hxtttextdialect.java

hibernate连接access数据库,以及一些其他的hibernate介绍

package com.hxtt.support.hibernate;

import java.sql.Types;

/**
 * An SQL dialect for HXTT Text (CSV).
 */
public class HxttTextDialect extends HxttDialect {

    public HxttTextDialect() {
        super();
        //complete map
        registerColumnType( Types.BIT, "boolean" );
        registerColumnType(Types.CHAR, "char(l)");
        registerColumnType( Types.VARCHAR, "varchar($l)" );
        //registerColumnType(Types.VARCHAR, 254, "varchar($l)");
        registerColumnType( Types.LONGVARCHAR,  "longvarchar");
        registerColumnType( Types.NUMERIC, "numeric($p,$s)" );
        registerColumnType( Types.DECIMAL, "decimal($p,$s)" );
        registerColumnType( Types.BIGINT, "bigint" );
        registerColumnType( Types.SMALLINT, "numeric(5,0)" ); // HXTT Text (CSV) DON'T SUPPORT SMALLINT
        registerColumnType( Types.TINYINT, "numeric(3,0)" );   // HXTT Text (CSV) DON'T SUPPORT TINYINT
        registerColumnType( Types.BOOLEAN, "boolean" );
        registerColumnType( Types.INTEGER, "integer" );

        registerColumnType( Types.FLOAT, "float" );
        registerColumnType( Types.DOUBLE, "double" );
        registerColumnType( Types.BINARY,  "binary" );
        registerColumnType( Types.VARBINARY,  "varbinary" );
        registerColumnType( Types.LONGVARBINARY, "longvarbinary");

        registerColumnType( Types.DATE, "date" );
        registerColumnType( Types.TIME, "time" );
        registerColumnType( Types.TIMESTAMP, "timestamp" );
        registerColumnType( Types.BLOB, "blob" );
        registerColumnType( Types.CLOB, "clob" );
        registerColumnType( Types.JAVA_OBJECT, "java_object" );
    }

    /**
     * Does this dialect support the <tt>ALTER TABLE</tt> syntax?
     *
     * @return True if we support altering of tables; false otherwise.
     */
    public boolean hasAlterTable() {
            return false;//true;
    }
    

    /**
     * Apply s limit clause to the query.
     * <p/>
     * Typically dialects utilize {@link #supportsVariableLimit() variable}
     * limit caluses when they support limits.  Thus, when building the
     * select command we do not actually need to know the limit or the offest
     * since we will just be using placeholders.
     * <p/>
     * Here we do still pass along whether or not an offset was specified
     * so that dialects not supporting offsets can generate proper exceptions.
     * In general, dialects will override one or the other of this method and
     * {@link #getLimitString(String, int, int)}.
     *
     * @param query The query to which to apply the limit.
     * @param hasOffset Is the query requesting an offset?
     * @return the modified SQL
     */    
    public String getLimitString(String sql, boolean hasOffset) {


        sql = sql.trim();
        boolean isForUpdate = false;
        if ( sql.toLowerCase().endsWith(" for update") ) {
            sql = sql.substring( 0, sql.length()-11 );
            isForUpdate = true;
        }

        StringBuffer pagingSelect = new StringBuffer( sql.length()+100 );
        if (hasOffset) {
            pagingSelect.append("select * from ( select row_.*, RECNO() rownum_ from ( ");
        }
        else {
            pagingSelect.append("select * from ( ");
        }
        pagingSelect.append(sql);
        if (hasOffset) {
            pagingSelect.append(" ) row_ where RECNO() <= ?) where rownum_ > ?");
        }
        else {
            pagingSelect.append(" ) where RECNO() <= ?");
        }

        if (isForUpdate) pagingSelect.append(" for update");

        return pagingSelect.toString();
    }

    /**
     * Does this dialect support identity column key generation?
     *
     * @return True if IDENTITY columns are supported; false otherwise.
     */
    public boolean supportsIdentityColumns() {
            return false;
    }

    /**
     * Whether this dialect have an Identity clause added to the data type or a
     * completely seperate identity data type
     *
     * @return boolean
     */
    public boolean hasDataTypeInIdentityColumn() {
            return false;
    }
}