Hibernate - Native SQL( Native SQL)
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。
您的应用程序将使用Session接口上的createSQLQuery()方法从会话创建本机SQL查询 -
public SQLQuery createSQLQuery(String sqlString) throws HibernateException
将包含SQL查询的字符串传递给createSQLQuery（）方法后，可以使用addEntity（），addJoin（）和addScalar（）方法将SQL结果与现有的Hibernate实体，连接或标量结果相关联分别。
标量查询
最基本的SQL查询是从一个或多个表中获取标量（值）列表。 以下是使用本机SQL进行标量值的语法 -
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
上面的查询都是关于返回标量值，基本上返回结果集中的“原始”值。 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();
命名的SQL查询
以下是通过addEntity（）和使用命名SQL查询从本机sql查询中获取实体对象的语法。
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();
本机SQL示例
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();
}
}
}
编译和执行 (Compilation and Execution)
以下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适当地设置了PATH和CLASSPATH。
按配置章节中的说明创建hibernate.cfg.xml配置文件。
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。
创建ManageEmployee.java源文件，如上所示并编译它。
执行ManageEmployee二进制文件以运行该程序。
您将获得以下结果，并且将在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>
