Taking
Apache Camel
For A Ride
Bruce Snyder
bsnyder@apache.org
7 Nov 2008
New Orleans, Louisiana

Protocol Integration
is Common

Data Format Integration
is Common

Integration is Messy!

SOA = Spaghetti Oriented
Architecture

Options For Integration
1 2
3

Too Many Choices!

The Easiest Solution - Apache
Camel
http://activemq.apache.org/camel/

What is
Apache Camel?

Enterprise Integration
Patterns
http://enterpriseintegrationpatterns.com/

Message Routing

Patterns

History of Apache Camel

Camel Components
http://activemq.apache.org/camel/components.html

Camel Components

Simple Routing

More Simple Routing

Pipeline Routing

Multicast Routing

Multicast-to-Many
Pipeline Routes

Language Support
For Message Processing
• BeanShell • JSP EL
• Javascript • OGNL
• Groovy • SQL
• Python • XPath
• PHP • XQuery
• Ruby

Getting Started -
The Camel Context
CamelContext context = new DefaultCamelContext();
context.addRoutes(new MyRouteBuilder());
context.start();
<camelContext
xmlns=\"http://activemq.apache.org/camel/schema/spring\">
<package>com.acme.quotes</package>
</camelContext>

Pattern
Examples

Patterns

Content Based Router
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from(\"seda:a\").choice().when(header(\"foo\")
.isEqualTo(\"bar\")).to(\"seda:b\")
.when(header(\"foo\").isEqualTo(\"cheese\"))
.to(\"seda:c\").otherwise().to(\"seda:d\");
}
};

Content Based Router
<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>

Message Filter
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"activemq:topic:Quotes).
filter().xpath(\"/quote/product = ‘widget’\").
to(\"mqseries:WidgetQuotes\");
}
}

Message Filter
<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>

Splitter
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"file://orders\").
splitter(body().tokenize(\"\\n\")).
to(\"activemq:Order.Items\");
}
}

Splitter Using XQuery
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"file://orders\").
splitter().xquery(\"/order/items\").
to(\"activemq:Order.Items\");
}
}

Aggregator
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"activemq:Inventory.Items\").
aggregator(header(\"symbol\").isEqualTo(\"IBM\").
to(\"activemq:Inventory.Order\");
}
}

Message Translator
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"file://incoming”).
to(\"xslt:com/acme/mytransform.xsl\").
to(\"http://outgoing.com/foo\");
}
}

Resequencer
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"direct:a”).
resequencer(header(\"customerRank\")).
to(\"seda:b\");
}
}

Routing Slip
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"direct:a”).routingSlip();
}
}

Throttler
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"seda:a”).
throttler(3).timePeriodMillis(30000).
to(\"seda:b\");
}
}

Delayer
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"seda:a”).
delayer(header(\"JMSTimestamp\", 3000).
to(\"seda:b\");
}
}

Load Balancer
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"file:/path/to/file\").
loadBalance().roundRobin().
to(\"seda:a\", \"seda:b\", \"seda:c\");
}
}
Policy Description
Round Robin Balance the exchange load across the available endpoints
Random Randomly choose an endpoint to send the exchange
Sticky Sticky load balancing of exchanges using an expression
Topic Send exchange to all endpoints (like a JMS topic)

Multicast
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"direct:a\").
multicast().
to(\"direct:x?x=y&amp;1=2\", \"direct:y\", \"direct:z\");
}
}

Demo

More
Patterns

Wire Tap
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"direct:a\").
to(\"log:com.mycompany.messages?level=info\").
to(\"mock:foo\");
}
}

Content Enricher
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"activemq:My.Queue\").
to(\"velocity:com/acme/MyResponse.vm\").
to(\"activemq:Another.Queue\");
}
}

More Content Enricher
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"activemq:My.Queue\").
beanRef(\"myBeanName\", \"myMethodName\").
to(\"activemq:Another.Queue\");
}
}

Content Filter
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
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\");
}
}

Combine Patterns
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"seda:a”).
resequencer(header(\"JMSGroupSeq\")).
delayer(3000).
to(\"mock:x\");
}
}

Configure Error Handling
Global Error Handler:
RouteBuilder builder = new RouteBuilder() {
public void configure() {
errorHandler(deadLetterChannel(\"file:errors\"));
from(\"bean:foo\").to(\"seda:b\");
}
};

