HHH-14478 : Allow DialectResolvers to be discovered by ServiceLoader

hibernate-core/src/main/java/org/hibernate/cfg/AvailableSettings.java

@@ -15,6 +15,7 @@
 import org.hibernate.boot.registry.classloading.internal.TcclLookupPrecedence;
 import org.hibernate.boot.spi.SessionFactoryOptions;
 import org.hibernate.cache.spi.TimestampsCacheFactory;
+import org.hibernate.engine.jdbc.dialect.spi.DialectResolver;
 import org.hibernate.jpa.spi.JpaCompliance;
 import org.hibernate.query.ImmutableEntityUpdateQueryHandlingMode;
 import org.hibernate.query.hql.HqlTranslator;
@@ -427,6 +428,59 @@ public interface AvailableSettings extends org.hibernate.jpa.AvailableSettings {
 	 */
 	String DIALECT_RESOLVERS = "hibernate.dialect_resolvers";
 
+	/**
+	 * Specifies the name of the database provider in cases where a Connection to the underlying database is
+	 * not available (aka, mainly in generating scripts).  In such cases, a value for this setting
+	 * *must* be specified.
+	 * <p/>
+	 * The value of this setting is expected to match the value returned by
+	 * {@link java.sql.DatabaseMetaData#getDatabaseProductName()} for the target database.
+	 * <p/>
+	 * Additionally specifying {@value #DIALECT_DB_MAJOR_VERSION} and/or {@value #DIALECT_DB_MINOR_VERSION}
+	 * may be required to understand exactly how to generate the required schema commands.
+	 *
+	 * @see #DIALECT_DB_VERSION
+	 * @see #DIALECT_DB_MAJOR_VERSION
+	 * @see #DIALECT_DB_MINOR_VERSION
+	 */
+	String DIALECT_DB_NAME = "javax.persistence.database-product-name";
+
+	/**
+	 * Specifies the name of the database provider in cases where a Connection to the underlying database is
+	 * not available (aka, mainly in generating scripts).  This value is used to help more precisely determine
+	 * how to perform schema generation tasks for the underlying database in cases where
+	 * {@value #DIALECT_DB_NAME} does not provide enough distinction.
+	 * <p/>
+	 * The value of this setting is expected to match the value returned by
+	 * {@link java.sql.DatabaseMetaData#getDatabaseProductVersion()} for the target database.
+	 *
+	 * @see #DIALECT_DB_NAME
+	 */
+	String DIALECT_DB_VERSION = "javax.persistence.database-product-version";
+
+	/**
+	 * Specifies the major version of the underlying database, as would be returned by
+	 * {@link java.sql.DatabaseMetaData#getDatabaseMajorVersion} for the target database.  This value is used to
+	 * help more precisely determine how to perform schema generation tasks for the underlying database in cases
+	 * where {@value #DIALECT_DB_NAME} does not provide enough distinction.
+
+	 * @see #DIALECT_DB_NAME
+	 * @see #DIALECT_DB_MINOR_VERSION
+	 */
+	String DIALECT_DB_MAJOR_VERSION = "javax.persistence.database-major-version";
+
+	/**
+	 * Specifies the minor version of the underlying database, as would be returned by
+	 * {@link java.sql.DatabaseMetaData#getDatabaseMinorVersion} for the target database.
+	 *
+	 * This setting is used in Dialect resolution
+	 *
+	 * @see #DIALECT_DB_NAME
+	 * @see #DIALECT_DB_MAJOR_VERSION
+	 * @see DialectResolver
+	 */
+	String DIALECT_DB_MINOR_VERSION = "javax.persistence.database-minor-version";
+
 	/**
 	 * Defines the default storage engine for the relational databases that support multiple storage engines.
 	 * This property must be set either as an Environment variable or JVM System Property.
@@ -1356,63 +1410,33 @@ public interface AvailableSettings extends org.hibernate.jpa.AvailableSettings {
 	/**
 	 * Allows passing a specific {@link java.sql.Connection} instance to be used by SchemaManagementTool.
 	 * <p/>
-	 * May also be used to determine the values for {@value #HBM2DDL_DB_NAME},
-	 * {@value #HBM2DDL_DB_MAJOR_VERSION} and {@value #HBM2DDL_DB_MINOR_VERSION}.
+	 * May also be used to determine the values for {@value #DIALECT_DB_NAME},
+	 * {@value #DIALECT_DB_MAJOR_VERSION} and {@value #DIALECT_DB_MINOR_VERSION}.
 	 */
 	String HBM2DDL_CONNECTION = "javax.persistence.schema-generation-connection";
 
