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Enable the REST JDBC Driver in KNIME

Use standard data access components in KNIME to create charts and reports with REST data.

One of the strengths of the CData JDBC Driver for REST is its cross-platform support, enabling integration with major BI tools. Follow the procedure below to access REST data in KNIME and to create a chart from REST data using the report designer.

Define a New JDBC Connection to REST Data

  1. Install the Report Designer extension: Click File -> Install KNIME Extensions, and filter on "Report".
  2. In a new workflow, click File -> Preferences and expand the KNIME -> Databases node to add cdata.jdbc.rest.jar. The driver JAR is located in the lib subfolder of the installation directory.
  3. In the Node Repository view, expand the Database -> Read/Write node and drag a Database Reader onto the workflow editor.
  4. Double-click the Database Reader and set the following properties:

    • Database Driver: In the menu, select the driver name, cdata.jdbc.rest.RESTDriver
    • Database URL: Enter the connection properties. The JDBC URL begins with jdbc:rest: and is followed by a semicolon-separated list of connection properties.

      See the Getting Started chapter in the data provider documentation to authenticate to your data source: The data provider models REST APIs as bidirectional database tables and XML/JSON files as read-only views (local files, files stored on popular cloud services, and FTP servers). The major authentication schemes are supported, including HTTP Basic, Digest, NTLM, OAuth, and FTP. See the Getting Started chapter in the data provider documentation for authentication guides.

      After setting the URI and providing any authentication values, set Format to "XML" or "JSON" and set DataModel to more closely match the data representation to the structure of your data.

      The DataModel property is the controlling property over how your data is represented into tables and toggles the following basic configurations.

      • Document (default): Model a top-level, document view of your REST data. The data provider returns nested elements as aggregates of data.
      • FlattenedDocuments: Implicitly join nested documents and their parents into a single table.
      • Relational: Return individual, related tables from hierarchical data. The tables contain a primary key and a foreign key that links to the parent document.

      See the Modeling REST Data chapter for more information on configuring the relational representation. You will also find the sample data used in the following examples. The data includes entries for people, the cars they own, and various maintenance services performed on those cars.

      Built-in Connection String Designer

      For assistance in constructing the JDBC URL, use the connection string designer built into the REST JDBC Driver. Either double-click the JAR file or execute the jar file from the command-line.

      java -jar cdata.jdbc.rest.jar

      Fill in the connection properties and copy the connection string to the clipboard.

      When you configure the JDBC URL, you may also want to set the Max Rows connection property. This will limit the number of rows returned, which is especially helpful for improving performance when designing reports and visualizations.

      A typical JDBC URL is below.

      jdbc:rest:DataModel=Relational;URI=C:\people.xml;Format=XML;
    • User Name: The username used to authenticate.
    • Password: The password used to authenticate.
    • SQL Statement: Enter an SQL query in the SQL Statement box or double-click a table. This article uses the query below to create a chart: SELECT [people].[personal.age] AS age, [people].[personal.gender] AS gender, [people].[personal.name.first] AS first_name, [people].[personal.name.last] AS last_name, [vehicles].[model], FROM [people] JOIN [vehicles] ON [people].[_id] = [vehicles].[people_id]
  5. Test the connection by clicking Fetch Metadata.

  6. Connect the Database Reader to a Data to Report node to supply the dataset to a range of data visualization controls. Click Execute and then click Edit Report at the top of the workflow to open the report designer perspective.
  7. You can now generate reports based on live data. To create a chart, drag the chart control from the palette to the report designer. In the resulting wizard, you can use the filtering and aggregation controls available in KNIME.

Troubleshooting

The following list shows how to resolve common errors:

  • Encountered duplicate row Id "Row1": To resolve this error, add the following to the knime.ini file located in your KNIME installation directory:-Dknime.database.fetchsize=0