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   *  distributed with this work for additional information
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   *  to you under the Apache License, Version 2.0 (the
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  package org.apache.cayenne.dba;
  
  import java.sql.PreparedStatement;
  import java.sql.SQLException;
  import java.util.Collection;
  import java.util.List;
  
  import org.apache.cayenne.CayenneRuntimeException;
  import org.apache.cayenne.access.DataNode;
  import org.apache.cayenne.access.sqlbuilder.sqltree.SQLTreeProcessor;
  import org.apache.cayenne.access.translator.ParameterBinding;
  import org.apache.cayenne.access.translator.ejbql.EJBQLTranslatorFactory;
  import org.apache.cayenne.access.translator.select.SelectTranslator;
  import org.apache.cayenne.access.types.ExtendedTypeMap;
  import org.apache.cayenne.di.Provider;
  import org.apache.cayenne.log.JdbcEventLogger;
  import org.apache.cayenne.map.DbAttribute;
  import org.apache.cayenne.map.DbEntity;
  import org.apache.cayenne.map.DbRelationship;
  import org.apache.cayenne.map.EntityResolver;
  import org.apache.cayenne.query.FluentSelect;
  import org.apache.cayenne.query.Query;
  import org.apache.cayenne.query.SQLAction;
  
  /**
   * A DbAdapter that automatically detects the kind of database it is running on
   * and instantiates an appropriate DB-specific adapter, delegating all
   * subsequent method calls to this adapter.
   *
   * @since 1.2
   */
  public class AutoAdapter implements DbAdapter {
  
  	protected Provider<DbAdapter> adapterProvider;
  	protected PkGenerator pkGenerator;
  	protected JdbcEventLogger logger;
  
  	/**
  	 * The actual adapter that is delegated methods execution.
  	 */
  	volatile DbAdapter adapter;
  
  	/**
  	 * Creates an {@link AutoAdapter} based on a delegate adapter obtained via
  	 * "adapterProvider".
  	 *
  	 * @since 3.1
  	 */
  	public AutoAdapter(Provider<DbAdapter> adapterProvider, JdbcEventLogger logger) {
  
  		if (adapterProvider == null) {
  			throw new CayenneRuntimeException("Null adapterProvider");
  		}
  
  		this.adapterProvider = adapterProvider;
  		this.logger = logger;
  	}
  
  	/**
  	 * Returns a proxied DbAdapter, lazily creating it on first invocation.
  	 */
  	protected DbAdapter getAdapter() {
  		if (adapter == null) {
  			synchronized (this) {
  				if (adapter == null) {
  					this.adapter = loadAdapter();
  				}
  			}
  		}
  
  		return adapter;
  	}
  
  	/**
  	 * Loads underlying DbAdapter delegate.
  	 */
  	protected DbAdapter loadAdapter() {
  		return adapterProvider.get();
  	}
  
  	/**
  	 * @since 4.2
  	 */
  	@Override
  	public SelectTranslator getSelectTranslator(FluentSelect<?, ?> query, EntityResolver entityResolver) {
  		return getAdapter().getSelectTranslator(query, entityResolver);
  	}
  
  	@Override
  	public String getBatchTerminator() {
  		return getAdapter().getBatchTerminator();
  	}
  
  	@Override
  	public SQLTreeProcessor getSqlTreeProcessor() {
  		return getAdapter().getSqlTreeProcessor();
  	}
  
  	@Override
  	public SQLAction getAction(Query query, DataNode node) {
  		return getAdapter().getAction(query, node);
  	}
  
  	@Override
  	public boolean supportsUniqueConstraints() {
  		return getAdapter().supportsUniqueConstraints();
  	}
  
  	@Override
  	public boolean supportsCatalogsOnReverseEngineering() {
  		return getAdapter().supportsCatalogsOnReverseEngineering();
  	}
  
