Xke - Introduction to Apache Camel

Apache CamelTaking Camel for a ride

Hands on XkeAlexis KinsellaJune 11, 2010

www.xebia.fr / blog.xebia.fr 2

What is camel ?

What is camel ?


It stands for :▶ Concise Application Message

Exchange Language (i.e. the Java DSL for routing)

▶ Its is a routing and mediation framework

Some people say that :▶ A camel is a horse designed by

committee (Not in that case ...)

What is camel ?

A powerful Spring based Integration Framework

It implements Enterprise Integration Patterns

Routing and mediation rules configured using :▶ Java DSL (or Fluent API)▶ Spring Xml Configuration files.


What is camel ?

Apache Camel uses URIs▶ Works with any kind of transport or messaging such as:

» HTTP, ActiveMQ, JMS, MINA or CXF Bus API, …» Working with pluggable Data Format options

▶ Works with the same API regardless which kind of Transport used.

A Java library with minimal dependencies:▶ easy embedding in any Java application.



Some informations before you start ...

About the authors (Camel Riders)

James Strachan▶ Technical director at FuseSource▶ Blog: http://macstrac.blogspot.com/▶ Co-founder: Scalate, ActiveMQ, Camel, ServiceMix,

Lingo, Jencks, Groovy, dom4j▶ Committer: jaxen, taglibs, commons

Claus Ibsen▶ Software Engineer employed by Progress Software

working in The FUSE team▶ Blog: http://davsclaus.blogspot.com/▶ Leader: Camel


About the authors (Camel Riders)

Jon Anstey▶ Senior Engineer at Progress Software▶ Blog: http://janstey.blogspot.com/▶ Committer: ActiveMQ, Camel, ServiceMix

Hiram Chirino▶ A Software Architect at FuseSource▶ Blog: http://hiramchirino.com/blog/▶ Co-founder: ActiveMQ, Camel▶ Committer: ServiceMix,Geronimo


Camel and friends

ActiveMQ▶ Open source messaging provider (JMS provider).▶ Web site: http://activemq.apache.org▶ Current version: 5.3.2

CXF▶ Open Source Service Framework (WebServices)▶ Web site: http://cxf.apache.org▶ Current version: 2.2.9

ServiceMix▶ Open source ESB (Enterprise Service Bus)▶ Web site: http://servicemix.apache.org▶ Current versions: 3.3.2 / 4.2.0 (OSGI Based)

Apache Mina ...


Professionnal Camel Support

FuseSource – Open Source SOA▶ Get supported and fixed versions for:

» ActiveMQ, Camel, Cxf, ServiceMix, FuseHQ

▶ Subscribe production and development support, Consulting, Virtual Training

▶ Provide first class support: Emploies many Apache project co-founders and commiters

▶ Provides Open Maven repositories (No need to contract support to gain access to supported and fixed versions)


Competitors and Families of products

ESB (Entreprise Service Bus):▶ ServiceMix (JBI compliant, integrates Apache Camel)▶ JbossESB▶ WebSphereESB (SCA compliant) ▶ SonicESB, OpenESB, Petals...

Lightweight Enterprise Integration Patterns Frameworks:▶ Camel▶ MuleESB▶ Spring Integration

Process Servers, EAI, …▶ WPS (Websphere Process Server)▶ Biztalk Server


Camel compared to Mule ...

Both based on Spring + POJO They can run in standalone mode or embedded in

an OSGI server, application server They are not based on based on JBI specification

▶ Where the messages send over the bus are XML normalized messages

Camel has more components than Mule now Camel proposes a DSL Language Mule has better monitoring & management tools


Camel compared to Mule ...

You don't need to create a lot of XML config files with inbound/outbound stuff like you have to do in Mule.

The routing in Mule is not so intuitive and not appear directly in the XML or DSL



The basics

Message Routing


Endpoint BEndpoint B

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facilisis nec, sagittis eget eros. Mauris scelerisque justo et ipsum scelerisque

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Endpoint AEndpoint A

Message

Camel Components


Kick Ass features

Integrates with almost everything … Support for:

