dialect.java

人力资源管理系统主要包括：人员管理、招聘管理、培训管理、奖惩管理和薪金管理五大管理模块。

//$Id: Dialect.java,v 1.20.2.23 2004/01/17 23:52:54 maxcsaucdk Exp $
package net.sf.hibernate.dialect;

import java.util.Properties;
import java.util.Map;
import java.util.HashMap;
import java.sql.Types;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import net.sf.hibernate.cfg.Environment;
import net.sf.hibernate.sql.ANSICaseFragment;
import net.sf.hibernate.sql.ANSIJoinFragment;
import net.sf.hibernate.sql.CaseFragment;
import net.sf.hibernate.sql.JoinFragment;
import net.sf.hibernate.util.ReflectHelper;
import net.sf.hibernate.util.StringHelper;
import net.sf.hibernate.HibernateException;
import net.sf.hibernate.MappingException;
import net.sf.hibernate.type.Type;
import net.sf.hibernate.engine.Mapping;
import net.sf.hibernate.Hibernate;
import net.sf.hibernate.QueryException;

/**
 * Represents a dialect of SQL implemented by a particular RDBMS.
 * Subclasses implement Hibernate compatibility with different systems.<br>
 * <br>
 * Subclasses should provide a public default constructor that <tt>register()</tt>
 * a set of type mappings and default Hibernate properties.<br>
 * <br>
 * Subclasses should be immutable.
 * @author Gavin King, David Channon
 */
public abstract class Dialect {

	static final String DEFAULT_BATCH_SIZE = "15";
	static final String NO_BATCH = "0";

	private static final Map STANDARD_AGGREGATE_FUNCTIONS = new HashMap();
	
	static {
		STANDARD_AGGREGATE_FUNCTIONS.put("count", new SQLFunction() {
			public Type getReturnType(Type columnType, Mapping mapping) {
				return Hibernate.INTEGER;
			}
			public boolean hasArguments() { return true; }
			public boolean hasParenthesesIfNoArguments() { return true; }
		});
		
		STANDARD_AGGREGATE_FUNCTIONS.put("avg", new SQLFunction() {
			public Type getReturnType(Type columnType, Mapping mapping) throws QueryException {
				int[] sqlTypes;
				try {
					sqlTypes = columnType.sqlTypes(mapping);
				}
				catch (MappingException me) {
					throw new QueryException(me);
				}
				if (sqlTypes.length!=1) throw new QueryException("multi-column type in avg()");
				int sqlType = sqlTypes[0];
				if (sqlType==Types.INTEGER || sqlType==Types.BIGINT || sqlType==Types.TINYINT) {
					return Hibernate.FLOAT;
				}
				else {
					return columnType;
				}	
			}
			public boolean hasArguments() { return true; }
			public boolean hasParenthesesIfNoArguments() { return true; }
		});
		
		STANDARD_AGGREGATE_FUNCTIONS.put( "max", new StandardSQLFunction() );
		STANDARD_AGGREGATE_FUNCTIONS.put( "min", new StandardSQLFunction() );
		STANDARD_AGGREGATE_FUNCTIONS.put( "sum", new StandardSQLFunction() );
	}
	
	private static final Log log = LogFactory.getLog(Dialect.class);
	
	protected Dialect() {
		log.info( "Using dialect: " + this );
		sqlFunctions.putAll(STANDARD_AGGREGATE_FUNCTIONS);
	}
	
	public String toString() {
		return getClass().getName();
	}
	
	private final TypeNames typeNames = new TypeNames("$l");
	private final Properties properties = new Properties();
	private final Map sqlFunctions = new HashMap();
	
	/**
	 * Characters used for quoting SQL identifiers
	 */
	public static final String QUOTE="`\"[";
	public static final String CLOSED_QUOTE="`\"]";
	
	
	/**
	 * Get the name of the database type associated with the given
	 * <tt>java.sql.Types</tt> typecode.
	 * @param code <tt>java.sql.Types</tt> typecode
	 * @return the database type name
	 * @throws HibernateException
	 */
	public String getTypeName(int code) throws HibernateException {
		String result = typeNames.get(code);
		if (result == null)
		throw new HibernateException("No default type mapping for (java.sql.Types) " + code);
		return result;
	}
	
