Exposing Cassandra as a Data Service

This tutorial will guide you on how to expose data stored in Cassandra as a data service. Also, see the samples in Data Integration Samples.

Prerequisites

Set up the Cassandra server with a keyspace and table for this tutorial:

Installing and starting Cassandra

A Cassandra server of version 3.0 should be already running in the default port. For instructions, go to Apache Cassandra Documentation.

Creating a keyspace and a table

Execute the SQL commands as given below.

• Create the keyspace named UsersKS:

  CREATE KEYSPACE UsersKS WITH replication = {'class':'SimpleStrategy', 'replication_factor':3};

• Create the table named Users in the UsersKS keyspace:

  CREATE TABLE UsersKS.Users (id uuid, name text, country text, age int, PRIMARY KEY (id));

Creating a data service

Now, let's start creating the data service from scratch:

1. Log in to the management console of ESB profile of WSO2 EI using the following URL on your browser:  "https://localhost:9443/carbon/".

2. Click Create under the Data Service menu to open the Create Data Service window.

3. Enter the following data service name.

4. Leave the default values for the other fields.

5. Click Next to go to the Datasources screen

Connecting to the datasource

1. Click Add New Datasource. and enter the following details:

   The rest of the datasource properties are optional. See the descriptions given below.

Creating a query to ADD user information

Now let's write a query for adding user information to the Users table of the UsersKS keyspace in your Cassandra server.

1. Click Add New Query and enter the following details:

2. Click Generate Input Mapping to create the input mappings.

   Open

   

3. Edit the id column and change the SQL Type to UUID.

4. Save the mapping.

5. Edit the age column and change the SQL Type to INTEGER.

6. Save the mapping and click Main Configuration to return to the query. You will now have the following input mappings:
   

7. Save the query.

Creating a query to GET data

Now let's start writing a query for getting data from the datasource. The query will specify the data that should be fetched by this query, and the format that should be used to display data when the query is invoked.

1. Click Add New Query and enter the following details:

2. Click Generate Input Mapping to create the input mapping. The id is the input as shown below.

   Open

   

3. Edit the id column and change the SQL Type to UUID.

4. Save the mapping and click Main Configuration to return to the query.

5. Click Generate Response to create the output mapping. This defines how the employee details retrieved from the datasource will be presented in the result. Note that, by default, the output type is XML. 

   Open

   

6. Save the query.

7. Click Next to open the Operations screen.

Creating SOAP operationa to invoke the queries

1. Click Add New Operation and enter the following information.

2. Save the operation.

3. Click Add New Operation and enter the following information.

4. Save the operation.

You can now invoke the data service query using SOAP.

Creating a REST resource to invoke the query

Now, let's create REST resources to invoke the query created above. Alternatively, you can create SOAP operations to invoke the queries. See the previous section for instructions.

1. Click Add New Resource and enter the following information.

2. Save the resource.

3. Click Add New Resource and enter the following information.

4. Save the resource.

You can now invoke the data service query using REST.

Finish creating the data service

Once you have defined the operation, click Finish to complete the data service creation process. You will now be taken to the Deployed Services screen, which shows all the data services deployed on the server.

Invoking your data service using SOAP

You can try the data service you created by using the TryIt tool that is in your product by default. 

1. Go to the Deployed Services screen.

2. Click the Try this service link for the Cassandra data service. The TryIt Tool will open with the data service.

Post new data

1. Select the addUsersOp operation you created earlier. 

2. You need to provide the user details. Be sure to enter a UUID value as the user ID.

3. Click Send.