Hibernate与Mybatis对比

在了解SSH中Hibernate之后，与另一SSM框架中的Mybatis相比确实缺少一定的灵活性。根据各种大神反馈来看，Hibernate与Mybatis的优缺点如下：

整体比较两者相同点

• Hibernate与MyBatis都可以是通过SessionFactoryBuider由XML配置文件生成SessionFactory，然后由SessionFactory 生成Session，最后由Session来开启执行事务和SQL语句。其中SessionFactoryBuider，SessionFactory，Session的生命周期都是差不多的。

• Hibernate和MyBatis都支持JDBC和JTA事务处理。

Hibernate优势

• Hibernate的DAO层开发比MyBatis简单，Mybatis需要维护SQL和结果映射。
• Hibernate对对象的维护和缓存要比MyBatis好，对增删改查的对象的维护要方便。
• Hibernate数据库移植性很好，MyBatis的数据库移植性不好，不同的数据库需要写不同SQL。
• Hibernate有更好的二级缓存机制，可以使用第三方缓存。MyBatis本身提供的缓存机制不佳。

Mybatis优势

• MyBatis可以进行更为细致的SQL优化，可以减少查询字段。
• MyBatis容易掌握，而Hibernate门槛较高。

下面通过例子来看看：

Mybatis的全局控制文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http:// mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <settings>
        <!-- Globally enables or disables any caches configured in any mapper under this configuration -->
        <!--该配置影响的所有映射器中配置的缓存的全局开关。-->
        <setting name="cacheEnabled" value="true"/>
        <!-- Sets the number of seconds the driver will wait for a response from the database -->
        <!--设置超时时间，它决定驱动等待数据库响应的秒数。-->
        <setting name="defaultStatementTimeout" value="3000"/>
        <!-- Enables automatic mapping from classic database column names A_COLUMN to camel case classic Java property names aColumn -->
        <!--是否开启自动驼峰命名规则（camel case）映射，即从经典数据库列名 A_COLUMN 到经典 Java 属性名 aColumn 的类似映射。-->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <!-- Allows JDBC support for generated keys. A compatible driver is required.
        This setting forces generated keys to be used if set to true,
         as some drivers deny compatibility but still work -->
        <!--允许 JDBC 支持自动生成主键，需要驱动兼容。 如果设置为 true 则这个设置强制使用自动生成主键，尽管一些驱动不能兼容但仍可正常工作（比如 Derby）。-->
        <setting name="useGeneratedKeys" value="true"/>
    </settings>

    <!-- Continue going here -->

    <environments default="development">
        <environment id="development">
            <transactionManager type="jdbc"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url"
                          value="jdbc:mysql://localhost:3306/test_db?serverTimeZone=UTC&amp;useSSL=false&amp;useUnicode=true&amp;characterEncoding=utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value=""/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="mapper/GetStudentInfo.xml"/>
    </mappers>

</configuration>

映射的学生类

import java.sql.Date;

/**
 * Created by lollipop on 07/12/2016.
 */
public class Student {
    private int sid;            /*学号*/
    private String name;        /*姓名*/
    private String gender;      /*年龄*/
    private String address;     /*地址*/
    private String phone;       /*电话*/
    private Date birthday;      /*出生日期*/

    public Student() {
    }

    public Student(String name, String gender, String address, String phone, Date birthday) {
        this.name = name;
        this.gender = gender;
        this.address = address;
        this.phone = phone;
        this.birthday = birthday;
    }

    public Student(int sid, String name, String gender, String address, String phone, Date birthday) {
        this.sid = sid;
        this.name = name;
        this.gender = gender;
        this.address = address;
        this.phone = phone;
        this.birthday = birthday;
    }

    public int getSid() {
        return sid;
    }

    public Student setSid(int sid) {
        this.sid = sid;
        return this;
    }

    public String getName() {
        return name;
    }

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

    public String getGender() {
        return gender;
    }

    public Student setGender(String gender) {
        this.gender = gender;
        return this;
    }

    public String getAddress() {
        return address;
    }

    public Student setAddress(String address) {
        this.address = address;
        return this;
    }

    public String getPhone() {
        return phone;
    }

    public Student setPhone(String phone) {
        this.phone = phone;
        return this;
    }

    public Date getBirthday() {
        return birthday;
    }

    public Student setBirthday(Date birthday) {
        this.birthday = birthday;
        return this;
    }

    @Override
    public String toString() {
        return "Student{" +
                "sid=" + sid +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", address='" + address + '\'' +
                ", phone='" + phone + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}