▶ Scripting languages» Groovy» Scala

▶ Google App Engine & Google APIs▶ …

Built-in BAM Features

Extendable


Simple Routing







Message FileJms

Pipeline







Message

Endpoint CEndpoint C




Endpoint DEndpoint D

Message

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Multicast







Message



File

IBatis

SMTP

SFTP

Message filter: Spring XML


<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:schemaLocation="…">

<camelContext xmlns="http://activemq.apache.org/camel/schema/spring"><route>

<from uri="activemq:topic:Quotes" /><filter>

<xpath>/quote/product = ‘widget’</xpath><to uri="mqseries:WidgetQuotes" />

</filter></route>

</camelContext>

</beans>

Message filter: Java DSL


package com.acme.quotes;

import org.apache.camel.builder.RouteBuilder;

public class MyRouteBuilder extends RouteBuilder {

public void configure() {// forward widget quotes to MQSeriesfrom("activemq:topic:Quotes").

filter().xpath("/quote/product = ‘widget’").to("mqseries:WidgetQuotes");

}}

Content Based Router: Java


from("activemq:NewOrders").choice().when().xpath("/quote/product = 'widget'").

to("activemq:Orders.Widgets").choice().when().xpath("/quote/product = 'gadget'").

to("activemq:Orders.Gadgets").otherwise().

to("activemq:Orders.Bad");

Content Based Router: Spring XML



<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:schemaLocation="...">

<camelContext xmlns="http://activemq.apache.org/camel/schema/spring"><route>

<from uri="activemq:NewOrders" /><choice>

<when><xpath>/order/product = 'widget'</xpath><to uri="activemq:Orders.Widgets" />

</when><when>

<xpath>/order/product = 'gadget'</xpath><to uri="activemq:Orders.Gadgets" />

</when><otherwise>

<to uri="activemq:Orders.Bad" /></otherwise>

</choice></route>

</camelContext>

</beans>

How camel do this routing work ?

Camel Components▶ Camel Endpoints

» Camel Consumer» Camel Producer

Camel-Core


Message processors


from("direct:start").process(new Processor() {

public void process(Exchange exchange) {

Message in = exchange.getIn();

in.setBody(in.getBody(String.class) + " World!");

}

}).to("mock:result");

<bean id="myProcessor" class="com.acme.MyProcessor"/>

from("activemq:myQueue").to("myProcessor");

The Processor interface is used to implement:▶ Consumers of message exchanges▶ A Message Translator

Expressions


Camel supports pluggable Expression strategies using a variety of different Languages (Dynamic rules):▶ Bean Language for using Java for expressions▶ The unified EL from JSP and JSF▶ JXPath, Mvel, OGNL▶ Scala DSL, Groovy▶ Python, PHP, Ruby, JavaScript▶ Simple, Constant▶ Xpath, Xquery, SQL

Predicates


Camel supports a pluggable interface called Predicate▶ Can be used to integrate a dynamic predicate into

Enterprise Integration Patterns such as when using: » Message Filter» Content Based Router.

A Predicate is being evaluated to a boolean value so the result is either true or false. ▶ This makes Predicate so powerful as it is often used to

control the routing of message in which path they should be routed.

Predicates examples


from("jms:queue:order")

.choice()

.when(header("type").isEqualTo("widget")).to("bean:widgetOrder")

.when(header("type").isEqualTo("wombat")).to("bean:wombatOrder")

.otherwise()

.to("bean:miscOrder")

.end();

Predicate isWidget = header("type").isEqualTo("widget");

from("jms:queue:order")

.choice()

.when(isWidget).to("bean:widgetOrder")

.when(isWombat).to("bean:wombatOrder")

.otherwise()

.to("bean:miscOrder")

.end();

Transaction Oriented Endpoints


Transaction Manager

<bean id="jmsTransactionManager" class="org.springframework.jms.connection.JmsTransactionManager">

<property name="connectionFactory" ref="jmsConnectionFactory" /> </bean> <bean id="jmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory"> <property name="brokerURL" value="tcp://localhost:61616"/> </bean>

Transaction Policies

<bean id="PROPAGATION_REQUIRED" class="org.apache.camel.spring.spi.SpringTransactionPolicy"> <property name="transactionManager" ref="jmsTransactionManager"/> </bean>

<bean id="PROPAGATION_REQUIRES_NEW" class="org.apache.camel.spring.spi.SpringTransactionPolicy">

<property name="transactionManager" ref="jmsTransactionManager"/> <property name="propagationBehaviorName" value="PROPAGATION_REQUIRES_NEW"/>

</bean>



Using policies in Java DSL (1)

public void configure() { ... Policy requried = bean(SpringTransactionPolicy.class, "PROPAGATION_REQUIRED")); Policy requirenew = bean(SpringTransactionPolicy.class, "PROPAGATION_REQUIRES_NEW")); ... }

