Modified Repository.Operation.invoke() to return a value so that it can be

used easily for database lookups as well as database stores.

Modified UserRepository to conform to the new signature as well as to use
execute() for all database operations.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@137 6335cc39-0255-0410-8fd6-9bcaacd3b74c

projects/samskivert/src/java/com/samskivert/jdbc/Repository.java

@@ -1,5 +1,5 @@
 //
-// $Id: Repository.java,v 1.6 2001/05/26 04:49:31 mdb Exp $
+// $Id: Repository.java,v 1.7 2001/06/01 07:27:59 mdb Exp $
 
 package com.samskivert.jdbc;
 
@@ -168,18 +168,20 @@ public abstract class Repository
      */
     protected interface Operation
     {
-	public void invoke () throws SQLException;
+	public Object invoke () throws SQLException;
     }
 
     /**
      * Executes the supplied operation. In the event of a transient
      * failure, the repository will attempt to reestablish the database
      * connection and try the operation again.
+     *
+     * @return whatever value is returned by the invoked operation.
      */
-    protected void execute (Operation op)
+    protected Object execute (Operation op)
 	throws SQLException
     {
-        execute(op, true);
+        return execute(op, true);
     }
 
     /**
@@ -191,22 +193,29 @@ public abstract class Repository
      * to a transient failure (like losing the connection to the database
      * or deadlock detection), the connection to the database will be
      * reestablished and the operation attempted once more.
+     *
+     * @return whatever value is returned by the invoked operation.
      */
-    protected void execute (Operation op, boolean retryOnTransientFailure)
+    protected Object execute (Operation op, boolean retryOnTransientFailure)
 	throws SQLException
     {
+        Object rv = null;
+
         // make sure our connection is established
         ensureConnection();
 
 	try {
 	    // invoke the operation
-	    op.invoke();
+	    rv = op.invoke();
 
 	    // commit the session
             if (supportsTransactions()) {
                 _session.commit();
             }
 
+            // return the operation result
+            return rv;
+
 	} catch (SQLException sqe) {
 	    // back out our changes if something got hosed
             if (supportsTransactions()) {
@@ -227,7 +236,7 @@ public abstract class Repository
                 // to reset the connection, we simply close it. it will be
                 // reopened on our subsequent call to execute()
                 shutdown();
-                execute(op, false);
+                return execute(op, false);
 
             } else {
                 throw sqe;

projects/samskivert/src/java/com/samskivert/servlet/user/UserRepository.java

@@ -1,5 +1,5 @@
 //
-// $Id: UserRepository.java,v 1.9 2001/05/26 07:09:38 mdb Exp $
+// $Id: UserRepository.java,v 1.10 2001/06/01 07:27:59 mdb Exp $
 
 package com.samskivert.servlet.user;
 
@@ -81,11 +81,13 @@ public class UserRepository extends MySQLRepository
 
 	try {
 	    execute(new Operation () {
-		public void invoke () throws SQLException
+		public Object invoke () throws SQLException
 		{
 		    _utable.insert(user);
 		    // update the userid now that it's known
 		    user.userid = lastInsertedId();
+                    // nothing to return
+                    return null;
 		}
 	    });
 
@@ -106,14 +108,15 @@ public class UserRepository extends MySQLRepository
      * @return the user with the specified user id or null if no user with
      * that id exists.
      */
-    public User loadUser (String username)
+    public User loadUser (final String username)
 	throws SQLException
     {
-        // make sure our session is established
+        return (User)execute(new Operation () {
-        ensureConnection();
+            public Object invoke () throws SQLException
-
+            {
                 // look up the user
-	Cursor ec = _utable.select("where username = '" + username + "'");
+                String query = "where username = '" + username + "'";
+                Cursor ec = _utable.select(query);
 
                 // fetch the user from the cursor
                 User user = (User)ec.next();
@@ -124,6 +127,8 @@ public class UserRepository extends MySQLRepository
 
                 return user;
             }
+        });
+    }
 
     /**
      * Looks up a user by userid.
@@ -131,12 +136,12 @@ public class UserRepository extends MySQLRepository
      * @return the user with the specified user id or null if no user with
      * that id exists.
      */
-    public User loadUser (int userid)
+    public User loadUser (final int userid)
 	throws SQLException
     {
-        // make sure our session is established
+        return (User)execute(new Operation () {
-        ensureConnection();
+            public Object invoke () throws SQLException
-
+            {
                 // look up the user
                 Cursor ec = _utable.select("where userid = " + userid);
 
