Pentaho 8 Reporting for Java Developers

Pentaho Reporting can be defined as a suite of open source tools and can be described as being composed of the following: 

In this book, we will look at the Report Designer and the Reporting SDK in detail, assuming they are the right tools for developers and report designers, to use the Reporting Engine in real life use cases.

Pentaho Reporting is designed and developed to make life easier for report designers, with less limitations on flexibility and the ability to develop sophisticated and rich reports. For this reason, the Report Designer can be used by developers (not necessarily Java developers) but also by information technologists with a basic knowledge of databases and technical concepts.

For advanced development, especially using the Reporting SDK, technical skills on Java development are required, and you must be familiar with importing JARs into a project and be comfortable reading inline comments in code, to figure out advanced functionality on your own.

If you are an information technologist with a basic knowledge of databases and technical concepts, the chapters dedicated to the Report Designer and how to use reports in Pentaho Data Integration and Pentaho Business Analytics Platform, are the topics you might be interested in. If you are a Java developer, the chapters about the Reporting SDK could also be interesting to you.

Pentaho Reporting offers the following unique functionalities, not found in competing embeddable solutions:

One very attractive feature of Pentaho Reporting is its license. Pentaho Reporting is available for free under the GNU LGPL. This license, as shown in the following screenshot, allows other open source and proprietary projects to embed Pentaho Reporting without fear of large license fees or viral open source limitations. As an open source project, developers also have unprecedented access to the engine and to a large group of software developers within the Pentaho Reporting community. This community includes open discussion forums and Internet Relay Chat (IRC), along with commercial support and licensing, if required.

One of the most commonly used forms of reporting is operational reporting. When a developer or an IT organization decides to generate reports directly from their operational data sources for the purpose of detailed transaction level reporting, it is referred to as operational reporting. In this scenario, the database is designed to solve an operational problem, and usually contains live data supporting critical business functions. Users of Pentaho Reporting can point directly to this data source and start generating reports.

Some examples of operational reporting include building custom reports directly based on a third-party software vendor's database schema. These reports might include summaries of daily activity, or detailed views into a particular project or users in the system. Reports might also be generated from data originating from an in-house custom application. These reports are typically based on an SQL backend, but could be generated from flat log files or directly from in-memory Java objects.

Pentaho Reporting's parameterization capabilities provide a powerful mechanism to render up-to-the-minute customized operational reports. With features such as cross tabs and interactive reporting, business users can quickly view their operational data and drill back into operational systems that might require attention.

However, there are limitations when developing reports based on live operational data. Developers need to be careful to make sure that queries in the operational system do not impact the performance of regular operations. An extreme CPU-intensive query could delay a transaction from taking place. Also, certain historical questions, for example, state transitions or changes to particular informational fields such as address, aren't traditionally captured in an operational schema design.

When you've reached the limits of operational reporting, the next logical step is to move your data into a data warehouse. This move is often referred to as business intelligence reporting. Reporting alone does not provide the necessary tools to make this transition. You will need an Extract, Transform, Load (ETL) tool, such as Pentaho Data Integration, along with a sensible warehouse design, such as a snowflake schema.

This type of use allows business users to monitor changes over time. It also helps gain performance benefits by pre-calculating aggregations and defining schemas that are built in mind for summarized reporting. Until recently, data warehousing and business intelligence had been limited to large enterprises due to the cost of software and limited expertise. With open source tools becoming more widely available, a large number of small and medium size businesses are deploying data warehouses in order to get solutions for the critical questions in their business domain. Common examples of data warehouse reporting include combining sales and inventory data into a single location for reporting, or combining internal proprietary sales data with publicly available market trends and analysis.

Pentaho Reporting's flexible data source support makes it easy to incorporate reports in your business intelligence solutions. Also, with Pentaho Reporting's speed and scalability, you can deploy Pentaho Reporting with the confidence that reports will be executed efficiently.

As with all approaches, there are limitations to this approach. In traditional warehousing, data is usually batched nightly, weekly, or monthly. Therefore, business users rarely get to see up-to-the-minute reports on business operations. Also, when designing a warehouse, it is important to ask the correct business questions. Unfortunately, it is possible to build a data warehouse and still not address the business users' needs, if not investigated ahead of time.