// Send to bar in a new transaction from("activemq:queue:foo").policy(requirenew).to("activemq:queue:bar");

// Send to bar without a transaction. from("activemq:queue:foo").policy(notsupported).to("activemq:queue:bar");



Using policies in Java DSL (2)

from("direct:mixed") // using required .transacted("PROPAGATION_REQUIRED") // all these steps will be okay .setBody(constant("Tiger in Action")).beanRef("bookService") .setBody(constant("Elephant in Action")).beanRef("bookService") .setBody(constant("Lion in Action")).beanRef("bookService") // continue on route 2 .to("direct:mixed2");

from("direct:mixed2") // using a different propagation which is requires new .transacted("PROPAGATION_REQUIRES_NEW") // tell Camel that if this route fails then only rollback this last route // by using (rollback only *last*) .onException(Exception.class).markRollbackOnlyLast().end() // this step will be okay .setBody(constant("Giraffe in Action")).beanRef("bookService") // this step will fail with donkey .setBody(constant("Donkey in Action")).beanRef("bookService");



Using policies in Spring XML (1) <camel:camelContext id="myroutes">

   <camel:route errorHandlerRef="transactionErrorHandler">  <camel:from uri="activemq:queue:okay"/>  <camel:transacted ref="required"/>  <camel:process ref="myProcessor"/>  <camel:to uri="mock:result"/> </camel:route>

  <camel:route errorHandlerRef="noErrorHandler"> <camel:from uri="activemq:queue:bad"/> <camel:to uri="log:bad"/> </camel:route>

</camel:camelContext>



Using policies in Spring XML (2)

<bean id="required" class="org.apache.camel.spring.spi.SpringTransactionPolicy"> <property name="transactionTemplate" ref="PROPAGATION_REQUIRED"/></bean>

<bean id="PROPAGATION_REQUIRED"

class="org.springframework.transaction.support.TransactionTemplate"> <property name="transactionManager" ref="jmsTransactionManager"/></bean>

<bean id="transactionErrorHandler"

class="org.apache.camel.spring.spi.TransactionErrorHandlerBuilder"> <property name="transactionTemplate" ref="PROPAGATION_REQUIRED"/></bean>

<bean id="noErrorHandler" class="org.apache.camel.builder.NoErrorHandlerBuilder"/>



TransactionErrorHandler

onException(ValidationException.class).handled(true).transform(body(constant("INVALID ORDER")));

from("jetty:http://localhost/myservice/order").transacted().to("bean:validateOrder").to("jms:queue:order");

errorHandler(transactionErrorHandler().maximumRedeliveries(6));

onException(IllegalArgumentException.class).maximumRedeliveries(4);

from("direct:okay") .transacted() .setBody(constant("Tiger in Action")).beanRef("bookService") .setBody(constant("Elephant in Action")).beanRef("bookService");

DefaultErrorHandler & DeadLetterChannel


Client notified (Default DLC behavior, not DEH )

errorHandler(deadLetterChannel("jms:queue:dead").

maximumRedeliveries(3).redeliverDealy(5000));

Client not notified errorHandler(deadLetterChannel("jms:queue:dead").

maximumRedeliveries(3).redeliverDealy(5000).handled(false));

Use original message errorHandler(deadLetterChannel("jms:queue:dead") .useOriginalMessage().mamimumRedeliveries(5).redeliverDelay(5000);

Using default error handleronException(ValidationException.class).handled(true).transform(body(constant("INVALID ORDER")));

Annotation support


Camel supports annotations

public class RouterBean {

@Consume(uri = "activemq:foo")

@RecipientList

public String[] route(String body) {

return new String[]{"activemq:bar", "activemq:whatnot"};

}

}

public class Foo {

@MessageDriven(uri = "activemq:my.queue")

public void doSomething(@XPath("/foo/bar/text()") String correlationID, @Body String body) {

// process the inbound message here

}

}

@Bean annotation


public class Foo {

@MessageDriven(uri = "activemq:my.queue")

public void doSomething(@Bean("myCorrelationIdGenerator") String correlationID, @Body String body) {

// process the inbound message here

}

}

public class MyIdGenerator {

private UserManager userManager;

public String generate(@Header(name = "user") String user, @Body String payload) throws Exception {

User user = userManager.lookupUser(user);

