[CONF] Apache Camel: Tutorial-Business-Partners (page edited)

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Page Edited : CAMEL : Tutorial-Business-Partners Tutorial-Business-Partners has been edited by Aaron Mulder (Sep 16, 2008). (View changes) Content: Under Construction This tutorial is a work in progress. Background and Introduction So there's a company, which we'll call Acme. Acme sells widgets, in a fairly unusual way. Their customers are responsible for telling Acme what they purchased. The customer enters into their own systems (ERP or whatever) which widgets they bought from Acme. Then at some point, their systems emit a record of the sale which needs to go to Acme so Acme can bill them for it. Obviously, everyone wants this to be as automated as possible, so there needs to be integration between the customer's system and Acme. Sadly, Acme's sales people are, technically speaking, doormats. They tell all their prospects, "you can send us the data in whatever format, using whatever protocols, whatever. You just can't change once it's up and running." The result is pretty much what you'd expect. Taking a random sample of 3 customers: Customer 1: XML over FTP Customer 2: CSV over HTTP Customer 3: Excel via e-mail Now on the Acme side, all this has to be converted to a canonical XML format and submitted to the Acme accounting system via JMS. Then the Acme accounting system does its stuff and sends an XML reply via JMS, with a summary of what it processed (e.g. 3 line items accepted, line item #2 in error, total invoice $123.45). Finally, that data needs to be formatted into an e-mail, and sent to a contact at the customer in question ("Dear Joyce, we received an invoice on 1/2/08. We accepted 3 line items totaling $123.45, though there was an error with line items #2 [invalid quantity ordered]. Thank you for your business. Love, Acme."). So it turns out Camel can handle all this: Listen for HTTP, e-mail, and FTP files Grab attachments from the e-mail messages Convert XML, XLS, and CSV files to a canonical XML format using XSLT, automatic data format conversion, and/or POJOs that write to JAXB objects read and write JMS messages route based on company ID format e-mails using Velocity templates send outgoing e-mail messages This tutorial will cover all that, plus setting up tests along the way. High-Level Diagram Here's more or less what the integration process looks like. First, the input from the customers to Acme: And then, the output from Acme to the customers: Tutorial Tasks To get through this scenario, we're going to break it down into smaller pieces, implement and test those, and then try to assemble the big scenario and test that. Here's what we'll try to accomplish: Create a Maven build for the project Get sample files for the customer Excel, CSV, and XML input Get a sample file for the canonical XML format that Acme's accounting system uses Create an XSD for the canonical XML format Create JAXB POJOs corresponding to the canonical XSD Create an XSLT stylesheet to convert the Customer 1 (XML over FTP) messages to the canonical format Create a unit test to ensure that a simple Camel route invoking the XSLT stylesheet works Create a POJO that converts a List<List<String>> to the above JAXB POJOs Note that Camel can automatically convert CSV input to a List of Lists of Strings representing the rows and columns of the CSV, so we'll use this POJO to handle Customer 2 (CSV over HTTP) Create a unit test to ensure that a simple Camel route invoking the CSV processing works Create a POJO that converts a Customer 3 Excel file to the above JAXB POJOs (using POI to read Excel) Create a unit test to ensure that a simple Camel route invoking the Excel processing works Create a POJO that reads an input message, takes an attachment off the message, and replaces the body of the message with the attachment This is assuming for Customer 3 (Excel over e-mail) that the e-mail contains a single Excel file as an attachment, and the actual e-mail body is throwaway Build a set of Camel routes to handle the entire input (Customer -> Acme) side of the scenario. Build unit tests for the Camel input. TODO: Tasks for the output (Acme -> Customer) side of the scenario Let's Get Started! Step 1: Initial Maven build We'll use Maven for this project as there will eventually be quite a few dependencies and it's nice to have Maven handle them for us. You should have a current version of Maven (e.g. 2.0.9) installed. You can start with a pretty empty project directory and a Maven POM file, or use a simple JAR archetype to create one. Here's a sample POM. We've added a dependency on camel-core, and set the compile version to 1.5 (so we can use annotations): pom.xml <?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0"> <modelVersion>4.0.0</modelVersion> <groupId>org.apache.camel.tutorial</groupId> <artifactId>business-partners</artifactId> <version>1.0-SNAPSHOT</version> <name>Camel Business Partners Tutorial</name> <dependencies> <dependency> <artifactId>camel-core</artifactId> <groupId>org.apache.camel</groupId> <version>1.4.0</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.5</source> <target>1.5</target> </configuration> </plugin> </plugins> </build> </project> Step 2: Get Sample Files You can make up your own if you like, but here are the "off the shelf" ones: Customer 1 (XML): input-customer1.xml Customer 2 (CSV): input-customer2.csv Customer 3 (Excel): input-customer3.xls Canonical Acme XML Request: canonical-acme-request.xml Canonical Acme XML Response: TODO If you look at these files, you'll see that the different input formats use different field names and/or ordering, because of course the sales guys were totally OK with that. Sigh. Step 3: XSD and JAXB Beans for the Canonical XML Format Here's the sample of the canonical XML file: <?xml version="1.0" encoding="UTF-8"?