如果要在Oracle中使用特定于数据库的功能(如查询提示或CONNECT关键字),则可以使用本机SQL来表示数据库查询. Hibernate 3.x允许您为所有创建,更新,删除和加载操作指定手写SQL,包括存储过程.
您的应用程序将从会话中创建本机SQL查询Session接口上的 createSQLQuery()方法 :
public SQLQuery createSQLQuery(String sqlString) throws HibernateException
将包含SQL查询的字符串传递给createSQLQuery()方法后,可以将SQL结果与现有的Hibernate实体,连接或标量结果分别使用addEntity(),addJoin()和addScalar()方法.
最基本的SQL查询是获取来自一个或多个表的标量(值)列表.以下是使用本机SQL进行标量值和减号的语法;
String sql = "SELECT first_name, salary FROM EMPLOYEE"; SQLQuery query = session.createSQLQuery(sql); query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP); List results = query.list();
以上查询都是关于返回标量值,基本上返回"原始"值来自结果集.以下是通过addEntity()从本机sql查询中获取整个实体对象的语法.
String sql = "SELECT * FROM EMPLOYEE"; SQLQuery query = session.createSQLQuery(sql); query.addEntity(Employee.class); List results = query.list();
以下是通过addEntity()从本机sql查询中获取实体对象的语法使用命名SQL查询.
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();
考虑以下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) );
以下将是映射文件 :
<?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,我们将使用main()方法创建应用程序类,以运行我们将使用 Native SQL 查询的应用程序 :
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(); } } }
这是编译和运行上述应用程序的步骤.确保在进行编译和执行之前已经适当地设置了PATH和CLASSPATH.
创建hibernate.cfg.xml配置文件,如配置章节中所述.
创建Employee.hbm.xml映射文件,如上所示.
如上所示创建Employee.java源文件并进行编译.
如上所示创建ManageEmployee.java源文件并进行编译.
执行ManageEmployee二进制文件以运行程序.
你会得到以下结果,并且会在EMPLOYEE表中创建记录.
$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
如果您检查您的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>