String id = user.getPrimaryId() + generateHashCodeForPayload(payload);

return id;

}

}

Groovy support


Using Java DSL

// lets route if a line item is over $100

from("queue:foo").filter(groovy("request.lineItems.any { i -> i.value > 100 }")).to("queue:bar");

Using Spring XML

<route>

<from uri="queue:foo"/>

<filter>

<groovy>request.lineItems.any { i -> i.value > 100 }</groovy>

<to uri="queue:bar"/>

</filter>

</route>

Testing with camel


Testing of distributed and asynchronous processing is notoriously difficult

Camel provides helpers:▶ Test URIs▶ Datasets▶ Mocks

Maven dependency for tests: <dependency>

<groupId>org.apache.camel</groupId>

<artifactId>camel-test</artifactId>

<version>${camel-version}</version>

<scope>test</scope>

</dependency>

Testing with camel


public class FilterTest extends CamelTestSupport {

@EndpointInject(uri = "mock:result") protected MockEndpoint resultEndpoint;

@Produce(uri = "direct:start") protected ProducerTemplate template;

public void testSendMatchingMessage() throws Exception {

String expectedBody = "<matched/>";

resultEndpoint.expectedBodiesReceived(expectedBody);

template.sendBodyAndHeader(expectedBody, "foo", "bar");

resultEndpoint.assertIsSatisfied();

}

public void testSendNotMatchingMessage() throws Exception {

resultEndpoint.expectedMessageCount(0);

template.sendBodyAndHeader("<notMatched/>", "foo", "notMatchedHeaderValue");


}

@Override

protected RouteBuilder createRouteBuilder() {

return new RouteBuilder() {

public void configure() {

from("direct:start").filter(header("foo").isEqualTo("bar")).to("mock:result");

}

};

}

}

Spring Test with Java Config


@ContextConfiguration( locations = "org.apache.camel.spring.javaconfig.patterns.FilterTest$ContextConfig", loader = JavaConfigContextLoader.class)

public class FilterTest extends AbstractJUnit4SpringContextTests {

@EndpointInject(uri = "mock:result") protected MockEndpoint resultEndpoint;

@Produce(uri = "direct:start") protected ProducerTemplate template;

@DirtiesContext

@Test

public void testSendMatchingMessage() throws Exception {

String expectedBody = "<matched/>";

resultEndpoint.expectedBodiesReceived(expectedBody);

template.sendBodyAndHeader(expectedBody, "foo", "bar");


}

@Configuration

public static class ContextConfig extends SingleRouteCamelConfiguration {

@Bean

public RouteBuilder route() {

return new RouteBuilder() {

public void configure() {

from("direct:start").filter(header("foo").isEqualTo("bar")).to("mock:result");

}

};

}

}

}

Camel riding from Java

/META-INF/spring/camelContext.xml

Set the CLASSPATH

Run Camel context from :▶ java org.apache.camel.spring.Main


Camel & Maven

mvn camel:run, camel:dot

Maven declaration:



<project><build>

<plugins><plugin>

<groupId>org.apache.camel</groupId><artifactId>camel-maven-plugin</artifactId>

</plugin></plugins>

</build><reporting>

<plugins><plugin>

<groupId>org.apache.camel</groupId><artifactId>camel-maven-plugin</artifactId>

</plugin></plugins>

</reporting></project>

Maven site report

Result of report plugin (Dot & GraphViz)


Where would I use Camel ?

Standalone or in any Spring application

Inside ActiveMQ’s JMS client or the broker

Inside your ESB such as ServiceMix via the servicemix-camel Service Unit

Inside CXF either as a transport or reusing CXF inside Camel



Going further with Apache Camel …

Books

Theme: ▶ This book is essentially the

Camel bible

Edition: ▶ Manning▶ Fall 2010 | 435 pages▶ ISBN: 9781935182368

Authors: ▶ Claus Ibsen, Committer and

lead▶ Jonathan Anstey, Committer▶ Hadrian Zbarcea, Committer,

Chair of PMC and Release Manager


Books

Theme: ▶ catalog of sixty-five patterns,

with real-world solutions

Edition: ▶ Addison-Wesley Professional▶ October 2003 | 736 pages▶ ISBN: 9780321200686

Authors: ▶ Gregor Hohpe, Software

engineer at Google.▶ Bobby Woolf, WebSphere

consultant at IBM.



Twitter: @alexiskinsella

Thank You

Technology

Xke - Introduction to Apache Camel