Criteria和DetachedCriteria的区别与应用

Hibernate 设计了CriteriaSpecification 作为 Criteria 的父接口，下面提供了 Criteria和DetachedCriteria 。 Criteria 和 DetachedCriteria 的主要区别在于创建的形式不一样， Criteria 是在线的，所以它是由 Hibernate Session 进行创建的；而 DetachedCriteria 是离线的，创建时无需 Session，DetachedCriteria 提供了 2 个静态方法 forClass(Class) 或 forEntityName(Name) 进行DetachedCriteria 实例的创建。 Spring 的框架提供了getHibernateTemplate ().findByCriteria(detachedCriteria) 方法可以很方便地根据DetachedCriteria来返回查询结 果。 Criteria 和 DetachedCriteria 均可使用 Criterion 和 Projection 设置查询条件。可以设置 FetchMode( 联合查询抓取的模式 ) ，设置排序方式。对于 Criteria 还可以设置 FlushModel （冲刷 Session 的方式）和 LockMode （数据库锁模式）。

下面对 Criterion 和 Projection 进行详细说明。 Criterion 是 Criteria 的查询条件。Criteria 提供了 add(Criterion criterion) 方法来 添加查询条件。Criterion 接口的主要实现包括： Example 、 Junction 和 SimpleExpression 。而 Junction 的实际使用是它的两个子类conjunction 和 disjunction ，分别是使用 AND 和 OR 操作符进行来联结查询条件集合。 Criterion 的实例可以通过 Restrictions 工具类来创建，Restrictions提供了大量的静态方法，如 eq （等于）、 ge （大于等于）、 between 等来方法的创建 Criterion 查询条件（SimpleExpression 实例）。除此之外，Restrictions 还提供了方法来创建 conjunction和 disjunction 实例，通过往该实例的add(Criteria) 方法来增加查询条件形成一个查询条件集合 。 至于 Example 的创建有所不同， Example 本身提供了一个静态方法create(Object entity) ，即根据一个对象（实际使用中一般是映射到数据库的对象）来创建。然后可以设置一些过滤条件： Example exampleUser =Example.create(u) .ignoreCase() // 忽略大小写 .enableLike(MatchMode.ANYWHERE); // 对 String 类型的属性，无论在那里值在那里都匹配。相当于 %value% Project 主要是让 Criteria能够进行报表查询，并可以实现分组。 Project 主要有 SimpleProjection 、ProjectionList 和 Property 三个实现。其中SimpleProjection 和 ProjectionList 的实例化是由内建的Projections 来完成，如提供的 avg 、 count 、 max 、 min 、 sum 可以让开发者很容易对某个字段进行统计查询。 Property 是对某个字段进行查询条件的设置，如通过Porperty.forName(“color”).in (new String[]{“black”,”red”,”write”}); 则可以创建一个Project 实例。通过 criteria 的 add(Project) 方法加入到查询条件中去。 使用 Criteria 进行查询，主要要清晰的是Hibernate 提供了那些类和方法来满足开发中查询条件的创建和组装，下面介绍几种用法：

创建一个Criteria 实例

org.hibernate.Criteria接口表示特定持久类的一个查询。Session是 Criteria实例的工厂。

Criteriacrit = sess.createCriteria(Cat. class );

crit.setMaxResults(50 );

Listcats = crit.list();

Criteriacrit = sess.createCriteria(Cat. class );

crit.setMaxResults(50 );

Listcats = crit.list();

Java代码

Criteria crit = sess.createCriteria(Cat.class); crit.setMaxResults(50); List cats = crit.list();

Criteriacrit = sess.createCriteria(Cat.class); crit.setMaxResults(50); List cats =crit.list();

限制结果集内容

一个单独的查询条件是org.hibernate.criterion.Criterion 接口的一个实例。 org.hibernate.criterion.Restrictions类 定义了获得某些内置Criterion类型的工厂方法。

Listcats = sess.createCriteria(Cat. class )

.add( Restrictions.like( "name" , "Fritz%" ) )

.add( Restrictions.between( "weight" , minWeight, maxWeight) )

.list();