	/**
	 * Get the name of the database type associated with the given
	 * <tt>java.sql.Types</tt> typecode.
	 * @param code <tt>java.sql.Types</tt> typecode
	 * @param length the length of the column
	 * @return the database type name
	 * @throws HibernateException
	 */
	public String getTypeName(int code, int length) throws HibernateException {
		String result = typeNames.get(code, length);
		if (result == null)
		throw new HibernateException("No type mapping for (java.sql.Types) " + code + " of length " + length);
		return result;
	}
	
	protected void registerFunction(String name, SQLFunction function) {
		sqlFunctions.put(name, function);
	}
	
	/**
	 * Subclasses register a typename for the given type code and maximum
	 * column length. <tt>$l</tt> in the type name with be replaced by the
	 * column length (if appropriate).
	 * @param code <tt>java.sql.Types</tt> typecode
	 * @param capacity maximum length of database type
	 * @param name the database type name
	 */
	protected void registerColumnType(int code, int capacity, String name) {
		typeNames.put(code, capacity, name);
	}
	
	/**
	 * Subclasses register a typename for the given type code. <tt>$l</tt> in
	 * the type name with be replaced by the column length (if appropriate).
	 * @param code <tt>java.sql.Types</tt> typecode
	 * @param name the database type name
	 */
	protected void registerColumnType(int code, String name) {
		typeNames.put(code, name);
	}
	
	/**
	 * Does this dialect support the <tt>ALTER TABLE</tt> syntax?
	 * @return boolean
	 */
	public boolean hasAlterTable() {
		return true;
	}
	
	/**
	 * Do we need to drop constraints before dropping tables in this dialect?
	 * @return boolean
	 */
	public boolean dropConstraints() {
		return true;
	}
	
	/**
	 * Do we need to qualify index names with the schema name?
	 * @return boolean
	 */
	public boolean qualifyIndexName() {
		return true;
	}
	
	/**
	 * Does this dialect support the <tt>FOR UPDATE</tt> syntax?
	 * @return boolean
	 */
	public boolean supportsForUpdate() {
		return true;
	}
	
	/**
	 * Does this dialect support <tt>FOR UPDATE OF</tt>, allowing
	 * particular rows to be locked?
	 */
	public boolean supportsForUpdateOf() {
		return false;
	}
	
	/**
	 * Does this dialect support the Oracle-style <tt>FOR UPDATE NOWAIT</tt> syntax?
	 * @return boolean
	 */
	public boolean supportsForUpdateNowait() {
		return false;
	}
	
	/**
	 * Does this dialect support the <tt>UNIQUE</tt> column syntax?
	 * @return boolean
	 */
	public boolean supportsUnique() {
		return true;
	}
	
	/**
	 * The syntax used to add a column to a table (optional).
	 */
	public String getAddColumnString() {
		throw new UnsupportedOperationException("No add column syntax supported by Dialect");
	}
	
	/**
	 * The syntax used to add a foreign key constraint to a table.
	 * @return String
	 */
	public String getAddForeignKeyConstraintString(String constraintName, String[] foreignKey, String referencedTable, String[] primaryKey) {
		return new StringBuffer(30)
			.append(" add constraint ")
			.append(constraintName)
			.append(" foreign key (")
			.append( StringHelper.join(StringHelper.COMMA_SPACE, foreignKey) )
			.append(") references ")
			.append(referencedTable)
			.toString();
	}
	
	/**
	 * The syntax used to add a primary key constraint to a table.
	 * @return String
	 */
	public String getAddPrimaryKeyConstraintString(String constraintName) {
		return " add constraint " + constraintName + " primary key ";
	}
	
	/**
	 * The keyword used to specify a nullable column.
	 * @return String
	 */
	public String getNullColumnString() {
		return StringHelper.EMPTY_STRING;
	}
	
	/**
	 * Does this dialect support identity column key generation?
	 * @return boolean
	 */
	public boolean supportsIdentityColumns() {
		return false;
	}
	
	/**
	 * Does this dialect support sequences?
	 * @return boolean
	 */
	public boolean supportsSequences() {
		return false;
	}

	/** 
	 * Generate SQL to get the identifier of an inserted row.
	 * If the returned value is not null, the caller will prepare a statement from it,
	 * set SQL parameters just as it would for insertSQL, and execute it as a query
	 * which is expected to return the identifier of the inserted row.
	 * If the returned value is null, the caller will execute insertSQL as an update
	 * and then execute getIdentitySelectString() as a query.