010_Mybatis简介

2021-07-12 21:29:59 作者：互联网

Mybatis简介

什么vb.net教程是 MyBatis？

MyBatis 是一款优秀c#教程的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置python基础教程参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

MyBatis 是一款优秀的持久层框架
它支持自定义 SQL、存储过程java基础教程以及高级映射。
MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。
MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。
MyBatis 本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code，并且改名为MyBatis 。2013年11月迁移到Github。

如何获得Mybatis

maven仓库

<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.7</version>
</dependency>

中文文档：https://mybatis.org/mybatis-3/zh/index.html
Github：https://github.com/mybatis/mybatis-3/releases

持久化

持久层

为什么需要Mybatis

第一个Mybatis程序

学习新东西方法：搭建环境-》导入mybatis-》编写代码-》测试

搭建sql教程环境

建库建表

CREATE DATABASE `mybatis`CHARACTER SET utf8 COLLATE utf8_general_ci; 
USE `mybatis`;
CREATE TABLE `mybatis`.`user` ( `id` INT(20) NOT NULL COMMENT '主键', `name` VARCHAR(100) NOT NULL COMMENT '用户名', `pwd` VARCHAR(100) NOT NULL COMMENT '密码', PRIMARY KEY (`id`) ) ENGINE=INNODB CHARSET=utf8 COLLATE=utf8_general_ci; 
DESCRIBE `mybatis`.`user`; 
INSERT INTO `mybatis`.`user` (`id`, `name`, `pwd`) VALUES ('1', 'zhangyq', '123456'); 
INSERT INTO `mybatis`.`user` (`id`, `name`, `pwd`) VALUES ('2', 'zhangsf', '123456'); 
INSERT INTO `mybatis`.`user` (`id`, `name`, `pwd`) VALUES ('3', 'zhangdl', '123456');

新建父工程

新建普通maven项目

删除src目录，作为父工程

导入maven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>

    <!--父工程-->
    <groupId>com.qing</groupId>
    <artifactId>mybatis-study</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
        </dependency>

    </dependencies>

</project>

创建第一个子模块

编写mybatis的核心配置文件

官网：https://mybatis.org/mybatis-3/zh/index.html

<?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">

<!--核心配置文件-->
<configuration>
    <!--指定默认数据源-->
    <environments default="development">
        <!--数据源-->
        <environment id="development">
            <!--事务管理器-->
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
</configuration>

编写mybatis工具类，获取SqlSession

SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。

package com.qing.utils;

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 java.io.IOException;
import java.io.InputStream;

public class MybatisUtils {

    // 构建 SqlSessionFactory 的实例
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 获取 SqlSession
     * @return
     */
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

编写代码测试

实体类

接口

package com.qing.dao;

import com.qing.pojo.User;

import java.util.List;

/**
 * 接口
 */
public interface UserMapper {

    List<User> getUserList();
}

Mapper

<?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">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
    <!--id对应接口的方法，返回值类型对应接口返回值，参数类型对应接口方法参数，集合类型写集合泛型类型-->
    <select id="getUserList" resultType="com.qing.pojo.User">
        select * from mybatis.user
    </select>
</mapper>

测试

package com.qing.dao;

import com.qing.pojo.User;
import com.qing.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {

    /**
     * 方式一：sqlSession.getMapper(UserMapper.class)
     */
    @Test
    public void test() {
        // 获取sqlSession
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        // 执行SQL
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        // 关闭sqlSession
        sqlSession.close();
    }
}

问题一：Mapper.xml未注册

org.apache.ibatis.binding.BindingException: Type interface com.qing.dao.UserMapper is not known to the MapperRegistry.

	at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:47)
	at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:845)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:288)
	at com.qing.dao.UserMapperTest.test(UserMapperTest.java:20)

解决：mybatis-config.xml中注册Mapper，resource绑定Mapper，必须使用路径/

<?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">

<!--核心配置文件-->
<configuration>
    <!--指定默认数据源-->
    <environments default="development">
        <!--数据源-->
        <environment id="development">
            <!--事务管理器-->
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/qing/dao/UserMapper.xml"/>
    </mappers>
</configuration>