Listcats = sess.createCriteria(Cat. class )

.add( Restrictions.like("name" , "Fritz%" ) )

.add( Restrictions.between("weight" , minWeight, maxWeight))

.list();

Java代码

List cats = sess.createCriteria(Cat.class) .add( Restrictions.like("name", "Fritz%") ) .add( Restrictions.between("weight", minWeight, maxWeight) ) .list();

List cats =sess.createCriteria(Cat.class) .add( Restrictions.like("name","Fritz%") ) .add(Restrictions.between("weight", minWeight, maxWeight) ) .list();

约束可以按逻辑分组。

Listcats = sess.createCriteria(Cat. class )

.add( Restrictions.like( "name" , "Fritz%" ) )

.add( Restrictions.or(

Restrictions.eq( "age" , new Integer( 0 )),

Restrictions.isNull( "age" )

) )

.list();

Listcats = sess.createCriteria(Cat. class )

.add( Restrictions.like("name" , "Fritz%" ) )

.add( Restrictions.or(

Restrictions.eq( "age" , new Integer( 0) ),

Restrictions.isNull("age" )

1. ) ) 2. .list(); 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.in( "name" , new String[] { "Fritz" ,"Izi" , "Pk" } ) ) 3. .add( Restrictions.disjunction() 4. .add( Restrictions.isNull( "age" ) ) 5. .add( Restrictions.eq( "age" , new Integer( 0) ) ) 6. .add( Restrictions.eq( "age" , new Integer( 1) ) ) 7. .add( Restrictions.eq( "age" , new Integer( 2) ) ) 8. ) ) 9. .list(); 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.in( "name" , new String[] { "Fritz" ,"Izi" , "Pk" } ) ) 3. .add( Restrictions.disjunction() 4. .add( Restrictions.isNull("age" ) ) 5. .add( Restrictions.eq("age" , new Integer( 0) ) ) 6. .add( Restrictions.eq("age" , new Integer( 1) ) ) 7. .add( Restrictions.eq("age" , new Integer( 2) ) ) 8. ) ) 9. .list(); Java代码

1. List cats = sess.createCriteria(Cat.class) .add( Restrictions.in( "name", new String[] { "Fritz", "Izi", "Pk" } ) ) .add( Restrictions.disjunction() .add( Restrictions.isNull("age") ) .add( Restrictions.eq("age", new Integer(0) ) ) .add( Restrictions.eq("age", new Integer(1) ) ) .add( Restrictions.eq("age", new Integer(2) ) ) ) ) .list(); List cats = sess.createCriteria(Cat.class) .add( Restrictions.in( "name",new String[] { "Fritz", "Izi", "Pk" } ) ) .add( Restrictions.disjunction() .add(Restrictions.isNull("age") ) .add( Restrictions.eq("age", new Integer(0) ) ) .add( Restrictions.eq("age",new Integer(1) ) ) .add(Restrictions.eq("age", new Integer(2) ) ) ) ) .list();Hibernate提供了相当多的内置criterion类型(Restrictions 子类), 但是尤其有用的是可以允许 你直接使用SQL。 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.sql( "lower({alias}.name) like lower(?)" ,"Fritz%" , 3. Hibernate.STRING)) 4. .list(); 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.sql("lower({alias}.name) like lower(?)" ,"Fritz%" , 3. Hibernate.STRING)) 4. .list(); Java代码