 	/**
-	 * Specifies the name of the database provider in cases where a Connection to the underlying database is
-	 * not available (aka, mainly in generating scripts).  In such cases, a value for this setting
-	 * *must* be specified.
-	 * <p/>
-	 * The value of this setting is expected to match the value returned by
-	 * {@link java.sql.DatabaseMetaData#getDatabaseProductName()} for the target database.
-	 * <p/>
-	 * Additionally specifying {@value #HBM2DDL_DB_MAJOR_VERSION} and/or {@value #HBM2DDL_DB_MINOR_VERSION}
-	 * may be required to understand exactly how to generate the required schema commands.
-	 *
-	 * @see #HBM2DDL_DB_MAJOR_VERSION
-	 * @see #HBM2DDL_DB_MINOR_VERSION
+	 * @deprecated Use {@link #DIALECT_DB_NAME} instead
 	 */
-	@SuppressWarnings("JavaDoc")
-	String HBM2DDL_DB_NAME = "javax.persistence.database-product-name";
+	@Deprecated
+	String HBM2DDL_DB_NAME = DIALECT_DB_NAME;
 
 	/**
-	 * Specifies the name of the database provider in cases where a Connection to the underlying database is
-	 * not available (aka, mainly in generating scripts).  This value is used to help more precisely determine
-	 * how to perform schema generation tasks for the underlying database in cases where
-	 * {@value #HBM2DDL_DB_NAME} does not provide enough distinction.
-	 * <p/>
-	 * The value of this setting is expected to match the value returned by
-	 * {@link java.sql.DatabaseMetaData#getDatabaseProductVersion()} for the target database.
-	 *
-	 * @see #HBM2DDL_DB_NAME
+	 * @deprecated Use {@link #DIALECT_DB_VERSION} instead
 	 */
-	@SuppressWarnings("JavaDoc")
+	@Deprecated
 	String HBM2DDL_DB_VERSION = "javax.persistence.database-product-version";
 
 	/**
-	 * Specifies the major version of the underlying database, as would be returned by
-	 * {@link java.sql.DatabaseMetaData#getDatabaseMajorVersion} for the target database.  This value is used to
-	 * help more precisely determine how to perform schema generation tasks for the underlying database in cases
-	 * where {@value #HBM2DDL_DB_NAME} does not provide enough distinction.
-
-	 * @see #HBM2DDL_DB_NAME
-	 * @see #HBM2DDL_DB_MINOR_VERSION
+	 * @deprecated Use {@link #DIALECT_DB_MAJOR_VERSION} instead
 	 */
+	@Deprecated
 	String HBM2DDL_DB_MAJOR_VERSION = "javax.persistence.database-major-version";
 
 	/**
-	 * Specifies the minor version of the underlying database, as would be returned by
-	 * {@link java.sql.DatabaseMetaData#getDatabaseMinorVersion} for the target database.  This value is used to
-	 * help more precisely determine how to perform schema generation tasks for the underlying database in cases
-	 * where the combination of {@value #HBM2DDL_DB_NAME} and {@value #HBM2DDL_DB_MAJOR_VERSION} does not provide
-	 * enough distinction.
-	 *
-	 * @see #HBM2DDL_DB_NAME
-	 * @see #HBM2DDL_DB_MAJOR_VERSION
+	 * @deprecated Use {@link #DIALECT_DB_MINOR_VERSION} instead
 	 */
+	@Deprecated
 	String HBM2DDL_DB_MINOR_VERSION = "javax.persistence.database-minor-version";
 