Configure Error Handling
Local Error Handler:
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from(\"seda:a\").
errorHandler(loggingErrorHandler(\"FOO.BAR\")).
to(\"seda:b\");
from(\"seda:b\").to(\"seda:c\");
}
};

Configure Exception Policies
RouteBuilder builder = new RouteBuilder() {
public void configure() {
exception(IOException.class)
.initialRedeliveryDelay(5000L)
.maximumRedeliveries(3)
.maximumRedeliveryDelay(30000L)
.backOffMultiplier(1.0)
.useExponentialBackOff()
.setHeader(MESSAGE_INFO, constant(\"Damned IOException!\"))
.to(\"activemq:errors\");
from(\"seda:a\").to(\"seda:b\");
}
};

Beans

Make Context Discover Beans
package com.mycompany.beans;
public class MyBean {
public void someMethod(String name) {
...
}
}
<camelContext
xmlns=\"http://activemq.apache.org/camel/schema/spring\">
<package>com.mycompany.beans</package>
</camelContext>

Bean as a Message Translator
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"activemq:Incoming”).
beanRef(\"myBean\").
to(\"activemq:Outgoing\");
}
}

Bean as a
Message Translator
*With Method Name
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"activemq:Incoming”).
beanRef(\"myBean\", \"someMethod\").
to(\"activemq:Outgoing\");
}
}

Binding Beans to
Camel Endpoints
public class Foo {
@MessageDriven(uri=\"activemq:cheese\")
public void onCheese(String name) {
...
}
}

Binding Method Arguments
public class Foo {
public void onCheese(
@XPath(\"/foo/bar\") String name,
@Header(\"JMSCorrelationID\") String id) {
...
}
}

Injecting Endpoints
Into Beans
public class Foo {
@EndpointInject(uri=\"activemq:foo.bar\")
ProducerTemplate producer;
public void doSomething() {
if (whatever) {
producer.sendBody(\"<hello>world!</hello>\");
}
}
}

Type Conversion

Type Conversion
@Converter
public class IOConverter {
@Converter
public static InputStream toInputStream(File file)
throws FileNotFoundException {
return new BufferedInputStream(
new FileInputStream(file));
}
}

Type Convertors
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
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\");
}
}
Support for the following types:
• File
• String
• byte[] and ByteBuffer
• InputStream and OutputStream
• Reader and Writer
• Document and Source

Message Mapper

Message Translator
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"file://incoming”).
to(\"xslt:com/acme/mytransform.xsl\").
to(\"http://outgoing.com/foo\");
}
}

Another
Message Translator
public class MyRouteBuilder extends RouteBuilder {
public void configure() {
from(\"activemq:FOO.TEST”).
transform(body().append(getDynamicText())).
to(\"http://outgoing.com/foo\");
}
}

Business Activity Monitoring
(BAM)

Business Activity Monitoring
(BAM)
public class MyActivities extends ProcessBuilder {
public void configure() throws Exception {
// lets define some activities, correlating on an
// XPath query of the message body
ActivityBuilder purchaseOrder = activity(\"activemq:PurchaseOrders\")
.correlate(xpath(\"/purchaseOrder/@id\").stringResult());
ActivityBuilder invoice = activity(\"activemq:Invoices\")
.correlate(xpath(\"/invoice/@purchaseOrderId\").stringResult());
// now lets add some BAM rules
invoice.starts().after(purchaseOrder.completes())
.expectWithin(seconds(1))
.errorIfOver(seconds(2)).to(\"activemq:FailedProcesses\");
}
}

Complex Routing is Easier
from(“http://localhost:8080/requests/”).
tryBlock().
to(“activemq:queue:requests”).
setOutBody(constant(“<ack/>”)).
handle(Throwable.class).
setFaultBody(constant(“<nack/>”));
from((“activemq:queue:requests?transacted=true”).
process(requestTransformer).
to(“http://host:8080/Request”).
filter(xpath(“//nack”)).
process(nackTransformer).
to(“jdbc:store”);
from(“http://localhost:8080/responses/”).
tryBlock().
to(“activemq:queue:responses”).
setOutBody(constant(“<ack/>”)).
handle(Throwable.class).
setFaultBody(constant(“<nack/>”));
from(“activemq:queue:responses?transacted=true”).
process(responseTransformer).
to(“jdbc:store”);
from(“http://localhost:8080/pull/”).
to(“jdbc:load”);

Finally, the Camel Truck!

Ride the Camel!
http://activemq.apache.org/camel/