Where did Configuration.generateSchemaCreationScri

问题:

In Hibernate 4.x, I used to generate and export the schema as defined in annotated entities as follows (using Spring to find annotated entities on the class path):

Connection connection = 
    DriverManager.getConnection("jdbc:h2:mem:jooq-meta-extensions", "sa", "");

Configuration configuration = new Configuration()
    .setProperty("hibernate.dialect", "org.hibernate.dialect.H2Dialect");

// [...] adding annotated classes to Configuration here...

configuration.generateSchemaCreationScript(
    Dialect.getDialect(configuration.getProperties()));
SchemaExport export = new SchemaExport(configuration, connection);
export.create(true, true);

This no longer works in Hibernate 5.0:

• Configuration.generateSchemaCreationScript() no longer exists
• The SchemaExport(configuration, connection) constructor is now deprecated

I didn't really find any obvious references to this change in the migration guide apart from:

Quite a few methods have been removed from Configuration

What is the correct way to generate and export a database on an existing JDBC connection with Hibernate 5.0 based on a set of annotated entities? (Pure JPA-based solutions are fine, too)

(note, just removing the call to generateSchemaCreationScript() seems to work, but I would prefer to be sure to get this right)

回答1:

Thanks to the answers by Vlad and Gunnar, I've managed to find my way through the new configuration API to produce the equivalent export logic with the following. Of course, history shows that this API will break again, so make sure to choose the appropriate version:

Hibernate 5.2:

MetadataSources metadata = new MetadataSources(
    new StandardServiceRegistryBuilder()
        .applySetting("hibernate.dialect", "org.hibernate.dialect.H2Dialect")
        .applySetting("javax.persistence.schema-generation-connection", connection)
        .build());

// [...] adding annotated classes to metadata here...
metadata.addAnnotatedClass(...);

SchemaExport export = new SchemaExport();
export.create(EnumSet.of(TargetType.DATABASE), metadata.buildMetadata());

Hibernate 5.2 (without warnings):

The above will produce some nasty warnings, which can either be ignored:

Okt 20, 2016 2:57:16 PM org.hibernate.engine.jdbc.connections.internal.ConnectionProviderInitiator initiateService
WARN: HHH000181: No appropriate connection provider encountered, assuming application will be supplying connections
Okt 20, 2016 2:57:16 PM org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator initiateService
WARN: HHH000342: Could not obtain connection to query metadata : The application must supply JDBC connections

... or you work around them by hacking the following ConnectionProvider into the settings (it shouldn't be required in my opinion)

        .applySetting(AvailableSettings.CONNECTION_PROVIDER, new ConnectionProvider() {
            @Override
            public boolean isUnwrappableAs(Class unwrapType) {
                return false;
            }
            @Override
            public <T> T unwrap(Class<T> unwrapType) {
                return null;
            }
            @Override
            public Connection getConnection() {
                return connection; // Interesting part here
            }
            @Override
            public void closeConnection(Connection conn) throws SQLException {}

            @Override
            public boolean supportsAggressiveRelease() {
                return true;
            }
        })

Hibernate 5.0:

MetadataSources metadata = new MetadataSources(
    new StandardServiceRegistryBuilder()
        .applySetting("hibernate.dialect", "org.hibernate.dialect.H2Dialect")
        .build());

// [...] adding annotated classes to metadata here...
metadata.addAnnotatedClass(...);

SchemaExport export = new SchemaExport(
    (MetadataImplementor) metadata.buildMetadata(),
    connection // pre-configured Connection here
);
export.create(true, true);

Hibernate 4:

As a reminder, here's how this worked in Hibernate 4:

Configuration configuration = new Configuration()
    .setProperty("hibernate.dialect", "org.hibernate.dialect.H2Dialect");

// [...] adding annotated classes to metadata here...
configuration.addAnnotatedClass(...);

configuration.generateSchemaCreationScript(
    Dialect.getDialect(configuration.getProperties()));
SchemaExport export = new SchemaExport(configuration, connection);
export.create(true, true);

回答2:

One example of the new SchemaExport initialization is found in SchemaExportTask:

final BootstrapServiceRegistry bsr = new BootstrapServiceRegistryBuilder().build();

final MetadataSources metadataSources = new MetadataSources( bsr );
final StandardServiceRegistryBuilder ssrBuilder = new StandardServiceRegistryBuilder( bsr );

if ( configurationFile != null ) {
    ssrBuilder.configure( configurationFile );
}
if ( propertiesFile != null ) {
    ssrBuilder.loadProperties( propertiesFile );
}
ssrBuilder.applySettings( getProject().getProperties() );

for ( String fileName : getFiles() ) {
    if ( fileName.endsWith(".jar") ) {
        metadataSources.addJar( new File( fileName ) );
    }
    else {
        metadataSources.addFile( fileName );
    }
}


final StandardServiceRegistryImpl ssr = (StandardServiceRegistryImpl) ssrBuilder.build();
final MetadataBuilder metadataBuilder = metadataSources.getMetadataBuilder( ssr );

ClassLoaderService classLoaderService = bsr.getService( ClassLoaderService.class );
if ( implicitNamingStrategy != null ) {
    metadataBuilder.applyImplicitNamingStrategy(
            (ImplicitNamingStrategy) classLoaderService.classForName( implicitNamingStrategy ).newInstance()
    );
}
if ( physicalNamingStrategy != null ) {
    metadataBuilder.applyPhysicalNamingStrategy(
            (PhysicalNamingStrategy) classLoaderService.classForName( physicalNamingStrategy ).newInstance()
    );
}

return new SchemaExport( (MetadataImplementor) metadataBuilder.build() )
    .setHaltOnError( haltOnError )
    .setOutputFile( outputFile.getPath() )
    .setDelimiter( delimiter );

Of course, you can customize it according to your needs.

回答3:

The new bootstrap API allows for many customizations, but assuming you don't need those, the shortest invocation would look like that, applying default values for service registries and all the settings:

Metadata metadata = new MetadataSources()
    .addAnnotatedClass( MyEntity.class )
    .build();

new SchemaExport( (MetadataImplementor) metadata )
    .setOutputFile( "my-statements.ddl" )
    .create( Target.NONE );

Update: Providing example for applying configuration propperties

There are several ways to inject properties for connection URL, dialect etc. E.g. you could provide a file hibernate.properties or you use a service registry customized with the required settings:

StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
    .applySetting( "hibernate.connection.url", "jdbc:h2:mem:db1;DB_CLOSE_DELAY=-1" )
    .build();

Metadata metadata = new MetadataSources( registry )
    .build();

回答4:

In case one is using JPA 2.1+ - there is a very simple build-in possibility to generate the ddl. just set the following jpa properties and the ddl files will be created. With spring boot one could write a separate main class with those specific config options.

JPA 2.1+

javax.persistence.schema-generation.scripts.action=drop-and-create
javax.persistence.schema-generation.scripts.create-target=create.ddl
javax.persistence.schema-generation.scripts.drop-target=drop.ddl

Spring Boot with JPA 2.1+

schemagenerator.properties (put in resources folder):

spring.jpa.properties.javax.persistence.schema-generation.scripts.action=drop-and-create
spring.jpa.properties.javax.persistence.schema-generation.scripts.create-target=create.ddl
spring.jpa.properties.javax.persistence.schema-generation.scripts.drop-target=drop.ddl
flyway.enabled=false // in case you use flyway for db maintenance

Spring Boot SchemaGenerator:

public class SchemaGenerator {
    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, new String[]{"--spring.config.name=schemagenerator"}).close();
    }
}