@@ -149,6 +154,8 @@ public class UserRepository extends MySQLRepository
 
                 return user;
             }
+        });
+    }
 
     /**
      * Looks up a user by a session identifier.
@@ -156,16 +163,16 @@ public class UserRepository extends MySQLRepository
      * @return the user associated with the specified session or null of
      * no session exists with the supplied identifier.
      */
-    public User loadUserBySession (String sessionKey)
+    public User loadUserBySession (final String sessionKey)
 	throws SQLException
     {
-        // make sure our session is established
+        return (User)execute(new Operation () {
-        ensureConnection();
+            public Object invoke () throws SQLException
-
+            {
+                String query = "where authcode = '" + sessionKey +
+                    "' AND sessions.userid = users.userid";
                 // look up the user
-	Cursor ec = _utable.select("sessions",
+                Cursor ec = _utable.select("sessions", query);
-				   "where authcode = '" + sessionKey +
-				   "' AND sessions.userid = users.userid");
 
                 // fetch the user from the cursor
                 User user = (User)ec.next();
@@ -176,6 +183,8 @@ public class UserRepository extends MySQLRepository
 
                 return user;
             }
+        });
+    }
 
     /**
      * Updates a user that was previously fetched from the repository.
@@ -184,9 +193,11 @@ public class UserRepository extends MySQLRepository
 	throws SQLException
     {
 	execute(new Operation () {
-	    public void invoke () throws SQLException
+	    public Object invoke () throws SQLException
 	    {
 		_utable.update(user);
+                // nothing to return
+                return null;
 	    }
 	});
     }
@@ -198,9 +209,11 @@ public class UserRepository extends MySQLRepository
 	throws SQLException
     {
 	execute(new Operation () {
-	    public void invoke () throws SQLException
+	    public Object invoke () throws SQLException
 	    {
 		_utable.delete(user);
+                // nothing to return
+                return null;
 	    }
 	});
     }
@@ -226,12 +239,14 @@ public class UserRepository extends MySQLRepository
 
 	// insert the session into the database
 	execute(new Operation () {
-	    public void invoke () throws SQLException
+	    public Object invoke () throws SQLException
 	    {
 		_session.execute("insert into sessions " +
 				 "(authcode, userid, expires) values('" +
 				 authcode + "', " + user.userid + ", '" +
 				 expires + "')");
+                // nothing to return
+                return null;
 	    }
 	});
 
@@ -246,10 +261,12 @@ public class UserRepository extends MySQLRepository
 	throws SQLException
     {
 	execute(new Operation () {
-	    public void invoke () throws SQLException
+	    public Object invoke () throws SQLException
 	    {
 		_session.execute("delete from sessions where " +
 				 "expires <= CURRENT_DATE()");
+                // nothing to return
+                return null;
 	    }
 	});
     }
@@ -276,19 +293,16 @@ public class UserRepository extends MySQLRepository
 	return loadNames(userids, "realname");
     }
 
-    protected String[] loadNames (int[] userids, String column)
+    protected String[] loadNames (int[] userids, final String column)
 	throws SQLException
     {
-        // make sure our session is established
-        ensureConnection();
-
         // if userids is zero length, we've got no work to do
         if (userids.length == 0) {
             return new String[0];
         }
 
 	// build up the string we need for the query
-	StringBuffer ids = new StringBuffer();
+	final StringBuffer ids = new StringBuffer();
 	for (int i = 0; i < userids.length; i++) {
 	    if (ids.length() > 0) {
 		ids.append(", ");
@@ -296,8 +310,12 @@ public class UserRepository extends MySQLRepository
 	    ids.append(userids[i]);
 	}
 
+	final IntMap map = new IntMap();
+
 	// do the query
-	IntMap map = new IntMap();
+        execute(new Operation () {
+            public Object invoke () throws SQLException
+            {
                 Statement stmt = _session.connection.createStatement();
                 try {
                     String query = "select userid, " + column +
@@ -310,9 +328,14 @@ public class UserRepository extends MySQLRepository
                         map.put(userid, name);
                     }
 
+                    // nothing to return
+                    return null;
+
                 } finally {
                     stmt.close();
                 }
+            }
+        });
 
 	// finally construct our result
 	String[] result = new String[userids.length];