Echo adapter
Let's start with a
brief discussion of the functionality provided by the Echo adapter. Like
its big brothers from the BizTalk Adapter Pack 2010, the Echo adapter
supports two message exchange patterns.
Inbound: In the
inbound scenario, the Echo adapter, being a part of the receive port
infrastructure, monitors a specified file folder for new files with TXT
extension; once a new file arrives, the adapter sends a notification to
the BizTalk application. The notification takes the form of an XML
message conforming to the following XSD schema:
The path element contains the name of the folder being monitored for new files; the content
element, as its name suggests, holds the content of a new file. If you
wish to map this operation to the functionality provided by the real
world adapters from BizTalk Adapters Pack 2010, it resembles the
notification operations supported by the SQL adapter. When configured
for notification, the adapter notifies the client application that there
are data in the database meeting the specified criteria.
Outbound: In the
outbound scenario, being a part of the send port infrastructure, the
adapter echoes (or repeats) an incoming string a specified number of
times then sends the response back to a caller. The XSD schema for
request and response messages are shown in the following image:
To make its operations fully configurable, the Echo adapter exposes two binding properties:
Since the Echo adapter is not
automatically installed with the WCF LOB Adapter SDK, we will have to
take care of it. The installation is straightforward and unlikely to
cause difficulties.
Here are the steps:
Navigate to C:\LOBIntegration\Exam01\EchoAdapter\Setup32 directory and get familiar with the readme.doc file. Launch setup.exe and follow the setup wizard. Accept the default values for all screens. If you are working in a 64-bit environment, now navigate to C:\LOBIntegration\Exam01\EchoAdapter\Setup64 and repeat the procedure.
Now that you have
installed the Echo adapter, we can proceed with building the BizTalk
application consuming the Echo adapter. For your convenience, we
provided a complete and ready to deploy application identical to what we
are going to build. The application is located in the C:\LOBIntegration\Exam01\Walkthrough directory; you can use it as a reference to be sure that you are on the right track building your own application.
Building the BizTalk application
Our BizTalk application will
consist of a single orchestration acting in a pretty much "pass-through"
mode. The orchestration will receive an inbound OnReceiveEcho message from the Echo adapter, construct an outbound EchoString message by mapping the content element of the inbound message to the aName
element of the outbound message, and then submit it to the adapter for
echoing. The response will be received by the orchestration and written
to the Application Event Log. When we complete the walkthrough, the orchestration will resemble the following image:
Here is the process to follow:
To get started, verify that the c:\temp folder exists on your computer. If not, please create it. If you recall, the adapter exposes the FileSystemWatcherFolder property to specify the folder to monitor for the files with *.txt extension. We will use the default value which is c:\temp.
Open
Visual Studio and create a new BizTalk project with the settings shown
in the following image. For the location, you can specify a folder of
your choice.
Now,
the most important part. We need to generate the schemas representing
the operations exposed by the adapter that you intend to use with the
current application. The tool of choice for the task is the Consume Adapter Service plug-in,
a metadata browser and artifacts generation tool, which you installed
recently as a part of the ASDK. Besides XSD schemas, this plugin also
generates a physical port binding file. This means that you can
configure the port automatically by importing the binding file using the
BizTalk Administration Console. The binding file typically contains
physical port configuration settings including the connection string to
the target LOB and the port SOAP actions based on the operations for
which metadata were generated.
Once the binding is set, click the Configure button to bring up the Configure Adapter dialog to configure the connection string and set credentials, URI, and binding properties.
The first step
to generating the artifacts is establishing a connection to the target
system. Most LOB systems require valid client credentials as part of the
connection procedure and our Echo system is not an exception, though it
is quite forgiving—after selecting Username for the Client credential type drop down, you can type in anything you like for the User name and Password, but please don't leave them blank.
Further, besides
valid credentials, in order to establish a connection we have to provide
additional parameters such as host name, port number, and other LOB
application specific parameters—this is what the URI Properties
tab is for. Switch to this tab and note the properties presented there.
As with the user name and password, you can type in anything you like
or accept the defaults.
While
the Echo Adapter requires only three elements to build the connection
URI, the real-world adapters from the BizTalk Adapters Pack 2010 require
more details in order to connect to their LOB systems. For comparison,
the following image shows the properties required to establish a
connection to SAP:
Finally, we need to configure the bindings exposed by the adapter by setting the properties presented on the Binding Properties tab. For our scenario, we can accept the default values for all properties.
Now, click OK to close the Configure Adapter dialog and return to the Consume Adapter Service window. Note that the Configure a URI text box now contains a configured connection string, which is built from the URI properties tab values.
