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Jini, also known as Apache River, is a network architecture for the construction of distributed systems in the form of modular co-operating services. Developed by Sun Microsystems, its creation was announced in July 1998, and it was officially discontinued by Oracle in 2015. Jini technology provides a simple infrastructure for delivering services in a network and for creating spontaneous interaction between programs that span across arbitrary boundaries. It uses Java's object-oriented programming language and its capabilities of "Write Once, Run Anywhere". The information about Jini can be found on Oracle's official website and Apache River project page.

Ask the right questions secure the right Jini talent among an increasingly shrinking pool of talent.

First 20 minutes

General Jini app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Jini application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What are the core components of Jini technology?

The core components of Jini technology are the Jini Lookup Service, JavaSpaces, and the Jini Transaction Manager.

How would you use the Jini Discovery Protocol?

The Jini Discovery Protocol is used to find lookup services in a network. It involves two steps: multicast request and multicast announcement. In the multicast request, a client sends a request to all lookup services in the network. In the multicast announcement, a lookup service announces its presence to all clients.

What is the role of the Jini Lookup Service?

The Jini Lookup Service acts as a directory for services. Services register with the lookup service, and clients query the lookup service to find services.

Describe the difference between Jini and RMI.

Jini and RMI are both technologies for distributed computing in Java, but they serve different purposes. RMI is a low-level protocol for invoking methods on remote objects, while Jini is a high-level framework for creating distributed systems that can adapt to changes in their environment.

How would you handle a failure in a Jini system?

Jini systems are designed to be resilient to failures. If a service fails, clients can use the lookup service to find a replacement. If the lookup service fails, clients can use the discovery protocol to find a new one. Additionally, Jini provides a leasing mechanism to ensure that resources are not held indefinitely by failed clients or services.

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What you’re looking for early on

Does the candidate have a solid understanding of Jini technology?

Has the candidate demonstrated the ability to work with distributed systems?

Is the candidate proficient in Java?

Has the candidate shown problem-solving skills?

Next 20 minutes

Specific Jini development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

What are JavaSpaces in Jini?

JavaSpaces is a service provided by Jini for storing and retrieving objects in a distributed system. It provides a simple and powerful model for concurrent computing, based on the concept of a space that can be written to and read from by multiple processes.

How would you use the Jini Transaction Manager?

The Jini Transaction Manager is used to coordinate transactions across multiple services. A client starts a transaction, performs operations on services that are part of the transaction, and then either commits the transaction, which makes all changes permanent, or aborts the transaction, which discards all changes.

Describe the difference between Jini leasing and traditional locking mechanisms.

Jini leasing is a mechanism for managing resources in a distributed system. Unlike traditional locking mechanisms, which hold resources until they are explicitly released, leasing allows a resource to be held for a specified period of time. If the lease is not renewed before it expires, the resource is automatically released. This helps to prevent resources from being held indefinitely by failed clients or services.

What is the role of the Jini Join Protocol?

The Jini Join Protocol is used by services to register with lookup services. A service uses the discovery protocol to find lookup services, and then uses the join protocol to register with them. The service provides a service object, which clients can use to interact with the service, and a set of attributes, which clients can use to find the service.

How would you design a Jini system to handle a large number of services?

A Jini system can handle a large number of services by using multiple lookup services. Services can register with multiple lookup services, and clients can query multiple lookup services to find services. This distributes the load across the lookup services and increases the resilience of the system.

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At this point, a skilled Jini engineer should demonstrate strong problem-solving abilities, proficiency in Jini programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Jini.

What does the following Jini code do?
ServiceRegistrar registrar = ServiceDiscoveryManager.getRegistrar("http://localhost:8080");
ServiceTemplate template = new ServiceTemplate(null, new Class[] {MyService.class}, null);
MyService service = (MyService) registrar.lookup(template);
This code is used to discover and lookup a Jini service. It first gets a ServiceRegistrar from the ServiceDiscoveryManager using a URL. Then it creates a ServiceTemplate for the service it wants to find. Finally, it uses the ServiceRegistrar to lookup the service.
What will be the output of the following Jini code?
Entry[] attributes = new Entry[] {new Name("MyService")};
ServiceItem item = new ServiceItem(null, new MyService(), attributes);
System.out.println(item.attributeSets[0].getClass().getName());
The output will be 'net.jini.core.entry.Name'. The code creates a ServiceItem with a Name attribute and then prints the class name of the first attribute.
What does the following Jini code do?
JavaSpace space = (JavaSpace) registrar.lookup(new ServiceTemplate(null, new Class[] {JavaSpace.class}, null));
MyEntry entry = new MyEntry();
entry.content = "Hello, world!";
space.write(entry, null, Lease.FOREVER);
This code writes an entry to a JavaSpace. It first looks up the JavaSpace service, then creates an entry and sets its content to 'Hello, world!'. Finally, it writes the entry to the JavaSpace with a lease that never expires.
What does the following Jini code do?
TransactionManager manager = (TransactionManager) registrar.lookup(new ServiceTemplate(null, new Class[] {TransactionManager.class}, null));
Transaction.Created created = TransactionFactory.create(manager, 30000);
Transaction transaction = created.transaction;
space.write(entry, transaction, Lease.FOREVER);
This code writes an entry to a JavaSpace within a transaction. It first looks up the TransactionManager service, then creates a transaction with a timeout of 30 seconds. Finally, it writes the entry to the JavaSpace within the transaction with a lease that never expires.

Wrap-up questions

Final candidate for Jini Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Jini application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the security features provided by Jini?

Jini provides a number of security features, including secure communication, authentication, and access control. Secure communication is provided by the underlying Java platform, which supports SSL and TLS. Authentication is provided by the Jini Lookup Service, which can authenticate services and clients. Access control is provided by the Java security model, which allows services to specify permissions for clients.

Describe the difference between Jini and web services.

Jini and web services are both technologies for building distributed systems, but they have different strengths and weaknesses. Jini is designed for dynamic, adaptive systems, and provides features such as discovery, leasing, and transactions. Web services are designed for interoperability, and use standard protocols such as HTTP and XML.

How would you use Jini to build a distributed system with real-time requirements?

Jini can be used to build a distributed system with real-time requirements by using the real-time features of the Java platform. The Java Real-Time System (RTS) provides features such as real-time threads, real-time garbage collection, and memory areas with deterministic allocation and deallocation. These features can be used in conjunction with Jini to build a distributed system that meets real-time requirements.

Jini application related

Product Perfect's Jini development capabilities

Beyond hiring for your Jini engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Jini projects, and can engage in multiple capacities.

Jini Consultive assessments

Jini Application Conversion Assessment Jini Application Integration Assessment Jini Data & Database Integration Assessment

Custom Jini development projects

Custom Jini App Conversion Jini Custom App Development Process App UI Design for Jini Facelifts

Hiring guide for Jini Engineers

Jini Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Jini engineer at this point.

Jini Consultive assessments

Custom Jini development projects