Java tutorial
// Copyright (C) 2009 The Android Open Source Project // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package com.google.gerrit.server.schema; import com.google.common.annotations.VisibleForTesting; import com.google.common.base.Stopwatch; import com.google.common.collect.Lists; import com.google.gerrit.reviewdb.client.CurrentSchemaVersion; import com.google.gerrit.reviewdb.server.ReviewDb; import com.google.gwtorm.jdbc.JdbcExecutor; import com.google.gwtorm.jdbc.JdbcSchema; import com.google.gwtorm.server.OrmException; import com.google.gwtorm.server.StatementExecutor; import com.google.inject.Provider; import java.sql.PreparedStatement; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.Collections; import java.util.List; import java.util.concurrent.TimeUnit; /** A version of the database schema. */ public abstract class SchemaVersion { /** The current schema version. */ public static final Class<Schema_145> C = Schema_145.class; public static int getBinaryVersion() { return guessVersion(C); } private final Provider<? extends SchemaVersion> prior; private final int versionNbr; protected SchemaVersion(final Provider<? extends SchemaVersion> prior) { this.prior = prior; this.versionNbr = guessVersion(getClass()); } public static int guessVersion(Class<?> c) { String n = c.getName(); n = n.substring(n.lastIndexOf('_') + 1); while (n.startsWith("0")) { n = n.substring(1); } return Integer.parseInt(n); } /** @return the {@link CurrentSchemaVersion#versionNbr} this step targets. */ public final int getVersionNbr() { return versionNbr; } @VisibleForTesting public final SchemaVersion getPrior() { return prior.get(); } public final void check(UpdateUI ui, CurrentSchemaVersion curr, ReviewDb db) throws OrmException, SQLException { if (curr.versionNbr == versionNbr) { // Nothing to do, we are at the correct schema. } else if (curr.versionNbr > versionNbr) { throw new OrmException( "Cannot downgrade database schema from version " + curr.versionNbr + " to " + versionNbr + "."); } else { upgradeFrom(ui, curr, db); } } /** Runs check on the prior schema version, and then upgrades. */ private void upgradeFrom(UpdateUI ui, CurrentSchemaVersion curr, ReviewDb db) throws OrmException, SQLException { List<SchemaVersion> pending = pending(curr.versionNbr); updateSchema(pending, ui, db); migrateData(pending, ui, curr, db); JdbcSchema s = (JdbcSchema) db; final List<String> pruneList = new ArrayList<>(); s.pruneSchema(new StatementExecutor() { @Override public void execute(String sql) { pruneList.add(sql); } @Override public void close() { // Do nothing. } }); try (JdbcExecutor e = new JdbcExecutor(s)) { if (!pruneList.isEmpty()) { ui.pruneSchema(e, pruneList); } } } private List<SchemaVersion> pending(int curr) { List<SchemaVersion> r = Lists.newArrayListWithCapacity(versionNbr - curr); for (SchemaVersion v = this; curr < v.getVersionNbr(); v = v.prior.get()) { r.add(v); } Collections.reverse(r); return r; } private void updateSchema(List<SchemaVersion> pending, UpdateUI ui, ReviewDb db) throws OrmException, SQLException { for (SchemaVersion v : pending) { ui.message(String.format("Upgrading schema to %d ...", v.getVersionNbr())); v.preUpdateSchema(db); } JdbcSchema s = (JdbcSchema) db; try (JdbcExecutor e = new JdbcExecutor(s)) { s.updateSchema(e); } } /** * Invoked before updateSchema adds new columns/tables. * * @param db open database handle. * @throws OrmException if a Gerrit-specific exception occurred. * @throws SQLException if an underlying SQL exception occurred. */ protected void preUpdateSchema(ReviewDb db) throws OrmException, SQLException { } private void migrateData(List<SchemaVersion> pending, UpdateUI ui, CurrentSchemaVersion curr, ReviewDb db) throws OrmException, SQLException { for (SchemaVersion v : pending) { Stopwatch sw = Stopwatch.createStarted(); ui.message(String.format("Migrating data to schema %d ...", v.getVersionNbr())); v.migrateData(db, ui); v.finish(curr, db); ui.message(String.format("\t> Done (%.3f s)", sw.elapsed(TimeUnit.MILLISECONDS) / 1000d)); } } /** * Invoked between updateSchema (adds new columns/tables) and pruneSchema (removes deleted * columns/tables). * * @param db open database handle. * @param ui interface for interacting with the user. * @throws OrmException if a Gerrit-specific exception occurred. * @throws SQLException if an underlying SQL exception occurred. */ protected void migrateData(ReviewDb db, UpdateUI ui) throws OrmException, SQLException { } /** Mark the current schema version. */ protected void finish(CurrentSchemaVersion curr, ReviewDb db) throws OrmException { curr.versionNbr = versionNbr; db.schemaVersion().update(Collections.singleton(curr)); } /** Rename an existing table. */ protected static void renameTable(ReviewDb db, String from, String to) throws OrmException { JdbcSchema s = (JdbcSchema) db; try (JdbcExecutor e = new JdbcExecutor(s)) { s.renameTable(e, from, to); } } /** Rename an existing column. */ protected static void renameColumn(ReviewDb db, String table, String from, String to) throws OrmException { JdbcSchema s = (JdbcSchema) db; try (JdbcExecutor e = new JdbcExecutor(s)) { s.renameColumn(e, table, from, to); } } /** Execute an SQL statement. */ protected static void execute(ReviewDb db, String sql) throws SQLException { try (Statement s = newStatement(db)) { s.execute(sql); } } /** Open a new single statement. */ protected static Statement newStatement(ReviewDb db) throws SQLException { return ((JdbcSchema) db).getConnection().createStatement(); } /** Open a new prepared statement. */ protected static PreparedStatement prepareStatement(ReviewDb db, String sql) throws SQLException { return ((JdbcSchema) db).getConnection().prepareStatement(sql); } /** Open a new statement executor. */ protected static JdbcExecutor newExecutor(ReviewDb db) throws OrmException { return new JdbcExecutor(((JdbcSchema) db).getConnection()); } }