 	/**

hibernate-core/src/main/java/org/hibernate/dialect/Database.java

@@ -14,6 +14,8 @@
 import org.hibernate.engine.jdbc.dialect.spi.BasicSQLExceptionConverter;
 import org.hibernate.engine.jdbc.dialect.spi.DialectResolutionInfo;
 
+import static org.hibernate.engine.jdbc.dialect.spi.DialectResolutionInfo.NO_VERSION;
+
 /**
  * A list of relational database systems for which Hibernate can resolve a {@link Dialect}.
  *
@@ -55,20 +57,25 @@ public String getDriverClassName(String jdbcUrl) {
 		@Override
 		public Dialect createDialect(DialectResolutionInfo info) {
 			String databaseVersion = info.getDatabaseVersion();
-			if ( databaseVersion == null ) {
-				return new DB2Dialect( info );
-			}
-			//See https://www.ibm.com/support/knowledgecenter/SSEPEK_12.0.0/java/src/tpc/imjcc_c0053013.html
-			switch ( databaseVersion.substring( 0, 3 ) ) {
-				case "SQL": // Linux, UNIX, Windows
-					return new DB2Dialect( info );
-				case "DSN": // z/OS
-					return new DB2zDialect( info );
-				case "QSQ": // i
-					return new DB2iDialect( info );
-				default:
-					return null;
+			if ( databaseVersion != null ) {
+				//See https://www.ibm.com/support/knowledgecenter/SSEPEK_12.0.0/java/src/tpc/imjcc_c0053013.html
+				switch ( databaseVersion.substring( 0, 3 ) ) {
+					case "SQL": {
+						// Linux, UNIX, Windows
+						return new DB2Dialect( info );
+					}
+					case "DSN": {
+						// z/OS
+						return new DB2zDialect( info );
+					}
+					case "QSQ": {
+						// i
+						return new DB2iDialect( info );
+					}
+				}
 			}
+
+			return new DB2Dialect( info );
 		}
 		@Override
 		public boolean productNameMatches(String databaseName) {
@@ -332,15 +339,18 @@ public String getDriverClassName(String jdbcUrl) {
 			return "org.postgresql.Driver";
 		}
 		private String getVersion(DatabaseMetaData databaseMetaData) {
-			try (Statement statement = databaseMetaData.getConnection().createStatement() ) {
-				final ResultSet rs = statement.executeQuery( "select version()" );
-				if ( rs.next() ) {
-					return rs.getString( 1 );
+			if ( databaseMetaData != null ) {
+				try ( Statement statement = databaseMetaData.getConnection().createStatement() ) {
+					final ResultSet rs = statement.executeQuery( "select version()" );
+					if ( rs.next() ) {
+						return rs.getString( 1 );
+					}
+				}
+				catch (SQLException e) {
+					throw BasicSQLExceptionConverter.INSTANCE.convert( e );
 				}
 			}
-			catch (SQLException e) {
-				throw BasicSQLExceptionConverter.INSTANCE.convert( e );
-			}
+
 			return "";
 		}
 	},

hibernate-core/src/main/java/org/hibernate/dialect/H2Dialect.java

@@ -127,7 +127,12 @@ public H2Dialect(int version) {
 	}
 
 	private static int parseBuildId(DialectResolutionInfo info) {
-		String[] bits = info.getDatabaseVersion().split("[. ]");
+		final String databaseVersion = info.getDatabaseVersion();
+		if ( databaseVersion == null ) {
+			return 0;
+		}
+
+		final String[] bits = databaseVersion.split("[. ]");
 		return bits.length > 2 ? Integer.parseInt( bits[2] ) : 0;
 	}
 

hibernate-core/src/main/java/org/hibernate/engine/jdbc/dialect/internal/DialectResolverInitiator.java

@@ -6,6 +6,7 @@
  */
 package org.hibernate.engine.jdbc.dialect.internal;
 
+import java.util.Collection;
 import java.util.Map;
 
 import org.hibernate.HibernateException;
@@ -18,7 +19,7 @@
 import org.hibernate.service.spi.ServiceRegistryImplementor;
 
