Apache Camel Interview Questions And Answers

Apache Camel Interview Questions And Answers prepared from Codingcompiler experts. These Apache Camel Interview Questions were asked in various interviews conducted by top multinational companies across the globe. We hope that these interview questions on Apache Camel will help you in cracking your next job interview. All the best and happy learning.

In this article, you’ll learn

Apache Camel Interview Questions

Apache Camel Interview Questions And Answers
Advanced Apache Camel Interview Questions And Answers
The Best Apache Camel Interview Questions And Answers

Apache Camel Interview Questions

  1. What is Apache Camel ?
  2. What are routes in Apache Camel?
  3. What is an exchange in Apache camel?
  4. What are endpoints in apache camel?
  5. What are various components in apache camel? Which ones have you used?
  6. What are routes in Apache Camel?
  7. What is a context in Apache Camel?
  8. What Are Eips In Apache Camel?
  9. What is apache jmeter?
  10. What is a Message in Apache Camel ?

Apache Camel Interview Questions And Answers

Q. What is Apache Camel ?

Answer: In an enterprise, a number of systems of different types exist. Some of these may be legacy systems while some may be new. These systems often interact with each other,and need to be integrated. This interaction or integration is not easy as the implementations of the systems, their message formats may differ. One way to achieve this is to implement code which bridges these differences. However this will be point to point integration. If tomorrow again if there is change in a system the other might also have to be changed which is not good. Instead of this point to point integration which causes tight coupling we can implement an additional layer to mediate the differences between the systems. This results in loose coupling and not affect much our existing systems. Apache Camel is a rule-based routing and mediation engine that provides a Java object- based implementation of the Enterprise Integration Patterns using an API (or declarative Java Domain Specific Language) to configure routing and mediation rules.

Q. What are routes in Apache Camel?

Answer: The core functionality of Apache Camel is its routing engine. It allocates messages based on the related routes. A route contains flow and integration logic. It is implemented using EIPs and a specific DSL.

Q. What is an exchange in Apache camel?

Answer: The message to be routed in Camel route is present in the Exchange. It is the message holder. Apache camel uses Message Exchange Patterns(MEP). Apache camel exchange can hold any kind of message. It supports a variety of formats like xml, JSON etc.


Q. What are endpoints in apache camel?

Answer: Camel supports the Message Endpoint pattern using the Endpoint interface. Endpoints are usually created by a Component and Endpoints are usually referred to in the DSL via their URIs.


Q. What are various components in apache camel? Which ones have you used?

Answer: Apache camel provides us with a number of components. These components make interacting create endpoints with which a system can interact with other external systems. For example using an ActiveMQ component we expose an ActiveMQ endpoint for interaction with external system. There are more than 100 components provided by Apache Camel. Some of them are FTP,JMX, Webservices, HTTP. Apache camel also allows users to create custom components.

Q. What are routes in Apache Camel?

Answer: Routes plays a critical role in Apache Camel. The application flow and logic are specified here.In Camel we can define routing rules using a Java DSL.

Q. What is a context in Apache Camel?

Answer: The context in Apache camel is a runtime system and loading container for all resources that are required for the execution of the routing. A context contains components and endpoints, type converters, data formats, registry and routing definition.

Q.  What Are Eips In Apache Camel?

Answer: EIPS (ENTERPRISE INTEGRATION PATTERNS) is an architectural design pattern that defines code-agnostic workflows for common business tasks.

Q. What is apache jmeter?

Answer: JMeter is an Apache project which is employed as a load measuring tool that analyzes the efficiency of a variety of a spread of services, with the most specialized on web applications.

JMeter is also employed as a unit-test means for JDBC database connections, FTP, Web services, JMS, HTTP, and TCP connections and OS native processes and one also can configure JMeter as a monitor, although this is used as a monitoring solution rather than advanced controlling and can be used for functional testing as well. Additionally, Jmeter encourages integration with Selenium which allows it to run automation scripts besides performance or load tests.


Q. What is a Message in Apache Camel ?

Answer: Message implements the Message pattern and represents an inbound or outbound message as part of an Exchange.It contains the data being transferred using Routes- It consists of the following fields-

  • Unique Identifier
  • Headers
  • Body
  • Fault Flag

Advanced Apache Camel Interview Questions And Answers


Q. What is an exchange in Apache Camel?

Answer: Camel Exchange represents an abstraction for an exchange of messages which involves a request message and its corresponding reply or an exception message. It consists of-

  • Exchange ID
  • Message Exchange Pattern
  • InOnly message
  • InOut message
  • Exception
  • Properties

Q. What are the different patterns of the exchange of messages in camel?

Ans:

  • In Camel, there are two types of patterns of message exchange:
  • In Only: Consumers create an exchange in this pattern of exchange that only includes an In message
  • In Out: Consumer creates an exchange in this exchange pattern that also contains the caller’s response message. This pattern is synchronous.

