Tutorial on using Camel in a Web Application
Camel has been designed to work great with the Spring framework; so if you are already a Spring user you can think of Camel as just a framework for adding to your Spring XML files.
So you can follow the usual Spring approach to working with web applications; namely to add the standard Spring hook to load a /WEB-INF/applicationContext.xml file. In that file you can include your usual Camel XML configuration.
Step1: Edit your web.xml
To enable spring add a context loader listener to your /WEB-INF/web.xml file
| Code Block | ||||
|---|---|---|---|---|
| ||||
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
</web-app>
|
This will cause Spring to boot up and look for the /WEB-INF/applicationContext.xml file.
Step 2: Create a /WEB-INF/applicationContext.xml file
Now you just need to create your Spring XML file and add your camel routes or configuration.
For example
| Code Block | ||||
|---|---|---|---|---|
| ||||
<?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:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://camel.apache.org/schema/spring
http://camel.apache.org/schema/spring/camel-spring.xsd">
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:foo"/>
<to uri="mock:results"/>
</route>
</camelContext>
</beans>
|
Then boot up your web application and you're good to go!
Hints and Tips
If you use Maven to build your application your directory tree will look like this...
| Code Block |
|---|
src/main/webapp/WEB-INF web.xml applicationContext.xml |
You should update your Maven pom.xml to enable WAR packaging/naming like this...
| Code Block | ||||
|---|---|---|---|---|
| ||||
<project>
...
<packaging>war</packaging>
...
<build>
<finalName>[desired WAR file name]</finalName>
...
</build>
|
To enable more rapid development we highly recommend the jetty:run maven plugin.
Please refer to the help for more information on using jetty:run - but briefly if you add the following to your pom.xml
| Code Block | ||||
|---|---|---|---|---|
| ||||
<build>
<plugins>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<configuration>
<webAppConfig>
<contextPath>/</contextPath>
</webAppConfig>
<scanIntervalSeconds>10</scanIntervalSeconds>
</configuration>
</plugin>
</plugins>
</build>
|
Then you can run your web application as follows
| Code Block |
|---|
mvn jetty:run |
Then Jetty will also monitor your target/classes directory and your src/main/webapp directory so that if you modify your spring XML, your web.xml or your java code the web application will be restarted, re-creating your Camel routes.
If your unit tests take a while to run, you could miss them out when running your web application via
| Code Block |
|---|
mvn -Dtest=false jetty:run |