Interview Questions.

Question 1. What Is Camel ?

Answer :

At a totally summary degree, camel may be delivered as a routing engine. Camel allows us to define our routing policies to direction messages from specific source to vacation spot.

Camel provides in-built support for lots protocols which makes it smooth for us to integrate exclusive structures.

For ex: Camel can effortlessly combine  distinctive programs working in ftp and jms respectively. Internally Camel performs all of the required protocol and datatype conversions for us.

Question 2. Why You Selected Camel For Your Application Or Why You Use Camel?

Answer :

Camel is very lightweight routing engine that allows us to combine extraordinary applications with minimal configuration. Inbuilt guide for distinct protocols lets in a developer to cognizance on enterprise problem than on integration trouble. Camel routing isn't constrained to xml payload however it can path any kind of message. Camel take a look at kit similarly helps to check the solution.

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Question three. Can We Call Camel An Esb (business enterprise Service Bus)?

Answer :

Although camel supports many features just like ESB like routing, transformation and many others., we can not name camel as ESB because it does now not have a box like ESBs. However, we are able to set up camel on to a few ESB box like service mix.

Question 4. What Are Different Message Exchange Patterns In Camel, Which One Of These Is Synchronous?

Answer :

There are  varieties of message alternate patterns in Camel:

In Only: In this change sample, purchaser creates a change which only carries an In message.

In Out: In this change sample, patron creates a exchange which additionally consists of reply message for the caller.

Out of above , InOut sample is synchronous due to the fact caller expects for an acknowledgement or reply for every change despatched.

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Question 5. What Is Camel Exchange? Explain Its Structure?

Answer :

A Camel Exchange can be called as an holder for containing message in the course of routing. A alternate helps numerous message change styles, like InOnly and InOut.

Following are the contents of camel alternate:

ExchangeId: A precise identifier for each change

Message Exchange Pattern: This discipline denotes whether or not you are the use of InOnly or InOut change pattern.

Exception: If any exception happens in the course of routing, it will be to be had in this discipline.

Properties: These are the residences that are available for entire period of alternate.

In Message: This is obligatory field which includes the input message.

Out Message: This is elective message which exists only if MEP is InOut.

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Question 6. What Are Routes In Apache Camel?

Answer :

The middle capability of Apache Camel is its routing engine. It allocates messages primarily based at the associated routes. A course contains flow and integration common sense. It is applied using EIPs and a selected DSL.

Question 7. What Are Dsls And Which Dsls Have You Used?

Answer :

Routes in a selection of area-particular languages (DSL).The maximum famous ones are Java DSL - A Java primarily based DSL using the fluent builder style. Spring XML - A XML based totally DSL in Spring XML documents.

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Question eight. What Is An Esb? Have You Deployed Camel On Any Esb?

Answer :

ESB stands for Enterprise Service Bus. It may be described as a device designed to assist put into effect an utility using SOA concepts Not for all tasks tasks is the usage of ESB an top-rated answer ESB have to be used while projects contain integrating some of Endpoints like Webservices, JMS, FTP and so forth. Have deployed JBoss Fuse ESB for Apache Camel Deployement.

Question 9. What Are Eips In Apache Camel?

Answer :

EIPs stand for Enterprise Integration Pattern. These are Design patterns for the usage of organisation utility integration and message-oriented middleware inside the shape of a pattern. Various EIPs are used in Apache Camel. Some of them are- Splitter Pattern? Split the records on the basis of a few token and then technique it. Content Based Router-The Content-Based Router inspects the content material of a message and routes it to every other channel based totally at the content material of the message. Using one of these router permits the message manufacturer to send messages to a single channel and go away it to the Content-Based Router to check out messages and course them to the right destination. This alleviates the sending application from this challenge and avoids coupling the message manufacturer to specific destination channels. Message Filter-A Message Filter is a unique form of a Content-Based Router. It examines the message content and passes the message to some other channel if the message content fits certain criteria. Otherwise, it discards the message. Recipient List-A Content-Based Router permits us to path a message to an appropriate machine primarily based on message content material. This process is obvious to the authentic sender in the sense that the originator in reality sends the message to a channel, wherein the router selections it up and takes care of everything. Wire Tap-Wire Tap permits you to path messages to a separate region while they are being forwarded to the final vacation spot.

