Category: apache Camel

Apache Camel – Components Camel provides several pre-built components. In this chapter, we will discuss a few important components from the camel-core module. Bean The Bean component binds beans to Camel message exchanges. The URI to create an Endpoint is specified as bean:beanID, where beanID is the name of the bean as specified in the Registry. JndiContext jndiContext = new JndiContext(); jndiContext.bind(“MilkOrder”, new MilkOrderProcessor()); CamelContext camelContext = new DefaultCamelContext(jndiContext); camelContext.addRoutes(new RouteBuilder() { public void configure() { from(“direct:bigBasket”) .to(“bean:MilkOrder?method=placeOrder”); } }); Note how the endpoint is specified using the bean: protocol. You may optionally specify the bean method that is to be invoked; in this case, the method called placeOrder will be invoked while evaluating the Endpoint expression. The MilkOrder is a JNDI name to the MilkOrderProcessor Javabean as registered in the first two lines of the code snippet. The definition of MilkOrderProcessor itself is omitted here for brevity. Direct You must have noticed the use of Direct in our previous examples. To send an order to an oil vendor, we used direct:oil in the Endpoint specification. The use of Direct component allows you to synchronously invoke an endpoint. The following two code snippets from our previous examples illustrate the use of Direct − .when(header(“order”).isEqualTo(“oil”)) .to(“direct:oil”) And, from(“direct:DistributeOrderDSL”) .process(myProcessor); File The File component provides access to the file system on your machine. Using this component, you will be able to save messages from other components to a local disk. In addition, it allows other Camel components to process the local files. You may use either file:directoryName[?options] or file://directoryName[?options] as a URI format while using the File component. You have earlier seen the use of this component − from (“file:/order”).to(“jms:orderQueue”); Note that the File component by default takes the directory name. Therefore, the contents of the order directory will be taken as input contents. To specify a particular file in the order directory, you will use the following statement − from (“file:/order?fileName = order.xml”).to(“jms:orderQueue”); Log The Log component allows you to log messages to the underlying logging mechanism. Camel uses Simple Logging Facade for Java (SLF4J) as an abstraction to various logging frameworks. You may use java.util.logging, logback, log4j for logging. This code snippet illustrates the use of the Log component − from(“direct:DistributeOrderDSL”) .to(“bean:MilkOrder?method = placeOrder”) .to(“log:com.example.com?level = INFO&showBody = true”); SEDA The SEDA component allows you to asynchronously call another endpoint in the same CamelContext. If you want to call across CamelContext instances, you need to use VM component. The use of SEDA is illustrated here − from(“direct:DistributeOrderDSL”) // send it to the seda queue that is async .to(“seda:nextOrder”) In this route, we will simply route the orders to nextOrder asynchronous queue. A client who has subscribed to this queue will pick up the messages from this queue. Timer The Timer component is used for sending out messages at regular intervals and can thus be very useful while testing Camel applications. The code snippet here fires a test message to the console every two seconds − from(“timer://testTimer?period = 2000”) .setBody() .simple(“This is a test message ${header.timer}”) .to(“stream:out”);

Apache Camel – Introduction Consider a situation where a large online grocery store in your town such as the Bigbasket in India invites you to design an IT solution for them. The stable and scalable solution will help them overcome the software maintenance problems they are facing today. This online store has been running its business for the last decade. The store accepts online orders for different categories of products from their customers and distributes those to the respective suppliers. For example, suppose you order some soaps, oil and milk; these three items will be distributed to the three respective suppliers. The three suppliers will then send their supplies to a common distribution point from where the entire order will be fulfilled by the delivery center. Now, let us look at the problem they are facing today. When this store started its business, it was accepting orders in a comma-separated plain text file. Over a period of time, the store switched to message-driven order placement. Later, some software developer suggested an XML based order placement. Eventually, the store even adapted a web service interface. Now, here comes the real problem. The orders now come in different formats. Obviously, every time the company upgraded the order acceptance format, it did not want to break the previously deployed interface so as not to cause confusions in the customer’s mind. At the same time, as the business kept on growing, the store periodically added new suppliers to its repertoire. Each such supplier had its own protocol for accepting orders. Once again, we face the integration issue; our application architecture must be scalable to accommodate new suppliers with their unique order placement mechanism. The entire situation is shown in the following figure − Now, let us see how Apache Camel can come to your rescue to provide an elegant, maintainable, scalable solution architecture for the described scenario. Before we proceed with the solution, we need to make a small assumption. For all the discussions in this tutorial, we will assume that the online orders are placed in XML format. A typical format for the order file that we will be using throughout our discussions is shown here − <?xml version = “1.0” encoding = “UTF-8”?> <OrderID Order = “001”> <order product = “soaps”> <items> <item> <Brand>Cinthol</Brand> <Type>Original</Type> <Quantity>4</Quantity> <Price>25</Price> </item> <item> <Brand>Cinthol</Brand> <Type>Lime</Type> <Quantity>6</Quantity> <Price>30</Price> </item> </items> </order> <order product = “Oil”> <items> <item> <Brand>Saffola</Brand> <Type>Gold</Type> <Quantity>2</Quantity> <Price>649</Price> </item> <item> <Brand>Fortune</Brand> <Type>Sunlite</Type> <Quantity>1</Quantity> <Price>525</Price> </item> </items> </order> <order product = “Milk”> <items> <item> <Product>Milk</Product> <Brand>Amul</Brand> <Type>Pure</Type> <Quantity>2</Quantity> <Price>60</Price> </item> </items> </order> </OrderID> We will be using the above XML template to illustrate the Camel examples in this tutorial.

Apache Camel – Useful Resources The following resources contain additional information on Apache Camel. Please use them to get more in-depth knowledge on this. Useful Links on Apache Camel − Official site of Apache Camel. − Apache Camel, its history and various other terms has been explained in simple language. Useful Books on Apache Camel To enlist your site on this page, please drop an email to [email protected]

Apache Camel Tutorial Job Search Apache Camel is an open source framework that provides rule-based routing and mediation engine. Apache Camel essentially provides an implementation of various EIPs. It makes integration easier by providing connectivity to a very large variety of transports and APIs. For example, you can easily route JMS to JSON, JSON to JMS, HTTP to JMS, FTP to JMS, even HTTP to HTTP, and connectivity to Microservices. You simply need to provide appropriate endpoints at both ends. Camel is extensible and thus in future more endpoints can be added easily to the framework. Audience This tutorial has been prepared for the beginners to help them understand the basic functionality of Apache Camel. Prerequisites For this tutorial, we assume the readers to have prior knowledge of basic software development using Java or any other programming language.