Writing a Java Class to Manage RPM Package Content
Now our basic class structure, which is able to manipulate headers of RPM packages, is in place, and it would be a good idea to add a minimal GUI interface to it. We will build this very simple interface using the Java Swing package, available with either JDK 1.1 or JDK 1.2.
This very simple GUI interface is managed by the RpmFilePanel.Java class. This class inherits the basic JPanel graphical component and divides the screen into three parts using a Java BorderLayout:
URL input field to input the RPM input file location in URL format
scrollable ListBox to display the RPM file information
button bar containing a “load” button, which proceeds with the URL RPM file loading Let's now explain how the GUI interface RpmFilePanel Java class interacts with the RpmFile class.
The RpmFilePanel.java file contains a static main method to launch the Swing frame inside a Java application. You can use the JDK Java utility from the shell to start it:
Warning: you should have compiled the Java package and installed it in a location accessible from your CLASSPATH.
You should provide a valid RPM package file in URL form and type it into the URL field as shown below. Finally, pushing on the Load button will:
instantiate a new RpmFile instance
call the set_rpmFileName method with the RPM of URL field
call the get_rpmReport method and display its String Vector result into the Swing List box as shown below
Figure 4 shows the screen layout after querying an RPM package.
When you need to build the provided source package, you may use either a JDK 1.1 version or a JDK 1.2.2 version. If you use JDK1.1, the prerequisite is to download the Swing package from Sun's site.
Using Java to analyse RPM file formats may be useful, and it gives you cross-platform portability, which may help you display RPM file contents on heterogeneous platforms. This basic tool may easily be enhanced, for instance to convert RPM contents into other formats or extract other parts of an RPM package.
Jean-Yves Mengant (firstname.lastname@example.org) is Chief Architect at SEFAS Technologies in Paris, France. He has been a professional programmer for more than 20 years on multiple OSes (MVS, Linux), languages (assemblers, C, C++, Java and Perl) and software topics (Network, Tp Monitors and GUI interfaces). He has used Linux systems professionally for programming tasks since 1995 and kernel 1.2, and the Java language since 1996 and JDK 1.0.
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