Provided the connection string we've built is correct, clicking the Connect
button establishes an active connection to the Echo system. If the
connection is accepted, we will see the category tree populated with
outbound categories—the outbound contract type is what the Consume
Adapter Service plugin chooses by default.
Next, we need to select
the operations that we want to use in our application and add them to
the list of desired operations. In the Select a category tree click the Echo Category node, then in the Available categories and operations panel, select EchoString and click the Add button. This action adds EchoString to the list of desired operations at the bottom of the screen. The last step is to help the Consume Adapter Service add-in to generate descriptive file names by setting the file name prefix at the bottom of the screen to EchoOutbound.
Finally, click OK to close the Consume Adapter Service Wizard
window and return to Visual Studio, where we see two new files added to
our BizTalk project. One file is the XSD schema for the EchoString
operation, the other is an XML binding file. After deploying the
application, you will import this file using the BizTalk Admin Console to create a physical WCF-Custom send port configured to perform the EchoString operation.
Unfortunately, one of the inconveniences we have to deal with is that the Consume Adapter Service add-in
doesn't allow generating artifacts for different contract types in one
run. To generate the schema and binding file for the inbound operation,
we need to open the Consume Adapter Service add-in again and repeat the
procedure. On the Security tab, specify the username and password, for
the properties on the URI Properties and Binding Properties tabs, you
can accept the default values.
Then, once you've established a successful connection, select Service in the Select contract type drop down, click EchoCategory in the Select a category panel, and add OnReceiveEcho to the list of desired operations. Set the Filename Prefix at the bottom of the screen to EchoInbound.
Technically speaking,
at this point, we have all bits and pieces required to build our BizTalk
application. Before we proceed, let's make a few cosmetic changes. First, rename the WcfSendPort_EchoAdapterBinding_Custom.bindinginfo.xml to SendPort.Bindinginfo.xml. Similarly, rename the WcfReceivePort_EchoAdapterBinding_Custom.bindinginfo.xml to ReceivePort.Bindinginfo.xml. Next, we need to give more descriptive names for the receive port and receive location. Open the ReceivePort.bindinginfo.xml file, and change the ReceivePort and ReceiveLocation Name attributes as follows:
Now that we have prepared all the artifacts, we can proceed and build our sample application. Add a BizTalk orchestration to the project and name it ProcessEcho.
Switch to the OrchestrationView and create three orchestration messages with the following values:
Identifier: msgReceiveNotification, Message Type: Walkthrough.EchoInbound
Identifier: msgEchoStringRequest, Type: Walkthrough.EchoOutbound.EchoString
Identifier: msgEchoStringResponse, Type: Walkthrough.EchoOutbound.EchoStringResponse
To construct the outbound message, add a map to the project and name it.
8. Inbound_To_Outbound.
Specify OnReceiveEcho as the source message type, for the destination schema, specify EchoOutbound, and select EchoString as the root node. Once the source and destination schemas are set, connect the content and aName elements.
Next,
we need to sketch the orchestration flow. From the toolbox, drag on the
orchestration surface the shapes in the order and with the properties
as follows: Shape: Receive, Name: ReceiveNotification, Activate: True, Message: msgReceiveNotification
Shape: Construct, Name: ConstructEchoOutbound, Message Constructed: msgEchoStringRequest. Inside the Construct drag the Transform shape and configure it with the following values: Name: Transform, Input Messages: msgReceiveNotification, Map Name: Inbound_To_Outbound, Output Messages: msgEchoStringRequest
Shape: Send, Name: SendEchoString, Message: msgEchoStringRequest
Shape: Receive, Name: ReceiveEchoResponse, Message: msgEchoStringResponse
Shape: Expression, Name: WriteToLog
Configure the WriteToLog expression shape to execute the following code:
To
enable the orchestration for receiving and sending messages, we need to
add two logical orchestration ports. The first port will be a one-way
port for receiving an initial inbound message; the second will be a
Request-Response port for sending an outbound message to the adapter for
processing and receiving a response. Right-click on the Port Surface and select New Configured Port to start the Port Configuration Wizard. Here are the settings for the first one-way port.