> <invoice xmlns="http://activemq.apache.org/camel/tutorial/partners/invoice"> <partner-id>2</partner-id> <date-received>9/12/2008</date-received> <line-item> <product-id>134</product-id> <description>A widget</description> <quantity>3</quantity> <item-price>10.45</item-price> <order-date>6/5/2008</order-date> </line-item> <!-- // more line-item elements here --> <order-total>218.82</order-total> </invoice> If you're ambitions, you can write your own XSD (XML Schema) for files that look like this. If not, you can download mine. In any case, save it to src/main/xsd. Generating JAXB Beans Down the road we'll want to deal with the XML as Java POJOs. We'll take a moment now to set up those XML binding POJOs. So we'll update the Maven POM to generate JAXB beans from the XSD file. We need a dependency: <dependency> <artifactId>camel-jaxb</artifactId> <groupId>org.apache.camel</groupId> <version>1.4.0</version> </dependency> And a plugin configured: <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>jaxb2-maven-plugin</artifactId> <executions> <execution> <goals> <goal>xjc</goal> </goals> </execution> </executions> </plugin> That should do it (it automatically looks for XML Schemas in src/main/xsd to generate beans for). Run mvn install and it should emit the beans into target/generated-sources/jaxb. Your IDE should see them there, though you may need to update the project to reflect the new settings in the Maven POM. Initial Work on Customer 1 Input (XML over FTP) To get a start on Customer 1, we'll create an XSLT template to convert the Customer 1 sample file into the canonical XML format, write a small Camel route to test it, and build that into a unit test. If we get through this, we can be pretty sure that the XSLT template is valid and can be run safely in Camel. Create an XSLT template Start with the Customer 1 sample input. You want to create an XSLT template to generate XML like the canonical XML sample above – an invoice element with line-item elements (one per item in the original XML document). If you're especially clever, you can populate the current date and order total elements too. My sample XSLT template isn't that smart, but it'll get you going if you don't want to write one of your own. Create a unit test Here's where we get to some meaty Camel work. We need to: Set up a unit test That loads a Camel configuration That has a route invoking our XSLT Where the test sends a message to the route And ensures that some XML comes out the end of the route The easiest way to do this is to set up a Spring context that defines the Camel stuff, and then use a base unit test class from Spring that knows how to load a Spring context to run tests against. So, the procedure is: Set Up a Skeletal Camel/Spring Unit Test Add dependencies on Camel-Spring, and the Spring test JAR (which will automatically bring in JUnit 3.8.x) to your POM: <dependency> <artifactId>camel-spring</artifactId> <groupId>org.apache.camel</groupId> <version>1.4.0</version> </dependency> <dependency> <artifactId>spring-test</artifactId> <groupId>org.springframework</groupId> <version>2.5.5</version> <scope>test</scope> </dependency> Create a new unit test class in src/test/java/your-package-here, perhaps called XMLInputTest.java Make the test extend Spring's AbstractJUnit38SpringContextTests class. Create a Spring context configuration file in src/test/resources, perhaps called XMLInputTest-context.xml In the unit test class, use the class-level @ContextConfiguration annotation to indicate that a Spring context should be loaded By default, this looks for a Context configuration file called TestClassName-context.xml in a subdirectory corresponding to the package of the test class. For instance, if your test class was org.apache.camel.tutorial.XMLInputTest, it would look for org/apache/camel/tutorial/XMLInputTest-context.xml To override this default, use the locations attribute on the @ContextConfiguration annotation to provide specific context file locations (starting each path with a / if you don't want it to be relative to the package directory) Add a CamelContext instance variable to the test class, with the @Autowired annotation Put in an empty test method just for the moment Add the Spring <beans> element (including the Camel Namespace) with an empty <camelContext> element to the Spring context, like this: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://activemq.apache.org/camel/schema/spring http://activemq.apache.org/camel/schema/spring/camel-spring-1.3.0.xsd"> <camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring"> </camelContext> </beans> Your test class might look something like this: src/test/java/org/apache/camel/tutorial/[XMLInputTest.java|^empty-XMLInputTest.java] src/test/resources/XMLInputTest-context.xml (same as just above) Test it by running mvn install and make sure there are no build errors. Initial Work on Customer 2 Input (CSV over HTTP) Create a CSV-handling POJO Create a unit test Initial Work on Customer 3 Input (Excel over e-mail) Create an Excel-handling POJO Create a unit test Put this all together into Camel routes for the Customer Input Create a unit test for the Customer Input Routes

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