Migrated the TransitionRepository here from Yohoho.

git-svn-id: https://samskivert.googlecode.com/svn/trunk@1930 6335cc39-0255-0410-8fd6-9bcaacd3b74c

src/java/com/samskivert/jdbc/TransitionRepository.java

@@ -0,0 +1,141 @@
+//
+// $Id$
+
+package com.samskivert.jdbc;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+import com.samskivert.io.PersistenceException;
+
+/**
+ * Used to note that transitionary code has been run to migrate persistent
+ * data. The TransitionRepository is especially useful for data that
+ * one cannot examine to determine if it's been transitioned.
+ */
+public class TransitionRepository extends SimpleRepository
+{
+    /** The identifier of this connection. */
+    public static final String TRANSITION_DB_IDENT = "transitiondb";
+
+    /**
+     * An interface for the transition.
+     */
+    public static interface Transition
+    {
+        /**
+         * Do the transition.
+         */
+        public void run () throws PersistenceException;
+    }
+
+    /**
+     * Construct a TransitionRepository for the server.
+     */
+    public TransitionRepository (ConnectionProvider conprov)
+        throws PersistenceException
+    {
+        super(conprov, TRANSITION_DB_IDENT);
+    }
+
+    /**
+     * Perform a transition if it has not already been applied, and record
+     * that it was applied.
+     */
+    public void transition (Class clazz, String name, Transition trans)
+        throws PersistenceException
+    {
+        if (!isTransitionApplied(clazz, name)) {
+            trans.run();
+            noteTransition(clazz, name);
+        }
+    }
+
+    /**
+     * Has the specified name transition been applied.
+     */
+    public boolean isTransitionApplied (Class clazz, final String name)
+        throws PersistenceException
+    {
+        final String cname = clazz.getName();
+        return execute(new Operation<Boolean>() {
+            public Boolean invoke (Connection conn, DatabaseLiaison liaison)
+                throws SQLException, PersistenceException
+            {
+                Object found = null;
+                PreparedStatement stmt = null;
+                try {
+                    stmt = conn.prepareStatement("select NAME " +
+                        "from TRANSITIONS where CLASS=? and NAME=?");
+                    stmt.setString(1, cname);
+                    stmt.setString(2, name);
+                    ResultSet rs = stmt.executeQuery();
+                    if (rs.next()) {
+                        while (rs.next()); // is this really necessary?
+                        return true;
+                    }
+                } finally {
+                    JDBCUtil.close(stmt);
+                }
+                return false;
+            }
+        });
+    }
+
+    /**
+     * Note in the database that a particular transition has been applied.
+     */
+    public void noteTransition (Class clazz, final String name)
+        throws PersistenceException
+    {
+        final String cname = clazz.getName();
+        executeUpdate(new Operation<Void>() {
+            public Void invoke (Connection conn, DatabaseLiaison liaison)
+                throws SQLException, PersistenceException
+            {
+                PreparedStatement stmt = null;
+                try {
+                    stmt = conn.prepareStatement("insert into TRANSITIONS " +
+                        "(CLASS, NAME) values (?, ?)");
+                    stmt.setString(1, cname);
+                    stmt.setString(2, name);
+
+                    JDBCUtil.checkedUpdate(stmt, 1);
+                } finally {
+                    JDBCUtil.close(stmt);
+                }
+                return null;
+            }
+        });
+    }
+
+    /**
+     * Clear the transition.
+     */
+    public void clearTransition (Class clazz, final String name)
+        throws PersistenceException
+    {
+        final String cname = clazz.getName();
+        executeUpdate(new Operation<Void>() {
+            public Void invoke (Connection conn, DatabaseLiaison liaison)
+                throws SQLException, PersistenceException
+            {
+                PreparedStatement stmt = null;
+                try {
+                    stmt = conn.prepareStatement("delete from TRANSITIONS " +
+                        "where CLASS=? and NAME=?");
+                    stmt.setString(1, cname);
+                    stmt.setString(2, name);
+
+                    stmt.executeUpdate(); // we don't care if it worked or not
+
+                } finally {
+                    JDBCUtil.close(stmt);
+                }
+                return null;
+            }
+        });
+    }
+}