INSTANT APACHE CAMEL MESSAGING SYSTEM PDF
Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. A beginner's . In normal use, an external system would be firing messages or events directly into . (pdf), which is highly recommended to read to get more familiar with Camel. Instant Apache Camel Messaging System - Kindle edition by Evgeniy Sharapov. Download it once and read it on your Kindle device, PC, phones or tablets.
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Sep 25, Tackle integration problems and learn practical ways to make data flow between your application and other systems using Apache Camel. Aug 26, Instant Apache Camel Message Routing Book Cover you how Apache Camel works and how it integrates disparate systems using Enterprise. EIP processors. Messaging systems EIPs. Message Channel. Message. Pipeline . Did you know that Packt offers eBook versions of every book published, with PDF and Do you need instant solutions to your IT questions? PacktLib is.
This allows your code to be fully decoupled from any Camel API so its easy to read, write and unit test. Message Translator How can systems using different data formats communicate with each other using messaging? Problem Each application uses its own data format, so we need to translate the message into the data format the application supports.
Solution Use a special filter, a messae translator, between filters or applications to translate one data format into another. Camel Camel supports the message translator using the processor, bean or transform nodes. TIP: Camel routes the message as a chain of processor nodes. An advantage of using a Bean over Processor is the fact that we do not have to implement or use any Camel specific interfaces or types.
Mastering Apache Camel
This allows you to fully decouple your beans from Camel. In case of ambiguity you can specify which methods to invoke by the method parameter: from "direct:transformOrder".
Notice we use a constant to build an "ACK" string as response. For example in the method below we consume from a JMS queue and do the transformation in regular Java code. Notice that the input and output parameters of the method is String. Camel will automatically coerce the payload to the expected type defined by the method. For instance you can use Body, Headers parameter annotations to bind parameters to the body and headers.
Message Filter How can a component avoid receiving unwanted messages? Problem How do you discard unwanted messages? Solution Use a special kind of Message Router, a Message Filter, to eliminate undesired messages from a channel based on a set of criteria.
Camel Camel has support for Message Filter using the filter node. The filter evaluates a predicate whether its true or false; only allowing the true condition to pass the filter, where as the false condition will silently be ignored. Java DSL We want to discard any test messages so we only route non-test messages to the order queue. Solution Use a Dynamic Router, a router that can self-configure based on special configuration messages from participating destinations.
Camel Camel has support for Dynamic Router using the Dynamic Recipient List combined with a data store holding the list of destinations. We could also have used a Bean instead.
Camel Design Patterns ebook
This allows us to extract the customer id as a string parameter. Header wil bind a JMS property with the key location. TIP: Camel uses its strong type converter feature to convert the payload to the type of the method parameter. We could use String and Camel will convert the body to a String instead. You can register your own type converters as well using the Converter annotation at the class and method level.
Recipient List How do we route a message to a list of statically or dynamically specified recipients? Problem How can we route messages based on a static or dynamic list of destinations?
Solution Define a channel for each recipient. Then use a Recipient List to inspect an incoming message, determine the list of desired recipients and forward the message to all channels associated with the recipients in the list.
Camel Camel supports the static Recipient List using the multicast node, and the dynamic Recipient List using the recipientList node. Java DSL Static In this route we route to a static list of two recipients, that will receive a copy of the same message simultaneously.
The bean processMails is used to add the header[mails] to the message. Map to store the recipients. Notice the flexibility of Camel as it can adapt accordingly to how you define what your methods are returning: a single element, a list, an iterator, etc. Problem How can we split a single message into pieces to be routed individually? Solution Use a Splitter to break out the composite message into a series of individual messages, each containing data related to one item.
Camel Camel has support for Splitter using the split node. Java DSL In this route we consume files from the inbox folder. Each file is then split into a new message. We use a tokenizer to split the file content line by line based on line breaks. We can split the stream by using a comma:.
Camel also supports parallel execution using the parallelProcessing node. Expression to provide something that is iterable to produce each individual new message. This allows you to provide any kind of expression such as a Bean invoked as a method call. Problem How do we combine multiple messages into a single combined message?
Solution Use a stateful filter, an Aggregator, to collect and store individual messages until it receives a complete set of related messages to be published.
Camel Camel has support for the Aggregator using the aggregate node.
Camel Design Patterns ebook
Camel uses a stateful batch processor that is capable of aggregating related messaged into a single combined message. A correlation expression is used to determine which messages should be aggregated. An aggregation strategy is used to combine aggregated messages into the result message. Java DSL Stock quote example We want to update a website every five minutes with the latest stock quotes. The quotes are received on a JMS topic. As we can receive multiple quotes for the same stock within this time period we only want to keep the last one as its the most up to date.
We can do this with the aggregator: from "jms:topic:stock:quote". As the aggregation strategy we use the default provided by Camel that picks the latest message, and thus also the most up to date.