Q. What are components in Apache Camel?

Answrer: The component in Apache Camel is the factory that is used to model the endpoint of the message channels that either consume or send a message. The component can be created by implementing the org.apache.camel.Component by a class.

Some of the pre-built components in the Camel are,

Bean – It invokes Java bean in the registry.
Direct – It is used to synchronously call other endpoints.
File – It is used to read or write to a file.
Log – It is used to log messages.
Mock – It tests the messages that flow through the route.
SEDA – It is used to asynchronously call another endpoint.
Timer – It sends a message at regular intervals in the route.

Q. What is a camel context?

Answer: The Camel context in the Apache camel is the loading container of all the resources that are required for the execution of the routing. It is the runtime system. It provides all the resources and access to all other services in the Apache camel. The different resources in the camel context are type converters, registry, components, endpoints, routes, data formats, and languages.

These resources in the context allow the user to execute the routing logic. It is described by org.apache.camel.CamelContext interface.


Q. What is RouterContext?

Answer: The router context is the tag that is used to define routes outside the <camelcontext/> tag in XML. A new route can be defined by the <routeContext/> tag. The definition of the route that is created in the <routeContext/> tag can be reused by different <camelContext/>. But at runtime, the camel context will create its own route instance based on the definition.

Q. How does Apache Camel work with ActiveMQ?

Answer: The ActiveMQ component is used to embed Apache Camel inside the ActiveMQ broker. It provides good flexibility in extending the message broker. The ActiveMQ component also avoids the serialization and network cost of connecting to ActiveMQ remotely.

This component is based on the JMS component and allows the messages to be sent or consumed using the JMS Queue.

Q. How do I disable JMX in Apache Camel?

Answer: The JMX instrumentation agent is enabled in Camel by default. To disable the JMX instrumentation agent, set the following property in the Java VM system property,

Dorg.apache.camel.jmx.disabled=true

Another way of disabling is by adding the JMX agent element inside the camel context element in the Spring configuration,

<camelContext id=”camel” xmlns=”http://camel.apache.org/schema/spring”>

<jmxAgent id=”agent” disabled=”true”/>

   …

</camelContext>

The Best Apache Camel Interview Questions And Answers

Q. How to restart CamelContext?

Answer: The camel context provides different methods like start, stop, suspend, resume to control the camel lifecycle. Restarting a service can be achieved by using two different methods. One is using stop the context and then starting the context. It is called cold restart and it makes all the endpoints obsolete by clearing the internal state, cache, etc. Another method is by using suspend and resume operations. It keeps all the endpoints, so you can use them after restarting.

Q. How to enable debug logging in Apache Camel?

Answer: To enable the debug logging, the log4j is used. Then, enable the DEBUG level logging in the log4j property file for the org.apache.camel package. To enable the debugging in the log4j.properties file add the following line.

log4j.logger.org.apache.camel = DEBUG

Q. In Apache Camel, what is an exchange?


Ans:

The message to be routed is present in the Exchange in the Camel route. Apache camel is the message holder and can hold any type of messages like json,xml formats. Apache Camel uses Message Exchange Patterns(MEP).

Q: What is Endpoint In Apache Camel?

Ans:

Camel uses the Endpoint interface to support the Message Endpoint pattern. Endpoints are usually created through a component, and endpoints are usually referenced through their URIs in the DSL.

Q. What is an endpoint?

A) A camel endpoint is similar to an entity that is capable of sending or receiving messages. For e.g., a JMS queue can be treated as an endpoint.

Q) What are components?

A) In simple terms, a component refers to an external entity that is communicating with camel. To write a camel route that work with files, file component is to be used. Similarly to work with JMS queue, jms component has to be used.

Ex – A FileComponent is referred to by file in a URI and it creates FileEndpoints.

Q) What is an URI?

A) URI is a naming scheme used in camel to refer to an endpoint. An URI tells camel, the component being used, the context path and the options applied against the component. URI contains 3 parts:

Scheme
Context path
Options

Example of a file URI working as a consumer –

 from(“file:src/data?fileName=demo.txt&fileExist=Append”);

Here the scheme points to file, the context path is “src/data” and the options are “fileName and fileExist” are options that can be used with file component or file endpoint.

Q) How is data passed between the routes?

A) The data is passed in the routes as an object of the class org.apache.camel.Exchange.

 
Q) How is a camel exchange created?

A) An exchange is created by the endpoint.

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