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Chapter 5. Adding a Content-Based Router

This tutorial shows how to add a Content-Based Router (CBR) and logging to a route.

A CBR routes a message to a destination based on its content. In this tutorial, the CBR that you create routes messages to different folders (valid or invalid) based on the value of each message’s quantity field (the number of animals in the order). The maximum value of animals for each order is 10. The CBR routes the messages to different folders, depending on whether the quantity is greater than 10. For example, if a zoo orders five zebras and only three zebras are available, the order is copied to the invalid order target folder.

Goals

In this tutorial you complete the following tasks:

Add a Content-Based Router to your route
Configure the Content-Based Router:
- Add a log endpoint to each output branch of the content-based router
- Add a Set Header EIP after each log endpoint
- Add an Otherwise branch to the content-based router

Prerequisites

To start this tutorial, you need the ZooOrderApp project resulting from one of the following:

Completing the Chapter 4, Running a Route tutorial.
or
Completing the Chapter 2, Setting up your environment tutorial and replacing your project’s blueprint.xml file with the provided blueprintContexts/blueprint1.xml file, as described in the section called “About the resource files”.

Adding and configuring a Content-Based Router

To add and configure a Content-Based Router for your route:

In Project Explorer, double-click ZooOrderApp/src/main/resources/OSGI-INF/blueprint/blueprint.xml to open it in the Editor view.
On the Design canvas, select the To_Received node and then select the trash can icon to delete it.
In the Palette, open the Routing drawer, click a Choice ( ) pattern, and then (in the Design canvas) click the From_from1 node.
The Route_route1 container expands to accommodate the Choice_choice1 node. The error icon indicates that the Choice_choice1 node requires a child node, which you add next.
From the Routing drawer, click the When ( ) pattern and then, in the canvas, click the Choice_choice1 node.
The Choice_choice1 container expands to accommodate the When_when1 node:
The decorating the When_when1 node indicates that one or more required property values must be set.
Note
The tooling prevents you from adding a pattern to an invalid drop point in a Route container.
On the canvas, select the When_when1 node, to open its properties in the Properties view:
Click the button in the Expression field to open the list of available options.
Select xpath (for the XML query language) because the test messages are written in XML.
Note
Once you select the Expression language, the Properties view displays its properties in an indented list directly below the Expression field. The Id property in this indented list sets the ID of the expression. The Id property following the Description field sets the ID of the When node.
In the indented Expression field, type: /order/orderline/quantity/text() > 10
This expression specifies that only messages in which the value of the quantity field is greater than 10 travel this path in the route (to the invalidOrders folder).
Leave each of the remaining properties as they are.
Note
The Trim option (enabled by default) removes any leading or trailing white spaces and line breaks from the message.
Save the routing context file.
Click the Source tab to view the XML for the route:

Adding and configuring logging

For the ZooOrder application example, you add a log message so that you can track an XML message as it passes through the route. When you run the route, the log message appears in the Console view.

Follow these steps to add logging to your CBR route:

In the Design tab’s Palette, open the Components drawer and click the Log component ( ).
In the canvas, click the When_when1 node.
The When_when1 container expands to accommodate the Log_log1 node:
On the canvas, select the Log_log1 node to open its properties in the Properties view.
In the Message field, type: The quantity requested exceeds the maximum allowed - contact customer.

Leave the remaining properties as they are.

Note

The tooling auto-generates a log node id value. In the Fuse Integration perspective’s Messages view, the tooling inserts the contents of the log node’s Id field in the Trace Node Id column for message instances, when tracing is enabled on the route (see the Chapter 8, Tracing a message through a route tutorial). In the Console, it adds the contents of the log node’s Message field to the log data whenever the route runs.

Save the routing context file.

Adding and configuring message headers

A message header contains information to process a message.

To add and configure message headers:

In the Palette, open the Transformation drawer and then click the Set Header ( ) pattern.
In the canvas, click the Log_log1 node.
The When_when1 container expands to accommodate the SetHeader_setHeader1 node:
On the canvas, select the SetHeader_setHeader1 node to open its properties in the Properties view:
Click the button in the Expression field to open the list of available languages, and then select constant.
In the indented Expression field, type Invalid.
In the Header Name field, type Destination.
Leave the remaining properties as they are.
In the Palette, open the Components drawer and then click the File ( ) component.
In the canvas, click the SetHeader_setHeader1 node.
The When_when1 container expands to accommodate the To_to1 node.
On the canvas, select the To_to1 node to open its properties in the Properties view:
On the Details tab, replace directoryName with target/messages/invalidOrders in the Uri field, and type _Invalid in the Id field:
Save the routing context file.
Click the Source tab to view the XML for the route:

Adding and configuring a branch to handle valid orders

So far, the CBR handles messages that contain invalid orders (orders where the quantity value is greater than 10).