  	@Override
  	public boolean supportsGeneratedKeys() {
  		return getAdapter().supportsGeneratedKeys();
  	}
  
  	/**
  	 * @since 4.2
  	 */
  	@Override
  	public boolean supportsGeneratedKeysForBatchInserts() {
  		return getAdapter().supportsGeneratedKeysForBatchInserts();
  	}
  
  	@Override
  	public boolean supportsBatchUpdates() {
  		return getAdapter().supportsBatchUpdates();
  	}
  
  	@Override
  	public boolean typeSupportsLength(int type) {
  		return getAdapter().typeSupportsLength(type);
  	}
  
  	/**
  	 * @since 5.0
  	 */
  	@Override
  	public boolean typeSupportsScale(int type) {
  		return getAdapter().typeSupportsScale(type);
  	}
  
  	@Override
  	public Collection<String> dropTableStatements(DbEntity table) {
  		return getAdapter().dropTableStatements(table);
  	}
  
  	@Override
  	public String createTable(DbEntity entity) {
  		return getAdapter().createTable(entity);
  	}
  
  	@Override
  	public String createUniqueConstraint(DbEntity source, Collection<DbAttribute> columns) {
  		return getAdapter().createUniqueConstraint(source, columns);
  	}
  
  	@Override
  	public String createFkConstraint(DbRelationship rel) {
  		return getAdapter().createFkConstraint(rel);
  	}
  
  	@Override
  	public String[] externalTypesForJdbcType(int type) {
  		return getAdapter().externalTypesForJdbcType(type);
  	}
  
  	@Override
  	public ExtendedTypeMap getExtendedTypes() {
  		return getAdapter().getExtendedTypes();
  	}
  
  	/**
  	 * Returns a primary key generator.
  	 */
  	@Override
  	public PkGenerator getPkGenerator() {
  		return (pkGenerator != null) ? pkGenerator : getAdapter().getPkGenerator();
  	}
  
  	/**
  	 * Sets a PK generator override. If set to non-null value, such PK generator
  	 * will be used instead of the one provided by wrapped adapter.
  	 */
  	public void setPkGenerator(PkGenerator pkGenerator) {
  		this.pkGenerator = pkGenerator;
  	}
  
  	@Override
  	public DbAttribute buildAttribute(String name, String typeName, int type, int size, int precision,
  			boolean allowNulls) {
  
  		return getAdapter().buildAttribute(name, typeName, type, size, precision, allowNulls);
  	}
  
  	@Override
  	public void bindParameter(PreparedStatement statement, ParameterBinding parameterBinding)
  			throws SQLException, Exception {
  		getAdapter().bindParameter(statement, parameterBinding);
  	}
  
  	@Override
  	public String tableTypeForTable() {
  		return getAdapter().tableTypeForTable();
  	}
  
  	@Override
  	public String tableTypeForView() {
  		return getAdapter().tableTypeForView();
  	}
  
  	@Override
  	public void createTableAppendColumn(StringBuffer sqlBuffer, DbAttribute column) {
  		getAdapter().createTableAppendColumn(sqlBuffer, column);
  	}
  
  	/**
  	 * @since 4.0
  	 */
  	@Override
  	public QuotingStrategy getQuotingStrategy() {
  		return getAdapter().getQuotingStrategy();
  	}
  
  	/**
  	 * @since 4.0
  	 */
  	@Override
  	public DbAdapter unwrap() {
  		return getAdapter();
  	}
  
  	/**
  	 * @since 4.0
  	 */
  	@Override
  	public EJBQLTranslatorFactory getEjbqlTranslatorFactory() {
  		return getAdapter().getEjbqlTranslatorFactory();
  	}
  
  	@Override
  	public List<String> getSystemCatalogs() {
  		return getAdapter().getSystemCatalogs();
  	}
  
  	@Override
  	public List<String> getSystemSchemas() {
  		return getAdapter().getSystemSchemas();
  	}
  
  }
  