What is java.library.path , How to set in Eclipse IDE

java.library.path is a System property, which is used by Java programming language, mostly JVM, to search native libraries, required by project. Similar to PATH and Classpath environment variable, java.library.path also includes a list of directory. When Java code loads a native library (a library or executable written in language like C, C++ or native code) using System.loadLibrary("name of library") method, java.library.path is scanned for specified library. If JVM doesn't found requested native library, then it throw java.lang.UnsatisfiedLinkError: no native library in java.library.path. Now some one may argue that, why does Java program should depend on native library, doesn't this make a Java application platform dependent? Well, he would be right, but there are situations, where most of code is already written in native languages, and you are just writing some Java code on top of that. In those scenario, instead of rewriting whole stuff, you tend to use native libraries. Sometimes a third party JAR (written in Java) depends upon some native components as well. If you have been using Tibco RV messaging, then you might know that Java API for Tibco RV depends upon several dll files, and until those files are present in java.library.path, you can not run those Java program successfully. Since most of us, run Java program from Eclipse IDE, it's important to know How to set java.library.path in Eclipse. In this Java tutorial, I will show you couple of ways to set java.library.path in Eclipse IDE, you can follow similar steps in other IDE like Netbeans or IntelliJ to set java.library.path

3 Ways to set java.library.path in Eclipse IDE

If you are already familiar with setting PATH and Classpath in Java, then this shouldn't be a problem. Since java.library.path is a system property, most common way to set this is by providing as JVM arguments. Since at low level (if you are using start-up scripts), Java program starts with "java" command, you can provide them system property using -Dpropery=value. In order to set java.library.path you can provide -Djava.library.path=C:\Windows to set it in Windows. By the way, it's little different in Eclipse, which we will see in next section, which shows three places to set java.library.path in Eclipse.

1) You can set java.library.path in Eclipse by providing native library location for you libraries inside "java build path". Just follow below steps :

        1.1) Select Project ==> Properties ==> Java Build Path ==> Libraries ==> JRE System Library ==> Native library location ==> Edit

        1.2) Edit will open a dialog box, which allows you to choose an external folder, or a workspace location, to find native libraries

2) Similar to above steps, you can also set native library location, which will then converted into java.library.path by Eclipse, into source tab. Each source folder allows you to specify a native library location.

       1.1) Open Java Build Path as shown in above step, then choose Source tab

       1.2) Each Source folder has one native library location, select and edit them to include your native libraries

3) Third way to set java.library.path is by using VM arguments. Open Run Configurations or Debug Configuration of your project and provide -Djava.library.path="native library path" in Arguments tab, under VM arguments.

So, you can see It's not difficult to set java.library.path in Eclipse. It's also worth noting that, this system property is only read, when JVM startup. IF you further change this System property using System.setProperty("java.library.path", "new path"), it won't take into effect.