Auto generate data schema from JPA 2.1 annotated entity classes without a database connection

Question

Two years ago I was working on a project using:

• spring 4.0.3.RELEASE
• jpa 2.0
• hibernate 4.2.7.Final
• java 1.6.X

This pr

Answer 1

As the other question, you can use hbm2ddl and an embedded database to provide a connection.

For exemple using H2 database (require h2, scannotation, hibernate and common-io):

package com.stackoverflow;
import java.io.File;
import java.io.FileWriter;
import java.io.InputStream;
import java.net.URL;
import java.util.Set;
import javax.persistence.Entity;
import org.apache.commons.io.IOUtils;
import org.hibernate.cfg.Configuration;
import org.hibernate.cfg.Environment;
import org.hibernate.connection.DriverManagerConnectionProvider;
import org.hibernate.dialect.PostgreSQLDialect;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.scannotation.AnnotationDB;

public class ExportShema {

    private static final String OUTPUT_SQL_FILE = "target/database.sql";
    private static final String INIT_FILE = "init.sql";
    private static final String DB_URL = "jdbc:h2:mem:test;DB_CLOSE_DELAY=-1";
    private static final String DB_USERNAME = "sa";
    private static final String DB_PASSWORD = "";
    private static final File HBM_DIRECTORY = new File("src/main/resources/com/stackoverflow/domain/");

    public static void main(final String[] args) throws Exception {
        final Configuration cfg = new Configuration();
        cfg.setProperty(Environment.CONNECTION_PROVIDER, DriverManagerConnectionProvider.class.getName());
        //for postgrest schema
        cfg.setProperty(Environment.DIALECT, PostgreSQLDialect.class.getName());
        cfg.setProperty(Environment.URL, DB_URL);
        cfg.setProperty(Environment.USER, DB_USERNAME);
        cfg.setProperty(Environment.PASS, DB_PASSWORD);

        //If you have HBM + annotated class
        cfg.addDirectory(HBM_DIRECTORY);

        final AnnotationDB db = new AnnotationDB();
        db.scanArchives(new URL("file:target/classes/"));
        final Set clazzNames = db.getAnnotationIndex().get(Entity.class.getName());
        for (final String clazzName : clazzNames) {
            cfg.addAnnotatedClass(Class.forName(clazzName));
        }

        final SchemaExport exporter = new SchemaExport(cfg);
        exporter.setOutputFile(OUTPUT_SQL_FILE);
        exporter.setDelimiter(";");
        exporter.setFormat(true);
        exporter.create(false, true);

        try (final InputStream init_file = ExportShema.class.getResourceAsStream(INIT_FILE)) {
            if (init_file != null) {
                final File output = new File(OUTPUT_SQL_FILE);
                try (final FileWriter fw = new FileWriter(output, true)) {
                    final String eol = System.getProperty("line.separator");
                    fw.append(eol + eol);
                    fw.append(IOUtils.toString(init_file));
                }
            }
        }
}
}

you can do this in a unit test or create an annotation processor.