📅 最后修改于: 2020-11-16 07:02:42 🧑 作者: Mango
如果要利用特定于数据库的功能(例如查询提示或Oracle中的CONNECT关键字)，则可以使用本机SQL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()方法从会话中创建本机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，联接或标量结果相关联。分别。
最基本的SQL查询是从一个或多个表中获取标量(值)列表。以下是将本机SQL用于标量值的语法-
String sql = "SELECT first_name, salary FROM EMPLOYEE";
SQLQuery query = session.createSQLQuery(sql);
query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
List results = query.list();
上面的查询都是关于返回标量值的，基本上是从结果集中返回“原始”值。以下是通过addEntity()从本机sql查询获取整体实体对象的语法。
String sql = "SELECT * FROM EMPLOYEE";
SQLQuery query = session.createSQLQuery(sql);
query.addEntity(Employee.class);
List results = query.list();
以下是通过addEntity()并使用命名的SQL查询从本机sql查询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();
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-
This class contains the employee detail.
最后，我们将使用main()方法创建应用程序类以运行应用程序，并在其中使用本机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();
}
}
}
这是编译和运行上述应用程序的步骤。在继续进行编译和执行之前，请确保已正确设置了PATH和CLASSPATH。
按照配置章节中的说明创建hibernate.cfg.xml配置文件。
如上所示，创建Employee.hbm.xml映射文件。
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。
您将得到以下结果，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EMPLOYEE表，则该表应具有以下记录-
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>