hibernate——实现简单的增、删、改、查

HQL(Hibernate Query Language)是完全面对对象的查询语句，查询功能强大，具备继承、多态和关联等特性。

Query是Hibernate的查询接口，用于从数据存储源查询对象及控制执行查询的过程，Query包装了一个HQL语句。

hibernate5中 org.hibernate.Query 被 org.hibernate.query.Query 替代。

创建dao层接口实现简单的增、删、改、查。

package com.dao;

import java.util.List;

import org.hibernate.Session;
import org.hibernate.query.Query;

import com.entity.Student;
import com.util.HibernateUtil;

public class StudentDao {
	private Session session = HibernateUtil.getSession();

	public Student selectStudentById(int ID) {
		Student stu = session.get(Student.class, ID);
		return stu;
	}

	public List<Student> selectStudentbyName(String name) {
		String sql = "FROM Student s WHERE s.name =?";
		Query<Student> query = session.createQuery(sql, Student.class);
		query.setParameter(0, name);
		List<Student> stus = query.list();
		return stus;
	}

	public List<Student> selectStudent() {
		String sql = "select * from STUDENT";
		Query<Student> query = session.createNativeQuery(sql, Student.class);
		List<Student> stus = (List<Student>) query.getResultList();
		return stus;
	}

	public int insertStudent(Student value) {
		session.beginTransaction();
		session.save(value);
		session.getTransaction().commit();
		return 1;
	}

	public int deleteStudentById(int ID) {
		session.beginTransaction();
		Student stu = session.get(Student.class, ID);
		session.delete(stu);
		session.getTransaction().commit();
		return 1;
	}

	public int updateStudentById(Student value) {
		session.beginTransaction();
		Student stu = session.get(Student.class, value.getID());
		stu = value;
		session.update(stu);
		session.getTransaction().commit();
		return 1;
	}
}

执行增添信息：

package com.test;

import com.dao.StudentDao;
import com.entity.Student;

public class insertMain {
	private static StudentDao studao = null;

	public static void main(String[] args) {
		studao = new StudentDao();
		Student stu = new Student();
		stu.setName("非常美丽的巨兔");
		stu.setGender("F");
		stu.setAge(22);
		System.out.println(studao.insertStudent(stu));
	}
}

返回结果：

Hibernate: select max(ID) from STUDENT
Hibernate: insert into STUDENT (NAME, GENDER, AGE, ID) values (?, ?, ?, ?)
1

执行修改信息

package com.test;

import java.util.List;

import com.dao.StudentDao;
import com.entity.Student;

public class updateMain {
	private static StudentDao studao = null;

	public static void main(String[] args) {
		studao = new StudentDao();
		// 先查询所有对象信息
		List<Student> stus = studao.selectStudent();
		for (Student s : stus) {
			System.out.println(s);
		}
		// 更改对象信息
		Student stu = stus.get(1);
		stu.setName("诸葛亮");
		System.out.println(studao.updateStudentById(stu));
		;
	}
}

返回结果：

Hibernate: select * from STUDENT
Student [ID=1, name=盖伦, gender=M, age=26]
Student [ID=2, name=亚瑟, gender=M, age=26]
Student [ID=3, name=非常美丽的巨兔, gender=F, age=22]
Student [ID=4, name=孙尚香, gender=M, age=18]
Hibernate: update STUDENT set NAME=?, GENDER=?, AGE=? where ID=?
1

实现简单的分组查询

package com.test;

import java.util.List;

import org.hibernate.Session;
import org.hibernate.query.Query;

import com.util.HibernateUtil;

public class Main0529 {
	public static void main(String[] args) {
		Session session = HibernateUtil.getSession();
		// 查询平均年龄并按性别分组
		String sql = "select s.gender,avg(age) from Student s group by s.gender";
		Query<Object[]> query = session.createQuery(sql, Object[].class);
		List<Object[]> list = query.list();
		for (Object[] s : list) {
			System.out.printf("%s:%s%n", s[0], s[1]);
		}
	}
}

返回结果：

Hibernate: select student0_.GENDER as col_0_0_, avg(student0_.AGE) as col_1_0_
from STUDENT student0_ group by student0_.GENDER
F:22.0
M:23.3333

删除信息不在展示。