SimpleQueryWriter.java

package com.spun.util.database;

import com.spun.util.DatabaseUtils;
import com.spun.util.database.SQLQuery.FromPart;
import com.spun.util.database.SQLQuery.OrderByPart;

class SimpleQueryWriter implements SQLQueryWriter
{
	private int databaseType;

	/**************************************************************************/
	public SimpleQueryWriter(int databaseType)
	{
		this.databaseType = databaseType;
	}
	/**************************************************************************/
	public String toString(SQLQuery query)
	{
		StringBuffer sql = new StringBuffer("SELECT ");
    if (query.isDistinct())
    {
      sql.append("DISTINCT ");
    }
    // limit
    if (DatabaseUtils.isSqlServer(databaseType) && query.getLimitPart() != null)
    {
      if (query.getLimitPart().getStartingZeroBasedIndex() != 0) 
      {
        throw new Error("Wrong Sql writer for lower bound of " + query.getLimitPart().getStartingZeroBasedIndex()); 
      }
      sql.append("TOP " + query.getLimitPart().numberOfRowsDesired + " ");
    }
		addSelectPart(sql, query.getSelectParts());
		addFromPart(sql, query.getFromParts());
    addWherePart(sql, query.getWherePart());
		addGroupBy(sql, query.getGroupByParts());
		addHaving(sql, query.getHavingParts());
		addOrderByPart(sql, query.getOrderByParts());
		//limit
    if ((databaseType == DatabaseUtils.POSTGRESQL || databaseType == DatabaseUtils.MY_SQL) && query.getLimitPart() != null)
    {
      sql.append(" LIMIT ");
      if (databaseType == DatabaseUtils.MY_SQL && query.getLimitPart().getStartingZeroBasedIndex() != 0) 
      {
        sql.append(query.getLimitPart().getStartingZeroBasedIndex() + ", ");
      }
      sql.append(query.getLimitPart().numberOfRowsDesired);
    }
		return sql.toString();
	}
  /***********************************************************************/
  private void addOrderByPart(StringBuffer sql, OrderByPart[] orderBys)
	{
		//order by 
		if (orderBys.length > 0)
		{
			sql.append(SQLQuery.BREAK + "ORDER BY ");
			for (int i = 0; i < orderBys.length; i++)
			{
				sql.append(orderBys[i].toString(i == 0));
			}
			sql.append(" ");
		}
	}
	/***********************************************************************/
	private void addWherePart(StringBuffer sql, SQLWhere wherePart)
	{
    if (wherePart != null )
    {
      sql.append(SQLQuery.BREAK + "WHERE ");
      sql.append(wherePart.toString());
    }		
	}
	/***********************************************************************/
	private void addFromPart(StringBuffer sql, FromPart[] froms)
	{
    if (froms.length > 0)
    {
      sql.append(SQLQuery.BREAK + "FROM ");
      for (int i = 0; i < froms.length; i++)
      {
        sql.append(froms[i].toString(i == 0));
      }
      sql.append(" ");
    }
	}
	/***********************************************************************/
	private void addGroupBy(StringBuffer sql, String[] groupBys)
	{
    if (groupBys.length > 0)
    {
      sql.append(SQLQuery.BREAK + "GROUP BY ");
      for (int i = 0; i < groupBys.length; i++)
      {
        sql.append(groupBys[i]);
        sql.append(", ");
      }
      sql.setLength(sql.length() - 2);
      sql.append(" ");
    }
	}
	/***********************************************************************/
	private void addHaving(StringBuffer sql, String[] havings)
	{
    if (havings.length > 0)
    {
      sql.append(SQLQuery.BREAK + "HAVING ");
      for (int i = 0; i < havings.length; i++)
      {
        sql.append(havings[i]);
        sql.append(", ");
      }
      sql.setLength(sql.length() - 2);
      sql.append(" ");
    }
	}
	/***********************************************************************/
	private void addSelectPart(StringBuffer sql, String[] selectParts)
	{
    for (int i = 0; i < selectParts.length; i++)
    {
      sql.append(selectParts[i]);
      sql.append(", ");
    }
    sql.setLength(sql.length() - 2);
    sql.append(" ");
    
	}
	/**************************************************************************/
	/**************************************************************************/

}