1. List cats = sess.createCriteria(Cat.class) .add( Restrictions.sql("lower({alias}.name) like lower(?)", "Fritz%", Hibernate.STRING) ) .list(); List cats = sess.createCriteria(Cat.class) .add(Restrictions.sql("lower({alias}.name) like lower(?)","Fritz%", Hibernate.STRING) ) .list();{alias}占位符应当被替换为被查询实体的列别名。 Property实例是获得一个条件的另外一种途径。你可以通过调用Property.forName() 创建一个 Property。 1. Property age =Property.forName( "age" ); 2. st cats =sess.createCriteria(Cat. class ) 3. .add(Restrictions.disjunction() 4. .add( age.isNull() ) 5. .add( age.eq( new Integer( 0 ) ) ) 6. .add( age.eq( new Integer( 1 ) ) ) 7. .add( age.eq( new Integer( 2 ) ) ) 8. ) ) 9. .add(Property.forName( "name" ).in( new String[] { "Fritz" ,"Izi" , "Pk" } ) ) 10. .list(); 1. Property age =Property.forName( "age" ); 2. st cats =sess.createCriteria(Cat.class ) 3. .add(Restrictions.disjunction() 4. .add( age.isNull() ) 5. .add( age.eq( new Integer( 0 ) )) 6. .add( age.eq( new Integer( 1 ) )) 7. .add( age.eq( new Integer( 2 ) )) 8. )) 9. .add(Property.forName("name" ).in( new String[] { "Fritz" ,"Izi" , "Pk" } ) ) 10. .list(); Java代码

1. Property age = Property.forName("age"); List cats = sess.createCriteria(Cat.class) .add( Restrictions.disjunction() .add( age.isNull() ) .add( age.eq( new Integer(0) ) ) .add( age.eq( new Integer(1) ) ) .add( age.eq( new Integer(2) ) ) ) ) .add( Property.forName("name").in( new String[] { "Fritz", "Izi", "Pk" } ) ) .list(); Property age = Property.forName("age"); List cats =sess.createCriteria(Cat.class) .add(Restrictions.disjunction() .add(age.isNull() ) .add( age.eq( newInteger(0) ) ) .add( age.eq( newInteger(1) ) ) .add( age.eq( newInteger(2) ) ) ) ) .add(Property.forName("name").in( new String[] { "Fritz","Izi", "Pk" } ) ) .list();3. 结果集排序 你可以使用org.hibernate.criterion.Order来为查询结果排序。 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.like( "name" , "F%" ) 3. .addOrder( Order.asc( "name" ) ) 4. .addOrder( Order.desc( "age" ) ) 5. .setMaxResults( 50 ) 6. .list(); 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.like("name" , "F%" ) 3. .addOrder( Order.asc("name" ) ) 4. .addOrder( Order.desc("age" ) ) 5. .setMaxResults(50 ) 6. .list(); Java代码

1. List cats = sess.createCriteria(Cat.class) .add( Restrictions.like("name", "F%") .addOrder( Order.asc("name") ) .addOrder( Order.desc("age") ) .setMaxResults(50) .list(); List cats = sess.createCriteria(Cat.class) .add( Restrictions.like("name","F%") .addOrder(Order.asc("name") ) .addOrder( Order.desc("age") ) .setMaxResults(50) .list();1. List cats =sess.createCriteria(Cat. class ) 2. .add( Property.forName( "name" ).like( "F%" ) ) 3. .addOrder( Property.forName( "name" ).asc() ) 4. .addOrder( Property.forName( "age" ).desc() ) 5. .setMaxResults( 50 ) 6. .list(); 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Property.forName("name" ).like( "F%" ) ) 3. .addOrder( Property.forName("name" ).asc() ) 4. .addOrder( Property.forName("age" ).desc() ) 5. .setMaxResults(50 ) 6. .list(); Java代码

1. List cats = sess.createCriteria(Cat.class) .add( Property.forName("name").like("F%") ) .addOrder( Property.forName("name").asc() ) .addOrder( Property.forName("age").desc() ) .setMaxResults(50) .list(); List cats = sess.createCriteria(Cat.class) .add(Property.forName("name").like("F%") ) .addOrder(Property.forName("name").asc() ) .addOrder( Property.forName("age").desc() ) .setMaxResults(50) .list();4. 关联 你可以使用createCriteria()非常容易的在互相关联的实体间建立约束。 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.like( "name" , "F%" ) 3. .createCriteria( "kittens" ) 4. .add( Restrictions.like( "name" , "F%" ) 5. .list(); 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.like("name" , "F%" ) 3. .createCriteria("kittens" ) 4. .add( Restrictions.like("name" , "F%" ) 5. .list(); Java代码

