Hibernate--HQL、QBC以及本地SQl查询

Hibernate中提供了HQL、QBC以及SQL的三种形式查询，HQL查询是一种根据映射文件的便捷查询，只要写部分SQL语句即可。QBC查询则是借助Criteria 进行快捷的查询。SQL查询是基于SQL语句的查询

以下案例用于查询的两个表结构

CREATE TABLE `department` (
`id` int(2) NOT NULL AUTO_INCREMENT,
`NAME` varchar(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8;

CREATE TABLE `employee` (
`Id` int(2) NOT NULL AUTO_INCREMENT,
`NAME` varchar(30) DEFAULT NULL,
`SALARY` float(10,2) DEFAULT NULL,
`EMAIL` varchar(30) DEFAULT NULL,
`DEPT_Id` int(2) DEFAULT NULL,
PRIMARY KEY (`Id`),
KEY `dept_id_fk` (`DEPT_Id`),
CONSTRAINT `dept_id_fk` FOREIGN KEY (`DEPT_Id`) REFERENCES `department` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=13 DEFAULT CHARSET=utf8;

department实体以及映射文件

public class Department implements java.io.Serializable {private static final long serialVersionUID = 1L;private Integer id;private String name;private Set<Employee> employees = new HashSet<>();
}

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<!-- Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping><class name="com.zhuojing.hibernate.hql.holleworld.Department" table="department" catalog="hibernate2"><id name="id" type="java.lang.Integer"><column name="id" /><generator class="identity" /></id><property name="name" type="java.lang.String"><column name="NAME" length="30" /></property><set name="employees" inverse="true"><key><column name="DEPT_Id" /></key><one-to-many class="com.zhuojing.hibernate.hql.holleworld.Employee" /></set></class>
</hibernate-mapping>

employee实体以及映射文件

public class Employee implements java.io.Serializable {private static final long serialVersionUID = 1L;private Integer id;private Department department;private String name;private Float salary;private String email;
}

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<!-- Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping><class name="com.zhuojing.hibernate.hql.holleworld.Employee" table="employee" catalog="hibernate2"><id name="id" type="java.lang.Integer"><column name="Id" /><generator class="identity" /></id><many-to-one name="department" class="com.zhuojing.hibernate.hql.holleworld.Department" fetch="select"><column name="DEPT_Id" /></many-to-one><property name="name" type="java.lang.String"><column name="NAME" length="30" /></property><property name="salary" type="java.lang.Float"><column name="SALARY" precision="5" scale="0" /></property><property name="email" type="java.lang.String"><column name="EMAIL" length="30" /></property></class><!-- 配置命名方式检查的 SQL 语句 --><query name="salaryEmp"><![CDATA[FROM Employee e WHERE e.salary > :minSay AND e.salary < :maxSay]]></query>
</hibernate-mapping>

一、HQL

1.命名参数：

@Test
public void testHQLParameter(){//1. 创建 Query 对象//基于命名参数String hql = "FROM Employee e WHERE e.salary > :sal AND e.email LIKE :email";Query query = session.createQuery(hql);//2. 绑定参数query.setFloat("sal", 7000).setString("email", "%com");//3. 执行查询List<Employee> employees = query.list();System.out.println(employees.size());}

2.分页查询

@Test
public void testPageQuery(){String hql = "FROM Employee";Query query = session.createQuery(hql);int pageNo = 3;int pageSize = 2;List<Employee> employees = query.setFirstResult((pageNo -1 )*pageSize).setMaxResults(pageSize).list();System.out.println(employees.toString());
}

3.命名方式：在映射文件中写SQL

//*映射文件
<!-- 配置命名方式检查的 SQL 语句 --><query name="salaryEmp"><![CDATA[FROM Employee e WHERE e.salary > :minSay AND e.salary < :maxSay]]></query>
*/
@Testpublic void testNamedQuery(){Query query = session.getNamedQuery("salaryEmp");List<Employee> employees = query.setFloat("minSay", 6000).setFloat("maxSay", 10000).list();System.out.println(employees.size());}

