Hibernate 原生 SQL

原生 SQL

如果你想使用数据库特定的功能如查询提示或 Oracle 中的 CONNECT 关键字的话,你可以使用原生 SQL 数据库来表达查询。Hibernate 3.x 允许您为所有的创建,更新,删除,和加载操作指定手写 SQL ,包括存储过程。

您的应用程序会在会话界面用 createSQLQuery() 方法创建一个原生 SQL 查询:

public SQLQuery createSQLQuery(String sqlString) throws HibernateException

当你通过一个包含 SQL 查询的 createsqlquery() 方法的字符串时,你可以将 SQL 的结果与现有的 Hibernate 实体,一个连接,或一个标量结果分别使用 addEntity(), addJoin(), 和 addScalar() 方法进行关联。

标量查询

最基本的 SQL 查询是从一个或多个列表中获取一个标量(值)列表。以下是使用原生 SQL 进行获取标量的值的语法:

String sql = "SELECT first_name, salary FROM EMPLOYEE"; SQLQuery query = session.createSQLQuery(sql query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP List results = query.list(

实体查询

以上的查询都是关于返回标量值的查询,只是基础性地返回结果集中的“原始”值。以下是从原生 SQL 查询中通过 addEntity() 方法获取实体对象整体的语法:

String sql = "SELECT * FROM EMPLOYEE"; SQLQuery query = session.createSQLQuery(sql query.addEntity(Employee.class List results = query.list(

指定 SQL 查询

以下是从原生 SQL 查询中通过 addEntity() 方法和使用指定 SQL 查询来获取实体对象整体的语法:

String sql = "SELECT * FROM EMPLOYEE WHERE id = :employee_id"; SQLQuery query = session.createSQLQuery(sql query.addEntity(Employee.class query.setParameter("employee_id", 10 List results = query.list(

原生 SQL 的例子

考虑下面的 POJO 类:

public class Employee { private int id; private String firstName; private String lastName; private int salary; public Employee() {} public Employee(String fname, String lname, int salary) { this.firstName = fname; this.lastName = lname; this.salary = salary; } public int getId() { return id; } public void setId( int id ) { this.id = id; } public String getFirstName() { return firstName; } public void setFirstName( String first_name ) { this.firstName = first_name; } public String getLastName() { return lastName; } public void setLastName( String last_name ) { this.lastName = last_name; } public int getSalary() { return salary; } public void setSalary( int salary ) { this.salary = salary; } }

让我们创建以下 EMPLOYEE 表来存储 Employee 对象:

create table EMPLOYEE ( id INT NOT NULL auto_increment, first_name VARCHAR(20) default NULL, last_name VARCHAR(20) default NULL, salary INT default NULL, PRIMARY KEY (id)

以下是映射文件:

<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="Employee" table="EMPLOYEE"> <meta attribute="class-description"> This class contains the employee detail. </meta> <id name="id" type="int" column="id"> <generator class="native"/> </id> <property name="firstName" column="first_name" type="string"/> <property name="lastName" column="last_name" type="string"/> <property name="salary" column="salary" type="int"/> </class> </hibernate-mapping>

最后,我们将用 main() 方法创建应用程序类来运行应用程序,我们将使用原生 SQL 查询:

import java.util.*; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.Transaction; import org.hibernate.SessionFactory; import org.hibernate.SQLQuery; import org.hibernate.Criteria; import org.hibernate.Hibernate; import org.hibernate.cfg.Configuration; public class ManageEmployee { private static SessionFactory factory; public static void main(String[] args) { try{ factory = new Configuration().configure().buildSessionFactory( }catch (Throwable ex) { System.err.println("Failed to create sessionFactory object." + ex throw new ExceptionInInitializerError(ex } ManageEmployee ME = new ManageEmployee( /* Add few employee records in database */ Integer empID1 = ME.addEmployee("Zara", "Ali", 2000 Integer empID2 = ME.addEmployee("Daisy", "Das", 5000 Integer empID3 = ME.addEmployee("John", "Paul", 5000 Integer empID4 = ME.addEmployee("Mohd", "Yasee", 3000 /* List down employees and their salary using Scalar Query */ ME.listEmployeesScalar( /* List down complete employees information using Entity Query */ ME.listEmployeesEntity( } /* Method to CREATE an employee in the database */ public Integer addEmployee(String fname, String lname, int salary){ Session session = factory.openSession( Transaction tx = null; Integer employeeID = null; try{ tx = session.beginTransaction( Employee employee = new Employee(fname, lname, salary employeeID = (Integer) session.save(employee tx.commit( }catch (HibernateException e) { if (tx!=null) tx.rollback( e.printStackTrace( }finally { session.close( } return employeeID; } /* Method to READ all the employees using Scalar Query */ public void listEmployeesScalar( ){ Session session = factory.openSession( Transaction tx = null; try{ tx = session.beginTransaction( String sql = "SELECT first_name, salary FROM EMPLOYEE"; SQLQuery query = session.createSQLQuery(sql query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP List data = query.list( for(Object object : data) { Map row = (Map)object; System.out.print("First Name: " + row.get("first_name") System.out.println(", Salary: " + row.get("salary") } tx.commit( }catch (HibernateException e) { if (tx!=null) tx.rollback( e.printStackTrace( }finally { session.close( } } /* Method to READ all the employees using Entity Query */ public void listEmployeesEntity( ){ Session session = factory.openSession( Transaction tx = null; try{ tx = session.beginTransaction( String sql = "SELECT * FROM EMPLOYEE"; SQLQuery query = session.createSQLQuery(sql query.addEntity(Employee.class List employees = query.list( for (Iterator iterator = employees.iterator( iterator.hasNext(){ Employee employee = (Employee) iterator.next( System.out.print("First Name: " + employee.getFirstName() System.out.print(" Last Name: " + employee.getLastName() System.out.println(" Salary: " + employee.getSalary() } tx.commit( }catch (HibernateException e) { if (tx!=null) tx.rollback( e.printStackTrace( }finally { session.close( } } }

编译和执行

这是编译并运行上述应用程序的步骤。确保你有适当的 PATH 和 CLASSPATH,然后执行编译程序。

  • 按照在配置一章讲述的方法创建 hibernate.cfg.xml 配置文件。

你会得到下面的结果,并且记录将会在 EMPLOYEE 表创建。

$java ManageEmployee .......VARIOUS LOG MESSAGES WILL DISPLAY HERE........ First Name: Zara, Salary: 2000 First Name: Daisy, Salary: 5000 First Name: John, Salary: 5000 First Name: Mohd, Salary: 3000 First Name: Zara Last Name: Ali Salary: 2000 First Name: Daisy Last Name: Das Salary: 5000 First Name: John Last Name: Paul Salary: 5000 First Name: Mohd Last Name: Yasee Salary: 3000

如果你检查你的 EMPLOYEE 表,它应该有以下记录:

mysql> select * from EMPLOYEE; +----+------------+-----------+--------+ | id | first_name | last_name | salary | +----+------------+-----------+--------+ | 26 | Zara | Ali | 2000 | | 27 | Daisy | Das | 5000 | | 28 | John | Paul | 5000 | | 29 | Mohd | Yasee | 3000 | +----+------------+-----------+--------+ 4 rows in set (0.00 sec) mysql>