1. List cats = sess.createCriteria(Cat.class) .add( Restrictions.like("name", "F%") .createCriteria("kittens") .add( Restrictions.like("name", "F%") .list(); List cats = sess.createCriteria(Cat.class) .add( Restrictions.like("name","F%") .createCriteria("kittens") .add( Restrictions.like("name", "F%") .list();注意第二个 createCriteria()返回一个新的 Criteria实例，该实例引用kittens 集合中的元素。 接下来，替换形态在某些情况下也是很有用的。 1. List cats =sess.createCriteria(Cat. class ) 2. .createAlias( "kittens" , "kt" ) 3. .createAlias( "mate" , "mt" ) 4. .add( Restrictions.eqProperty( "kt.name" , "mt.name" ) ) 5. .list(); 1. List cats =sess.createCriteria(Cat. class ) 2. .createAlias("kittens" , "kt" ) 3. .createAlias("mate" , "mt" ) 4. .add( Restrictions.eqProperty("kt.name" , "mt.name" )) 5. .list(); Java代码

1. List cats = sess.createCriteria(Cat.class) .createAlias("kittens", "kt") .createAlias("mate", "mt") .add( Restrictions.eqProperty("kt.name", "mt.name") ) .list(); List cats = sess.createCriteria(Cat.class) .createAlias("kittens","kt") .createAlias("mate", "mt") .add(Restrictions.eqProperty("kt.name", "mt.name") ) .list();(createAlias()并不创建一个新的 Criteria实例。) Cat实例所保存的之前两次查询所返回的kittens集合是 没有被条件预过滤的。如果你希望只获得符合条件的kittens， 你必须使用returnMaps()。1. List cats =sess.createCriteria(Cat. class ) 2. .createCriteria( "kittens" , "kt" ) 3. .add( Restrictions.eq( "name" , "F%" ) ) 4. .returnMaps() 5. .list(); 6. Iterator iter =cats.iterator(); 7. while (iter.hasNext() ) { 8. Map map = (Map) iter.next(); 9. Cat cat = (Cat) map.get(Criteria.ROOT_ALIAS); 10. Cat kitten = (Cat) map.get( "kt" ); 11. } 1. List cats =sess.createCriteria(Cat. class ) 2. .createCriteria("kittens" , "kt" ) 3. .add( Restrictions.eq("name" , "F%" ) ) 4. .returnMaps() 5. .list(); 6. Iterator iter =cats.iterator(); 7. while (iter.hasNext() ) { 8. Map map = (Map) iter.next(); 9. Cat cat = (Cat) map.get(Criteria.ROOT_ALIAS); 10. Cat kitten = (Cat) map.get("kt" ); 11. } Java代码

1. List cats = sess.createCriteria(Cat.class) .createCriteria("kittens", "kt") .add( Restrictions.eq("name", "F%") ) .returnMaps() .list(); Iterator iter = cats.iterator(); while ( iter.hasNext() ) { Map map = (Map) iter.next(); Cat cat = (Cat) map.get(Criteria.ROOT_ALIAS); Cat kitten = (Cat) map.get("kt"); } List cats = sess.createCriteria(Cat.class) .createCriteria("kittens","kt") .add(Restrictions.eq("name", "F%") ) .returnMaps() .list(); Iterator iter = cats.iterator();while ( iter.hasNext() ) { Map map =(Map) iter.next(); Cat cat = (Cat)map.get(Criteria.ROOT_ALIAS); Catkitten = (Cat) map.get("kt"); }5. 动态关联抓取 你可以使用setFetchMode()在运行时定义动态关联抓取的语义。 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.like( "name" , "Fritz%" ) ) 3. .setFetchMode( "mate" , FetchMode.EAGER) 4. .setFetchMode( "kittens" , FetchMode.EAGER) 5. .list(); 1. List cats =sess.createCriteria(Cat. class ) 2. .add( Restrictions.like("name" , "Fritz%" ) ) 3. .setFetchMode("mate" , FetchMode.EAGER) 4. .setFetchMode("kittens" , FetchMode.EAGER) 5. .list(); Java代码

