Issue 467: OSGi Class Loader (ability to create reference to class in other…

Issue 467: OSGi Class Loader (ability to create reference to class in other ClassLoader, for example in another OSGi bundle).

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,8 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>-
+<ul><li>Issue 467: OSGi Class Loader (ability to create reference to class 
+    in other ClassLoader, for example in another OSGi bundle).
 </li></ul>
 
 <h2>Version 1.3.173 (2013-07-28)</h2>

h2/src/main/META-INF/MANIFEST.MF

@@ -36,6 +36,7 @@ Import-Package: javax.management,
  org.h2.jdbcx;version="[${version},1.4.0)",
  org.h2.tools;version="[${version},1.4.0)",
  org.h2.util;version="[${version},1.4.0)",
+ org.h2.value;version="[${version},1.4.0)",
  org.osgi.framework;version="1.5",
  org.osgi.service.jdbc;version="1.0",
  org.slf4j;version="[1.6.0,1.7.0)";resolution:=optional
@@ -46,5 +47,6 @@ Export-Package: org.h2;version="${version}",
  org.h2.jdbc;version="${version}",
  org.h2.jdbcx;version="${version}",
  org.h2.tools;version="${version}",
- org.h2.util;version="${version}"
+ org.h2.util;version="${version}",
+ org.h2.value;version="${version}"
 Premain-Class: org.h2.util.Profiler

h2/src/main/org/h2/util/DbDriverActivator.java

@@ -5,18 +5,24 @@
  */
 package org.h2.util;
 
-import java.util.Properties;
 import org.h2.engine.Constants;
+import org.osgi.framework.Bundle;
 import org.osgi.framework.BundleActivator;
 import org.osgi.framework.BundleContext;
+import org.osgi.framework.ServiceReference;
 import org.osgi.service.jdbc.DataSourceFactory;
 
+import java.util.Properties;
+
 /**
  * The driver activator loads the H2 driver when starting the bundle. The driver
  * is unloaded when stopping the bundle.
  */
 public class DbDriverActivator implements BundleActivator {
     
