利用二级缓存和查询缓存结合缓存一些属性，通过query.list()方法返回属性列表。

首先在hibernate.cfg.xml开启二级缓存和查询缓存:

 <?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE hibernate-configuration PUBLIC"-//Hibernate/Hibernate Configuration DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration><session-factory><!--数据库连接信息略--><property name="show_sql">true</property><property name="cache.provider_class">org.hibernate.cache.EhCacheProvider</property><!-- 启用查询缓存 --><property name="cache.use_query_cache">true</property><!-- 启用二级缓存 --><property name="cache.use_second_level_cache">true</property><mapping resource="com/kin/entity/ErmEmployee.hbm.xml" /><mapping resource="com/kin/entity/SysDepartment.hbm.xml" /> </session-factory> </hibernate-configuration>

 

SysDepartment.java类：

package com.kin.entity;import java.util.Date; import java.util.HashSet; import java.util.Set;public class SysDepartment implements Comparable, java.io.Serializable {private Integer dptId;private String dptName;private Set ermEmployees = new HashSet(0); //getter,setter方法略 //重写compare方法public int compareTo(Object obj) { if (obj instanceof SysDepartment) { SysDepartment sysDepartment = (SysDepartment) obj; if (sequence > sysDepartment.getSequence()){return 1;}else if (sequence < sysDepartment.getSequence()){return -1;}else{return 0;}}else{throw new ClassCastException("对象类型不一样，不能进行比较");}} @Overridepublic boolean equals(Object obj) {return this.getDptId().equals(((SysDepartment)obj).getDptId());} }

 

SysDepartment.hbm.xml

<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Mapping file autogenerated by MyEclipse Persistence Tools --> <hibernate-mapping package="com.kin.entity"><class name="SysDepartment" table="SYS_Department" schema="dbo" catalog="doss"lazy="false"><!--启用二级缓存--><cache usage="read-write"/><id name="dptId" type="java.lang.Integer"><column name="DPT_ID" /><generator class="identity" /></id><property name="parentId" type="java.lang.Integer"><column name="ParentID" /></property><property name="dptName" type="java.lang.String"><column name="DPT_Name" length="50" /></property><set name="ermEmployees" inverse="true"><key><column name="DPT_ID" /></key><one-to-many class="com.kin.entity.ErmEmployee" /></set></class> </hibernate-mapping>

ErmEmployee.java

package com.kin.entity;public class ErmEmployee{private Integer eplId; private SysDepartment sysDepartment;private String eplName;public ErmEmployee() {}// getter,setter方法略 }

 

ErmEmployee.hbm.xml

<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Mapping file autogenerated by MyEclipse Persistence Tools --> <hibernate-mapping package="com.kin.entity"><class name="ErmEmployee" table="ERM_Employee" schema="dbo" catalog="doss"lazy="false"><!-- 启用二级缓存 缓存策略为read-write--><cache usage="read-write"/><id name="eplId" type="java.lang.Integer"><column name="EPL_ID" /><generator class="identity" /></id><many-to-one name="sysDepartment" class="com.kin.entity.SysDepartment" fetch="select"><column name="DPT_ID" /></many-to-one><property name="eplName" type="java.lang.String"><column name="EPL_Name" length="20" /></property></class> </hibernate-mapping>

 

测试用例：

package com.kin.entity;import java.util.Iterator; import java.util.List;import org.hibernate.HibernateException; import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration;public class CacheTest {//开启了二级缓存和查询缓存。用query.list()查询实体@org.junit.Testpublic void testCache_query_list() {Configuration cfg = new Configuration().configure();SessionFactory sessionFactory = cfg.buildSessionFactory();Session session = null;//第一个sessiontry {session = sessionFactory.openSession();session.beginTransaction();Query query = session.createQuery("from SysDepartment d ");query.setCacheable(true);List<SysDepartment> dList = query.list();//会发出查询所有SysDepartment实例的sqlList<Object[]> eplList = null;String getEplSQL = "select e.eplId,e.eplName from ErmEmployee e where e.sysDepartment.dptId = ? and e.esId in(1801,1802)";for (SysDepartment sysDepartment : dList) {System.out.println(sysDepartment.getDptId() + ":"+ sysDepartment.getDptName());query=session.createQuery(getEplSQL);query.setCacheable(true);query.setParameter(0, sysDepartment.getDptId());eplList = query.list();//会发出根据SysDepartment的id查询所有的ErmEmployee实例的sql语句for (Object[] e : eplList) {System.out.println(e[0] + ":" + e[1]);}}session.getTransaction().commit();} catch (HibernateException e) {session.getTransaction().rollback();e.printStackTrace();} finally {session.close();}System.out.println("----------------------------------------------------");//开启另一sessiontry {session = sessionFactory.openSession();session.beginTransaction();Query query = session.createQuery("from SysDepartment d ");query.setCacheable(true);List<SysDepartment> dList = query.list();//不会发出查询所有SysDepartment实例的sqlList<Object[]> eplList = null;String getEplSQL = "select e.eplId,e.eplName from ErmEmployee e where e.sysDepartment.dptId = ? and e.esId in(1801,1802)";for (SysDepartment sysDepartment : dList) {System.out.println(sysDepartment.getDptId() + ":"+ sysDepartment.getDptName());query=session.createQuery(getEplSQL);query.setCacheable(true);query.setParameter(0, sysDepartment.getDptId());eplList = query.list();//不会发sql语句for (Object[] e : eplList) {System.out.println(e[0] + ":" + e[1]);}}session.getTransaction().commit();} catch (HibernateException e) {session.getTransaction().rollback();e.printStackTrace();} finally {session.close();}}}

 

当String getEplSQL = "select e.eplId,e.eplName from ErmEmployee e where e.sysDepartment.dptId = ? and e.esId in(1801,1802)";

改为String getEplSQL = "select e.eplId,e.eplName from ErmEmployee e where e.sysDepartment = ? and e.esId in(1801,1802)";

之时，第二次session中，执行eplList = query.list();查询，则还是会发出sql，这是因为sysDepartment对象不同，所以还是会执行查询