Name: ReceiveInitialEcho
Port Type: Create New Port, Port Type Name: InitialEchoType, Communication Pattern: One-Way, Access Restriction: Internal
Port Direction of Communication: I will always be receiving messages on this port, Port Binding: Specify later
Run the Wizard one more time to create a logical port for the outbound operation. Name: SendEchoString
Port Type: Create New Port, Port Type Name: SendEchoStringType, Communication Pattern: Request-Response, Access Restriction: Internal
Port Direction of Communication: I will always be sending request, and receiving response on this port, Port Binding: Specify later
Join the logical ports with the relevant shapes. Connect Request of the ReceiveNotification receive port with the ReceiveNotification shape. For the SendEchoString send port, connect Request with the SendEchoString shape, and Response with the ReceiveEchoResponse shape. When you finish, the orchestration should match the following image:
Build the application and address error messages, if any. The
last thing to do before we deploy the application is specify a strong
name key for the application assembly, and provide the name for the
BizTalk application. In the Solution Explorer, right-click on the project name and select Properties. From the Project Properties window, switch to the Signing
tab to specify a strong name key file. You can either generate a new,
or use any existing key file from your computer. Then, activate the Deployment tab and type Exam01_Walkthrough for the application name.
Almost there; we are finally at the deployment stage. Go to the BizTalk Admin Console and create a new application named Exam01_Walkthrough.
You have to create the application first; otherwise Visual Studio will
deploy the solution in the default application in the group. In the Solution Explorer, right-click on the solution name, select Deploy, and wait for the message confirming that the deployment succeeded.
To
complete the deployment, we need to create the application physical
ports. This is where the binding files, generated for us by the Consume
Adapter Service plugin, come into play. Open the BizTalk Administration
Console, expand the Applications node, right-click Exam01_Walkthrough, and select Import|Bindings.
Navigate to the solution directory and import the binding file for the
receive port. Then, repeat the procedure to import the bindings for the
send port. Disregard a pop-up message informing you of the application
name not matching and click Yes.
For security reasons, the Consume Adapter Service
addin doesn't include the usernames and passwords when generating
binding files. For the physical ports, we have to set them manually
using the WCF-Custom Transport Properties window. Let's start with the send port. In BizTalk Administration Console, double-click the SendEchoString port, then click Configure, switch to the Credentials tab, and type in any username and password.
Specify the username and password for the receive location. In the BizTalk Admin Console, double-click the EchoWcfCustom_ReceiveNotification receive location and then click Configure to open the WCF-Custom Transport Properties window. As you can see, for the receive location, this window has a slightly different look. There is no Credentials tab; instead, you have to switch to the Other tab and specify the username and password there.
The last step before we start the application is to bind the orchestration. In the BizTalk Administration Console, double click ProcessEcho orchestration to open the Orchestration Properties window. Activate the Bindings tab and set the properties as shown in the following image:
Click OK to close the Orchestration Properties window and then start the application.
If we submit a file to the c:\temp folder monitored by the adapter, we will get the following error message:
The adapter failed to transmit message going to send port "SendEchoString" with URL " echo://host/temp?EchoPrefix=pre ".
It will be retransmitted after the retry interval specified for this Send Port.
Details:"Microsoft.ServiceModel.Channels.Common.UnsupportedOperationException: Incorrect Action
<BtsActionMapping xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Operation Name="EchoString" Action="Echo/EchoString" />
</BtsActionMapping>. Correct the specified Action, or refer to the documentation on the allowed formats for the Actions. Note that Actions are case-sensitive.
The problem is exactly what
the error message is telling us—the SOAP action settings applied to the
send port are not understood by the adapter. One of the most often asked
questions on the MSDN forums is "I imported bindings with the SOAP
action settings as generated by the Consume Adapter Service plug-in, so
why are they nor understood by the adapter?". We will demystify the
subject and shed some light on how the WCF-custom adapter processes the
actions shortly, right after we finish the walkthrough. For now, to fix
the problem and complete the application, go to the BizTalk Admin
Console and do the following:
Double-click the SendEchoString send port. In the Send Port Properties windows click Configure to open the WCF-Custom Transport Properties window.
In the Action text box of the SOAP Action Header section, note the value of the Name attribute, which is EchoString. What you have to do is to make your orchestration logical send port name match the value of the Name attribute. The first option is to change the logical port name from Operation_1 to EchoString and then, of course, to re-deploy the application.
An alternative option, if you don't want to redeploy the application, is to set the Name attribute value to Operation_1, so that the content of the Action box looks as follows:
Although
from a pure technical standpoint this is a perfectly valid solution,
using such non-descriptive names is a questionable practice and should
be avoided. We presented it here with the only purpose being to
illustrate the concept. The best approach is not to leave the operation
name with the default value Operation_1, but to give it a descriptive name upon designing the orchestration and then adjust the physical port action mapping. So,
let's do it right and just change the logical port operation name to
EchoString. Once done, re-deploy the application. Now, you can create a
file containing a single word "Echo", drop it to the C:\temp folder, and
watch the event log for the echoed messages returned by the Echo
adapter. Please don't forget, the file must have a TXT extension.
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