Mybatis主要将相应的配置文件中对数据库的操作，映射到相应的接口中的方法，通过接口中的方法来完成相应的数据库操作。

接口代码：

/**
 * Created by lollipop on 07/12/2016.
 */
public interface GetStudentInfo {
    Student getStudent(int sid);
    void updateStudent(Student student);
    void deleteStudent(int sid);
    void addStudent(Student student);

}

接口相应的映射配置文件：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="GetStudentInfo">
    <insert id="addStudent" parameterType="Student" useGeneratedKeys="true" keyProperty="sid">
        INSERT INTO STUDENT (NAME, GENDER, ADDRESS, PHONE, BIRTHDAY)
            VALUE (#{name}, #{gender}, #{address}, #{phone}, #{birthday})
    </insert>

    <update id="updateStudent" parameterType="Student">
        UPDATE STUDENT
        SET NAME = #{name}, gender = #{gender}, address = #{address}, phone = #{phone}, birthday = #{birthday}
        WHERE sid = #{sid}
    </update>

    <delete id="deleteStudent" parameterType="int">
        DELETE FROM STUDENT
        WHERE SID = #{sid}
    </delete>

    <select id="getStudent" resultType="Student" parameterType="int">
        SELECT
            SID,
            NAME,
            GENDER,
            ADDRESS,
            PHONE,
            BIRTHDAY
        FROM STUDENT
        WHERE SID = #{sid}
    </select>
</mapper>

具体的Main类对，Mybatis进行基本的数据库增，删，改，查操作。

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.InputStream;
import java.sql.Date;

/**
 * Created by lollipop on 07/12/2016.
 */
public class Main {
    public static void main (String args[]) {
        String resource = "conf.xml";
        InputStream is = Main.class.getResourceAsStream(resource);
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
        SqlSession session = factory.openSession(true);
        try{

            GetStudentInfo getStudentInfo = session.getMapper(GetStudentInfo.class);
            /*查询*/
            Student student = getStudentInfo.getStudent(1);
            System.out.println(student);


            /*插入*/
            student = new Student("小智","男","荆州","123456789", Date.valueOf("2000-08-08"));
            getStudentInfo.addStudent(student);


            /*清除*/
            getStudentInfo.deleteStudent(student.getSid());

            /*更新*/
            student.setName("小猪");
            getStudentInfo.updateStudent(student);
        }finally {
            session.close();
        }

    }
}

接下来，我们来看看Hibernate是怎么实现对数据库中数据进行增，删，改，查操作的。

package Study;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.query.Query;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.util.Iterator;
import java.util.List;

/**
 * Created by lollipop on 02/12/2016.
 */
public class TestStudent {
    private Session session;
    private SessionFactory sessionFactory;
    private Transaction transaction;

    @Before
    public void init() {
        Configuration configuration = new Configuration().configure();
        sessionFactory = configuration.buildSessionFactory();
        session = sessionFactory.openSession();
        transaction = session.beginTransaction();
    }

    @Test
    public void test() {

        /*添加*/
        StudentEntity student = new StudentEntity(16, "王子", "男", "北京", "16", Date.valueOf("1996-10-01"));
        session.save(student);

        /*删除数据库中的表有满足属性为16的学生*/
        StudentEntity delStudent = session.load(StudentEntity.class, 16);

        session.delete(delStudent);


        /*指定对象删除操作*/
//        删除sid 为 2的数据
        StudentEntity studentEntity2 = new StudentEntity();
        studentEntity2.setSid(2);
        session.delete(studentEntity2);




//        使用下面语句会报错 但使用上面则正确
//        session.delete(new StudentEntity().setSid(2));


//        下面引号部分 为参数（from 类）





        /*遍历打印*/
        Query query = session.createQuery("from StudentEntity ");
        List userList = query.list();

        System.out.println("利用foreach语句输出表中信息");
        for (Object s : userList) {
            StudentEntity ste = (StudentEntity) s;
            System.out.println(ste.toString());
        }
        System.out.println("");
        System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>");
        System.out.println("");
        System.out.println("利用迭代器输出表中信息");
        for (Iterator iterator = userList.iterator(); iterator.hasNext(); ) {
            StudentEntity ste = (StudentEntity) iterator.next();
            System.out.println(ste.toString());
        }

        /*更新*/
        StudentEntity studentEntity =  session.load(StudentEntity.class,1);
        studentEntity.setGender("女");
        session.update(studentEntity);

    }

    @After
    public void destroy() {
        transaction.commit();
        session.close();
        sessionFactory.close();

    }
}

通过对比明显发现，Mybatis比Hibernate灵活得多，用户可以根据自己的编写的SQL语句对数据库进行操作，这也同时要求程序猿，要更加熟练的掌握相关的SQL语句。