java基础-day47-Mybatis-CFANZ编程社区

一、引言

1.1 什么是框架？

1.2 什么是ORM框架？

1.3 使用JDBC完成ORM操作的缺点？

二、MyBatis框架

2.1 概念

2.2 访问与下载

三、构建Maven项目

3.1 新建项目

使用IDEA打开已创建的文件夹目录

3.2 选择Maven目录

选择Maven项目

3.3 GAV坐标

GAV坐标

四、MyBatis入门案例【`重点`】

4.1 pom.xml中引入MyBatis核心依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.qf</groupId>
    <artifactId>mybatis-02</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.21</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
        </dependency>
        
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>

</project>

4.2 创建db.properties配置文件

jdbc.url=jdbc:mysql://localhost:3306/java2002?serverTimezone=Asia/Shanghai
jdbc.username=root
jdbc.password=root
jdbc.driver=com.mysql.cj.jdbc.Driver

4.3 创建log4j.properties配置文件

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# MyBatis logging configuration...
log4j.logger.org.mybatis.example.BlogMapper=TRACE
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

4.4 创建mybatis-config.xml配置文件

<?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">

<!-- mybatis的主配置文件 -->
<configuration>
    <!-- 配置外部文件 -->
    <properties resource="db.properties"></properties>
    <!-- 配置别名 -->
    <typeAliases>
<!--        <typeAlias type="com.qf.entity.User" alias="user"></typeAlias>-->
        <package name="com.qf.entity"/>
    </typeAliases>
    <!-- 配置环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <!-- 配置数据源（连接池） -->
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

</configuration>

4.5 建表

create table t_user(
  id int primary key auto_increment,
  name varchar(50),
  password varchar(50)
)default charset = utf8;

INSERT INTO t_user(NAME,PASSWORD) VALUES("jack","123");
INSERT INTO t_user(NAME,PASSWORD) VALUES("tom","456");
INSERT INTO t_user(NAME,PASSWORD) VALUES("rose","789");

4.6 定义实体类

package com.qf.entity;

import lombok.Data;

import java.io.Serializable;

@Data
public class User implements Serializable {

    private Integer id;
    private String name;
    private String password;

}

4.7 定义DAO接口

package com.qf.dao;

import com.qf.entity.User;

public interface UserDao {
    
    public List<User> findAll();

}

4.8 编写Mapper.xml

<?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">

<!--namespace = 所需实现的接口全限定名-->
<mapper namespace="com.qf.dao.UserDao">

    <!--配置查询所有-->
    <!--id = 所需重写的接口抽象方法名，resultType = 查询后所需返回的对象类型-->
    <select id="findAll" resultType="user">
        select * from t_user
    </select>

</mapper>

4.9 注册Mapper

<!-- 指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件 -->
<mappers>
    <!--<mapper resource="com/qf/dao/UserDao.xml"/>-->
    <!--<mapper class="com.qf.dao.UserDao"/>-->
    <package name="com.qf.dao"/>
</mappers>

测试

package com.qf.demo;

import com.qf.dao.UserDao;
import com.qf.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.InputStream;
import java.util.List;

public class MybatisTest {

    //查询所有
    @Test
    public void testfindAll()throws Exception {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession session = factory.openSession();
        //4.使用SqlSession创建Dao接口的代理对象
        UserDao userDao = session.getMapper(UserDao.class);
        
        //5.使用代理对象执行方法
        List<User> users = userDao.findAll();
        for(User user : users){
            System.out.println(user);
        }
        
        //6.释放资源
        session.close();
        in.close();
    }

}

五、MyBatis的CRUD操作【`重点`】

7.1 在Dao添加方法

package com.qf.dao;

import com.qf.entity.User;
import org.apache.ibatis.annotations.Param;

import java.util.HashMap;
import java.util.List;

public interface UserDao {

    public List<User> findAll();

    public User findById(@Param("id") Integer id);

    public void add(User user);

    public void update(User user);

    public void delete(String id);

    //模糊查询1
    public List<User> findByUserName1(String username);

    //模糊查询2
    public List<User> findByUserName2(String username);

    //模糊查询3
    public List<User> findByUserName3(String username);

    //获取总记录数
    public Integer getTotalCount();

    //获取分页数据
    public List<User> findPageData(HashMap<String,Integer> hashMap);

}

7.2 在Mapper.xml中添加对应的方法

 <delete id="deleteUser" parameterType="int">
    DELETE FROM t_users
    WHERE id = #{id} <!--只有一个参数时，#{任意书写}-->
</delete>

7.3 测试

package com.qf.demo;

import com.qf.dao.UserDao;
import com.qf.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.InputStream;
import java.util.HashMap;
import java.util.List;

public class Demo {

    //查询所有
    @Test
    public void testfindAll()throws Exception {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession session = factory.openSession();
        //4.使用SqlSession创建Dao接口的代理对象
        UserDao userDao = session.getMapper(UserDao.class);
        //5.使用代理对象执行方法
        List<User> users = userDao.findAll();
        for(User user : users){
            System.out.println(user);
        }
        //6.释放资源
        session.close();
        in.close();
    }

    //查询单个
    @Test
    public void testfindById()throws Exception {

        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        SqlSession session = factory.openSession();
        //---------------------------------------------

        UserDao userDao = session.getMapper(UserDao.class);
        //5.使用代理对象执行方法
        User user = userDao.findById(1);

        System.out.println(user);

        //---------------------------------------------
        session.close();
        in.close();
    }

    //添加
    @Test
    public void testadd()throws Exception {

        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        SqlSession session = factory.openSession();
        //---------------------------------------------

        UserDao userDao = session.getMapper(UserDao.class);

        User user = new User();
        user.setName("张三");
        user.setPassword("123");

        userDao.add(user);