+    private OSGIClassFactory osgiClassFactory;
+    private OSGIServiceClassFactory osgiServiceClassFactory;
+
     /**
      * Start the bundle. This will load the database driver and register the
      * DataSourceFactory service.
@@ -26,6 +32,10 @@ public class DbDriverActivator implements BundleActivator {
     @Override
     public void start(BundleContext bundleContext) {
         org.h2.Driver driver = org.h2.Driver.load();
+        osgiClassFactory = new OSGIClassFactory(bundleContext);
+        osgiServiceClassFactory = new OSGIServiceClassFactory(bundleContext);
+        Utils.addClassFactory(osgiClassFactory);
+        Utils.addClassFactory(osgiServiceClassFactory);
         Properties properties = new Properties();
         properties.put(DataSourceFactory.OSGI_JDBC_DRIVER_CLASS, org.h2.Driver.class.getName());
         properties.put(DataSourceFactory.OSGI_JDBC_DRIVER_NAME, "H2 JDBC Driver");
@@ -42,7 +52,121 @@ public class DbDriverActivator implements BundleActivator {
      */
     @Override
     public void stop(BundleContext bundleContext) {
+        Utils.removeClassFactory(osgiClassFactory);
+        Utils.removeClassFactory(osgiServiceClassFactory);
         org.h2.Driver.unload();
+        osgiClassFactory = null;
+    }
+
+    /**
+     * Extend the H2 class loading in order to find class defined in other bundles.
+     *
+     * The class format for bundle class is the following:
+     * BundleSymbolicName:BundleVersion:BinaryClassName
+     */
+    private static class OSGIClassFactory implements Utils.ClassFactory {
+        
+        /**
+         * Separator character to merge bundle name,version and class binary
+         * name
+         */
+        public static final String SEPARATOR = ":";
+        private static final int BUNDLE_SYMBOLIC_NAME_INDEX = 0;
+        private static final int BUNDLE_VERSION_INDEX = 1;
+        private static final int BINARY_CLASS_NAME_INDEX = 2;
+        private BundleContext bundleContext;
+
+        /**
+         * Constructor
+         * 
+         * @param bundleContext Valid bundleContext instance
+         */
+        OSGIClassFactory(BundleContext bundleContext) {
+            this.bundleContext = bundleContext;
+        }
+
+        @Override
+        public boolean match(String name) {
+            // OSGi binary class name must contain two SEPARATOR character
+            int index = name.indexOf(SEPARATOR);
+            return !(index == -1 || name.indexOf(SEPARATOR, index + 1) == -1);
+        }
+
+        @Override
+        public Class<?> loadClass(String name) throws ClassNotFoundException {
+            String[] parts = name.split(SEPARATOR);
+            if (parts.length != 3) {
+                throw new ClassNotFoundException(
+                        "OSGi class binary name must contain only 2 '"
+                                + SEPARATOR + "' characters");
+            }
+            for (Bundle bundle : bundleContext.getBundles()) {
+                if (bundle.getSymbolicName().equals(
+                        parts[BUNDLE_SYMBOLIC_NAME_INDEX])
+                        && bundle.getVersion().toString()
+                                .equals(parts[BUNDLE_VERSION_INDEX])) {
+                    // Found the right bundle
+                    return bundle.loadClass(parts[BINARY_CLASS_NAME_INDEX]);
+                }
+            }
+            throw new ClassNotFoundException("OSGi Bundle not found "
+                    + parts[BUNDLE_SYMBOLIC_NAME_INDEX] + " "
+                    + parts[BUNDLE_VERSION_INDEX]);
+        }
+    }
+    
+    /**
+     * Extend the H2 class loading in order to find class defined in other bundles.
+     *
+     * The Class must be registered as a service.
+     *
+     * The main difference with {@link OSGIClassFactory} is that it does not rely to a specific bundle.
+     * OSGIServiceClassFactory is the preferred way to register function used in table constraints,
+     * theses functions should not be removed of the DataBase.
+     *
+     * The class format for bundle service class is the following :
+     * OSGI:BinaryClassNameService
+     */
+    private static class OSGIServiceClassFactory implements Utils.ClassFactory {
+        
+        /**
+         * Separator character to merge bundle name, version and class binary
+         * name
+         */
+        public static final String SEPARATOR = "=";
+
+        private static final int BINARY_CLASS_NAME_INDEX = 1;
+        
+        private BundleContext bundleContext;
+
+        /**
+         * Constructor
+         * @param bundleContext Valid bundleContext instance
+         */
+        OSGIServiceClassFactory(BundleContext bundleContext) {
+            this.bundleContext = bundleContext;
+        }
+
+        @Override
+        public boolean match(String name) {
+            return name.startsWith("OSGI" + SEPARATOR);
+        }
+
+        @Override
+        public Class<?> loadClass(String name) throws ClassNotFoundException {
+            String[] parts = name.split(SEPARATOR);
+            if (parts.length != 2) {
+                throw new ClassNotFoundException(
+                        "OSGi class binary name must contain only 1 '"
+                                + SEPARATOR + "' characters");
+            }
+            ServiceReference serviceReference = bundleContext
+                    .getServiceReference(parts[BINARY_CLASS_NAME_INDEX]);
+            if (serviceReference != null) {
+                return bundleContext.getService(serviceReference).getClass();
+            }
+            throw new ClassNotFoundException("OSGi Service not found "+parts[BINARY_CLASS_NAME_INDEX]);
+        }
     }
     
 }

h2/src/main/org/h2/util/Utils.java

@@ -21,8 +21,10 @@ import java.util.Arrays;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.List;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipInputStream;
+
 import org.h2.api.JavaObjectSerializer;
 import org.h2.constant.ErrorCode;
 import org.h2.constant.SysProperties;
@@ -61,6 +63,10 @@ public class Utils {
 
     private static boolean allowAllClasses;
     private static HashSet<String> allowedClassNames;
+    /**
+     *  In order to manage more than one class loader
+     */
+    private static List<ClassFactory> userClassFactories = new ArrayList<ClassFactory>();
     private static String[] allowedClassNamePrefixes;
 
     static {
@@ -78,6 +84,22 @@ public class Utils {
         // utility class
     }
 
