A handy DropTableMigration.

src/main/java/com/samskivert/depot/impl/DropTableMigration.java

@@ -0,0 +1,61 @@
+//
+// Depot library - a Java relational persistence library
+// https://github.com/threerings/depot/blob/master/LICENSE
+
+package com.samskivert.depot.impl;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+
+import com.samskivert.depot.DataMigration;
+import com.samskivert.depot.DatabaseException;
+import com.samskivert.depot.PersistenceContext;
+
+import com.samskivert.jdbc.DatabaseLiaison;
+
+/**
+ * Migration to drop a table.
+ */
+public class DropTableMigration extends DataMigration
+{
+    /**
+     * Creates a migration that will drop the given table if it exists.
+     */
+    public DropTableMigration (PersistenceContext ctx, String ident, String table)
+    {
+        super(ident);
+        _ctx = ctx;
+        _table = table;
+    }
+
+    @Override
+    public void invoke ()
+        throws DatabaseException
+    {
+        // delete the table
+        _ctx.invoke(new Modifier() {
+                @Override protected int invoke (Connection conn, DatabaseLiaison liaison)
+                    throws SQLException
+                {
+                    return liaison.dropTable(conn, _table) ? 1 : 0;
+                }
+            });
+        // delete the schema version
+        _ctx.invoke(new Modifier.Simple() {
+                @Override protected String createQuery (DatabaseLiaison liaison)
+                {
+                    return "delete from " +
+                            liaison.tableSQL(DepotMetaData.SCHEMA_VERSION_TABLE) +
+                            " where " +
+                            liaison.columnSQL(DepotMetaData.P_COLUMN) +
+                            " = '" + _table + "'";
+                }
+            });
+    }
+
+    /** Our persistence context. */
+    protected final PersistenceContext _ctx;
+
+    /** The table to drop, if it exists. */
+    protected final String _table;
+}