only one instance while providing a global point of access to this instance. It uses a private constructor and a static instance variable to ensure that only one instance can be created. Unlike a Static class, a Singleton class can have both static and instance members.

What is State pattern?

  • A design pattern in which an object, called the composite, is composed of one-to-many other objects, in a tree-like structure, allowing the client to interact with individual objects and compositions of objects uniformly
  • A design pattern in which an object, called the context, holds a reference to an instance of one of several possible concrete state objects, each of which represents a distinct state of the context and implements a common state interface
  • A design pattern in which an object, called the decorator, adds or overrides behavior of an existing object, dynamically
  • A design pattern in which an object, called the prototype, is used as a template to create new objects, without specifying their concrete classes
The State pattern is a design pattern in which an object, called the context, holds a reference to an instance of one of several possible concrete state objects, each of which represents a distinct state of the context and implements a common state interface. The State pattern allows the context's behavior to be altered dynamically by changing its state. The State pattern is used to implement state machines, allowing an object's behavior to be altered as its internal state changes.

What will you choose: Repository Pattern or "smart" business objects?

  • It depends on the complexity of the project, but in general "smart" business objects is a better choice as it allows for easier management of business logic.
  • It depends on the requirements of the project, but in general Repository Pattern is a better choice as it provides separation of concerns between the data access and business logic.
  • It depends on the size of the project, but in general "smart" business objects is a better choice as it reduces the number of classes needed.
  • It depends on the team's experience, but in general Repository Pattern is a better choice as it provides a common interface for data access.
The choice between Repository Pattern and "smart" business objects depends on the specific requirements of the project, but in general the Repository Pattern provides better separation of concerns and a common interface for data access.