Access file (JAVA)

Access resource / file packaged inside a jar or a located on classpath. Two ways to access the file located inside jar or located on classpath.

1. Use getResourceAsStream("filename") on ClassLoader, one can retrieve the class loader instance from class instance of any class or Thread.currentThread().getClassLoader(). When you try to load the file using class loader, file will be always searched inside root folder on classpath. e.g. Thread.currentThread().getClassLoader().getResourceAsStream("config.properties") and Thread.currentThread().getClassLoader().getResourceAsStream("/config.properties") either way class loader will try to search file from root folder which is on class path or from root folder inside jar.
2. Use getResourceAsStream("filename") on Class instance of a class. One can retrieve the class instance using ClassName.class or this.getClass(). When you try to load the file using class, file search will depend on how do you specify the file name. When you specify file config.properties this.getClass().getResourceAsStream("config.properties"), file will be searched inside same package as that of given class on which you are calling getResourceAsStream(). When you specify file like /config.properties given file will be searched from root folder which is on class path or from root folder inside jar.

Access resource / file from file location

To access file form given path outside the class path, one need to make use of java.io.File

File file = new File(“filename with absolute path”);
FileInputStream fStream = new FileInputStream(file);   

See also

• Install ZeroMQ on ubuntu with Java Binding
• Compare more than two war files and repackage them excluding common jars
• Tomcat 7 onwards set additional JAVA_OPTS options
• Jersey REST retrieve List of custom object
• Generate complete package (ZIP) of Java (executable jar) application with required dependencies in it using Maven