Apache Camel Interview Questions | CodeUsingJava

Apache Camel Interview Questions

Q: What is Apache Camel ?
A:
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. To better understand what is apache camel, lets first understand what are Enterprise Applications and Enterprise Integration Patterns.
What is Apache Camel?

Q: What is Processor in Apache Camel ?
A:
The Processor interface is used to implement consumers of message exchanges or to implement a Message Translator. It is an important building block of Camel.

public class TestProcessor implements Processor {
  public void process(Exchange exchange) throws Exception {
// logic here
  }
}


Q: How to implement Error Handling using Apache Camel ?
A:
Error handling in Camel can roughly be separated into two distinct types:
  • non transactional
  • transactional
Q: What is a Message in Apache Camel ?
A:
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
Q: What is an exchange in Apache Camel ?
A:
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: How to read data from queues using Apache Camel ?
A:
We make use of Apache Camel JMS Component. We will be reading from one JMS Queue and sending the message to another jms queue. Also we will be making use of ActiveMQ queues.
Apache Camel + JMS (ActiveMQ) Hello World Example

Q: What are Routes in Apache Camel ?
A:
A Route consists of Message Channel for using which applications communicate using Messages. The end points of these message channels either consume of produce messages.

Apache Camel Endpoints

Q: What are Components in Apache Camel ?
A:
Component act as an endpoint factory using which we can interact with external systems. Camel provides a large number of components using which we can interact with externals systems.
For example here we have to transfer files from one folder to another, so we make use of the file component at both the end of the message channel.

Apache Camel File Copy Example
Apache Camel Hello World Example

Q: What is CamelContext ?
A:
We cannot run our Camel Application only using the route. We also need the camel context which acts as a runtime system that runs and manages the routes. It is responsible for all managing all aspects of a route.
Apache Camel Maven Project