Hibernate QBC查询实例

我们的教材上多讲的是HQL的查询比较多，这里给大家补充一下QBC的查询，感觉QBC才是真正面向对象的。还是以我们上课的员工和部门表为例子。

 

实体类Employee.java

package org.newboy.entity; import java.sql.Date; /** * Employee entity. */ public class Employee implements java.io.Serializable { // Fields private Integer id; private Depart depart; private String name; private Boolean sex; private Date joinDay; private Double salary; // Constructors /** default constructor */ public Employee() { } /** minimal constructor */ public Employee(Depart depart, String name, Date joinDay) { this.depart = depart; this.name = name; this.joinDay = joinDay; } /** full constructor */ public Employee(Depart depart, String name, Boolean sex, Date joinDay, Double salary) { this.depart = depart; this.name = name; this.sex = sex; this.joinDay = joinDay; this.salary = salary; } // Property accessors public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } public Depart getDepart() { return this.depart; } public void setDepart(Depart depart) { this.depart = depart; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public Boolean getSex() { return this.sex; } public void setSex(Boolean sex) { this.sex = sex; } public Date getJoinDay() { return this.joinDay; } public void setJoinDay(Date joinDay) { this.joinDay = joinDay; } public Double getSalary() { return this.salary; } public void setSalary(Double salary) { this.salary = salary; } }

 

映射文件：

<?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"> <hibernate-mapping> <class name="org.newboy.entity.Employee" table="employee" catalog="y2"> <id name="id" type="integer"> <column name="id" /> <generator class="native"></generator> </id> <many-to-one name="depart" class="org.newboy.entity.Depart" fetch="select" lazy="false"> <column name="depart_id" not-null="true" /> </many-to-one> <property name="name" type="string"> <column name="name" length="20" not-null="true" unique="true" /> </property> <property name="sex" type="boolean"> <column name="sex" /> </property> <property name="joinDay" type="date"> <column name="joinDay" length="10" not-null="true" /> </property> <property name="salary" type="double"> <column name="salary" precision="15" scale="3" /> </property> </class> </hibernate-mapping>

 

部门类：

package org.newboy.entity; import java.util.HashSet; import java.util.Set; public class Depart implements java.io.Serializable { private Integer id; private String name; private String description; private Set<Employee> employees = new HashSet<Employee>(0); // Constructors /** default constructor */ public Depart() { } /** minimal constructor */ public Depart(String name) { this.name = name; } /** full constructor */ public Depart(String name, String description, Set<Employee> employees) { this.name = name; this.description = description; this.employees = employees; } // Property accessors public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public String getDescription() { return this.description; } public void setDescription(String description) { this.description = description; } public Set<Employee> getEmployees() { return this.employees; } public void setEmployees(Set<Employee> employees) { this.employees = employees; } /* * ID相等或是名字相等，则认为是同一个对象 * * @see java.lang.Object#equals(java.lang.Object) */ @Override public boolean equals(Object obj) { if (obj instanceof Depart) { Depart depart = (Depart) obj; boolean flag = (this.id == depart.getId() || this.name.equals(depart.getName())); return flag; } else { return false; } } }

 

映射文件：

<?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"> <hibernate-mapping> <class name="org.newboy.entity.Depart" table="depart" catalog="y2"> <id name="id" type="integer"> <column name="id" /> <generator class="native"></generator> </id> <property name="name" type="string"> <column name="name" length="20" not-null="true" unique="true" /> </property> <property name="description" type="string"> <column name="description" length="300" /> </property> <set name="employees" inverse="true" lazy="false"> <key> <column name="depart_id" not-null="true" /> </key> <one-to-many class="org.newboy.entity.Employee" /> </set> </class> </hibernate-mapping>

 

