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Reflections & Reference Objects ClassLoader.getResourceAsStream vs. Class.getResourceAsStream Sun Forums

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medale94 Posts:4 Registered: 10/29/99

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ClassLoader.getResourceAsStream vs. Class.getResourceAsStream May 3, 2002 10:52 AM

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Does anyone know why the two methods are implemented with different semantics? It seems that Class.getResourceAsStream supports the more intuitive absolute vs. relative path concept, while ClassLoader.getResourceAsStream only supports absolute path with "/" implied: Directory structure (where classpath will be set to "classes" dir) and content of the hello.txt file: classes/hello.txt -> (content: File in /hello.txt) classes/medale/test/hello.txt -> (content: File in /medale/test/hello.txt) classes/medale/test/medale/test/hello.txt -> (content: File in /medale/test/medale/test/hello.txt) All methods are executed from a class in package medale.test (see source code and ant file below): Using: this.getClass().getResourceAsStream("hello.txt") prints out: File in /medale/test/hello.txt - File read in relative to current class which was loaded from /medale/test Using: this.getClass().getResourceAsStream("/hello.txt") prints out: File in /hello.txt - File read using absolute path Using: this.getClass().getResourceAsStream("medale/test/hello.txt") prints out:

2/22/2008 12:27 PM

Reflections & Reference Objects - ClassLoader.getResourceAsStream vs...

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File in /medale/test/medale/test/hello.txt - again relative Using: this.getClass().getResourceAsStream("/medale/test/hello.txt") prints out:File in /medale/test/hello.txt - absolute path So far - as expected however: this.getClass().getClassLoader().getResourceAsStream("hello.txt") Prints out: File in /hello.txt Using: this.getClass().getClassLoader().getResourceAsStream("/hello.txt") Returns null Same with "/medale/test/hello.txt" -> null and "medale/test/hello.txt" -> File in /medale/test/hello.txt" Why the differing implementations? Here is the code I used for testing this: package medale.test; import java.io.*; public class CLTest { public CLTest() throws IOException { final String[] RES_FILES = {"hello.txt", "/hello.txt", "medale/test/hello.txt", "/medale/test/hello.txt"}; System.out.println("Running code using this.getClass()." + "getResourceAsStream(RES_FILES)"); for (int i=0; i < RES_FILES.length; i++) { try { System.out.print("Result generated using file path >>" + RES_FILES +"<< : "); BufferedReader bin = new BufferedReader (new InputStreamReader (this.getClass().getResourceAsStream(RES_FILES))); if (bin != null) { System.out.println(bin.readLine()); bin.close(); } else { System.out.println("Unable to retrieve InputStream"); } } catch (Exception e) { System.out.println(e); } } System.out.println("\n\nRunning code using this.getClass()." + "getClassLoader()." + "getResourceAsStream(RES_FILES)"); for (int i=0; i < RES_FILES.length; i++) { try { System.out.print("Result generated using file path >>" + RES_FILES +"<< : "); BufferedReader bin = new BufferedReader (new InputStreamReader

2/22/2008 12:27 PM

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(this.getClass(). getClassLoader(). getResourceAsStream(RES_FILES))); if (bin != null) { System.out.println(bin.readLine()); bin.close(); } else { System.out.println("Unable to retrieve InputStream"); } } catch (Exception e) { System.out.println(e); } } System.out.println("\n\nRunning code using Thread.currentThread()." + "getContextClassLoader()." + "getResourceAsStream(RES_FILES)"); for (int i=0; i < RES_FILES.length; i++) { try { System.out.print("Result generated using file path >>" + RES_FILES +"<< : "); BufferedReader bin = new BufferedReader (new InputStreamReader (Thread.currentThread(). getContextClassLoader(). getResourceAsStream(RES_FILES))); if (bin != null) { System.out.println(bin.readLine()); bin.close(); } else { System.out.println("Unable to retrieve InputStream"); } } catch (Exception e) { System.out.println(e); } } } public static void main(String[] args) throws Exception { CLTest test = new CLTest(); } } And here is my ant file that runs the test: <project name="Testing" default="compile" basedir="."> <property name="src.dir" value="src"/> <property name="class.dir" value="classes"/> <mkdir dir="${class.dir}/medale/test/medale/test"/>

2/22/2008 12:27 PM

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<javac classpath="${class.dir}" srcdir="${src.dir}" destdir="${class.dir}"/> <java classpath="${class.dir}" fork="yes" classname="medale.test.CLTest"> <delete dir="${class.dir}"/> Any thoughts on this differing behaviour would be much appreciated (maybe I am doing something wrong?) Thanks, Markus fiontan Posts:761 Registered: 11/12/97

Re: ClassLoader.getResourceAsStream vs. Class.getResourceAsStream May 4, 2002 1:49 AM (reply 1 of 1)

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Does anyone know why the two methods are implemented with different semantics? It seems that Class.getResourceAsStream supports the more intuitive absolute vs. relative path concept, while ClassLoader.getResourceAsStream only supports absolute path with "/" implied:

Well, a Class has a path relative to which a resouce may be located - its package. A ClassLoader simply has a findResource method to determine where to look. Given the difference in context, I'm not particularly surprised that the implementations differ. The system ClassLoader will search for the given file relative to the system classpath... although I am surprised that including a leading slash means that /classes/hello.txt isn't found. I'd generally suggest that using Class.getResourceAsStream usually makes more sense, unless you need to specifically control where the resource is going to be located and/or which classloader is going to load the resource. This topic has 1 reply on 1 page. Read the Developer Forums Code of Conduct

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2/22/2008 12:27 PM