1. List cats = sess.createCriteria(Cat.class) .add( Restrictions.like("name", "Fritz%") ) .setFetchMode("mate", FetchMode.EAGER) .setFetchMode("kittens", FetchMode.EAGER) .list(); List cats = sess.createCriteria(Cat.class) .add( Restrictions.like("name","Fritz%") ) .setFetchMode("mate", FetchMode.EAGER) .setFetchMode("kittens",FetchMode.EAGER) .list();这个查询可以通过外连接抓取mate和kittens。 6. 查询示例 org.hibernate.criterion.Example类允许你通过一个给定实例 构建一个条件查询。 1. Cat cat = newCat(); 2. cat.setSex( 'F' ); 3. cat.setColor(Color.BLACK); 4. List results =session.createCriteria(Cat. class ) 5. .add( Example.create(cat) ) 6. .list(); 1. Cat cat = new Cat(); 2. cat.setSex('F'); 3. cat.setColor(Color.BLACK); 4. List results =session.createCriteria(Cat.class ) 5. .add( Example.create(cat) ) 6. .list(); Java代码

1. Cat cat = new Cat(); cat.setSex('F'); cat.setColor(Color.BLACK); List results = session.createCriteria(Cat.class) .add( Example.create(cat) ) .list(); Cat cat = new Cat(); cat.setSex('F'); cat.setColor(Color.BLACK); Listresults = session.createCriteria(Cat.class) .add( Example.create(cat) ) .list();版本属性、标识符和关联被忽略。默认情况下值为null的属性将被排除。可以自行调整Example使之更实用。 1. Example example =Example.create(cat) 2. .excludeZeroes() //exclude zero valued properties 3. .excludeProperty( "color" ) //exclude the property named"color" 4. .ignoreCase() //perform case insensitive string comparisons 5. .enableLike(); //use like for string comparisons 6. List results =session.createCriteria(Cat. class ) 7. .add(example) 8. .list(); 1. Example example =Example.create(cat) 2. .excludeZeroes() //excludezero valued properties 3. .excludeProperty("color" ) //exclude the property named"color" 4. .ignoreCase() //performcase insensitive string comparisons 5. .enableLike(); //uselike for string comparisons 6. List results =session.createCriteria(Cat.class ) 7. .add(example) 8. .list(); Java代码

1. Example example = Example.create(cat) .excludeZeroes() //exclude zero valued properties .excludeProperty("color") //exclude the property named "color" .ignoreCase() //perform case insensitive string comparisons .enableLike(); //use like for string comparisons List results = session.createCriteria(Cat.class) .add(example) .list(); Example example = Example.create(cat) .excludeZeroes() //exclude zero valued properties .excludeProperty("color") //exclude the property named "color" .ignoreCase() //perform case insensitive stringcomparisons .enableLike(); //use like for string comparisonsList results = session.createCriteria(Cat.class) .add(example) .list();甚至可以使用examples在关联对象上放置条件。 1. List results =session.createCriteria(Cat. class ) 2. .add( Example.create(cat) ) 3. .createCriteria( "mate" ) 4. .add( Example.create( cat.getMate() ) ) 5. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .add( Example.create(cat) ) 3. .createCriteria("mate" ) 4. .add( Example.create( cat.getMate() ) ) 5. .list(); Java代码

1. List results = session.createCriteria(Cat.class) .add( Example.create(cat) ) .createCriteria("mate") .add( Example.create( cat.getMate() ) ) .list(); List results = session.createCriteria(Cat.class) .add( Example.create(cat) ) .createCriteria("mate") .add( Example.create( cat.getMate() )) .list();7. 投影(Projections)、聚合（aggregation）和分组（grouping） org.hibernate.criterion.Projections是 Projection 的实例工厂。我们通过调用 setProjection()应用投影到一个查询。 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.rowCount() ) 3. .add( Restrictions.eq( "color" , Color.BLACK) ) 4. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.rowCount() ) 3. .add( Restrictions.eq("color" , Color.BLACK) ) 4. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.projectionList() 3. .add( Projections.rowCount() ) 4. .add( Projections.avg( "weight" ) ) 5. .add( Projections.max( "weight" ) ) 6. .add( Projections.groupProperty( "color" ) ) 7. ) 8. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.projectionList() 3. .add( Projections.rowCount() ) 4. .add( Projections.avg("weight" ) ) 5. .add( Projections.max("weight" ) ) 6. .add( Projections.groupProperty("color" ) ) 7. ) 8. .list(); Java代码