QBC实例：

 package org.newboy.dao; import java.sql.Date; import java.util.ArrayList; import java.util.Collection; import java.util.List; import org.hibernate.Criteria; import org.hibernate.Session; import org.hibernate.criterion.DetachedCriteria; import org.hibernate.criterion.Example; import org.hibernate.criterion.Expression; import org.hibernate.criterion.MatchMode; import org.hibernate.criterion.Projections; import org.hibernate.criterion.Property; import org.hibernate.criterion.Restrictions; import org.hibernate.criterion.Subqueries; import org.newboy.common.HibernateSessionFactory; import org.newboy.entity.Depart; import org.newboy.entity.Employee; public class EmployeeDao { /** * In的使用: 有两种形式，即数组或者Collection的方式 找姓名为：张三、李四、王五的三个人 */ @SuppressWarnings("unchecked") public List<Employee> findUseIn() { Collection<String> col = new ArrayList<String>(); col.add("张三"); col.add("李四"); col.add("王五"); Session session = HibernateSessionFactory.getSession(); List<Employee> employees = session.createCriteria(Employee.class).add( Restrictions.in("name", col)).list(); HibernateSessionFactory.closeSession(); return employees; } /** * 找最少有一名员工的部门，查的属性必须是一个集合 * * @return */ @SuppressWarnings("unchecked") public List<Depart> findUseIsNull() { Session session = HibernateSessionFactory.getSession(); List<Depart> departs = session.createCriteria(Depart.class).add( Restrictions.isNotEmpty("employees")).list(); HibernateSessionFactory.closeSession(); return departs; } /** * 得到所有员工的平均工资，聚合函数使用Projections类 * * @return */ public double averageSalary() { Session session = HibernateSessionFactory.getSession(); double avg = (Double) session.createCriteria(Employee.class).setProjection( Projections.avg("salary")).uniqueResult(); HibernateSessionFactory.closeSession(); return avg; } /** * 实体类中属性不为NULL的做为查询条件，而且用Example类，一定要将原始类型设置为引用类型，如:double用成java.lang.Double */ @SuppressWarnings("unchecked") public List<Employee> findUseExample() { Employee condtion = new Employee(); condtion.setName("龙"); //包含龙字的 condtion.setSex(true); //找所有的男性 Session session = HibernateSessionFactory.getSession(); List<Employee> employees = session.createCriteria(Employee.class).add( Example.create(condtion).enableLike(MatchMode.ANYWHERE)).list(); HibernateSessionFactory.closeSession(); return employees; } /** * 连续or的操作 salary >= 7000 or sex = false or ... * 连接的and操作用conjunction() * @return */ @SuppressWarnings("unchecked") public List<Employee> findByJunction() { Session session = HibernateSessionFactory.getSession(); Criteria criteria = session.createCriteria(Employee.class) .add(Restrictions.disjunction() .add(Expression.ge("salary", 7000d)) .add(Expression.eq("sex", false))); List<Employee> employees = criteria.list(); HibernateSessionFactory.closeSession(); return employees; } /** * 找所有学术部的职工 */ @SuppressWarnings("unchecked") public List<Employee> findByDepart() { Session session = HibernateSessionFactory.getSession(); Criteria criteria = session.createCriteria(Employee.class) .createCriteria("depart").add(Restrictions.eq("name", "学术部")); List<Employee> employees = criteria.list(); HibernateSessionFactory.closeSession(); return employees; } /** * 找大于3名员工的部门 */ @SuppressWarnings("unchecked") public List<Depart> findByAmount() { Session session = HibernateSessionFactory.getSession(); List<Depart> departs = session.createCriteria(Depart.class) .add(Restrictions.sizeGt("employees", 3)).list(); HibernateSessionFactory.closeSession(); return departs; } /** * 可以利用DetachedCriteria对一些常用的Criteria查询条件进行抽离， * 当需要进行检索时再与Session实例关联，从而获得运行期的Criteria实例 * 也可以用于完成子查询功能 */ @SuppressWarnings("unchecked") public List<Employee> findByDetachedCriteria() { DetachedCriteria dc= DetachedCriteria.forClass(Employee.class); dc.setProjection(Projections.avg("salary")); Session session = HibernateSessionFactory.getSession(); Criteria criteria=session.createCriteria(Employee.class); criteria.add(Subqueries.propertyGt("salary",dc)); //找工资大于平均工资的员工，子查询 List<Employee> employees=criteria.list(); HibernateSessionFactory.closeSession(); return employees; } /** * Property 是对某个字段进行查询条件的设置 * 找参加工作时间在2000-1-1到2002-1-1之间的员工 */ @SuppressWarnings("unchecked") public List<Employee> findByProperty() { Session session = HibernateSessionFactory.getSession(); Criteria criteria=session.createCriteria(Employee.class); criteria.add(Property.forName("joinDay").between(Date.valueOf("2000-1-1"), Date.valueOf("2002-1-1"))); List<Employee> employees=criteria.list(); HibernateSessionFactory.closeSession(); return employees; } }