4.查找部分属性

@Test
public void testFieldQuery(){String hql = "SELECT e.name, e.email, e.department FROM Employee e WHERE e.department = :dept";Query query = session.createQuery(hql);Department department = new Department();department.setId(3);List<Object[]> objects = query.setEntity("dept", department).list();for(Object[] obj : objects){System.out.println(Arrays.asList(obj));}
}

5.查找部分属性，返回结果为一个实体类：实体类需要提供对应的构造方法

@Test
public void testFieldQuery2(){String hql = "SELECT new Employee(e.name, e.email, e.department) FROM Employee e WHERE e.department = :dept";Query query = session.createQuery(hql);Department department = new Department();department.setId(3);List<Employee> employees = query.setEntity("dept", department).list();for(Employee employee : employees){System.out.println(employee);}}

6.迫切左外连接：使用LEFT JOIN FETCH 进行迫切左外连接

用于：查询一个实体的一个实体类的成员变量时，不会在使用 SQL 语句去查询，在第一次就将结果初始化好

@Test
public void testLeftJoinFetch(){String hql = "FROM Department d LEFT JOIN FETCH d.employees";Query query = session.createQuery(hql);List<Department> departments = query.list();departments = new ArrayList<>(new LinkedHashSet<>(departments));for(Department department : departments){System.out.println(department.getName() +"--"+department.getEmployees().size());}}

7.左外连接

@Test
public void testLefJoin(){String hql = "SELECT DISTINCT d FROM Department d LEFT JOIN d.employees";Query query = session.createQuery(hql);List<Department> departments = query.list();for(Department department : departments){System.out.println(department.getName() +"--"+department.getEmployees().size());}}

二、QBC查询主要使用Criteria进行查询

1.QBC的HelloWorld

@Testpublic void testQBC(){//创建一个 Criteria 对象Criteria criteria = session.createCriteria(Employee.class);//2.添加查询条件：在QBC 中查询条件使用 Criterion 表示// Criterion 可以通过Restrictions 的静态方法得到criteria.add(Restrictions.eq("email", "bb@zhuoojing.com"));criteria.add(Restrictions.ge("salary", 6000F));//3.执行查询Employee employee = (Employee)criteria.uniqueResult();System.out.println(employee);}

2.QBC 统计查询：

@Testpublic void testQBC3(){Criteria criteria= session.createCriteria(Employee.class);//统计查询：使用 Projection 来表示：可以由 Projections 的静态方法得到criteria.setProjection(Projections.max("salary"));//Employee employee = (Employee)criteria.uniqueResult();System.out.println(criteria.uniqueResult());}

3.排序和分页

@Test
public void testQBC4(){Criteria criteria = session.createCriteria(Employee.class);//添加排序criteria.addOrder(Order.asc("salary"));criteria.addOrder(Order.desc("email"));List<Employee> employees = criteria.list();System.out.println(employees);//2.添加分页方法int pageSize = 2;int pageNo = 3;Criteria criteria3 = session.createCriteria(Employee.class);criteria3.setFirstResult((pageNo - 1) *pageSize).setMaxResults(pageSize);List<Employee> employees2 = criteria3.list();System.out.println(employees2);}

三、SQL查询（使用sql语句）

@Testpublic void testNativeSQL(){//String sql = "INSERT INTO employee(NAME,SALARY,EMAIL,DEPT_Id) VALUES('ZZ',7000,'zz@zhuojing.com',5)";String sql = "INSERT INTO department(NAME) VALUES('ZHUOJING')";Query query = session.createSQLQuery(sql);/*query.setString(0, "ZZ").setFloat(1, 7000F).setString(2, "zz@zhuojing.com").setInteger(3, 4).executeUpdate();*/query.executeUpdate();}

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