1. List results = session.createCriteria(Cat.class) .setProjection( Projections.projectionList() .add( Projections.rowCount() ) .add( Projections.avg("weight") ) .add( Projections.max("weight") ) .add( Projections.groupProperty("color") ) ) .list(); List results = session.createCriteria(Cat.class) .setProjection(Projections.projectionList() .add( Projections.rowCount() ) .add( Projections.avg("weight") ) .add(Projections.max("weight") ) .add( Projections.groupProperty("color") ) ) .list(); 在一个条件查询中没有必要显式的使用 "groupby" 。某些投影类型就是被定义为 分组投影，他 们也出现在SQL的group by子句中。 可以选择把一个别名指派给一个投影，这样可以使投影值被约束或排序所引用。下面是两种不同的 实现方式：1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.alias( Projections.groupProperty( "color"), "colr" ) ) 3. .addOrder( Order.asc( "colr" ) ) 4. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.alias( Projections.groupProperty("color"), "colr" ) ) 3. .addOrder( Order.asc("colr" ) ) 4. .list(); Java代码

1. List results = session.createCriteria(Cat.class) .setProjection( Projections.alias( Projections.groupProperty("color"), "colr" ) ) .addOrder( Order.asc("colr") ) .list(); List results = session.createCriteria(Cat.class) .setProjection( Projections.alias(Projections.groupProperty("color"), "colr" ) ) .addOrder( Order.asc("colr")) .list();1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.groupProperty( "color" ).as("colr" ) ) 3. .addOrder( Order.asc( "colr" ) ) 4. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.groupProperty("color" ).as("colr" ) ) 3. .addOrder( Order.asc("colr" ) ) 4. .list(); Java代码

1. List results = session.createCriteria(Cat.class) .setProjection( Projections.groupProperty("color").as("colr") ) .addOrder( Order.asc("colr") ) .list(); List results = session.createCriteria(Cat.class) .setProjection(Projections.groupProperty("color").as("colr") ) .addOrder( Order.asc("colr")) .list();alias()和as()方法简便的将一个投影实例包装到另外一个别名的Projection实例中。简而言之， 当你添加一个投影到一个投影列表中时 你可以为它指定一个别名： 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.projectionList() 3. .add( Projections.rowCount(), "catCountByColor" ) 4. .add( Projections.avg( "weight" ), "avgWeight" ) 5. .add( Projections.max( "weight" ), "maxWeight" ) 6. .add( Projections.groupProperty( "color" ), "color" ) 7. ) 8. .addOrder( Order.desc( "catCountByColor" ) ) 9. .addOrder( Order.desc( "avgWeight" ) ) 10. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.projectionList() 3. .add( Projections.rowCount(), "catCountByColor" ) 4. .add( Projections.avg("weight" ), "avgWeight" ) 5. .add( Projections.max("weight" ), "maxWeight" ) 6. .add( Projections.groupProperty("color" ), "color") 7. ) 8. .addOrder( Order.desc("catCountByColor" ) ) 9. .addOrder( Order.desc("avgWeight" ) ) 10. .list(); 1. List results =session.createCriteria(Domestic. class , "cat" ) 2. .createAlias( "kittens" , "kit" ) 3. .setProjection( Projections.projectionList() 4. .add( Projections.property( "cat.name" ), "catName" ) 5. .add( Projections.property( "kit.name" ), "kitName" ) 6. ) 7. .addOrder( Order.asc( "catName" ) ) 8. .addOrder( Order.asc( "kitName" ) ) 9. .list(); 1. List results =session.createCriteria(Domestic. class , "cat" ) 2. .createAlias("kittens" , "kit" ) 3. .setProjection( Projections.projectionList() 4. .add( Projections.property("cat.name" ), "catName") 5. .add( Projections.property("kit.name" ), "kitName") 6. ) 7. .addOrder( Order.asc("catName" ) ) 8. .addOrder( Order.asc("kitName" ) ) 9. .list(); Java代码

