Flink-ESB Tutorials

Use case: create "customer-api" application to store/retrieve data in DB over HTTP (part 5)

Short description: Create Flink-ESB application offering 4 HTTP services to read / insert / update / delete customer data in the database.

Customer data is stored in the database in one table, called CUSTOMER.

Part 5: add project variables to make environment specific data configurable

Following Flink-ESB components are introduced in this part of tutorial:

First level components:

Property-Placeholder : a component holding a list of project variables with their defaut values. Every project variable is represented by property name and property value. Any parameter (or part of the parameter) in the application can be replaced by project variable, which makes it configurable.

See also:

Part 1: create new application and develop HTTP GET service reading data from database

Part 2: add a service to insert data into DB using HTTP POST request

Part 3: add a service to update data in DB using HTTP PUT request

Part 4: add a service to delete data in DB using HTTP DELETE request

Step 1: adding "Property-Placeholder" to the application

Go to Flink-ESB Editor. After finishing part 4 of the tutorial you should have an application looking similar to the one on picture below:

You should have a DB connection pool, HTTP server, HTTP connector and eight routes with names "get-customer", "insert-customer", "update-customer", "delete-customer", "http-get-customer", "http-insert-customer", "http-update-customer" and "http-delete-customer".

Click on "Blueprint Elements" palette drawer to expand it, and place a "Property-Placeholder" on editor canvas.

Enter following data on properties window: "Persistent-Id" : customer.api:

Press "Save Changes".

Step 2: replacing environment specific values within "Database Connection" component with project variables

Select "Database Connection" component in Flink-ESB Editor and check its properties. What properties should be made configurable? Database hostname, port, name, username and password are environment specific, and therefore must always be configurable.

Select "Property-Placeholder" component and click "Project Variables" tab in the properties window.

Right click on empty row and select "Add new entry" from the context menu. A new row appears in the table containing default values for property name and property value:

Click on property name and type: db.host, click on property value and type: localhost. This creates a project variable with name "db.host" and default value "localhost".

Right click in the table again to add the second variable. Enter db.port as varable name, and 1521 as variable default value.

Add another variable. Enter db.name as variable name, and testdb as variable default value (adjust it to your DB name).

Add another variable. Enter db.user as variable name, and test as variable default value (adjust it to your DB username).

Add another variable. Enter db.password as variable name, and test as variable default value (adjust it to your DB password).

Select "Database Connection" component in Flink-ESB Editor and modify its properties as on picture below:

Step 3: replacing environment specific values within "HTTP Connector" component with project variables

Select "HTTP Connector" component in Flink-ESB Editor and check its properties. What properties should be made configurable? Hostname and port are environment specific, and therefore must always be configurable. We could also make other parameters ("Min-Threads", "Max-Threads", "Max-Idle-Time" and SSL parameters in "SSL Parameters" tab) configurable. But to make this tutorial short, we will leave them hard coded.

Select "Property-Placeholder" component and add another variable. Enter http.host as variable name, and 0.0.0.0 as variable default value.

Add another variable. Enter http.port as variable name, and 4545 as variable default value (adjust it if needed).

Now the project variables should look like on picture below:

Select "HTTP Connector" component in Flink-ESB Editor and modify its properties as on picture below:

Click "Save Changes".

Step 4: adding "customer.xsd" schema file to the application archive

"Validator" components within "insert-customer" and "update-customer" routes parse incoming messages against schema file:

This schema file is referenced by its absolute path on the local machine. We could replace this path with project variable to make it configurable. But still it has a drawback: we will have to make sure this file exists on every machine, where this application will be installed.

Much better solution would be to include this schema file in application archive, so that we don't need to copy it explicitly on every machine.

Right click on "customer-api" project in "Project Explorer" view and select "New -> Folder". Type xsd as folder name to create a new folder within application. Press "Finish" button to create a new folder.

Open "Windows Explorer" on your Windows PC, go to the folder where "customer.xsd" file is stored, select it and copy it to the buffer. Go to Flink-ESB Editor, select "xsd" folder within "customer-api" application and press Ctrl-V to paste the content of file there.

Select "Validator" component within "insert-customer" route and modify its "Schema-Location" property to jar:/xsd/customer.xsd:

Press "Save Changes". Now select "Validator" component within "update-customer" route and modify its "Schema-Location" property to jar:/xsd/customer.xsd.

Now we have to make sure "xsd" folder is copied to the application archive when the application is build. Double click on "build.properties" file within "customer-api" application in "Project Explorer" view. Find a checkbox beside "xsd" folder in the "Binary Build" panel and select this checkbox:

Save "build.properties" file and then save Flink-ESB project file.

Step 5: testing application

Restart "customer-api" application in Flink-ESB Editor.

Go to the browser and type http://localhost:4545/customer?id=1 as URL. You should get following response:

Now try inserting new data. For this you can use either some browser plugin, or some GUI tool like SoapUI, or some command tool like curl. For curl run this command:

curl -k -i -X POST http://localhost:4545/customer -d '
<customer>
	<name>test</name>
	<city>test</city>
	<zip>11111</zip>
</customer>'

You should get a response as on picture below:

You can also try running update and delete services as on part 3 and part 4 of this tutorial. All services should be working fine.

Now when the application is going to be installed on Flink-ESB runtime environment, you just have to make sure to adjust project variables in file "customer.api.cfg" in "appconf" folder of Flink-ESB runtime instance.

The format of "customer.api.cfg" properties file on the runtime instance could be like the one below:

db.host=localhost
db.port=1521
db.name=testdb
db.user=test
db.password=#!8L4uMEZaOuE=
http.host=0.0.0.0
http.port=4545

You don't need to define all properties there, as for "Property-Placeholder" component in Flink-ESB Editor. You could add just the parameters, whose values you want to adjust:

db.host=192.168.2.105
http.port=8080

In this case all parameters will be used with their default values (as defined in Flink-ESB Editor), just for "db.host" and "http.port" custom values will be used.

See also:

Part 1: create new application and develop HTTP GET service reading data from database

Part 2: add a service to insert data into DB using HTTP POST request

Part 3: add a service to update data in DB using HTTP PUT request

Part 4: add a service to delete data in DB using HTTP DELETE request