select.java

一个Java持久层类库

//$Id: Select.java 7143 2005-06-15 02:57:03Z oneovthafew $
package org.hibernate.sql;

import org.hibernate.LockMode;
import org.hibernate.dialect.Dialect;
import org.hibernate.util.StringHelper;


/**
 * A simple SQL <tt>SELECT</tt> statement
 * @author Gavin King
 */
public class Select {

	private String selectClause;
	private String fromClause;
	private String outerJoinsAfterFrom;
	private String whereClause;
	private String outerJoinsAfterWhere;
	private String orderByClause;
	private String groupByClause;
	private String comment;
	private LockMode lockMode;
	public final Dialect dialect;

	private int guesstimatedBufferSize = 20;
	
	public Select(Dialect dialect) {
		this.dialect = dialect;
	}

	/**
	 * Construct an SQL <tt>SELECT</tt> statement from the given clauses
	 */
	public String toStatementString() {
		StringBuffer buf = new StringBuffer(guesstimatedBufferSize);
		if ( StringHelper.isNotEmpty(comment) ) {
			buf.append("/* ").append(comment).append(" */ ");
		}
		
		buf.append("select ").append(selectClause)
				.append(" from ").append(fromClause);
		
		if ( StringHelper.isNotEmpty(outerJoinsAfterFrom) ) {
			buf.append(outerJoinsAfterFrom);
		}
		
		if ( StringHelper.isNotEmpty(whereClause) || StringHelper.isNotEmpty(outerJoinsAfterWhere) ) {
			buf.append(" where " );
			// the outerJoinsAfterWhere needs to come before where clause to properly
			// handle dynamic filters
			if ( StringHelper.isNotEmpty(outerJoinsAfterWhere) ) {
				buf.append(outerJoinsAfterWhere);
				if ( StringHelper.isNotEmpty(whereClause) ) {
					buf.append( " and " );
				}
			}
			if ( StringHelper.isNotEmpty(whereClause) ) {
				buf.append(whereClause);
			}
		}
		
		if ( StringHelper.isNotEmpty(groupByClause) ) {
			buf.append(" group by ").append(groupByClause);
		}
		
		if ( StringHelper.isNotEmpty(orderByClause) ) {
			buf.append(" order by ").append(orderByClause);
		}
		
		if (lockMode!=null) {
			buf.append( dialect.getForUpdateString(lockMode) );
		}
		
		return dialect.transformSelectString( buf.toString() );
	}

	/**
	 * Sets the fromClause.
	 * @param fromClause The fromClause to set
	 */
	public Select setFromClause(String fromClause) {
		this.fromClause = fromClause;
		this.guesstimatedBufferSize += fromClause.length();
		return this;
	}

	public Select setFromClause(String tableName, String alias) {
		this.fromClause = tableName + ' ' + alias;
		this.guesstimatedBufferSize += fromClause.length();
		return this;
	}

	public Select setOrderByClause(String orderByClause) {
		this.orderByClause = orderByClause;
		this.guesstimatedBufferSize += orderByClause.length();
		return this;
	}

	public Select setGroupByClause(String groupByClause) {
		this.groupByClause = groupByClause;
		this.guesstimatedBufferSize += groupByClause.length();
		return this;
	}

	public Select setOuterJoins(String outerJoinsAfterFrom, String outerJoinsAfterWhere) {
		this.outerJoinsAfterFrom = outerJoinsAfterFrom;

		// strip off any leading 'and' token
		String tmpOuterJoinsAfterWhere = outerJoinsAfterWhere.trim();
		if ( tmpOuterJoinsAfterWhere.startsWith("and") ) {
			tmpOuterJoinsAfterWhere = tmpOuterJoinsAfterWhere.substring(4);
		}
		this.outerJoinsAfterWhere = tmpOuterJoinsAfterWhere;

		this.guesstimatedBufferSize += outerJoinsAfterFrom.length() + outerJoinsAfterWhere.length();
		return this;
	}


	/**
	 * Sets the selectClause.
	 * @param selectClause The selectClause to set
	 */
	public Select setSelectClause(String selectClause) {
		this.selectClause = selectClause;
		this.guesstimatedBufferSize += selectClause.length();
		return this;
	}

	/**
	 * Sets the whereClause.
	 * @param whereClause The whereClause to set
	 */
	public Select setWhereClause(String whereClause) {
		this.whereClause = whereClause;
		this.guesstimatedBufferSize += whereClause.length();
		return this;
	}

	public Select setComment(String comment) {
		this.comment = comment;
		this.guesstimatedBufferSize += comment.length();
		return this;
	}

	public LockMode getLockMode() {
		return lockMode;
	}
	
	public Select setLockMode(LockMode lockMode) {
		this.lockMode = lockMode;
		return this;
	}
}