Hibernate - 原生SQL

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如果您想利用資料庫特定功能（例如 Oracle 中的查詢提示或 CONNECT 關鍵字），可以使用原生 SQL 來表達資料庫查詢。Hibernate 3.x 允許您為所有建立、更新、刪除和載入操作指定手寫的 SQL，包括儲存過程。

您的應用程式將使用 Session 介面上的 createSQLQuery() 方法從會話中建立原生 SQL 查詢：

public SQLQuery createSQLQuery(String sqlString) throws HibernateException

將包含 SQL 查詢的字串傳遞給 createSQLQuery() 方法後，您可以使用 addEntity()、addJoin() 和 addScalar() 方法分別將 SQL 結果與現有的 Hibernate 實體、連線或標量結果關聯。

標量查詢

最基本的 SQL 查詢是從一個或多個表中獲取標量 (值) 列表。以下是使用原生 SQL 獲取標量值的語法：

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

實體查詢

以上查詢都是關於返回標量值，基本上是從結果集中返回“原始”值。以下是透過 addEntity() 從原生 sql 查詢中獲取整個實體物件的語法。

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

命名 SQL 查詢

以下是透過 addEntity() 使用命名 SQL 查詢從原生 sql 查詢中獲取實體物件的語法。

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 示例

考慮以下 POJO 類：

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;
   }
}

讓我們建立以下 EMPLOYEE 表來儲存 Employee 物件：

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)
);

對映檔案將如下所示：

<?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>

最後，我們將建立包含 main() 方法的應用程式類來執行應用程式，在其中我們將使用 原生 SQL 查詢：

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(); 
      }
   }
}

編譯和執行

以下是編譯和執行上述應用程式的步驟。在進行編譯和執行之前，請確保已正確設定 PATH 和 CLASSPATH。

  • 建立 hibernate.cfg.xml 配置檔案，如配置章節中所述。

  • 建立 Employee.hbm.xml 對映檔案，如上所示。

  • 建立 Employee.java 原始檔，如上所示，並編譯它。

  • 建立 ManageEmployee.java 原始檔，如上所示，並編譯它。

  • 執行 ManageEmployee 二進位制檔案以執行程式。

您將得到以下結果，並且記錄將被建立到 EMPLOYEE 表中。

$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

如果您檢查您的 EMPLOYEE 表，它應該包含以下記錄：

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>
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