Use JFreeChart to display your Oracle database data (1)

Charts, numbers, and graphs help you quickly understand and analyze large datasets. As the saying goes, "Never heard of anyone", because images can convey important summary and comparison information about data that is difficult to obtain from text data. JFreeChart is a Java-based open-source free) library that allows you to easily create a variety of data-centric high-quality charts. This powerful Library provides a very convenient API that allows developers who are not familiar with JFreeChart to quickly create high-quality charts that represent their data.

In this article, we will use Oracle Database 10GThe HR mode data in quick edition (XE) provides an example of this process.

JFreeChart Introduction

The JFreeChart Project was launched in May 2000. The latest version 1.0.6 of this library was released on July 6, June 2007. This version is used in this article.

JFreeChart supports generating multiple types of charts, common types, such as pie chart, bar chart, Area Chart, line chart, bar chart, and Gantt Chart, are recommended to be professional and infrequently used types such as Candlestick, Wind, and Wafer Map. One of the quickest ways to determine the types of ready-to-use charts supported by JFreeChart is to check the Javadoc API documentation for the ChartFactory class of JFreeChart.

In some development environments, you can use JFreeChart to effectively generate data-oriented charts, including:

◆ The generated file can be in PNG or JPEG format.
◆ Java SE Swing-based applications, including applets
◆ Java EE servlet and JavaServer Page (JSP)
◆ Integrate with iText to create a PDF file
◆ Integrate with Batik to create SVG format

Data to be drawn into a chart

The data to be Graphically displayed in the chart in this article comes from the HR mode provided by the quick Oracle database. Figure 1 shows the table in HR mode displayed in the SQL * Plus editor attached to the Oracle database quick edition.

:HR mode table displayed in SQL command line tool

Oracle Database quick edition also provides a very useful and easy-to-use Web-based management tool built on Oracle Application Express. Figure 2 demonstrates the tool and again shows some objects in HR mode as tables in this example ).

: HR mode table in Oracle Application Express

Oracle Database quick edition provides developers with many advantages and is compatible with JFreeChart. Oracle provides the quick version of Oracle Database for development and production for free. In addition to the free advantage, a small footprint, easy installation and management, and very useful integrated Web management tools are also one of the other advantages of this database product. Its disadvantages mainly affect large enterprise users because the defects involve storage space, memory size, and feature sets smaller than traditional Oracle database products. Quick Oracle database is ideal for development and prototyping, and even for small production databases. This is especially true for companies or projects with limited budgets.

The snapshot in Figure 3 shows the Web-based management tool again, which shows some of the most important restrictions of the Oracle database quick edition. The storage space of an instance in the Oracle database quick edition is limited to 5 GB including the system tablespace ), therefore, the 710 MB used so far is described as about 14% of the limit on the screen of the tool. The memory usage is limited to 1 GB, so the 314 mb ram usage of the instance is described accordingly. Log on to the management tool as a SYSTEM to display more specific storage and memory information on the management screen. The screen in Figure 3 also shows all the sub-menu options provided by the tool for database management.

: Tool and usage monitoring for quick Oracle Database Edition

After introducing the Oracle database quick edition and the HR mode used as the data source generated in this chart, we will continue to introduce JFreeChart itself.