Apache Camel Interview Questions and Answers
Experienced / Expert level questions & answers
Ques 1. What are EIPs in Apache Camel?
EIPs stand for Enterprise Integration Pattern. These are Design patterns for the use of enterprise application integration and message-oriented middleware in the form of a pattern. Various EIPs are used in Apache Camel. Some of them are:
- Splitter Pattern: Split the data on the basis of some token and then process it.
- Content Based Router: The Content-Based Router inspects the content of a message and routes it to another channel based on the content of the message. Using such a router enables the message producer to send messages to a single channel and leave it to the Content-Based Router to inspect messages and route them to the proper destination. This alleviates the sending application from this task and avoids coupling the message producer to specific destination channels.
- Message Filter: A Message Filter is a special form of a Content-Based Router. It examines the message content and passes the message to another channel if the message content matches certain criteria. Otherwise, it discards the message.
- Recipient List: A Content-Based Router allows us to route a message to the correct system based on message content. This process is transparent to the original sender in the sense that the originator simply sends the message to a channel, where the router picks it up and takes care of everything.
- Wire Tap: Wire Tap allows you to route messages to a separate location while they are being forwarded to the ultimate destination.
Ques 2. Have you used Apache Camel with Spring?
Maven dependencies to be used:
- <dependency>
- <groupId>org.apache.camel</groupId>
- <artifactId>camel-core</artifactId>
- <version>2.13.0</version>
- </dependency>
- <dependency>
- <groupId>org.apache.camel</groupId>
- <artifactId>camel-spring</artifactId>
- <version>2.13.0</version>
- </dependency>
Ques 3. What is Redelivery policy in Apache Camel?
A redelivery policy defines rules when Camel Error Handler perform redelivery attempts. For example you can setup rules that state how many times to try redelivery, and the delay in between attempts, and so forth.
Ques 4. How to use Quartz Scheduler in Apache Camel?
You can use quartz scheduler in apache camel.
- <dependency>
- <groupId>org.apache.camel</groupId>
- <artifactId>camel-quartz</artifactId>
- <version>2.13.0</version>
- </dependency>
Coding Example:
- @Override
- public void configure() throws Exception {
- CronScheduledRoutePolicy startPolicy = new CronScheduledRoutePolicy();
- startPolicy.setRouteStartTime(”0 0/3 * * * ?”);
- from(”file:C:/inputFolder? noop=true”).routePolicy(startPolicy).noAutoStartup().process(new MyProcessor()) .to(”file:C:/outputFolder”);
- }
Ques 5. What is Idempotent Consumer pattern in Apache Camel?
In Apache Camel we use the Idempotent Consumer pattern to filter out duplicate messages. Consider a scenario where we have to process messages only once. If there are any duplicates they should be skipped. Using Apache Camel we can use Idempotent Consumer directly within the component so it will skip messages that are processed once. This feature is be enabled by setting the idempotent=true option. In order to achieve this Apache Camel keeps track of the consumed messages using a message id which is stored in the repository called Idempotent Repository. Apache Camel provides the following types of IdempotentRepository.
Ques 6. How to connect with AWS service from Apache Camel?
Yes we can connect AWS services from Apache Camel using connector components.
Ques 7. How to connect with Azure from Apache Camel?
Yes. We can connect with azure services using Apache camel connector components.
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