问题二：Mapper文件编译后不存在

java.lang.ExceptionInInitializerError
	at com.qing.dao.UserMapperTest.test(UserMapperTest.java:18)
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error building SqlSession.
### The error may exist in com/qing/dao/UserMapper.xml
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource com/qing/dao/UserMapper.xml
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)

解决：pom.xml中配置编译配置

<?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">
    <parent>
        <artifactId>mybatis-study</artifactId>
        <groupId>com.qing</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybatis-01</artifactId>

    <!--配置resources，防止资源导出失败问题-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

问题三：数据库连接SSL错误

org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 2,729 milliseconds ago.  The last packet sent successfully to the server was 2,715 milliseconds ago.
### The error may exist in com/qing/dao/UserMapper.xml
### The error may involve com.qing.dao.UserMapper.getUserList
### The error occurred while executing a query
### Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Caused by: javax.net.ssl.SSLHandshakeException: java.security.cert.CertificateException: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors

Caused by: java.security.cert.CertificateException: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors

解决：mybatis-config.xml中useSSL=true改为useSSL=false

<?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">

<!--核心配置文件-->
<configuration>
    <!--指定默认数据源-->
    <environments default="development">
        <!--数据源-->
        <environment id="development">
            <!--事务管理器-->
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/qing/dao/UserMapper.xml"/>
    </mappers>
</configuration>

测试成功

CRUD

namespace中的包名要和Mapper接口的包名一致

<?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">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
    <!--id对应接口的方法，返回值类型对应接口返回值，参数类型对应接口方法参数，集合类型写集合泛型类型-->
    <select id="getUserList" resultType="com.qing.pojo.User">
        select * from mybatis.user
    </select>
</mapper>

package com.qing.dao;

import com.qing.pojo.User;
import java.util.List;

/**
 * 接口
 */
public interface UserMapper {

    /**
     * 查询全部用户
     * @return
     */
    List<User> getUserList();
}

select 选择，查询语句

id 对应接口中的方法名

parameterType 对应接口中方法的请求参数

resultType 对应接口中方法的返回值

集合类型写集合泛型类型

<?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">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
    <!--查询全部用户-->
    <select id="getUserList" resultType="com.qing.pojo.User">
        select * from mybatis.user
    </select>
    <!--id对应接口的方法，返回值类型对应接口返回值，参数类型对应接口方法参数，集合类型写集合泛型类型-->
    <!--根据ID查询用户-->
    <select id="getUserById" parameterType="int" resultType="com.qing.pojo.User">
        select * from mybatis.user where id=#{id}
    </select>
</mapper>

package com.qing.dao;

import com.qing.pojo.User;
import java.util.List;

/**
 * 接口
 */
public interface UserMapper {

    /**
     * 查询全部用户
     * @return
     */
    List<User> getUserList();

    /**
     * 根据ID查询用户
     * @param id
     * @return
     */
    User getUserById(int id);
}

package com.qing.dao;

import com.qing.pojo.User;
import com.qing.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {

    /**
     * 查询全部用户
     */
    @Test
    public void getUserList() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            List<User> userList = mapper.getUserList();
            for (User user : userList) {
                System.out.println(user);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }

    /**
     * 根据ID查询用户
     */
    @Test
    public void getUserById() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            User user = mapper.getUserById(1);
            System.out.println(user);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }
}

insert/update/delete 增删改必须提交事务

编写接口

package com.qing.dao;

import com.qing.pojo.User;

import java.util.List;

/**
 * 接口
 */
public interface UserMapper {

    /**
     * 查询全部用户
     *
     * @return
     */
    List<User> getUserList();

    /**
     * 根据ID查询用户
     *
     * @param id
     * @return
     */
    User getUserById(int id);

    /**
     * 新增用户
     *
     * @param user
     * @return
     */
    int insert(User user);

    /**
     * 修改用户
     * @param user
     * @return
     */
    int update(User user);

    /**
     * 删除用户
     * @param id
     * @return
     */
    int delete(int id);
}

