十六、Hibernate 原生 SQL
大约 4 分钟Hibernate
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。
- 如上述所示创建 employee.hbm.xml 映射文件。
- 如上述所示创建 employee.java 源文件并编译。
- 如上述所示创建 manageemployee.java 源文件并编译。
- 执行 manageemployee 二进制代码运行程序。
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>