1. List results = session.createCriteria(Domestic.class, "cat") .createAlias("kittens", "kit") .setProjection( Projections.projectionList() .add( Projections.property("cat.name"), "catName" ) .add( Projections.property("kit.name"), "kitName" ) ) .addOrder( Order.asc("catName") ) .addOrder( Order.asc("kitName") ) .list(); List results = session.createCriteria(Domestic.class,"cat") .createAlias("kittens", "kit") .setProjection(Projections.projectionList() .add(Projections.property("cat.name"), "catName" ) .add(Projections.property("kit.name"), "kitName" ) ) .addOrder( Order.asc("catName") ) .addOrder( Order.asc("kitName")) .list();也可以使用Property.forName()来表示投影： 1. List results = session.createCriteria(Cat.class ) 2. .setProjection( Property.forName( "name" ) ) 3. .add( Property.forName( "color" ).eq(Color.BLACK) ) 4. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Property.forName("name" ) ) 3. .add( Property.forName("color" ).eq(Color.BLACK) ) 4. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.projectionList() 3. .add( Projections.rowCount().as( "catCountByColor" ) ) 4. .add( Property.forName( "weight" ).avg().as( "avgWeight" )) 5. .add( Property.forName( "weight" ).max().as( "maxWeight" )) 6. .add( Property.forName( "color" ).group().as( "color" ) 7. ) 8. .addOrder( Order.desc( "catCountByColor" ) ) 9. .addOrder( Order.desc( "avgWeight" ) ) 10. .list(); 1. List results =session.createCriteria(Cat. class ) 2. .setProjection( Projections.projectionList() 3. .add( Projections.rowCount().as("catCountByColor" ) ) 4. .add( Property.forName("weight" ).avg().as( "avgWeight" )) 5. .add( Property.forName("weight" ).max().as( "maxWeight" )) 6. .add( Property.forName("color" ).group().as( "color") 7. ) 8. .addOrder( Order.desc("catCountByColor" ) ) 9. .addOrder( Order.desc("avgWeight" ) ) 10. .list(); Java代码

1. List results = session.createCriteria(Cat.class) .setProjection( Projections.projectionList() .add( Projections.rowCount().as("catCountByColor") ) .add( Property.forName("weight").avg().as("avgWeight") ) .add( Property.forName("weight").max().as("maxWeight") ) .add( Property.forName("color").group().as("color" ) ) .addOrder( Order.desc("catCountByColor") ) .addOrder( Order.desc("avgWeight") ) .list(); List results = session.createCriteria(Cat.class) .setProjection(Projections.projectionList() .add( Projections.rowCount().as("catCountByColor") ) .add(Property.forName("weight").avg().as("avgWeight") ) .add(Property.forName("weight").max().as("maxWeight") ) .add( Property.forName("color").group().as("color") ) .addOrder(Order.desc("catCountByColor") ) .addOrder( Order.desc("avgWeight") ) .list();8. 离线(detached)查询和子查询 DetachedCriteria类使你在一个session范围之外创建一个查询，并且可以使用任意的 Session来 执行它。1. DetachedCriteriaquery = DetachedCriteria.forClass(Cat. class ) 2. .add( Property.forName( "sex" ).eq( 'F' ) ); 3. //创建一个Session 4. Session session =.; 5. Transaction txn =session.beginTransaction(); 6. List results =query.getExecutableCriteria(session).setMaxResults( 100).list(); 7. txn.commit(); 8. session.close(); 1. DetachedCriteriaquery = DetachedCriteria.forClass(Cat. class ) 2. .add( Property.forName("sex" ).eq( 'F' ) ); 3. //创建一个Session 4. Session session =.; 5. Transaction txn =session.beginTransaction(); 6. List results =query.getExecutableCriteria(session).setMaxResults(100).list(); 7. txn.commit(); 8. session.close(); Java代码

