FileInputStream Question

Question

Hi All
I need some information on using a relative path in a FileInputStream.
I want to use the following code:
JasperReport template = JasperManager.loadReport (new FileInputStream ("reports//Main.jasper"));to reference a file in the reports directory in the directory where my class files are located. How do I do this without using an absolute path.
Hope to hear from you soon.
Regards,
C

Answer 1

I'm feeling like a nice guy, so I'm going to post some code that I use quite often for doing this sort of thing.
The class is below. Here's how I use it to set up logging using log4j (I use the LOGROOT environment variable in my log4j.properties to help define where the log files should actually get generated):
     static private void configureLoggers() throws MaestroStartupFailedException{
          File appRoot = ClassUtilities.getClassPathComponentFile(MaestroApp.class);
          if (appRoot.getName().toLowerCase().endsWith(".jar")) // if we are in a JAR, then the app path is going to be below us a couple of levels
               appRoot = appRoot.getParentFile().getParentFile(); // this will drop us to the lib, then to the app base path
          File logRoot = new File(appRoot, "logs/");
          File log4jPropFile = new File(logRoot, "log4j.properties");
          if (!log4jPropFile.exists())
               throw new Exception("Unable to find logging definition file at " + log4jPropFile);
          System.setProperty("LOGROOT", logRoot.getAbsolutePath());
          System.out.println("Logging using properties from " + log4jPropFile.getAbsolutePath());
          System.out.println("LOGROOT set to " + System.getProperty("LOGROOT"));
          PropertyConfigurator.configureAndWatch(log4jPropFile.getAbsolutePath(), 60000);
     }And here's the utility class (ClassUtilities) implementation
package com.trumpetinc.util;
import java.io.File;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
* @author Kevin Day
* Trumpet, Inc.
* www.trumpetinc.com
* Use this code at your own risk - I don't claim that it actually works,
* will not be held liable for how you choose to use it, etc..., etc...
* If you choose to use this class, please keep the entire thing together and
* leave these comments at the top.
public class ClassUtilities {
      * Constructor for ClassUtilities.
     private ClassUtilities() {
          super();
        * Returns the classpath component from which a class with the
        * supplied name was loaded, or <code>null</code> if a class with
        * the supplied name could not be loaded.  The supplied {@link
        * java.lang.ClassLoader <code>ClassLoader</code>} is used, unless
        * it is <code>null</code>, in which case the system classloader is
        * used instead.
        * @param className the name of a class to load
        * @param loader a {@link java.lang.ClassLoader
        * <code>ClassLoader</code>} to use to attempt to load the class
        * specified by <code>className</code>; if <code>null</code> the
     system
        * classloader will be used instead
        * @return a {@link java.net.URL <code>URL</code>} to the classpath
        * component that the class corresponding to the supplied name
        * was loaded from, or <code>null</code> if no such class was
        * found
        * @exception org.gjt.ljn.core.NullArgumentException if
        * <code>className</code> is <code>null</code>
       public static final URL getClassPathComponentURL(Class aClass,
                                      ClassLoader loader)
          if (aClass == null) {
            return null;
          String resourceName = aClass.getName().replace('.', '/') + ".class";
          return getClassPathComponentURL(resourceName, loader);
      * Returns a File pointing to the ROOT of the resource specified.  If the resource is
      * in a .jar file, the folder that the jar file is located in is returned.  If the
      * resource is located in a directory structure beneath a classpath folder, then the
      * classpath folder will be returned.
      * @param resourceName
      * @return File
     public static final File getClassPathComponentRoot(String resourceName){
          try {
               File aRoot = new File(new URI(ClassUtilities.getClassPathComponentURL(resourceName, null).toExternalForm()));
               if (aRoot.isDirectory()) return aRoot;
               return aRoot.getParentFile();
          } catch (URISyntaxException e) {
               return null;
     public static final File getClassPathComponentRoot(Class aClass){
          try {
               File aRoot = new File(new URI(ClassUtilities.getClassPathComponentURL(aClass, null).toExternalForm()));
               if (aRoot.isDirectory()) return aRoot;
               return aRoot.getParentFile();
          } catch (URISyntaxException e) {
               return null;
     public static final URL getClassPathComponentURL(String resourceName,
                                    ClassLoader loader){
                                        URL resource = null;
               if (loader == null) {
                 resource = ClassLoader.getSystemResource(resourceName);
               } else {   resource = loader.getResource(resourceName);
               if (resource == null) {
                 return null;
               String resourceURLString = resource.toString();
               if (resourceURLString == null) {
                 // don't think this could ever happen
                 return null;
               String temp =
                    resourceURLString.substring(0, resourceURLString.indexOf(resourceName)     - 1);
               if (temp.startsWith("jar:")) {
                 temp = temp.substring("jar:".length(), temp.length() - 1);
               try {
                 return new URL(temp);
               } catch (Exception anything) {
                 throw new Error("This should never happen! (" +
                           anything.toString() + ")");
     public static final File getClassPathComponentFile(Object o){
          try {
               Class c = o instanceof Class ? (Class)o : o.getClass();
               return new File(new URI(ClassUtilities.getClassPathComponentURL(c, null).toExternalForm()));
          } catch (URISyntaxException e) {
               return null;
     public static void printSerialVersionUID(Class c){
          long verID = java.io.ObjectStreamClass.lookup(c).getSerialVersionUID();
          System.out.println(c + "\n==========================");
          System.out.println("     static final long serialVersionUID = " + verID + "L;\n");
}