Developing an Application Using the Eclipse BIRT Report Engine API

By Jason Weathersby, Tom Bondur, Jane Tatchell	Article Rating:
February 20, 2007 02:45 PM EST	Reads:	58,291

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In turn, you can use the Bookmark object as an argument to the getPageNumber( ) method, which returns the number of the page to which the bookmark links. With this information, you can specify particular pages to render to a formatted report.

Listing 3 shows how to open a report document and navigate its table of contents to find a page. If the engine cannot open the specified report design, the code shuts down the engine. The variable, engine, is a ReportEngine object.

Accessing a Report Parameter Programmatically
A report parameter is a report element that provides input to a report design before the application generates the report. Report parameters have attributes that a reporting application can access. The most commonly used attributes are name and value. The report engine uses the report design logic and the report parameter values to perform tasks such as filtering a data set or displaying an external value in the report. After the reporting application sets the values for the report parameters, it passes these values to the task that generates the report.

Listing 4 shows how to set the value of a report parameter that has a known name. The sample creates a HashMap object that contains the parameter values to use later to run the report. The variable, engine, is a ReportEngine object. The variable, runnable, is an object of type IReportRunnable.

This sample does not show the details of the code for retrieving the parameter value from a user interface or a database. The code to perform these tasks depends on your application's requirements.

Preparing to Generate the Report
BIRT provides two output formats for reports: HTML and PDF. You can also provide custom output formats by creating a new renderer from the rendering extension points.

Three task classes support generating a report from a source. The tasks that you use to generate a report from the source are:

IRunAndRenderTask: An object of this type creates a report in unpaginated HTML format by running a report design directly. To instantiate this object, call the ReportEngine method, createRunAndRenderTask( ).
IRunTask: An object of this type creates a report document (.rptdocument) file from a report design. To instantiate this object, call the ReportEngine method, createRunTask( ). After creating the report document, create the report with an IRenderTask object.
IRenderTask: An object of this type creates a complete report or a set of pages from a report by formatting the contents of a report document. To instantiate this object, call the ReportEngine method, createRenderTask( ).

Each type of task object can act on multiple sources. When the application no longer needs the task object, call the task's close( ) method.

Before generating a report to either HTML or PDF, the application must set options that determine the features of the output. The options must specify either an output file name or a stream. Other configuration options, such as setting whether to create embeddable HTML, are optional. BIRT supports two types of HTML output: HTML and embeddable HTML. Embeddable HTML is suitable for including inside another Web page. This format contains no header information or an <html> tag.

The application uses a rendering options object to set the output options on an IRunAndRenderTask or an IRenderTask object. The format-specific rendering options classes implement IRenderOption and extend RenderOptionBase. The rendering options class supporting the HTML format is HTMLRenderOption. There are no format-specific options for PDF output. To set options for PDF output, use the RenderOptionBase class.

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Listing 5 shows how to use rendering options on an IRunAndRenderTask object to set report parameter values, the output format of the report, and the output file name. The variable, engine, is a ReportEngine object. The variable, runnable, is an object of type IReportRunnable. The variable, name, is the name of the report design.

Accessing a Data Source
Ensure that the report engine can locate the classes that connect to the data source and supply data to the data set. The report engine can either create a connection to the data source or use a Connection object that the application provides.

In many application server environments, Web applications have access to a pool of Connection objects. In order to use an external connection from such a pool for the data source in a report design, you must pass information to the data driver plug-in that the report design uses. Pass the information in the rendering context HashMap object. For example, the code in Listing 6 sets up the connection to a custom driver, mydatapluginname. The variable task is an IRunAndRenderTask object or an IRunTask object.

The standard data drivers in BIRT do not support using an external connection. You must extend the drivers to perform this task.

Generating the Formatted Output Programmatically
To generate a report, the application must call the run( ) method on an IRunAndRenderTask or an IRunTask object. The application must handle the EngineException that run( ) can throw.

After generating the report, the application can re-use the report engine to generate further reports. If your application generates only a single report, shut down the engine after performing the report generation.

The code in Listing 7 generates a report and shuts down the report engine. The variable, engine, is a ReportEngine object. The variable, task, is an IRunAndRenderTask or an IRunTask object. The variable, name, is the name of the report design. The variable, output, is the name of the output file.

When you generate a report document as a file on disk, you can access the report in the same way as any other file. For example, open HTML documents in a Web browser and PDF documents using Adobe Reader. If you send the report to a stream, the stream must be able to process the information. Shut down the report engine if the application does not need to generate more reports.

About the Book
This article is an excerpt from the book, Integrating and Extending BIRT, by Jason Weathersby, Don French, Tom Bondur, Jane Tatchell, and Iana Chatalbasheva, recently published by Addison-Wesley. The book is the second volume in a two-book series about Eclipse Business Intelligence and Reporting Technology. The book introduces programmers to BIRT architecture and the reporting framework. It shows programmers how to build and deploy customized reports using scripting and BIRT APIs. It also describes how to use key extension points to create a customized report item, a rendering extension for generating output other than HTML or PDF, and an Open Data Access (ODA) driver for a new data source.

Integrating and Extending BIRT, Copyright 2007 Actuate; ISBN 0321443853.
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