        System.out.println(user.getId());

        //提交
        session.commit();
        //---------------------------------------------
        session.close();
        in.close();
    }

    //修改
    @Test
    public void testupdate()throws Exception {

        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        SqlSession session = factory.openSession();
        //---------------------------------------------

        UserDao userDao = session.getMapper(UserDao.class);

        User user = userDao.findById(4);
        //user.setId(5);
        user.setName("李四");
        user.setPassword("456");

        userDao.update(user);

        //提交
        session.commit();
        //---------------------------------------------
        session.close();
        in.close();
    }


    //删除
    @Test
    public void testdelete()throws Exception {

        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        SqlSession session = factory.openSession();
        //---------------------------------------------

        UserDao userDao = session.getMapper(UserDao.class);

        userDao.delete("4");

        //提交
        session.commit();
        //---------------------------------------------
        session.close();
        in.close();
    }

    //模糊查询
    @Test
    public void testfindByUserName()throws Exception {

        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        SqlSession session = factory.openSession();
        //---------------------------------------------

        String name = "张";

        UserDao userDao = session.getMapper(UserDao.class);

        //List<User> users = userDao.findByUserName1(name);
        //List<User> users = userDao.findByUserName2("%" + name + "%");
        List<User> users = userDao.findByUserName3(name);

        for(User user : users){
            System.out.println(user);
        }

        //提交
        session.commit();
        //---------------------------------------------
        session.close();
        in.close();
    }

    //查询总记录数
    @Test
    public void testgetTotalCount()throws Exception {

        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        SqlSession session = factory.openSession();
        //---------------------------------------------

        UserDao userDao = session.getMapper(UserDao.class);

        System.out.println(userDao.getTotalCount());

        //提交
        session.commit();
        //---------------------------------------------
        session.close();
        in.close();
    }

    //查询分页数据
    @Test
    public void testfindPageData()throws Exception {

        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        SqlSession session = factory.openSession();
        //---------------------------------------------

        UserDao userDao = session.getMapper(UserDao.class);

        HashMap<String, Integer> hashMap = new HashMap<>();
        hashMap.put("first",0);
        hashMap.put("second",3);

        List<User> users = userDao.findPageData(hashMap);

        for(User user : users){
            System.out.println(user);
        }

        //提交
        session.commit();
        //---------------------------------------------
        session.close();
        in.close();
    }

}

六、Druid连接池

6.1 概念

6.2基准测试结果对比

JDBC-Conn Pool	1 Thread	2 threads	5 threads	10 threads	20 threads	50 threads
Druid	898	1,191	1,324	1,362	1,325	1,459
tomcat-jdbc	1,269	1,378	2,029	2,103	1,879	2,025
DBCP	2,324	5,055	5,446	5,471	5,524	5,415
BoneCP	3,738	3,150	3,194	5,681	11,018	23,125
jboss-datasource	4,377	2,988	3,680	3,980	32,708	37,742
C3P0	10,841	13,637	10,682	11,055	14,497	20,351
Proxool	16,337	16,187	18,310(Ex)	25,945	33,706(Ex)	39,501 (Ex)

6.3 测试结论

Druid 是性能最好的数据库连接池，tomcat-jdbc 和 druid 性能接近。
Proxool 在激烈并发时会抛异常，不适用。
C3P0 和 Proxool 都相当慢，影响 sql 执行效率。
BoneCP 性能并不优越，采用 LinkedTransferQueue 并没有能够获得性能提升。
除了 bonecp，其他的在 JDK 7 上跑得比 JDK 6 上快。
jboss-datasource 虽然稳定，但性能很糟糕。

6.4 配置pom.xml

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.21</version>
</dependency>

6.5 创建DruidDataSourceFactory

package com.qf.utils;

import com.alibaba.druid.pool.DruidDataSource;
import org.apache.ibatis.datasource.pooled.PooledDataSourceFactory;

public class MyDruidDataSourceFactory extends PooledDataSourceFactory {
    public MyDruidDataSourceFactory() {
        this.dataSource = new DruidDataSource();//替换数据源
    }
}

6.6修改mybatis-config.xml

<!--连接池-->
<dataSource type="com.qf.utils.MyDruidDataSourceFactory">
    <property name="driverClass" value="${jdbc.driver}"/>
    <property name="jdbcUrl" value="${jdbc.url}"/>
    <property name="username" value="${jdbc.username}"/>
    <property name="password" value="${jdbc.password}"/>
</dataSource>

注意：< property name="属性名" />属性名必须与com.alibaba.druid.pool.DruidAbstractDataSource中一致。

七、PageHelper

7.1 概念

7.2 访问与下载

7.3 开发步骤

<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper</artifactId>
    <version>5.1.11</version>
</dependency>

<configuration>
    <typeAliases></typeAliases>
        
   <plugins>
       <!-- com.github.pagehelper为PageHelper类所在包名 -->
        <plugin interceptor="com.github.pagehelper.PageInterceptor">
            <property name="helperDialect" value="mysql"/>
            <property name="reasonable" value="true"/>
            <property name="supportMethodsArguments" value="true"/>
        </plugin>
    </plugins>
  
    <environments>...</environments>
</configuration>

//查询分页
    @Test
    public void testfindByPage()throws Exception {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession session = factory.openSession();
        //4.使用SqlSession创建Dao接口的代理对象
        UserDao userDao = session.getMapper(UserDao.class);

        //5.使用代理对象执行方法
        PageHelper.startPage(1,2);//设置当前页和每页显示记录数
        List<User> users = userDao.findAll();
        PageInfo<User> userPageInfo = new PageInfo<>(users);//封装到PageInfo对象中
        System.out.println(userPageInfo);

        //6.释放资源
        session.close();
        in.close();
    }