The time period is set as a timeout value in milliseconds. Loan broker example We aggregate responses from various banks for their quote for a given loan request. You can upgrade to the ebook version at and as a print book customer, you are entitled to a discount on the ebook copy. Get in touch with us at for more details. At you can also read a collection of free technical articles, sign up for a range of free newsletters and receive exclusive discounts and offers on Packt books and ebooks.
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Simply use your login credentials for immediate access. Find out when new books are published by on Twitter or the Packt Enterprise Facebook page. It provides a very flexible and efficient way to integrate applications and systems all together. Camel provides a complete set of features, based on simple but powerful concepts, allowing you to easily implement very rich integration logic.
Using this book, you will have a detailed understanding, with how to steps to implement integration logics. Chapter 2, Core Concepts, introduces the basis of all the functionalities provided by Camel. Chapter 3, Routing and Processors, introduces Camel routing and the usage of processors. Chapter 4, Beans, explains how to use beans in Camel routes and the different registries in which the beans live. Chapter 5, Enterprise Integration Patterns, introduces one of the most interesting features of Camel the ready-to-use patterns, which serve as an answer to classic integration problems.
Chapter 6, Components and Endpoints, introduces Camel components and endpoints, both how to use them and implement your own. Chapter 7, Error Handling, introduces how to deal with errors in Camel routes. Chapter 8, Testing, introduces how to implement both unit tests and integration tests on your Camel routes. They will get details about Camel, from basic usage, up to the custom development of their own components.
Thanks to the first few chapters, even beginners unfamiliar with Camel will receive a comprehensive look into Camel before jumping into the details. Here are some examples of these styles and an explanation of their meaning. Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: " A message is described in the org.
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Instant Apache Camel Message Routing by Bilgin Ismet Ibryam
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Please contact us at with a link to the suspected pirated material. We appreciate your help in protecting our authors and our ability to bring you valuable content. Key Features After a quick introduction about what Apache Camel is, this chapter will introduce the key features provided by Camel. It provides just an overview of these features; the details will come in dedicated chapters. In an enterprise, you see a lot of different software and systems in the IT ecosystem.
In order to consolidate the data and sync the systems, the enterprise would want to implement communication and integration of these systems. This communication or integration is not so easy, as we have to deal with the specifications on each system the protocol and the message's data format are different most of the time, so we have to transform and adapt to each system.
Using point-to-point communication is one option. However, the problem with this approach is that we tighten the integration of a couple of systems. Changing to other systems or protocols requires refactoring of the implementation. Moreover, dealing with multiple systems is not so easy with point-to-point. So, instead of point-to-point, we use mediation. Mediation reduces complexity and provides a more flexible approach by adding and using a tier between the systems man in the middle.
The purpose is to facilitate the information flow and integration of the systems. Apache Camel is a mediation framework. Apache Camel originated in Apache ServiceMix. JBI was based on WebService concepts and standards.
Camel reuses some of these concepts, for instance, you will see that we have the concept of MEP in Camel. As all messages in the NMR have the same format, it's easy to audit messages and the format is predictable.
However, the JBI XML format has an important drawback for performances: it needs to marshall and unmarshall the messages. For instance, REST can work in stream mode. It doesn't make sense to marshall streams in XML. Camel is payload-agnostic. This means that you can transport any kind of messages with Camel not necessary XML formatted. JBI describes a packaging. We distinguish the binding components responsible for the interaction with the system outside of the NMR and the handling of the messages in the NMR , and the service engines responsible for transforming the messages inside the NMR.
However, it's not possible to directly deploy the endpoints based on these components. JBI also splits the description of the endpoint from its configuration. In Camel, the configuration and definition of the endpoints are gathered in a simple URI.
It's easier to read. This book describes design patterns answering classical problems while dealing with enterprise application integration and message oriented middleware. The book describes the problems and the patterns to solve them.
Camel strives to implement the patterns described in the book to make them easy to use and let the developer concentrate on the task at hand. This is what Camel is: an open source framework that allows you to integrate systems and that comes with a lot of connectors and Enterprise Integration Patterns EIP components out of the box. And if that is not enough, one can extend and implement custom components.
We can see: The connectivity components that allow exposure of endpoints for external systems or communicate with external systems.
Creating an endpoint and the associated configuration for these components is easy, by directly using a URI. The internal components applying rules to the messages internally to Camel. These kinds of components apply validation or transformation rules to the inflight message.
For instance, validation or XSLT are internal components. Thanks to this, Camel brings a very powerful connectivity and mediation framework.
Moreover, it's pretty easy to create new custom components, allowing you to extend Camel if the default components set doesn't match your requirements. It's also very easy to implement complex integration logic by creating your own processors and reusing your beans.
Camel supports beans frameworks IoC , such as Spring or Blueprint. The rule is described using an expression. It means that we have to define expressions or predicates in the Enterprise Integration Patterns. An expression returns any kind of value, whereas a predicate returns true or false only. Camel supports a lot of different languages to declare expressions or predicates.
