Hi,
Test your knowledge on Apache camel by answering the below basic yet important questions about Camel. These will be a series of articles wherein i will try to cover most of the basic aspects of camel that you will be asked or the questions you can ask to a person who is an expert in camel framework.
Q) What are routes in camel?
A) Routes are the building blocks in camel. Routes contain the routing logic or rules which specifies the source system to read the messages and the destination system which receives the messages.
Q) How do you define routes in camel?
A) Routes can written using one of the DSL languages. The popular DSLs used are Java and Spring XML. Below is a snippet of defining the routes in Spring and Java DSL.
Spring:
<camel:route>
<camel:from uri="...."></camel:from>
<camel:to uri="..."></camel:to>
</camel:route>
Java:
public class MyRouteBuilder extends org.apache.camel.builder.RouteBuilder
{
public void configure() {
from("...")
.to("...");
}
}
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.
Q) What is a producer and a consumer endpoint?
A) A camel route is similar to a channel though which data flows. Producer and consumer are two endpoints that are present at each end of the channel.
A consumer endpoint is the starting point of the route. A definition of a camel route starts by writing a camel consumer endpoint.
A producer endpoint appears (not always) at the end of the route. It consumes the data that is passed through the route.
Q) What type of object(s) can the exchange hold?
A) A camel Exchange can hold any sub type of java.lang.Object including primitive data types.
Q) What is a camel context?
A) A camel context is a container in camel that holds the camel routes among many others. Everything written in a camel is contained within the camel container. At the core of this container is the routing engine that allows us to define and execute the routes.
Programatically, the container can be referenced using an object of type org.apache.camel.CamelContext.
Please feel free to provide your comments regarding the contents of this post.
References:
http://camel.apache.org/faq.html
http://stackoverflow.com/questions/tagged/apache-camel
http://www.ezdev.org/view/apache-camel/7165
Thanks,
Kalyan
onegoodexample 