Hibernate(31)Hibernate的原生SQL查询是什么?

Hibernate的原生SQL查询

在某些情况下,HQL(Hibernate Query Language)或Criteria API可能无法满足复杂查询的需要,这时可以使用原生SQL查询(Native SQL Query)。原生SQL查询允许开发者直接编写SQL语句,并通过Hibernate执行这些语句,将结果映射为实体类或自定义结果集。

使用原生SQL查询

原生SQL查询主要分为两种:

  1. 实体查询:返回实体对象。
  2. 非实体查询:返回自定义对象或投影结果。

示例代码

实体类定义

我们将定义两个实体类:PersonAddress

Person类
java 复制代码
package com.example.domain;

import javax.persistence.*;

@Entity
@Table(name = "person")
public class Person {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "name")
    private String name;

    @Column(name = "age")
    private int age;

    public Person() {}

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Getters 和 Setters

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}
Address类
java 复制代码
package com.example.domain;

import javax.persistence.*;

@Entity
@Table(name = "address")
public class Address {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "street")
    private String street;

    @ManyToOne
    @JoinColumn(name = "person_id", nullable = false)
    private Person person;

    public Address() {}

    public Address(String street, Person person) {
        this.street = street;
        this.person = person;
    }

    // Getters 和 Setters

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getStreet() {
        return street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    public Person getPerson() {
        return person;
    }

    public void setPerson(Person person) {
        this.person = person;
    }
}

Hibernate配置文件 hibernate.cfg.xml

xml 复制代码
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- 数据库连接配置 -->
        <property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/your_database</property>
        <property name="hibernate.connection.username">your_username</property>
        <property name="hibernate.connection.password">your_password</property>

        <!-- Hibernate 属性配置 -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.format_sql">true</property>
        <property name="hibernate.hbm2ddl.auto">update</property>

        <!-- 映射类 -->
        <mapping class="com.example.domain.Person"/>
        <mapping class="com.example.domain.Address"/>
    </session-factory>
</hibernate-configuration>

HibernateUtil类

java 复制代码
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
    private static final SessionFactory sessionFactory;

    static {
        try {
            // 从配置文件创建SessionFactory
            sessionFactory = new Configuration().configure("hibernate.cfg.xml").buildSessionFactory();
        } catch (Throwable ex) {
            // 记录启动失败的错误
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

使用原生SQL查询示例

插入示例数据

java 复制代码
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;

public class HibernateInsertData {
    public static void main(String[] args) {
        // 获取SessionFactory
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

        // 插入示例数据
        insertSampleData(sessionFactory);

        // 关闭SessionFactory
        sessionFactory.close();
    }

    private static void insertSampleData(SessionFactory sessionFactory) {
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();
        try {
            Person person1 = new Person("John Doe", 30);
            Person person2 = new Person("Jane Doe", 28);

            session.save(person1);
            session.save(person2);
            transaction.commit();
            System.out.println("Inserted sample data");
        } catch (Exception e) {
            if (transaction != null) {
                transaction.rollback();
            }
            e.printStackTrace();
        } finally {
            if (session != null) {
                session.close();
            }
        }
    }
}

使用原生SQL查询

查询所有Person记录
java 复制代码
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.query.NativeQuery;

import java.util.List;

public class HibernateNativeQueryExample {
    public static void main(String[] args) {
        // 获取SessionFactory
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

        // 使用原生SQL查询所有Person记录
        queryAllPersons(sessionFactory);

        // 关闭SessionFactory
        sessionFactory.close();
    }

    private static void queryAllPersons(SessionFactory sessionFactory) {
        Session session = sessionFactory.openSession();
        try {
            String sql = "SELECT * FROM person";
            NativeQuery<Person> query = session.createNativeQuery(sql, Person.class);
            List<Person> persons = query.getResultList();
            System.out.println("Query all persons:");
            for (Person person : persons) {
                System.out.println(person.getName() + " - " + person.getAge());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (session != null) {
                session.close();
            }
        }
    }
}
使用投影查询返回自定义结果

假设我们只想查询Person的姓名和年龄,而不是整个实体,这时可以使用投影查询(Projection Query)。

java 复制代码
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.query.NativeQuery;

import java.util.List;

public class HibernateProjectionQueryExample {
    public static void main(String[] args) {
        // 获取SessionFactory
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

        // 使用原生SQL投影查询
        queryPersonNameAndAge(sessionFactory);

        // 关闭SessionFactory
        sessionFactory.close();
    }

    private static void queryPersonNameAndAge(SessionFactory sessionFactory) {
        Session session = sessionFactory.openSession();
        try {
            String sql = "SELECT name, age FROM person";
            NativeQuery<Object[]> query = session.createNativeQuery(sql);
            List<Object[]> results = query.getResultList();
            System.out.println("Query person name and age:");
            for (Object[] row : results) {
                String name = (String) row[0];
                Integer age = (Integer) row[1];
                System.out.println(name + " - " + age);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (session != null) {
                session.close();
            }
        }
    }
}

原生SQL查询详细解释

  1. 插入示例数据 :向数据库中插入两个Person对象供查询使用。

    java 复制代码
    public class HibernateInsertData {
        public static void main(String[] args) {
            // 获取SessionFactory
            SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    
            // 插入示例数据
            insertSampleData(sessionFactory);
    
            // 关闭SessionFactory
            sessionFactory.close();
        }
    
        private static void insertSampleData(SessionFactory sessionFactory) {
            Session session = sessionFactory.openSession();
            Transaction transaction = session.beginTransaction();
            try {
                Person person1 = new Person("John Doe", 30);
                Person person2 = new Person("Jane Doe", 28);
    
                session.save(person1);
                session.save(person2);
                transaction.commit();
                System.out.println("Inserted sample data");
            } catch (Exception e) {
                if (transaction != null) {
                    transaction.rollback();
                }
                e.printStackTrace();
            } finally {
                if (session != null) {
                    session.close();
                }
            }
        }
    }
  2. 查询所有Person记录 :使用原生SQL查询所有Person记录并映射为Person实体。

    java 复制代码
    public class HibernateNativeQueryExample {
        public static void main(String[] args) {
            // 获取SessionFactory
            SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    
            // 使用原生SQL查询所有Person记录
            queryAllPersons(sessionFactory);
    
            // 关闭SessionFactory
            sessionFactory.close();
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