DbDiffCommand.java

package bo.gotthardt.ebean;

import com.avaje.ebean.EbeanServer;
import com.avaje.ebean.EbeanServerFactory;
import com.avaje.ebean.config.ServerConfig;
import com.codahale.metrics.MetricRegistry;
import io.dropwizard.Configuration;
import io.dropwizard.cli.ConfiguredCommand;
import io.dropwizard.db.DataSourceFactory;
import io.dropwizard.db.ManagedDataSource;
import io.dropwizard.migrations.CloseableLiquibase;
import io.dropwizard.setup.Bootstrap;
import liquibase.diff.DiffResult;
import liquibase.diff.compare.CompareControl;
import liquibase.diff.output.DiffOutputControl;
import liquibase.diff.output.changelog.DiffToChangeLog;
import liquibase.exception.LiquibaseException;
import net.sourceforge.argparse4j.inf.Namespace;

import java.sql.SQLException;

/**
 * Dropwizard command for creating Liquibase database changelogs.
 * @param <T>
 */
public class DbDiffCommand<T extends Configuration & HasDatabaseConfiguration> extends ConfiguredCommand<T> {
    public DbDiffCommand() {
        super("dbdiff", "Creates a Liquibase changelog that migrates from the current database to one created freshly by Ebean.\nAn empty database named 'migrationdiff' must exist.");
    }

    @Override
    protected void run(Bootstrap<T> bootstrap, Namespace namespace, T configuration) throws Exception {
        // The existing database with migrations managed by Liquibase.
        DataSourceFactory outdatedDb = configuration.getDatabaseConfig();

        try (CloseableLiquibase outdatedLiquibase = createLiquibase(outdatedDb)) {
            // A temporary database that starts out empty and then gets the autogenerated Ebean table definitions applied.
            DataSourceFactory freshDb = EbeanConfigUtils.clone(outdatedDb);
            String url = outdatedDb.getUrl();
            freshDb.setUrl(url.substring(0, url.lastIndexOf("/")) + "/migrationdiff");

            // Creating the Ebean server makes it apply its table definitions to the database immediately.
            ServerConfig serverConfig = EbeanConfigUtils.createServerConfig(freshDb);
            serverConfig.setDdlGenerate(true);
            serverConfig.setDdlRun(true);
            EbeanServer ebeanServer = EbeanServerFactory.create(serverConfig);

            try (CloseableLiquibase freshLiquibase = createLiquibase(freshDb)) {
                // Create and print the differences between the two databases, i.e. a migration that should be applied to update to the newest Ebean definitions.
                DiffResult diff = outdatedLiquibase.diff(freshLiquibase.getDatabase(), outdatedLiquibase.getDatabase(), CompareControl.STANDARD);
                DiffToChangeLog diffToChangeLog = new DiffToChangeLog(diff, new DiffOutputControl(false, false, true));
                diffToChangeLog.print(System.out);
            }
        }
    }

    private static CloseableLiquibase createLiquibase(DataSourceFactory dbConfig) throws SQLException, LiquibaseException {
        ManagedDataSource dataSource = dbConfig.build(new MetricRegistry(), "liquibase");
        return new CloseableLiquibase(dataSource);
    }
}