 

上面代码中用到的工具类：

package org.newboy.common; import java.text.DecimalFormat; import java.text.SimpleDateFormat; import java.util.List; import org.newboy.entity.Depart; import org.newboy.entity.Employee; public class EmployeeUtils { /** * 显示所有员工的信息 */ public static void printEmployees(List<Employee> employees) { for (Employee employee : employees) { System.out.println("---------------------------------"); printEmployee(employee); System.out.println("---------------------------------"); } } /** * 显示一名员工信息 */ public static void printEmployee(Employee employee) { System.out.println("主键：/t" + employee.getId()); System.out.println("姓名：/t" + employee.getName()); System.out.println("工资：/t" + new DecimalFormat("￥#,###.##").format(employee.getSalary())); System.out.println("入职：/t" + new SimpleDateFormat("yyyy年MM月dd日").format(employee.getJoinDay())); System.out.println("性别：/t" + (employee.getSex() == true ? "男" : "女")); System.out.println("部门：/t" + employee.getDepart().getName()); } /** * 输出一个部门的信息 * @param depart */ public static void printDepart(Depart depart) { System.out.println("================="); System.out.println("主键：/t" + depart.getId()); System.out.println("职门：/t" + depart.getName()); System.out.println("说明：/t" + depart.getDescription()); System.out.println("员工：/t" + depart.getEmployees().size() + "人"); System.out.println("================="); } /** * 输出所有部门 * @param departs */ public static void printDeparts(List<Depart> departs) { for (Depart depart : departs) { printDepart(depart); } } }

 

会话工厂类，这个由MyEclipse自己产生的：

package org.newboy.common; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.cfg.Configuration; /** * Configures and provides access to Hibernate sessions, tied to the current * thread of execution. Follows the Thread Local Session pattern, see * {@link http://hibernate.org/42.html }. */ public class HibernateSessionFactory { /** * Location of hibernate.cfg.xml file. Location should be on the classpath * as Hibernate uses #resourceAsStream style lookup for its configuration * file. The default classpath location of the hibernate config file is in * the default package. Use #setConfigFile() to update the location of the * configuration file for the current session. */ private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml"; private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); private static Configuration configuration = new Configuration(); private static org.hibernate.SessionFactory sessionFactory; private static String configFile = CONFIG_FILE_LOCATION; static { try { configuration.configure(configFile); sessionFactory = configuration.buildSessionFactory(); } catch (Exception e) { System.err.println("%%%% Error Creating SessionFactory %%%%"); e.printStackTrace(); } } private HibernateSessionFactory() { } /** * Returns the ThreadLocal Session instance. Lazy initialize the * <code>SessionFactory</code> if needed. * * @return Session * @throws HibernateException */ public static Session getSession() throws HibernateException { Session session = (Session) threadLocal.get(); if (session == null || !session.isOpen()) { if (sessionFactory == null) { rebuildSessionFactory(); } session = (sessionFactory != null) ? sessionFactory.openSession() : null; threadLocal.set(session); } return session; } /** * Rebuild hibernate session factory * */ public static void rebuildSessionFactory() { try { configuration.configure(configFile); sessionFactory = configuration.buildSessionFactory(); } catch (Exception e) { System.err.println("%%%% Error Creating SessionFactory %%%%"); e.printStackTrace(); } } /** * Close the single hibernate session instance. * * @throws HibernateException */ public static void closeSession() throws HibernateException { Session session = (Session) threadLocal.get(); threadLocal.set(null); if (session != null) { session.close(); } } /** * return session factory * */ public static org.hibernate.SessionFactory getSessionFactory() { return sessionFactory; } /** * return session factory * * session factory will be rebuilded in the next call */ public static void setConfigFile(String configFile) { HibernateSessionFactory.configFile = configFile; sessionFactory = null; } /** * return hibernate configuration * */ public static Configuration getConfiguration() { return configuration; } }