什么是MyBatis框架 第一节

1.简绍Mybatis框架

什么是框架：框架就是别人搭建好的某些功能，你只需要引用该框架并加入自己的业务代码。

好处: 提高我们的开发效率。

mybatis的介绍:

MyBatis 是一款优秀的持久层Dao框架，它支持定制化 SQL、存储过程以及高级映射。

MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。

MyBatis 可以使用简单的 XML 或注解来配置和映射原生信息，将接口和 Java 的 POJOs(Java实体类)映射成数据库中的记录。

MyBatis会将输入参数，输出结果进行映射。

2.我们为什么要用MyBatis框架

可以简化jdbc的操作以及占位符赋值以及查询结果集的封装。

3.使用MyBatis

3.1.引入MyBatis和Mysql的jar包

<!--https://mvnrepository.com/artifact/org.mybatis/mybatis-->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.4.6</version>
</dependency>
<!--mysql的驱动-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.28</version>
</dependency>

3.2.创建MyBatis的配置文件

<?xml version="1.0" encoding="UTF-8"?>
        <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTDConfig 3.0//EN"
                "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--起别名-->
    <typeAliases>
        <!--单独为某个实体类起别名-->
        <typeAlias type="com.wzl.entity.Student" alias="s"/>
        <!--为指定包下的实体类起别名就是实体类名   与上面两者不起冲突  -->
        <package name="com.wzl.entity"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!--数据源的配置:name的值固定 value的值要根据客
            户自己修改-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/student?serverTimezone=Asia/Shanghai"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>

3.3.创建数据库和表

CREATE TABLE `t_student`  (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '学生表的主键列',
  `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
  `age` int(11) NULL DEFAULT NULL,
  `address` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 16 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `t_student` VALUES (1, '张三', 18, '北京');
INSERT INTO `t_student` VALUES (2, '李四', 19, '北京');
INSERT INTO `t_student` VALUES (4, '钱七', 19, '北京');
INSERT INTO `t_student` VALUES (5, '关羽', 25, '南京');
INSERT INTO `t_student` VALUES (6, '张飞', 25, '南京');
INSERT INTO `t_student` VALUES (7, '赵云', 28, '南京');
INSERT INTO `t_student` VALUES (8, '项羽', 19, '南京');
INSERT INTO `t_student` VALUES (9, '刘备', 30, '上海');
INSERT INTO `t_student` VALUES (10, '曹操', 40, '许昌');
INSERT INTO `t_student` VALUES (11, '夏侯', 36, '许昌');
INSERT INTO `t_student` VALUES (12, '诸葛亮', 38, '上海');
INSERT INTO `t_student` VALUES (13, '周瑜', 78, '江东');
INSERT INTO `t_student` VALUES (14, '小乔', 56, '江东');
INSERT INTO `t_student` VALUES (15, '孙尚香', 59, '江东');

3.4.创建实体类 跟添加lombok

@Data //set和get方法以及toString方法
@NoArgsConstructor //无参构造方法
@AllArgsConstructor //所有参数的构造方法
public class User {
    private int userid;
    private String username;
    private String realname;
}

3.5.创建MyBatis和数据库的映射文件 并实现 增删改查 应用

作用：映射实体和表之间的映射关系。

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
        <!--namespace:命名空间可以随便起名，
        但是后期我们要求命名空间的值必须和所对应的dao相同
        -->
        <mapper namespace="qy151.user">
        <!--查询 根据id查询用户信息
            select标签用于查询的标签
                id:标签的唯一标识
                resultType: 定义返回的类型 把sql查询的结果封装到哪个实体类钟
                    #{id}===表示占位符等价于? 这是mybatis框架的语法
        -->
        <!--id查询学生所有信息-->
        <select id="findById" resultType="s">
            select * from t_student where id=#{id}
        </select>
        <!--添加学生信息
                parametertype: 参数类型 20 #{必须和属性对应}
        -->
        <insert id="add" parameterType="Student">
            insert into t_student(name,age,address) values (#{name},#{age},#{address})
        </insert>
        <!--删除学生信息-->
        <delete id="delete" parameterType="s">
            delete from t_student where id=#{id}
        </delete>
        <!--修改-->
        <update id="update" parameterType="s">
                update t_student set name = #{name} , age = #{age} , address = #{address} where id = #{id}
        </update>
        <!--查询所有的方法-->
        <select id="findAll" resultType="s">
                select * from t_student
        </select>
        </mapper>

3.6.注意：一定要把映射文件注册到配置文件上 mybatis.xml 上

mybatis.xml

<?xml version="1.0" encoding="UTF-8"?>
        <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTDConfig 3.0//EN"
                "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--起别名-->
    <typeAliases>
        <!--单独为某个实体类起别名-->
        <typeAlias type="com.wzl.entity.Student" alias="s"/>
        <!--为指定包下的实体类起别名就是实体类名   与上面两者不起冲突  -->
        <package name="com.wzl.entity"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!--数据源的配置:name的值固定 value的值要根据客
            户自己修改-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/student?serverTimezone=Asia/Shanghai"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>
    <!--映射文件位置-->
    <mappers>
        <mapper resource="mapper/StuMapper.xml"/>
    </mappers>
</configuration>

