运用HIBERNATE的DetachedCriteria无限级联取部份字段的查询结果集转换

criteria.setResultTransformer(Transformers.aliasToBean(pojoClass));

////////SERVICE中查询的方法
public List<User> findUsers(){
//要查的部份字段，ID，用户名和所在组织的名称
String[] columns = {"id","name","organization.name"};
//构造查询器
DetachedCriteria criteria = DetachedCriteria.forClass(User.class,"_user");
//筛选字段
DetachedCriteriaUntils.selectColumn(criteria,columns,Class pojoClass, String rootAlias,boolean forJoinTable);
//查询数据库
return userDAO.findByCriteria(criteria)
}

/**
	 * 该方法提供DetachedCriteria对查询字段的封装，
	 * 可支持无限级联取部分字段  ser.organization.parentOrganization.parentOrganization.orgName
	 * 但请注意1点 ,连接采用内联，级联越多，结果集可能就越少；
	 * @param columnNames
	 *            字符串数组，以数据的形式接收要查询的字段属性，如String[] column={"属性1","属性2","属性3"};
	 * @param pojoClass
	 *            实体类的Class,如Mobile.class;
	 * @param rootAials
	 *            为要查询的POJO对象指定一个别名
	 * @return DetachedCriteria 的一个对象，如果需要查询条件，在些对象后追加查询条件。
	 * 
	 * @param forJoinTable 是否多表连接查询
	 */
	public static void selectColumn(DetachedCriteria criteria, String[] columnNames,
			Class<? extends BaseModel> pojoClass, String rootAlias,boolean forJoinTable) {
		if (null == columnNames) {
			return;
		}
	
		//使用这个临时变量集合，是因为dinstinct关键字要放在最前面，而distinct关键字要在下面才决定放不放，
		List<Projection> tempProjectionList = new ArrayList<Projection>();;
		
		Set<String> aliases = getAliasFromRequest();
		boolean hasJoniTable = false;
		for (String property : columnNames) {
			if(property.contains(POINT)){
				String[] propertyChain = property.split("\\.");
				if(aliases==null){aliases=new HashSet<String>(3);}
				createAlias(criteria,rootAlias,aliases,propertyChain,0);
				tempProjectionList.add(Projections.property(getAliasFromPropertyChainString(property)).as(property));
				hasJoniTable = true;
			}else{
				tempProjectionList.add(Projections.property(rootAlias + POINT + property).as(property));
			}
		}
		
		ProjectionList projectionList = Projections.projectionList();
		if(hasJoniTable || forJoinTable ||  getHasJoinTatleFromRequest()){//这个一定要放在tempProjectionList的前面，因为distinct要在最前面
			projectionList.add(Projections.distinct(Projections.id()));
		}
		
		for (Projection proj : tempProjectionList) {
			projectionList.add(proj);
		}
		
		criteria.setProjection(projectionList);
		
		if(!hasJoniTable){
			criteria.setResultTransformer(Transformers.aliasToBean(pojoClass));
		}else{//注意，重点就在这里，这里检测到如果有类类似于user.organization.name这种字段，就表示是级联其它表的部份字段，那么要使用下面的这个EscAliasToBean来转换结果集，而不能使用上面那个HIBERNATE提供的类
			criteria.setResultTransformer(new EscAliasToBean(pojoClass));
		}
	}

package com.lgdlgd.hibernate;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import ognl.Ognl;

import org.hibernate.HibernateException;
import org.hibernate.transform.ResultTransformer;

import com.opensymphony.xwork2.util.InstantiatingNullHandler;
import com.opensymphony.xwork2.util.OgnlUtil;

/**
 * 支持属性为自定义对象的结果集转换的部份属性查询
 */
@SuppressWarnings({"serial","unchecked"})
public class EscAliasToBean implements ResultTransformer {

	private static final Map<String,Boolean> context = new HashMap<String,Boolean>(1);
	static{
		context.put(InstantiatingNullHandler.CREATE_NULL_OBJECTS, true);
	}
	
	/** POJO的class */
	private final Class resultClass;

	
	public EscAliasToBean(Class pojoClass) {
		if(pojoClass==null) throw new IllegalArgumentException("resultClass cannot be null");
		this.resultClass = pojoClass;		
	}

	@Override
	public List transformList(List collection) {
		return collection;
	}

	/**
	 * 结果集转换
	 * @param tuple 属性值集合
	 * @param aliases 属性名集合，就是上面的{id,name,organization.name};
	 * @return 单个POJO实例--查询结果
	 */
	@Override
	public Object transformTuple(Object[] tuple, String[] aliases) {
		try {
			Object root = resultClass.newInstance();
			for (int i = 0; i < aliases.length; i++) {
				Ognl.setValue(OgnlUtil.compile(aliases[i]), context, root, tuple[i]);
			}
			return root;
		} catch (Exception e) {
			throw new HibernateException(e.getMessage(),e);
		}
	}

}

ProjectionList projectionList = Projections.projectionList(); 
....
取部份字段，并创建级联关系
....
criteria.setProjection(projectionList); 

criteria.setResultTransformer(...));   

ProjectionList projectionList = Projections.projectionList();  
...  
criteria.setProjection(projectionList); 

String[] columns = new String[]{property1,property2,property3.property4};
DetachedCriteria criteria = getDetachedCriteria(POJO.class,columns,alias);
DAO.findByCriteria(criteria);

ProjectionList projectionList = Projections.projectionList();  
...  
criteria.setProjection(projectionList); 

String[] columns = new String[]{property1,property2,property3.property4};
DetachedCriteria criteria = getDetachedCriteria(POJO.class,columns,alias);
DAO.findByCriteria(criteria);