+    /**
+     * Add a class factory in order to manage more than one class loader.
+     * @param classFactory An object that implements ClassFactory
+     */
+    public static void addClassFactory(ClassFactory classFactory) {
+        userClassFactories.add(classFactory);
+    }
+
+    /**
+     * Remove a class factory
+     * @param classFactory Already inserted class factory instance
+     */
+    public static void removeClassFactory(ClassFactory classFactory) {
+        userClassFactories.remove(classFactory);
+    }
+    
     private static int readInt(byte[] buff, int pos) {
         return (buff[pos++] << 24) + ((buff[pos++] & 0xff) << 16) + ((buff[pos++] & 0xff) << 8) + (buff[pos] & 0xff);
     }
@@ -569,18 +591,20 @@ public class Utils {
                 throw DbException.get(ErrorCode.ACCESS_DENIED_TO_CLASS_1, className);
             }
         }
-        // the following code might be better for OSGi (need to verify):
-        /*
+        // Use provided class factory first.
+        for (ClassFactory classFactory : userClassFactories) {
+            if (classFactory.match(className)) {
                 try {
-            return Utils.class.getClassLoader().loadClass(className);
-        } catch (Throwable e) {
-            try {
-                return Thread.currentThread().getContextClassLoader().loadClass(className);
-            } catch (Throwable e2) {
-                DbException.get(ErrorCode.CLASS_NOT_FOUND_1, e, className);
+                    Class<?> userClass = classFactory.loadClass(className);
+                    if (!(userClass == null)) {
+                        return userClass;
+                    }
+                } catch (Exception e) {
+                    throw DbException.get(ErrorCode.CLASS_NOT_FOUND_1, e, className);
                 }
             }
-        */
+        }
+        // Use local ClassLoader
         try {
             return Class.forName(className);
         } catch (ClassNotFoundException e) {
@@ -878,4 +902,31 @@ public class Utils {
         return defaultValue;
     }
 
+    /**
+     * The utility methods will try to use the provided class factories to
+     * convert binary name of class to Class object. Used by H2 OSGi Activator
+     * in order to provide a class from another bundle ClassLoader.
+     */
+    public interface ClassFactory {
+        
+        /**
+         * Check whether the factory can return the named class.
+         * 
+         * @param name the binary name of the class
+         * @return true if this factory can return a valid class for the
+         *         provided class name
+         */
+        boolean match(String name);
+        
+        /**
+         * Load the class.
+         * 
+         * @param name the binary name of the class
+         * @return the class object
+         * @throws ClassNotFoundException If the class is not handle by this
+         *             factory
+         */
+        Class<?> loadClass(String name)
+                throws ClassNotFoundException;
+    }
 }

h2/src/test/org/h2/test/jdbc/TestCallableStatement.java

@@ -17,6 +17,7 @@ import java.sql.Types;
 import org.h2.constant.ErrorCode;
 import org.h2.test.TestBase;
 import org.h2.tools.SimpleResultSet;
+import org.h2.util.Utils;
 
 /**
  * Tests for the CallableStatement class.
@@ -39,6 +40,7 @@ public class TestCallableStatement extends TestBase {
         testCallWithResultSet(conn);
         testCallWithResult(conn);
         testPrepare(conn);
+        testClassLoader(conn);
         conn.close();
         deleteDb("callableStatement");
     }
@@ -147,6 +149,28 @@ public class TestCallableStatement extends TestBase {
                 getString("X");
     }
 
+    private void testClassLoader(Connection conn) throws SQLException {
+        Utils.ClassFactory myFactory = new TestClassFactory();
+        Utils.addClassFactory(myFactory);
+        try {
+            Statement stat = conn.createStatement();
+            stat.execute("CREATE ALIAS TCLASSLOADER FOR \"TestClassFactory.testClassF\"");
+            ResultSet rs = stat.executeQuery("SELECT TCLASSLOADER(true)");
+            assertTrue(rs.next());
+            assertEquals(false, rs.getBoolean(1));
+        } finally {
+            Utils.removeClassFactory(myFactory);
+        }
+    }
+
+    /**
+     * Class factory unit test
+     * @param b boolean value
+     * @return !b
+     */
+    public static Boolean testClassF(Boolean b) {
+        return !b;
+    }
     /**
      * This method is called via reflection from the database.
      *
@@ -168,4 +192,19 @@ public class TestCallableStatement extends TestBase {
         return rs;
     }
     
+    /**
+     * A class factory used for testing.
+     */
+    static class TestClassFactory implements Utils.ClassFactory {
+        
+        @Override
+        public boolean match(String name) {
+            return name.equals("TestClassFactory");
+        }
+
+        @Override
+        public Class<?> loadClass(String name) throws ClassNotFoundException {
+            return TestCallableStatement.class;
+        }
+    }
 }