3.7.测试 增删改查 mybatis

package com.test;/*
 * @author     : 王磊
 * @date       : 2022/5/31 20:49
 * @description: some description
 */
import com.wzl.entity.Student;
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.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.List;
public class Test01 {
    @Test
    public void testFindById() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        Student student = session.selectOne("qy151.student001.findById",6);
        System.out.println(student);
        session.close();
    }
    @Test
    public void testAdd() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        Student student = new Student();
        student.setName("数码宝贝");
        student.setAge(15);
        student.setAddress("天津");
        int row = session.insert("qy151.student001.add",student);
        System.out.println(row);
        session.commit();
        session.close();
    }
    @Test
    public void testDelete() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        int dele = session.delete("qy151.student001.delete",85);
        System.out.println(dele);
        session.commit();
        session.close();
    }
    @Test
    public void testUpdate() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        Student student = new Student(83,"小明",18,"北京");
        int upda = session.update("qy151.student001.update",student);
        System.out.println(upda);
        session.commit();
        session.close();
    }
    @Test
    public void testFindAll() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        List<Student> students = session.selectList("qy151.student001.findAll");
        System.out.println(students);
        session.commit();
        session.close();
    }
}

4.LomBok插件

它可以帮你生成实体类的get和set方法 而且可以帮你生成构造方法。重写toString方法

（1） idea安装lombok插件---

 (2) 工程中引入lombok依赖

<!--lombok的依赖-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.24</version>
        </dependency>

（3）在实体类上添加lombok注解

@Data //set和get方法以及toString方法
@NoArgsConstructor //无参构造方法
@AllArgsConstructor //所有参数的构造方法
public class User {
    private int userid;
    private String username;
    private String realname;
}

5. 使用mybatis完成crud

package com.test;/*
 * @author     : 王磊
 * @date       : 2022/5/31 20:49
 * @description: some description
 */
import com.wzl.entity.Student;
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.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.List;
public class Test01 {
    @Test
    public void testFindById() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        Student student = session.selectOne("qy151.student001.findById",6);
        System.out.println(student);
        session.close();
    }
    @Test
    public void testAdd() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        Student student = new Student();
        student.setName("数码宝贝");
        student.setAge(15);
        student.setAddress("天津");
        int row = session.insert("qy151.student001.add",student);
        System.out.println(row);
        session.commit();
        session.close();
    }
    @Test
    public void testDelete() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        int dele = session.delete("qy151.student001.delete",85);
        System.out.println(dele);
        session.commit();
        session.close();
    }
    @Test
    public void testUpdate() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        Student student = new Student(83,"小明",18,"北京");
        int upda = session.update("qy151.student001.update",student);
        System.out.println(upda);
        session.commit();
        session.close();
    }
    @Test
    public void testFindAll() throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = factory.openSession();
        List<Student> students = session.selectList("qy151.student001.findAll");
        System.out.println(students);
        session.commit();
        session.close();
    }
}

6.mybatis一些优化

        mybatis.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">
<configuration>
    <!--起别名-->
    <typeAliases>
        <typeAlias type="com.wzl.entity.Student" alias="s"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!--数据源的配置:name的值固定  value的值要根据客户自己修改-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver" />
                <property name="url"    value="jdbc:mysql://localhost:3306/student?serverTimezone=Asia/Shanghai" />
                <property name="username" value="root" />
                <property name="password" value="1234" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/StuMapper.xml"/>
    </mappers>
</configuration>

 7.添加sql日志

        （1）添加日志的jar.

<?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.wzl</groupId>
    <artifactId>mybatis-02</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <!--引入mybatis-->
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <!--引入mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <!--引入lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.24</version>
        </dependency>
        <!--引入单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <!--log4j  安全日志-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>RELEASE</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>
</project>

(2) 添加日志的文件配置--log4j.properties必须

log4j.rootLogger=DEBUG, Console
#Console
log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
log4j.appender.Console.layout.ConversionPattern=%d [%t] %-5p [%c] - %m%n
log4j.logger.java.sql.ResultSet=INFO
log4j.logger.org.apache=INFO
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

详细日志：

#将等级为DEBUG的日志信息输出到console和file这两个目的地，console和file的定义在下面的代码
log4j.rootLogger=DEBUG,console,file

#控制台输出的相关设置
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target = System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=[%c]-%m%n

#文件输出的相关设置
log4j.appender.file = org.apache.log4j.RollingFileAppender
log4j.appender.file.File=D:/qy151/log/qy151.log
log4j.appender.file.MaxFileSize=10mb
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[%p][%d{yy-MM-dd}][%c]%m%n

#日志输出级别
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG