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Here's what we'll try to accomplish in this tutorial:

1. Create a Maven build for the project
2. Get sample files for the customer Excel, CSV, and XML input
3. Get a sample file for the canonical XML format that Acme's accounting system uses
4. Create an XSD for the canonical XML format
5. Create JAXB POJOs corresponding to the canonical XSD
6. Create an XSLT stylesheet to convert the Customer 1 (XML over FTP) messages to the canonical format
7. Create a unit test to ensure that a simple Camel route invoking the XSLT stylesheet works
8. 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)
9. Create a unit test to ensure that a simple Camel route invoking the CSV processing works
10. Create a POJO that converts a Customer 3 Excel file to the above JAXB POJOs (using POI to read Excel)
11. Create a unit test to ensure that a simple Camel route invoking the Excel processing works
12. 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
13. Build a set of Camel routes to handle the entire input (Customer -> Acme) side of the scenario.
14. Build unit tests for the Camel input.
15. 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):

<?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>trading-partners</artifactId>
    <version>1.0</version>
    <name>Camel Trading 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:

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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 items-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

Now we need to 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.