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Question 10. What Is An Exchange In Apache Camel?

Answer :

The message to be routed in Camel path is present within the Exchange. It is the message holder. Apache camel makes use of Message Exchange Patterns(MEP). Apache camel exchange can preserve any sort of message. It helps a diffusion of codecs like xml, JSON etc. 

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Question eleven. What Are Endpoints In Apache Camel?

Answer :

Camel supports the Message Endpoint pattern the usage of the Endpoint interface. Endpoints are commonly created by way of a Component and Endpoints are commonly referred to in the DSL through their URIs.

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Question 12. What Are Various Components In Apache Camel? Which Ones Have You Used?

Answer :

Apache camel provides us with a number of additives. These components make interacting create endpoints with which a device can engage with different outside systems. For example using an ActiveMQ issue we expose an ActiveMQ endpoint for interplay with outside system. There are extra than a hundred components furnished by means of Apache Camel. Some of them are FTP,JMX, Webservices, HTTP. Apache camel additionally lets in customers to create custom components. 

Here are examples of FileComponent, JMSComponent, CXF Component. 

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Question thirteen. Have You Use Database With Apache Camel?

Answer :

Yes. Have incorporated Apache Camel MySQL Database the usage of SQL Queries 

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Question 14. Have You Used Apache Camel With Spring?

Answer :

Yes. Have included Apache Camel with Spring. It allows in making use of functions like Spring Dependency injection, Datasource and Transaction control. 

Question 15. Have You Exposed A Webservice Endpoint Using Apache Camel?

Answer :

Yes. Using Apache CXF exposed a webservice to be consumed. Used Contract first method to generate the training from wsdl. 

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Question 16. How Did You Integrate Apache Camel With Database?

Answer :

Using Apache Camel SQL factor. 

Apache Camel + SQL element(MySQL DB) 

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Question 17. How Did You Execute Junit Test Cases For Apache Camel?

Answer :

Using CamelSpringTestSupport - Apache Camel Unit Testing

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Question 18. How Are Exception Handled Using Apache Camel?

Answer :

Exception may be treated the use of the <try> <catch> block, <OnException> block or the <errorHandler> block.

The errorHandler is used to address any uncaught Exception that receives thrown during the routing and processing of a message. Conversely, onException is used to handle specific Exception sorts whilst they're thrown. 

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Question 19. What Is Redelivery Policy In Apache Camel?

Answer :

A redelivery coverage defines policies when Camel Error Handler perform redelivery tries. For example you could setup policies that nation how typically to attempt redelivery, and the postpone in among attempts, and so on.

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Question 20. What Is Camelcontext?

Answer :

The CamelContext represents a single Camel routing rulebase. We use the CamelContext in a similar manner to the Spring ApplicationContext. Public interface CamelContext extends SuspendableService, RuntimeConfiguration. Interface used to symbolize the context used to configure routes and the guidelines to apply during message exchanges among endpoints. 

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Question 21. What Is Routercontext?

Answer :

It is now viable to outline routes outside <camelContext/> which you do in a new <routeContext/> tag. The routes described in <routeContext/> may be reused with the aid of a couple of <camelContext/>. However its simplest the definition that is reused. At runtime every CamelContext will create its personal example of the route based totally at the definition. 

Question 22. Have You Used Apache Camel With Spring Boot?

Answer :

Have integrated Apache Camel with Spring Boot. Made use of Apache Camel Spring Boot starter dependency. Apache Camel + Spring Boot

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Question 23. Is Camel An Esb?

Answer :

Typically companies claim nearly the entirety is an ESB in recent times, so the solution might be sure (smile)

However our view is that an ESB is more of a box of integration additives, so we view Apache ServiceMix to be a true ESB primarily based around OSGi (and optionally JBI) to provide a standards primarily based integration platform of components.