It doesn't force you to use one, it allows you to use the most appropriate one. It also provides native Camel prebuilt functions and languages that are easy to use such as header, constant, or simple languages. This means that it can support any kind of message. Depending on the endpoints, it could be required to convert from one format to another. That's why Camel supports different data formats, in a pluggable way.
This means that Camel can marshall or unmarshall a message in a given format. Depending on the endpoints and your need, you can explicitly define the data format during the processing of the message. On the other hand, Camel knows the expected format and type of endpoints.
Thanks to this, Camel looks for a type converter, allowing to implicitly transform a message from one format to another. You can also explicitly define the type converter of your choice at some points during the processing of the message.
Camel provides a set of ready-to-use type converters, but, as Camel supports a pluggable model, you can extend it by providing your own type converters. It's a simple POJO to implement. The endpoint itself and its configuration are on the URI. The URI is human readable and provides the details of the endpoint, which is the endpoint component and the endpoint configuration.
As this URI is part of the complete configuration which defines what we name a route, as we will see later , it's possible to have a complete overview of the integration logic and connectivity in a row. We will cover this in detail in Chapter 2, Core Concepts. The Camel core is only around 2 MB, and contains everything required to run Camel.
As it's based on a pluggable architecture, all Camel components are provided as external modules, allowing you to install only what you need, without installing superfluous and needlessly heavy modules. As we saw, Camel is based on simple POJO, which means that the Camel core doesn't depend on other frameworks: it's an atomic framework and is ready to use.
All other modules components, DSL, and so on are built on top of this Camel core.
Moreover, Camel is not tied to one container for deployment. Camel supports a wide range of containers to run. For instance: The application to integrate with has not yet been downloadd or not yet ready The remote system to integrate with has a heavy cost, not acceptable during the development phase Multiple teams work in parallel, so we may have some kinds of deadlocks between the teams As a complete integration framework, Camel provides a very easy way to prototype part of the integration logic.
Even if you don't have the actual system to integrate, you can simulate this system mock , as it allows you to implement your integration logic without waiting for dependencies.
The mocking support is directly part of the Camel core and doesn't require any additional dependency. Along the same lines, testing is also crucial in an integration project. In such a kind of project, a lot of errors can happen and most are unforeseen. Moreover, a small change in an integration process might impact a lot of other processes.
Camel provides the tools to easily test your design and integration logic, allowing you to integrate this in a continuous integration platform. They also provide the operations to manage Camel. For instance, the operations allow you to stop an integration process, to suspend an endpoint, and so on. Using a combination of metrics and operations, you can configure a very agile integration solution.
This means that potential issues are identified very quickly and a fix is available soon after. However, it also means that a lot of ideas and contributions are proposed, giving more and more features to Camel. Another big advantage of an active community is that you will never be alone; a lot of people are active on the mailing lists who are ready to answer your question and provide advice.
Apache Camel is an enterprise integration solution used in many large organizations with enterprise support available through RedHat or Talend. It mainly introduced Camel's key features. In the next chapter, before dealing with some of these features in detail, we will introduce the Camel core concepts, which will help you easily understand the further chapters.
Core Concepts This chapter introduces the core concepts of Camel. These concepts are the key basis of all functionalities provided by Camel. We will use them in the next chapters. As we have seen in the previous chapter, Camel is an integration framework. This means that it provides everything to implement your mediation logic: messaging, routing, transformation, and connectivity.
We will look at the following concepts: Messages Exchanges Camel contexts 43 Messages Messages transport the data between the different parts of the mediation logic. Your mediation logic will define the flow of messages between different nodes.
A message flows in one direction, from a sender to a receiver. It's not possible to use the same message to answer the sender, we will have to use another message. A message is described in the org. Camel creates an ID for you. This ID identifies the message and can be used for correlation or storage.
For instance, we will see that the message ID is used in the idempotent consumer pattern to identify the message in a store.
Header: A set of headers, allowing you to store any kind of data associated with a message. The headers are stored as org. This means you can store any kinds of objects including very large objects in the header. To access the map use a String key, which is case insensitive.
The lifetime of the headers is the same as the message as the headers are part of the message itself. The purpose of the headers is to add hints about the content encoding, authentication information, and so on.
As we will see in the next chapters, Camel itself uses and populates the headers for its own needs and configurations.Batch is similar to the aggregator but with sorting. Camel provides the org. Find downloads, tutorials, examples, getting started guides, issue tracker, roadmap, mailing lists, irc chat rooms, and how to get help. Transform is a particular processor allowing you to set a response to be returned to the original caller. Problem How can we split a single message into pieces to be routed individually?
Camel uses a stateful batch processor that is capable of aggregating related messaged into a single combined message. I would have liked to see how to create new projects without the command-line such as from the wizards built-in Eclipse. You signed out in another tab or window. Solution Use a special kind of Message Router, a Message Filter, to eliminate undesired messages from a channel based on a set of criteria.
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