To add and configure an otherwise branch of your route to handle valid orders (that is, any XML messages that do not match the XPath expression set for the When_when1 node):

In the Palette, open the Routing drawer and click the Otherwise ( ) pattern.
In the canvas, click the Choice_choice1 container:
The Choice_choice1 container expands to accommodate the Otherwise_otherwise1 node.
On the canvas, select the Otherwise_otherwise1 node to open its properties in the Properties view.
In the Id field, change _otherwise1 to _elseValid:

To configure logging for the otherwise branch:

In the Palette, open the Components drawer and and then click the Log ( ) component.
In the canvas, click the Otherwise_elseValid node:
The Otherwise-elseValid container expands to accommodate the Log_log2 node.
On the canvas, select the Log_log2 node to open its properties in the Properties view.
In the Message field, type This is a valid order - OK to process.
Leave the remaining properties as they are.
Save the route.

To configure a message header for the otherwise branch:

In the Palette, open the Transformation drawer and then click the Set Header pattern.
In the canvas, click the Log_log2 node.
The Otherwise_elseValid container expands to accommodate the SetHeader_setHeader2 node.
Note
You can collapse containers to free up space when the diagram becomes congested. To do so, select the container you want to collapse, and then click its button:
To reopen the container, select it and then click its button:
Collapsing and expanding containers in the Design tab does not affect the routing context file. It remains unchanged.
On the canvas, select the SetHeader_setHeader2 node to open its properties in the Properties view.
Click the button in the Expression field to open the list of available languages, and select constant.
In the indented Expression field, type ReadyForDispatcher.
In the Header Name field, type Destination.
Leave the remaining properties as they are.

To specify the target folder for the valid messages:

In the Palette, open the Components drawer and then select the File ( ) component.
In the canvas, click the SetHeader_setHeader2 node.
The Otherwise_elseValid container expands to accommodate the To_to1 node.
On the canvas, select the To_to1 node to open its properties in the Properties view.
In the URI field, replace directoryName with target/messages/validOrders, and in the Id field, type _Valid.
Save the routing context file.
The completed content-based router should look like this:

Click the Source tab at the bottom, left of the canvas to display the XML for the route.

<?xml version="1.0" encoding="UTF-8"?>
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.osgi.org/xmlns/blueprint/v1.0.0
    https://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd
    http://camel.apache.org/schema/blueprint
    http://camel.apache.org/schema/blueprint/camel-blueprint.xsd">

<camelContext id="_context1" xmlns="http://camel.apache.org/schema/blueprint">
        <route id="_route1">
            <from id="_from1" uri="file:src/data?noop=true"/>
            <choice id="_choice1">
                <when id="_when1">
                    <xpath>/order/orderline/quantity/text() &gt; 10</xpath>
                    <log id="_log1" message="The quantity requested exceeds the maximum allowed - contact customer."/>
                    <setHeader headerName="Destination" id="_setHeader1">
                        <constant>Invalid</constant>
                    </setHeader>
                    <to id="_Invalid" uri="file:target/messages/invalidOrders"/>
                </when>
                <otherwise id="_elseValid">
                    <log id="_log2" message="This is a valid order - OK to process."/>
                    <setHeader headerName="Destination" id="_setHeader2">
                        <constant>ReadyForDispatcher</constant>
                    </setHeader>
                    <to id="_Valid" uri="file:target/messages/validOrders"/>
                </otherwise>
            </choice>
        </route>
    </camelContext>
</blueprint>

Verifying the CBR

You can run the new route as described in the the section called “Running the route” tutorial and look at the Console view to see the log messages.

After you run it, to verify whether the route executed properly, check the target destination folders in the Project Explorer:

Select ZooOrderApp.
Right-click it to open the context menu, and then select Refresh.
Under the project root node (ZooOrderApp), locate the target/messages/ folder and expand it.
Check that the target/messages/invalidOrders folder contains message1.xml and message3.xml.
In these messages, the value of the quantity element exceeds 10.
Check that the target/messages/validOrders folder contains the four message files that contain valid orders:
- message2.xml
- message4.xml
- message5.xml
- message6.xml
  In these messages, the value of the quantity element is less than or equal to 10.
  Note
  To view message content, double-click each message to open it in the route editor’s XML editor.

Next steps

In the next tutorial, Chapter 6, Adding another route to the routing context, you add a second route that further processes valid order messages.