 /**
- * Standard initiator for the standard {@link DialectResolver} service
+ * Standard initiator for the {@link DialectResolver} service
  *
  * @author Steve Ebersole
  */
@@ -36,25 +37,25 @@ public Class<DialectResolver> getServiceInitiated() {
 
 	@Override
 	public DialectResolver initiateService(Map configurationValues, ServiceRegistryImplementor registry) {
-		final DialectResolverSet resolver = new DialectResolverSet();
+		final DialectResolverSet resolverSet = new DialectResolverSet();
 
-		applyCustomerResolvers( resolver, registry, configurationValues );
-		resolver.addResolver( new StandardDialectResolver() );
+		applyCustomerResolvers( resolverSet, registry, configurationValues );
+		resolverSet.addResolver( new StandardDialectResolver() );
 
-		return resolver;
+		return resolverSet;
 	}
 
 	private void applyCustomerResolvers(
-			DialectResolverSet resolver,
+			DialectResolverSet resolverSet,
 			ServiceRegistryImplementor registry,
-			Map configurationValues) {
+			Map<?,?> configurationValues) {
 		final String resolverImplNames = (String) configurationValues.get( AvailableSettings.DIALECT_RESOLVERS );
 
+		final ClassLoaderService classLoaderService = registry.getService( ClassLoaderService.class );
 		if ( StringHelper.isNotEmpty( resolverImplNames ) ) {
-			final ClassLoaderService classLoaderService = registry.getService( ClassLoaderService.class );
 			for ( String resolverImplName : StringHelper.split( ", \n\r\f\t", resolverImplNames ) ) {
 				try {
-					resolver.addResolver(
+					resolverSet.addResolver(
 							(DialectResolver) classLoaderService.classForName( resolverImplName ).newInstance()
 					);
 				}
@@ -66,5 +67,8 @@ private void applyCustomerResolvers(
 				}
 			}
 		}
+
+		final Collection<DialectResolver> resolvers = classLoaderService.loadJavaServices( DialectResolver.class );
+		resolverSet.addDiscoveredResolvers( resolvers );
 	}
 }

hibernate-core/src/main/java/org/hibernate/engine/jdbc/dialect/internal/DialectResolverSet.java

@@ -8,6 +8,7 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.List;
 
 import org.hibernate.dialect.Dialect;
@@ -60,23 +61,19 @@ public Dialect resolveDialect(DialectResolutionInfo info) {
 		return null;
 	}
 
-	/**
-	 * Add a resolver at the end of the underlying resolver list.  The resolver added by this method is at lower
-	 * priority than any other existing resolvers.
-	 *
-	 * @param resolver The resolver to add.
-	 */
-	public void addResolver(DialectResolver resolver) {
-		resolvers.add( resolver );
+	public void addResolver(DialectResolver... resolvers) {
+		this.resolvers.addAll( Arrays.asList( resolvers ) );
 	}
 
-	/**
-	 * Add a resolver at the beginning of the underlying resolver list.  The resolver added by this method is at higher
-	 * priority than any other existing resolvers.
-	 *
-	 * @param resolver The resolver to add.
-	 */
-	public void addResolverAtFirst(DialectResolver resolver) {
-		resolvers.add( 0, resolver );
+	public void addResolverAtFirst(DialectResolver... resolvers) {
+		// in reverse so that the first item in the incoming list is added
+		// to the first position in `this.resolutions`
+		for ( int i = resolvers.length - 1; i >= 0; i-- ) {
+			this.resolvers.add( 0, resolvers[i] );
+		}
+	}
+
+	public void addDiscoveredResolvers(Collection<DialectResolver> resolvers) {
+		this.resolvers.addAll( 0, resolvers );
 	}
 }

hibernate-core/src/main/java/org/hibernate/engine/jdbc/dialect/internal/StandardDialectResolver.java

@@ -17,6 +17,8 @@
  * @author Steve Ebersole
  */
 public final class StandardDialectResolver implements DialectResolver {
+	public StandardDialectResolver() {
+	}
 
 	@Override
 	public Dialect resolveDialect(DialectResolutionInfo info) {