编写Mapper

<?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">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
    <!--查询全部用户-->
    <select id="getUserList" resultType="com.qing.pojo.User">
        select * from mybatis.user
    </select>
    <!--id对应接口的方法，返回值类型对应接口返回值，参数类型对应接口方法参数，集合类型写集合泛型类型-->
    <!--根据ID查询用户-->
    <select id="getUserById" parameterType="int" resultType="com.qing.pojo.User">
        select * from mybatis.user where id=#{id}
    </select>
    <!--新增用户-->
    <insert id="insert" parameterType="com.qing.pojo.User">
        insert into mybatis.user(id,name,pwd) values(#{id},#{name},#{pwd})
    </insert>
    <!--修改用户-->
    <update id="update" parameterType="com.qing.pojo.User">
        update mybatis.user set name=#{name},pwd=#{pwd} where id=#{id}
    </update>
    <!--删除用户-->
    <delete id="delete" parameterType="int">
        delete from mybatis.user where id=#{id}
    </delete>
</mapper>

测试

package com.qing.dao;

import com.qing.pojo.User;
import com.qing.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {

    /**
     * 查询全部用户
     */
    @Test
    public void getUserList() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            List<User> userList = mapper.getUserList();
            for (User user : userList) {
                System.out.println(user);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }

    /**
     * 根据ID查询用户
     */
    @Test
    public void getUserById() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            User user = mapper.getUserById(1);
            System.out.println(user);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }

    /**
     * 新增用户
     */
    @Test
    public void insert() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            User user = new User(4, "张仲景", "123456");
            int rows = mapper.insert(user);
            System.out.println(rows);
            // 提交事务
            sqlSession.commit();
            System.out.println("提交事务");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }

    /**
     * 修改用户
     */
    @Test
    public void update() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            User user = new User(4, "张仲景二号", "123456");
            int rows = mapper.update(user);
            System.out.println(rows);
            // 提交事务
            sqlSession.commit();
            System.out.println("提交事务");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }

    /**
     * 删除用户
     */
    @Test
    public void delete() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            int rows = mapper.delete(4);
            System.out.println(rows);
            // 提交事务
            sqlSession.commit();
            System.out.println("提交事务");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }
}

Map的应用

Map传递参数，用key获取即可

对象传递参数，用属性获取即可

只有一个基本类型参数，可以直接获取，可不写parameterType

编写接口

package com.qing.dao;

import com.qing.pojo.User;

import java.util.List;
import java.util.Map;

/**
 * 接口
 */
public interface UserMapper {

    /**
     * 通过Map新增用户
     * @param map
     * @return
     */
    int insertByMap(Map<String,Object> map);

    /**
     * 通过Map查询用户
     * @param map
     * @return
     */
    List<User> getByMap(Map<String,Object> map);
}

编写Mapper

<?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">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
    <!--通过Map新增用户-->
    <insert id="insertByMap" parameterType="map">
        insert into mybatis.user(id,name,pwd) values(#{userId},#{userName},#{password})
    </insert>
    <!--通过Map查询用户-->
    <select id="getByMap" parameterType="map" resultType="com.qing.pojo.User">
        select * from mybatis.user where id=#{userId} and name=#{userName}
    </select>
</mapper>

测试

package com.qing.dao;

import com.qing.pojo.User;
import com.qing.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

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

public class UserMapperTest {

    /**
     * 通过Map新增用户
     */
    @Test
    public void insertByMap() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            Map<String,Object> map = new HashMap<String, Object>();
            map.put("userId",4);
            map.put("userName","张仲景");
            map.put("password","123456");
            int rows = mapper.insertByMap(map);
            System.out.println(rows);
            // 提交事务
            sqlSession.commit();
            System.out.println("提交事务");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }

    /**
     * 通过Map查询用户
     */
    @Test
    public void getByMap() {
        SqlSession sqlSession = null;
        try {
            // 获取sqlSession
            sqlSession = MybatisUtils.getSqlSession();
            // 执行SQL
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            Map<String,Object> map = new HashMap<String, Object>();
            map.put("userId",4);
            map.put("userName","张仲景");
            List<User> userList = mapper.getByMap(map);
            for (User user : userList) {
                System.out.println(user);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }
}

分类: 100_Mybatis

标签：qing,简介,010,mybatis,sqlSession,user,Mybatis,import,com
来源： https://blog.csdn.net/chinaherolts2008/article/details/118684168