An operation that automatically closes all opened statements when it completes.

Courtesy of Mr Groves.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@2580 6335cc39-0255-0410-8fd6-9bcaacd3b74c

src/java/com/samskivert/jdbc/AutoCloseOperation.java

@@ -0,0 +1,85 @@
+//
+// $Id$
+//
+// samskivert library - useful routines for java programs
+// Copyright (C) 2001-2009 Michael Bayne
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.samskivert.jdbc;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.samskivert.io.PersistenceException;
+
+/**
+ * An {@link Repository.Operation} wrapper that automatically closes all statements opened by the
+ * operation.
+ *
+ * @author Charlie Groves
+ */
+public abstract class AutoCloseOperation<V>
+    implements Repository.Operation<V>
+{
+    /**
+     * See {@link Repository.Operation#invoke}. Any Statement or PreparedStatement objects created
+     * during the invocation of this method will automatically be closed.
+     */
+    public abstract V cleanInvoke (Connection conn, DatabaseLiaison liason)
+        throws SQLException, PersistenceException;
+
+    /**
+     * Invokes {@link #cleanInvoke} and then closes any statements opened by that call.
+     */
+    public final V invoke (final Connection conn, DatabaseLiaison liaison)
+        throws SQLException, PersistenceException
+    {
+        // create a proxy to conn that collects any returned instances of Statement in stmts
+        final List<Statement> stmts = new ArrayList<Statement>(1);
+        Connection proxy = (Connection)Proxy.newProxyInstance(
+            Connection.class.getClassLoader(), PROXY_IFACES, new InvocationHandler() {
+            public Object invoke (Object proxy, Method method, Object[] args) throws Throwable {
+                Object result = method.invoke(conn, args);
+                if (result instanceof Statement) {
+                    stmts.add((Statement)result);
+                }
+                return result;
+            }
+        });
+
+        try {
+            return cleanInvoke(proxy, liaison);
+        } finally {
+            // if closing a statement throws an SQLException, we don't attempt to close the rest of
+            // the statements -- an SQLException thrown on close is a problem with the underlying
+            // connection and the SimpleRepository closes the connection when it gets an exception
+            // like that; the resources for the remaining statements will be collected in that case
+            for (Statement stmt : stmts) {
+                JDBCUtil.close(stmt);
+            }
+        }
+    }
+
+    protected static Class<?>[] PROXY_IFACES = { Connection.class };
+}