The financial reporting is a very specific, but very common, form of reporting, geared towards generating financial summaries for accountants, managers, and business investors. Standard reports that fall into this category include balance sheets, income statements, retained earning statements, and cash flow statements. Unlike business intelligence or operational reporting, many of these reports are required by law, with regulations around their content and presentation. Financial reports often include computations for assets, liabilities, revenues, and expenses.

Following is a screenshot showing one such report:

With features such as group summary aggregations, Pentaho Reporting makes it very easy for developers to implement custom financial reports that business managers and owners require.

Typically, this type of data exists in a controlled form, be it in a proprietary system such as QuickBooks or SAP, or in a secure database system such as Oracle or MySQL. Due to the sensitivity of this data, developers need to be conscious of who has access to the reports and may want to implement features such as audit logging.

Another typical use of Pentaho Reporting includes production reporting. This type of reporting includes reports such as customized form letter, invoice, or postcard for a large audience, as well as automated mail merging. Normally, batch processing is involved in this form of reporting. However, custom reports based on a standard template, generated for individuals, can also fall under this category. 

The following is a screenshot that presents such a report:

There are certain specific features in Pentaho Reporting, such as dynamically incorporating images from a data source, as well as pixel accurate formatting, which can be of real help when implementing production reporting.

The reporting algorithm is at the heart of Pentaho Reporting. This algorithm manages the layout and rendering of the entire report, no matter which output format is being rendered. This algorithm combines a reporting template and a dataset on the fly, in order to generate the final report. There is no unnecessary compilation step. All other Pentaho Reporting features can be described in the context of the overall reporting algorithm.

This algorithm allows reports to render with a page header and footer, a report header and footer, group headers and footers, as well as a details band. The reporting algorithm traverses the dataset multiple times to render the report. In the first pass, the algorithm performs calculations and determines how to separate the data into groups, along with calculating the height and width of text and images. After the initial pass, the algorithm traverses the dataset a second time, in order to render the output.

Pentaho Reporting defines a standard Java API for accessing data. Many data source implementations are made available with Pentaho Reporting. The most commonly used implementations include JDBC and JNDI database connectivity, XML XPATH capability, and multidimensional OLAP data access using MDX and MongoDB NoSQL database support.

Additional data sources that are available include a Pentaho Data Integration data source, a Hibernate Query Language (HQL) data source, a Pentaho Metadata data source, a scripting data source (in JavaScript, Python, TCL, Groovy, and BeanShell), a simple table defined as a static list of rows and columns, and other advanced data sources (OpenERP data access, community data access, and sequence generator).

Using Pentaho's Data Integration data source, it is easy to use Excel, logs, or other file formats as inputs to a report, without the need to write any code. All these data sources interact with the Reporting Engine through a standard API, which is easy to extend.

The following screenshot shows the available data sources in Pentaho Reporting:

By combining Pentaho Reporting's data source functionality with Pentaho's Data Integration Engine, most known data formats and systems are available for input. This includes combining data sources into a single report. An example might include a Microsoft Excel file on a remote shared drive, with a plain text log file from an HTTP server.

Pentaho Reporting has the ability to render to the most widely used output formats, including Adobe's PDF standard using the iText library, Microsoft's Excel standard using the POI library, and HTML, all highlighted in the following screenshot. Other available formats include XML, plain text, RTF, and CSV. In addition to these output formats, a Pentaho report can be rendered in Swing and directly printed using PostScript formatting, allowing print previewing capabilities.

The following is a screenshot showing one such report obtained using Report Designer and rendered in PDF (top left), Microsoft Excel (top right), HTML (bottom left), and CSV (bottom right):

Reports defined in Pentaho Reporting can specify at the pixel level where objects such as text or images should render. Using Pentaho Report Designer, it is easy to align fields and group items that need to stay aligned. While not always possible due to different format types, such as XML, CSV, and plain text, the three main graphical outputs, HTML, PDF, and Excel, strive to look as similar as possible.

