优化Hibernate的SQLCriterion_支持同时多表别名
Criteria rootCr = session.createCriteria(entityClazz);Criteria subACr = rootCr.createCriteria("subA","a");Criteria subBCr = rootCr.createCriteria("subB","b");String sql = "{alias}.root_time > date_add({a}.a_time, interval 20 hour or {b}.b_time > date_add({a}.a_time, interval 20 hour "rootCr.add(Restrictions.sqlRestriction(sql));?
注：date_add函数是MySQL的，无需理会
上面这段代码使用Hibernate3是会报错的，Hibernate只会将{alias}替换成加入了SQLCriterion的Criteria的别名，此处是rootCr，默认为this_，而对于{a}和{b}都无视。在生成的sql中subA和subB表的别名分别为a1_和b2_，所以会报错
?
修改SQLCriterion的实现可以达到多表别名替换的效果：
import java.util.Iterator;import org.hibernate.Criteria;import org.hibernate.EntityMode;import org.hibernate.HibernateException;import org.hibernate.criterion.CriteriaQuery;import org.hibernate.criterion.Criterion;import org.hibernate.engine.TypedValue;import org.hibernate.impl.CriteriaImpl;import org.hibernate.impl.CriteriaImpl.Subcriteria;import org.hibernate.type.Type;import org.hibernate.util.StringHelper;/** * Hack the original class * 2012-04-10 * @author wangzhen * */public class SQLCriterion implements Criterion {private static final longserialVersionUID= 561456879784847643L;private final String sql;private final TypedValue[] typedValues;public String toSqlString(Criteria criteria,CriteriaQuery criteriaQuery)throws HibernateException {CriteriaImpl rootCriteria = null;if(criteria instanceof CriteriaImpl){rootCriteria = (CriteriaImpl)criteria;}else if(criteria instanceof Subcriteria){rootCriteria = (CriteriaImpl) ((Subcriteria)criteria).getParent();}else {throw new HibernateException("暂不支持其他Criteria的实现");}Iterator iterateSubcriteria = rootCriteria.iterateSubcriteria();String tempSql = sql;//replace subcriterias' aliaswhile (iterateSubcriteria.hasNext()) {Subcriteria subCriteria = (Subcriteria) iterateSubcriteria.next();tempSql = StringHelper.replace( tempSql, "{"+subCriteria.getAlias()+"}", criteriaQuery.getSQLAlias(subCriteria) );}return StringHelper.replace( tempSql, "{alias}", criteriaQuery.getSQLAlias(criteria) );}public TypedValue[] getTypedValues(Criteria criteria, CriteriaQuery criteriaQuery)throws HibernateException {return typedValues;}public String toString() {return sql;}public SQLCriterion(String sql, Object[] values, Type[] types) {this.sql = sql;typedValues = new TypedValue[values.length];for ( int i=0; i<typedValues.length; i++ ) {typedValues[i] = new TypedValue( types[i], values[i], EntityMode.POJO );}}}?