建议你看下这个：
一．hibernate 抓取策略(Fetch) 单端代理批量抓取 1.fetch=”select” 关联实体//fetch 默认是select<many-to-one name="businessId" column="business_id" insert="true" update="true" fetch="select"> Student student = (Student)session.load(Student.class,1);System.out.println(student.getName());System.out.println(student.getClasses().getName()); //多对一中的属性班级，获取班级名称 Fetch=”select” ,上面程序会发2条sql语句，第二条发送一条select语句抓取当前对象关联实体或集合 (这里指是班级名称) 2.fetch=” join” 关联实体//fetch 设置成 join<many-to-one name="businessId" column="business_id" insert="true" update="true"fetch=" join "> Student student = (Student)session.load(Student.class,1);System.out.println(student.getName());System.out.println(student.getClasses().getName()); //多对一中的属性班级，获取班级名称 fetch=” join” , 上面程序会发1条sql语句， hibernate会通过select使用外链接来加载其关联实体或集合，此时lazy会失效 二．hibernate 抓取策略(Fetch) 集合代理批量抓取 1. fetch=”select”//fetch 默认是select<set name="students" inverse="true" cascade="all" fetch="select"> <key column="classid" /> <one-to-many class="com.Student" /></set> Classes cla = (Classes)session.load(Classes.class,1);System.out.println(cla.getName());for(Iterator iter = cla.getStudents().iterator();iter.hasNext();){ Student student = (Student)iter.next(); System.out.println(student.getName());} fetch=”select” ,上面程序用到了就发sql语句,第二从循环中发了N条,如果：fetch=”subselect”,则只是发送一条语句，见下面 2 fetch=”join”//fetch 设置成join<set name="students" inverse="true" cascade="all" fetch="join"> <key column="classid" /> <one-to-many class="com.Student" /></set> Classes cla = (Classes)session.load(Classes.class,1);System.out.println(cla.getName());for(Iterator iter = cla.getStudents().iterator();iter.hasNext();){ Student student = (Student)iter.next(); System.out.println(student.getName());} Fetch=”select” ,上面程序只发了一条sql语句 三．hibernate 抓取策略(Fetch) 集合代理批量抓取 2. fetch=”subselect”//fetch设置成subselect<set name="students" inverse="true" cascade="all" fetch="subselect"> <key column="classid" /> <one-to-many class="com.Student" /></set> List classesList = session.createQuery(“select c from Classes c where c.id in(1,2,3)”);for(Iterator iter=classesList.iterator();iter.hasNext();){ Classess classess = (Classess)iter.next(); System.out.println(“classes.name=”+ classes.getName()); for(Iterator iter1 = classess.getStudents().iterator();iter1.hasNext();){ Student student = (Student)iter1.next(); System.out.println(student.getName());}} Fetch=”subselct” ,另外发送一条select语句抓取在前面查询到的所有实体对象的关联集合 四．hibernate 批量策略batch-size属性，可以批量加载实体类，参见Classes.hbm.xml，同时集合也可以是使用，如： <set name="students" inverse="true" cascade="save-update" batch-size=”5”> 在配置文件hbm.xml 设置中：<class name="com.Classes " table="tb_classes" batch-size=”3”> List students = session.createQuery(“select s from Student s where s.id in(:ids)”).setParameterList(“:ids”,new Object[]{1,11,21,31,41,51,61,71,81,91}).list(); for(Iterator iter=students.iterator();iter.hasNext();){ Student student = (Sutdent)iter.next(); System.out.println(student.getName()); System.out.println(student.getClassess().getName()); } 当第二个for循环时，每次加载 之前设置的 数量 实体对象, 如：现在设置3，那么当Iterator iter=students.iterator();iter.hasNext();时候，他会查询出3个student对象
一．hibernate 抓取策略(Fetch) 单端代理批量抓取 1.fetch=”select” 关联实体//fetch 默认是select<many-to-one name="businessId" column="business_id" insert="true" update="true" fetch="select"> Student student = (Student)session.load(Student.class,1);System.out.println(student.getName());System.out.println(student.getClasses().getName()); //多对一中的属性班级，获取班级名称 Fetch=”select” ,上面程序会发2条sql语句，第二条发送一条select语句抓取当前对象关联实体或集合 (这里指是班级名称) 2.fetch=” join” 关联实体//fetch 设置成 join<many-to-one name="businessId" column="business_id" insert="true" update="true"fetch=" join "> Student student = (Student)session.load(Student.class,1);System.out.println(student.getName());System.out.println(student.getClasses().getName()); //多对一中的属性班级，获取班级名称 fetch=” join” , 上面程序会发1条sql语句， hibernate会通过select使用外链接来加载其关联实体或集合，此时lazy会失效 二．hibernate 抓取策略(Fetch) 集合代理批量抓取 1. fetch=”select”//fetch 默认是select<set name="students" inverse="true" cascade="all" fetch="select"> <key column="classid" /> <one-to-many class="com.Student" /></set> Classes cla = (Classes)session.load(Classes.class,1);System.out.println(cla.getName());for(Iterator iter = cla.getStudents().iterator();iter.hasNext();){ Student student = (Student)iter.next(); System.out.println(student.getName());} fetch=”select” ,上面程序用到了就发sql语句,第二从循环中发了N条,如果：fetch=”subselect”,则只是发送一条语句，见下面 2 fetch=”join”//fetch 设置成join<set name="students" inverse="true" cascade="all" fetch="join"> <key column="classid" /> <one-to-many class="com.Student" /></set> Classes cla = (Classes)session.load(Classes.class,1);System.out.println(cla.getName());for(Iterator iter = cla.getStudents().iterator();iter.hasNext();){ Student student = (Student)iter.next(); System.out.println(student.getName());} Fetch=”select” ,上面程序只发了一条sql语句 三．hibernate 抓取策略(Fetch) 集合代理批量抓取 2. fetch=”subselect”//fetch设置成subselect<set name="students" inverse="true" cascade="all" fetch="subselect"> <key column="classid" /> <one-to-many class="com.Student" /></set> List classesList = session.createQuery(“select c from Classes c where c.id in(1,2,3)”);for(Iterator iter=classesList.iterator();iter.hasNext();){ Classess classess = (Classess)iter.next(); System.out.println(“classes.name=”+ classes.getName()); for(Iterator iter1 = classess.getStudents().iterator();iter1.hasNext();){ Student student = (Student)iter1.next(); System.out.println(student.getName());}} Fetch=”subselct” ,另外发送一条select语句抓取在前面查询到的所有实体对象的关联集合 四．hibernate 批量策略batch-size属性，可以批量加载实体类，参见Classes.hbm.xml，同时集合也可以是使用，如： <set name="students" inverse="true" cascade="save-update" batch-size=”5”> 在配置文件hbm.xml 设置中：<class name="com.Classes " table="tb_classes" batch-size=”3”> List students = session.createQuery(“select s from Student s where s.id in(:ids)”).setParameterList(“:ids”,new Object[]{1,11,21,31,41,51,61,71,81,91}).list(); for(Iterator iter=students.iterator();iter.hasNext();){ Student student = (Sutdent)iter.next(); System.out.println(student.getName()); System.out.println(student.getClassess().getName()); } 当第二个for循环时，每次加载 之前设置的 数量 实体对象, 如：现在设置3，那么当Iterator iter=students.iterator();iter.hasNext();时候，他会查询出3个student对象
from Cat as cat
inner join fetch cat.mate
left join fetch cat.kittens