Q. What is Mule ESB?

Mule ESB is a Java-based enterprise service bus (ESB) and integration platform, developer can connect their application with ESB. Mule use service oriented architecture. Apart from of the different technologies the applications use, including JMS, Web Services, SMTP, HTTP. The advantage of ESB, it’s allow communicate different application. Messages can be any format SOAP to JSON. Mule ESB Development provide messaging framework that enable exchange of data among application.

Q. Why Mule ESB?

Mule ESB is lightweight integration framework but highly scalable, allowing you to start small application and connect multiple applications. Mule manages all the interactions between applications and components transparently, ESB will take care of the multiple applications, and we can easily integrate third party application using Mule.

Q. What are the Features of Mule ESB?

An ESB is a used for integration using a service-oriented approach. Its main features are:

• Set of Service Container
• Message Transformation Service
• Message Routing Service
• Web Service Security 

Q. What are different types of primitives used in Mediation?

These are the different types of primitives in mediation:

• Message Filter
• Type Filter
• Endpoint Lookup
• Service Invoke
• Fan-out
• Fan-in
• XSLT
• BO Map
• Message Element Setter
• DB lookup
• Data Handler
• Custom Mediation
• Header Setters
• Message Logger
• Even Emitter
• Stop
• Fail
• Sub Flow

Q. What are various types of Exception Handling?

• Choice Exception Handling.
• Catch Exception Handling.
• Rollback Exception Handling.
• Global Exception Handling.
• Default Exception Handling.

Q. What is Shared Resource in Mule and how they have been used?

We can make connectors as an reusable component by defining them as common resources and expose them to all applications deployed under a same domain, these resources are known as shared resources. This shared resource needs to be defined inside Mule Domain Project and then referred to each of the projects that are meant to use the elements in it.

Q. What are the different ESBs in the market?

There are various ESB’s available in the market. Some are open source, some licensed:

• Talend
• Mule ESB
• JBoss Fuse ESB

Q. Various types of variables in mule?

• Record Variable.
• Flow Variable.
• Session Variable.

Q. What is the definition of Web Services?

Web service is a function or program in any language that can be accessed over HTTP. Message format can be XML or JSON or any other program as long as the other programs can understand and communicate. Any web service has server-client relationship. Web services can be synchronous or asynchronous. Any web service can have multiple clients.

Q. How to find when the project needs ESB?

ESB implementation is not suitable for all projects. Proper analysis should be done if the use of ESB will really benefit the project.

Some of the points to be considered while analyzing the need of ESB are as follows:

• If project requires integrating 3 or more applications/services. If the need is to communicate between two applications, using point-to-point integration would suffice.
• If the project would need to be scaled in future where it might be needed to interact with more services in future. Not all projects need this as they may perform not that big a task.
• If the project needs message routing capabilities such as forking and aggregating message flows. Such features are not required by all projects.
• Is the architecture of what is to be achieved clear? It’s much better to do simple POCs integrating small parts to evaluate the benefits.
• Most ESBs are a costly affair. Does the project budget allow use of ESB.

Q. What are the different types of flow processing strategies?

There are six different types of Flow Processing Strategies. They are

• Asynchronous Flow Processing Strategy.
• Custom Processing Strategy.
• Thread Per Processing Strategy.
• Queued Asynchronous Flow Processing Strategy.
• Synchronous Flow Processing Strategy.
• Non-blocking Flow Processing Strategy.
• Queued Flow Processing Strategy.

Q. How to create and consume SOAP in Mule?

Creating SOAP Service – We can create a SOAP service same as we create Mule Project With RAML, the only change is instead of RAML we need to import Concert WSDL.
Consuming SOAP Service – We can use Web Service Consumer or CXF component in our mule flow to access/consume SOAP service.

Q. Explain ESB integration core principles?

Transformation – Data transformation between canonical data formats and specific data formats required by each ESB connector.

Transportation – Transport protocol negotiation between multiple formats. Such as HTTP, JMS, JDBC.
Mediation – Providing multiple interfaces for the purpose of a) supporting multiple versions of a service for backwards compatibility or alternatively, b) to allow for multiple channels to the same underlying component implementation. This second requirement may involve providing multiple interfaces to the same component, one legacy interface (flat file) and one standards compliant (SOAP/XML) interface.

Non-functional consistency – For a typical ESB initiative, this can include consistency around the way security and monitoring policies are applied and implemented.

Mule ESB Interview Questions For Experienced:

Q. How to select an ESB?

Usability: How complicated is the installation process? The learning curve of the ESB should not be long.

Maintainability: How to monitor the product? If any GUI terminal is available for monitoring the services.
Community: Is there active community for the ESB. Various discussion forums, tutorials etc.
Enterprose Support- Is the product support reliable. What services are available.
Flexibility: Can the ESB be configured to meet the business requirements.
Reliability: The reliability of the ESB. Its current users and various case studies if available.
Cost: The cost of the ESB. Its License policies. Support cose. etc.

Q. What are the advantages of using an ESB?

• Provides a way for end points to connect to each other without having to directly talk to each other. It simplifies the communications for the end points as they only have to conform to a standard communication interface, the bus.
• An ESB provides a single place to get some key end point metrics: frequency, availability, and performance.
• An ESB tends to provide more than one communication interface. However, a developer only needs to choose the easiest one to get and receive the data from the bus.

Q. What is REST?

      REST stands for Representational State Transfer or Restful web service. REST is a client-server architecture which means each unique URL is representation of some object or resource. Any REST API developed uses HTTP methods explicitly and in a way that’s consistent with the protocol definition. This basic REST design principle establishes a one-to-one mapping between create, read, update, and delete (CRUD) operations and HTTP methods. According to this mapping:

1. To create a resource on the server, use POST.

2. To retrieve a resource, use GET.

3. To change the state of a resource or to update it, use PUT.

4. To remove or delete a resource, use DELETE.

Q. What is RAML and why we use it?

• RAML—RESTful API Modeling Language RAML is similar to WSDL, it contains endpoint URL, request/response schema, HTTP methods and query and URL parameter.
• RAML helps client (a consumer of the service) know, what the service is and what/how all operations can be invoked.
• RAML helps the developer in creating the initial structure of this API. RAML can also be used for documentation purpose.

Q. What are the Message Sources in Mule ESB?

• Message sources in Mule are usually Any point Connectors, elements which provide connectivity to a specific external source, either via a standard protocol (such as HTTP, FTP, SMTP) or a third-party API (such as Salesforce.com, Twitter, or MongoDB).

Q. What is the difference between ESB and JMS?

• ESB provides the middleware and interfaces that allow businesses to connect their applications without writing code.
• JMS provides messaging capability and facilitates communication between the modules/applications.

Q. Why the Mulesoft is preferred than other ESB implementations?

• Mule is lightweight but highly scalable, allowing you to start small and connect more applications over time. The ESB manages all the interactions between applications and components transparently, regardless of whether they exist in the same virtual machine or over the Internet, and regardless of the underlying transport protocol used.
• Several commercial ESB implementations provide limited functionality or built on top of an existing application server or messaging server, locking you into that specific vendor. Mule is vendor-neutral, so different vendor implementations can plug in to it. You are never locked in to a specific vendor when you use Mule.