We view Camel as being a rule based routing & mediation engine which can be used inner a full blown ESB, a message broker or an internet services clever consumer. Though if you need to, you could recollect that Camel is a small, lightweight embeddable ESB considering the fact that it is able to provide a few of the not unusual ESB offerings like clever routing, transformation, mediation, monitoring, orchestration and many others.

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Question 24. What Are The Dependencies?

Answer :

Camel 2.6 or older can run on JDK 1.5 or higher.

Camel 2.7 onwards calls for JDK 1.6 or JDK 1.7.

Camel 2.14 onwards requires JDK 1.7 or better.

Camel 2.18 onwards requires JDK 1.8.

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Question 25. What Platforms Are Supported?

Answer :

Any platform supporting JDK 6.

We frequently test Camel on Linux, Windows and OS X.

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Question 26. What Is The License?

Answer :

This software program is open source the use of the Apache 2.Zero licence (a liberal BSD fashion license which is very commercial friendly)

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Question 27. What Is A Router?

Answer :

We often communicate about that Camel is a mediation and routing framework; so what exactly is a router and what does it do?

Basically a router just consumes Message exchanges from a few Endpoint, then sends them directly to a few other Endpoint the usage of some form of Enterprise Integration Patterns.

For example a router should enforce the Content Based Router sample, to route from an endpoint to 1 or extra vacation spot endpoints the use of a Predicate based at the message content material.

Typically a course or router includes one or greater customers; either an Event Driven Consumer or a Polling Consumer or probable a Transactional Client. Then there are one or more Processor times which can ship the message to at least one or more endpoints.

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Question 28. What Jars Do I Need?

Answer :

Camel is designed to be small light-weight and extremely modular so you handiest pay for what you operate. The core of camel, camel-center.Jar is small and has minimal dependencies.

On Java 6 camel-core.Jar most effective depends on

commons-management.Jar (for Camel 2.8 or older)

commons-logging.Jar (for Camel 2.6 or older)

slf4j-api.Jar (from Camel 2.7 onwards)

On Java five camel-core.Jar depends also on activation.Jar and a JAXB2 implementation which commonly entails jaxb-api.Jar, jaxb-impl.Jar and a StAX API which may be stax-api.Jar and *woodstox.Jar

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Question 29. How Is A Camel Exchange Created?

Answer :

An trade is created via the endpoint.

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Question 30. How Is Data Passed Between The Routes?

Answer :

The records is handed in the routes as an object of the class org.Apache.Camel.Exchange.

Question 31. What Is An Uri?

Answer :

URI is a naming scheme used in camel to consult an endpoint. An URI tells camel, the factor getting used, the context course and the options implemented against the element. URI consists of 3 elements:

Scheme
Context course
Options
Example of a record URI working as a customer :

 from("document:src/data?FileName=demo.Txt&fileExist=Append");

Here the scheme factors to record, the context direction is “src/facts” and the alternatives are “fileName and fileExist” are alternatives that can be used with record aspect or report endpoint.

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Question 32. What Is An Endpoint?

Answer :

A camel endpoint is just like an entity this is able to sending or receiving messages. For e.G., a JMS queue may be treated as an endpoint.

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Question 33. What Are Components?

Answer :

In easy terms, a issue refers to an external entity this is communicating with camel. To write a camel course that paintings with documents, file aspect is to be used. Similarly to paintings with JMS queue, jms thing has to be used.

Ex – A FileComponent is stated via file in a URI and it creates FileEndpoints.

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Question 34. What Type Of Object(s) Can The Exchange Hold?

Answer :

A camel Exchange can preserve any sub sort of java.Lang.Object consisting of primitive data types.

Question 35. What Is A Producer And A Consumer Endpoint?

Answer :

A camel course is just like a channel although which records flows. Producer and patron are  endpoints which can be present at every give up of the channel.

A consumer endpoint is the place to begin of the route. A definition of a camel direction starts offevolved by using writing a camel purchaser endpoint.

A manufacturer endpoint seems (no longer always) on the end of the route. It consumes the statistics that is passed through the direction.