Loading, Exporting and Deleting Wrappers¶

Usually, wrappers are deployed in the Wrapper Server directly from the wrapper generation tool. However, VQL files containing the definition of a wrapper can also be loaded manually from the Virtual DataPort administration tool. To do so, click on the “Load wrapper” button, then select the file to load by clicking the “Choose File” button and graphically selecting the file. Once the path is ready, click on the “Upload” button. The wrapper will be loaded into the currently selected database, and the wrapper list for that database will be updated in the administration tool.

Wrappers deployed in the Wrapper Server can be exported as VQL files. To do so, the user must select the wrappers he wants to export by marking the check boxes to the left of their respective entries in the wrapper list, and then click on the button . He will then be presented with a window, where he can choose to export some elements whose presence in the generated VQL is optional: the scanners, extension jar files, and custom components used by the wrapper or wrappers being exported. If those dependencies are not exported along with the wrappers themselves, any Wrapper Server which imports the generated VQL file must already have them installed, in order for the wrappers to load correctly.

To delete a wrapper deployed in the Wrapper Server, the user must mark its associated check box in the wrapper list and then click on the button . Multiple wrappers can be deleted simultaneously in this manner.

Marking the topmost check box, the one with the label “All/None”, will select all the wrappers currently visible in the list.

Wrapper Options¶

Wrappers in a Wrapper Server can be put under automatic verification. This means the Verification Server will monitor the execution of those wrappers, and if it detects anomalies in the returned results, it will send an e-mail to a configured address, warning that the source pages may have changed and the wrapper may need to be modified accordingly.

Wrappers under automatic verification display “true” in the Verification column, for the rest of wrappers “false” will be displayed. To enable or disable automatic verification for one or more wrappers, the user have to select the wrappers, marking the check boxes to the left of their respective entries in the wrapper list, and then click on the button . A popup menu will appear, showing the options “Enable verification” and “Disable verification”.

Note that enabling automatic verification is not enough by itself; the user should define rules in the Verification Server specifying what counts as an “anomalous result” that triggers the notification (see section Configuring the Verification Server).

In order to increase the efficiency of the Denodo Browser, components that execute sequences using this browser can be configured, at generation time, to execute a test of the sequence to collect and store optimization information. During the test execution the browser detects what elements of the accessed pages are needed to execute the sequence and stores information to identify them. Then, using that information, subsequent executions of the sequence can only load those elements.

Wrappers using the Denodo Browser optimization information collected at generation time display “true” in the Denodo browser optimization column. To enable or the use of the optimization information for one or more wrappers, the user have to select the wrappers, marking the check boxes to the left of their respective entries in the wrapper list, and then click on the button . A popup menu will appear, showing the options “Enable optimization” and “Disable optimization”.

Note that enabling Denodo Browser optimization is not enough by itself; the user should configure the sequence components to collect the automatic optimization information during the generation of the wrapper.

The information collection process needs to be rerun when the sequence is changed. In some cases, it can also need to be rerun when the pages of the source changes although the navigation sequence is still valid. If the collection process is not rerun in this scenario, the execution of the sequence using the optimization information will fail. If you do not want to regenerate the optimization information and redeploy the wrapper, then you need to configure the wrapper to not use the Denodo Browser optimization, as explained above.

Wrapper Execution¶

The administration tool allows queries to be made against wrappers deployed on a Wrapper Server.

Clicking on the Execution icon for a wrapper in the wrapper list will lead to the wrapper execution page.

Wrapper Execution Page displays the execution page for a wrapper. The check boxes under “Output parameters” allow selecting which output fields of the wrapper are going to be displayed in the result table. Input parameters for the wrapper are supplied using the text fields under “Input parameters”. The “Set as Null” check box allows the user to not provide any value for an optional input parameter (i.e. setting it as null). This check box is disabled for mandatory input parameters. The types of both the input parameters and output fields are shown between parentheses.

Wrapper Execution Page¶

After filling the input values and selecting the output fields, by clicking the “Accept” button the administration tool will start the execution of the query. To achieve this, it will call the Wrapper Server to invoke the query on the selected wrapper, which will be in turn communicated to the appropriate data source. The results, properly structured, will be shown in the execution window result list in an asynchronous way: the individual rows will appear in the results table as soon as they are available.

Before pressing the “Accept” button, the results of the execution can be configured to be stored in a CSV (Comma-Separated Value)-type file, marking the check box “Export results to CSV file”. The “Include headers” check box allows including the names of the output fields as headers in the CSV file. The column separator is also configurable. When the export check box is marked, clicking on the “Accept” button will show a standard download dialog for choosing the desired target folder/file. The file will be created as the execution starts, and new results will be written as they arrive.