Rich formatting includes the TrueType system font selection, the ability to render geometrical shapes and lines, along with the ability to include images and other objects in a report. This rich formatting is specified under the covers through styles similar to CSS, separating out the format from the report detail. This makes it easier to modify and maintain reports, and also to apply corporate styles through the report wizard, as shown in the following image:

The Pentaho Reporting Engine and suite of tools make it easy to embed charts in reports, originally developed using the JFreeChart Engine. Many chart types are available, including bar, histogram, pie, and line charts, as shown in the following diagram:

Pentaho Reporting provides easy-to-use tools to parameterize a report, allowing users to specify ranges and other values to customize the output of a report. Parameter values can be selected from a list of hardcoded values or driven from a query. With parameterization, end users may control the amount of information that is displayed on a report. The following screenshot is an example of parameter input from within Pentaho's business intelligence server:

Report builders may define custom formulas and style expressions, using the OpenFormula standard, allowing for calculated values and dynamic formatting in their reports, such as aggregations, number formatting, as well as traffic lighting.

Pentaho Reporting allows report developers to include subreports within a master report. This provides a powerful capability, which allows reports to contain different smaller reports, both side-by-side and within the various bands of a report. These subreports may be based on different data sources. The following screenshot is an example of a report that includes a separate chart subreport:

Cross tab reports present data in a spreadsheet-like format, making it easy to view summaries of data. Cross tab reports present both row and column headers, as well as cells of data, all of which can be customized through report elements. The following image shows how a cross tab report looks:

While most reports are static after being rendered, a subset of reporting includes functionalities such as drill through, pivoting, and other interactivity. Pentaho Reporting provides a straightforward Java and JavaScript API for manipulating a report after it has been rendered, allowing report builders to create very interactive reports. Pentaho Reporting's interactive functionality is available when rendering a report in HTML, Excel, or Swing. Links to external documents can also be added to PDF documents.

The following screenshot shows a report with links, that when clicked, collapses/expands the row in detail:

While it is possible to build Pentaho reports using either XML or a Java API, most reports begin as templates built by the Pentaho Report Designer. Pentaho Report Designer is a What You See Is What You Get (WYSIWYG) report editor that exposes the rich set of features provided by the Pentaho Reporting Engine. In addition to building a report from scratch, the Report Design Wizard, included as a part of the Pentaho Report Designer, walks a report author through building a report, which will then be displayed in the Report Designer, as shown in the following screenshot, for further customization:

As part of the Pentaho suite, reports created by Pentaho Reporting may be published, executed, and scheduled on Pentaho's Analytics Platform. The Pentaho Analytics Platform offers authentication and authorization, as well as a central repository, to manage your business reports. The Pentaho Analytics Platform also hosts the web-based ad hoc reporting user interface for creating Pentaho Metadata-based reports. By combining the use of Pentaho Report Designer and Pentaho Analytics Platform, there is no need to write any code to get your business up and running with Pentaho Reporting.

Pentaho Reporting comes with a well-documented Java API for building reports from the ground up, so developers can stick with the Java programming language when customizing existing report templates or building reports from scratch. This Java API allows the developers to create and modify the various sections of a report, including the various header, footer, group, and detail bands, along with creating and modifying objects within each section of a report.

Pentaho Reporting is designed from the ground up in pure Java, exposing many interfaces for extension. From implementing basic formulas and functions that can be embedded in reports, to writing a custom data source or output format, Pentaho Reporting's source code and API interfaces are well documented and easy to work with.

In addition to these features, Pentaho Reporting is in active development. Visit http://community.pentaho.com/projects/reporting/ to learn more about what additional features and functionalities are being considered for development, or to access early release versions of the product.

The Pentaho Reporting Engine uses the following libraries to render reports:

The Reporting Engine core project contains the main reporting algorithm for rendering reports, along with the necessary functionality to support styling. This project also contains the algorithms for rendering specific outputs, including PDF, Excel, CSV, XML, and more. The engine relies on the already mentioned libraries for managing the loading, parsing, formatting, rendering, and archiving of generated reports.

The Reporting Engine extensions project contains third-party extensions to the Reporting Engine, which are very useful, but increase dependencies. Extensions in this project include JavaScript expression support using the Rhino project, a hibernate data source factory, bar code support using Barbecue, sparkline support using the LibSparkline, along with additional JDK 1.4 support for configuration and printing. Additional extension projects exist that include charting and many of the data sources discussed in this book.