Survive in open-source Java

Survive in open-source Java-general Linux technology-Linux programming and kernel information. The following is a detailed description. Since Sun claims to "publish" most of the Java code base, the Internet is filled with the question: what does this mean for Java, open-source, and developer communities?

First, let's take a look at the announcement that the key part of Java will be released in compliance with the Open-Source GPL V2 license and the Classpath exception. The release of this important set of Java software that complies with the open-source license can be seen as the greatest contribution to the code of the open-source community and has also produced a lot of responses, from worrying about the collapse of the enterprise's Java Community to the inevitable decline of many private software. Java technicians who do not understand software licenses may wonder what is surprising or what the impact of this announcement on them.

The GNU General Public License or GPL is a license for open-source software supported by the Free Software Foundation. Once a software project uses code that complies with the GPL license, the project must also comply with the GPL, which means that its license does not add any additional constraints to project use. The next point is the "copyleft" that we often mention in the open-source community, which is also the source of debate. Does Java open source mean that, if you use a recently released Java virtual machine that complies with the GPL license to develop a Java project, it will also be mandatory to follow the GPL license? Critics refer to the previous situation as "License virus nature": the GPL-compliant code will "Infect" other code interpreted by it and force the author to publish the source code under GPL.

Obviously, this will cause some panic-the demand for free open source will threaten the business model of Enterprise Java developers. However, Sun quickly removed everyone's concerns. For existing Java developers, the release of Software means everything is normal. Sun's confidence lies in the Classpath exception mentioned earlier. The Classpath exception is developed for the Classpath project: it is a Java class standard written through open source, it is also used in other open-source Java projects, such as Kaffe. the content of the Classpath exception is short, so it is worth reading:

Link the java library with other modules statically or dynamically to complete the Combination Based on this library. In this way, the gnu gpl rules and conditions will cover the entire assembly.

As a special exception, the copyright holder of this library assigns you permissions to link independent modules used to produce executable programs to this library. Regardless of how these independent modules are authorized, how to copy and issue executable programs depends on your choice. The independent module here refers to a module that does not come from or is based on this library. If you modify this library, you can extend this exception to your version. However, this is not a necessary obligation. If you do not want to do so, you can delete this exception from your version.

The essence of this section is about Java code. Your code does not need to follow the GPL standard when you just use the Java method through links or extend the Java class. The GPL "copylef" rule must be followed only when Java code is directly modified. For example, if you extend a Java class that complies with the GPL license and use it in your project. The Classpath exception means that you do not release your project according to the GPL requirements, but if you modify the original class and want to release the project, you must follow the GPL license. The result is that only developers engaged in the Java language need to publish their source code, rather than those who use the Java language for project development.