1. DetachedCriteria query = DetachedCriteria.forClass(Cat.class) .add( Property.forName("sex").eq('F') ); //创建一个Session Session session = .; Transaction txn = session.beginTransaction(); List results = query.getExecutableCriteria(session).setMaxResults(100).list(); txn.commit(); session.close(); DetachedCriteria query = DetachedCriteria.forClass(Cat.class) .add(Property.forName("sex").eq('F') ); //创建一个Session Session session = .;Transaction txn = session.beginTransaction(); List results = query.getExecutableCriteria(session).setMaxResults(100).list();txn.commit(); session.close();DetachedCriteria也可以用以表示子查询。条件实例包含子查询可以通过 Subqueries或者 Property获得。 1. DetachedCriteriaavgWeight = DetachedCriteria.forClass(Cat. class ) 2. .setProjection( Property.forName( "weight" ).avg() ); 3. session.createCriteria(Cat.class ) 4. .add( Property.forName("weight).gt(avgWeight) ) 5. .list(); 6. DetachedCriteriaweights = DetachedCriteria.forClass(Cat. class ) 7. .setProjection( Property.forName( "weight" ) ); 8. session.createCriteria(Cat.class ) 9. .add( Subqueries.geAll( "weight" , weights) ) 10. .list(); 1. DetachedCriteriaavgWeight = DetachedCriteria.forClass(Cat. class ) 2. .setProjection( Property.forName("weight" ).avg() ); 3. session.createCriteria(Cat.class) 4. .add( Property.forName("weight).gt(avgWeight) ) 5. .list(); 6. DetachedCriteriaweights = DetachedCriteria.forClass(Cat.class ) 7. .setProjection( Property.forName("weight" ) ); 8. session.createCriteria(Cat.class) 9. .add( Subqueries.geAll("weight" , weights) ) 10. .list(); Java代码

1. DetachedCriteria avgWeight = DetachedCriteria.forClass(Cat.class) .setProjection( Property.forName("weight").avg() ); session.createCriteria(Cat.class) .add( Property.forName("weight).gt(avgWeight) ) .list(); DetachedCriteria weights = DetachedCriteria.forClass(Cat.class) .setProjection( Property.forName("weight") ); session.createCriteria(Cat.class) .add( Subqueries.geAll("weight", weights) ) .list(); DetachedCriteria avgWeight = DetachedCriteria.forClass(Cat.class) .setProjection(Property.forName("weight").avg() );session.createCriteria(Cat.class) .add( Property.forName("weight).gt(avgWeight) ) .list(); DetachedCriteria weights =DetachedCriteria.forClass(Cat.class) .setProjection( Property.forName("weight") ); session.createCriteria(Cat.class) .add( Subqueries.geAll("weight",weights) ) .list();相互关联的子查询也是有可能的： 1. DetachedCriteriaavgWeightForSex = DetachedCriteria.forClass(Cat. class , "cat2" ) 2. .setProjection( Property.forName( "weight" ).avg() ) 3. .add( Property.forName( "cat2.sex" ).eqProperty( "cat.sex") ); 4. session.createCriteria(Cat.class , "cat" ) 5. .add( Property.forName("weight).gt(avgWeightForSex) ) 6. .list(); 1. DetachedCriteriaavgWeightForSex = DetachedCriteria.forClass(Cat. class , "cat2") 2. .setProjection( Property.forName("weight" ).avg() ) 3. .add( Property.forName("cat2.sex" ).eqProperty( "cat.sex" )); 4. session.createCriteria(Cat.class, "cat" ) 5. .add( Property.forName("weight).gt(avgWeightForSex) ) 6. .list(); 在hibernate中要实现动态查询或者子查询等可以用DetachedCriteria来动态构造sql语句比如要实现类似这样一个sql语句：select* from Table1 t1 where t1.field1 in(select field2 from Table2 t2 wheret2.field3=value)实现方法：Sessionsession = HibernateSessionFactory.currentSession();Criteriacriteria = session.createCriteria(Table1.class);DetachedCriteriadc =DetachedCriteria.forClass(Table2.class).setProjection(Property.forName("field2"));dc.add(Expression.eq("field3",value));criteria.add(Property.forName("field1").in(dc));Listlist = criteria.list()HibernateSessionFactory.closeSession();