Dynamic classpath setup in case not all required dependencies are available in the given classpath.

Useful when starting FOP using "java -jar fop.jar". This is actually a replacement for the manifest "Class-Path" entry and even picks up additional JARs it finds.

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@219531 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/fop/apps/Fop.java

@@ -20,8 +20,14 @@ package org.apache.fop.apps;
 
 // Java
 import java.io.BufferedOutputStream;
+import java.io.File;
+import java.io.FileFilter;
 import java.io.FileOutputStream;
 import java.io.OutputStream;
+import java.lang.reflect.Method;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.List;
 
 // XML
 import org.xml.sax.helpers.DefaultHandler;
@@ -131,10 +137,108 @@ public class Fop implements Constants {
     }
 
     /**
-     * The main routine for the command line interface
-     * @param args the command line parameters
+     * @return the list of URLs to all libraries.
+     * @throws MalformedURLException In case there is a problem converting java.io.File
+     * instances to URLs.
      */
-    public static void main(String[] args) {
+    public static URL[] getJARList() throws MalformedURLException {
+        File baseDir = new File(".").getAbsoluteFile().getParentFile();
+        File buildDir;
+        if ("build".equals(baseDir.getName())) {
+            buildDir = baseDir;
+            baseDir = baseDir.getParentFile();
+        } else {
+            buildDir = new File(baseDir, "build");
+        }
+        File fopJar = new File(buildDir, "fop.jar");
+        if (!fopJar.exists()) {
+            fopJar = new File(baseDir, "fop.jar");
+        }
+        if (!fopJar.exists()) {
+            throw new RuntimeException("fop.jar not found in directory: " 
+                    + baseDir.getAbsolutePath() + " (or below)");
+        }
+        List jars = new java.util.ArrayList();
+        jars.add(fopJar.toURL());
+        File[] files;
+        FileFilter filter = new FileFilter() {
+            public boolean accept(File pathname) {
+                return pathname.getName().endsWith(".jar");
+            }
+        };
+        File libDir = new File(baseDir, "lib");
+        if (!libDir.exists()) {
+            libDir = baseDir;
+        }
+        files = libDir.listFiles(filter);
+        if (files != null) {
+            for (int i = 0, size = files.length; i < size; i++) {
+                jars.add(files[i].toURL());
+            }
+        }
+        String optionalLib = System.getProperty("fop.optional.lib");
+        if (optionalLib != null) {
+            files = new File(optionalLib).listFiles(filter);
+            if (files != null) {
+                for (int i = 0, size = files.length; i < size; i++) {
+                    jars.add(files[i].toURL());
+                }
+            }
+        }
+        URL[] urls = (URL[])jars.toArray(new URL[jars.size()]);
+        /*
+        for (int i = 0, c = urls.length; i < c; i++) {
+            System.out.println(urls[i]);
+        }*/
+        return urls;
+    }
+    
+    /**
+     * @return true if FOP's dependecies are available in the current ClassLoader setup.
+     */
+    public static boolean checkDependencies() {
+        try {
+            //System.out.println(Thread.currentThread().getContextClassLoader());
+            Class clazz = Class.forName("org.apache.batik.Version");
+            if (clazz != null) {
+                clazz = Class.forName("org.apache.avalon.framework.configuration.Configuration");
+            }
+            return (clazz != null);
+        } catch (Exception e) {
+            return false;
+        }
+    }
+    
+    /**
+     * Dynamically builds a ClassLoader and executes FOP.
+     * @param args command-line arguments
+     */
+    public static void startFOPWithDynamicClasspath(String[] args) {
+        try {
+            URL[] urls = getJARList();
+            //System.out.println("CCL: " 
+            //    + Thread.currentThread().getContextClassLoader().toString());
+            ClassLoader loader = new java.net.URLClassLoader(urls, null);
+            Thread.currentThread().setContextClassLoader(loader);
+            Class clazz = Class.forName("org.apache.fop.apps.Fop", true, loader);
+            //System.out.println("CL: " + clazz.getClassLoader().toString());
+            Method mainMethod = clazz.getMethod("startFOP", new Class[] {String[].class});
+            mainMethod.invoke(null, new Object[] {args});
+        } catch (Exception e) {
+            System.err.println("Unable to start FOP:");
+            e.printStackTrace();
+            System.exit(-1);
+        }
+    }
+    
+    /**
+     * Executes FOP with the given ClassLoader setup.
+     * @param args command-line arguments
+     */
+    public static void startFOP(String[] args) {
+        //System.out.println("static CCL: " 
+        //    + Thread.currentThread().getContextClassLoader().toString());
+        //System.out.println("static CL: " + Fop.class.getClassLoader().toString());
         CommandLineOptions options = null;
         FOUserAgent foUserAgent = null;
         BufferedOutputStream bos = null;
@@ -173,6 +277,19 @@ public class Fop implements Constants {
             System.exit(1);
         }
     }
+    
+    /**
+     * The main routine for the command line interface
+     * @param args the command line parameters
+     */
+    public static void main(String[] args) {
+        if (checkDependencies()) {
+            startFOP(args);
+        } else {
+            startFOPWithDynamicClasspath(args);
+        }
+    }
+
 
     /**
      * Get the version of FOP