简单易懂的Mybatis环境的搭建

妖狐艹你老母 2022-12-13 11:27 95阅读 0赞

思路：搭建环境 --> 导入MyBatis --> 编写代码 --> 测试

**新建项目**

1.  创建一个普通的maven项目
2.  导入maven依赖
    
        
        <dependencies>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>8.0.12</version>
            </dependency>
            
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.4</version>
            </dependency>
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
                <scope>test</scope>
            </dependency>
        </dependencies>
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**编写mybatis的核心配置文件**

<?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>
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/mybatis?userSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC"/>
                    <property name="username" value="root"/>
                    <property name="password" value="root"/>
                </dataSource>
            </environment>
        </environments>
    </configuration>
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**编写mybatis工具类**

//sqlSessionFactory --> sqlSession
    public class MybatisUtils { 
    
        static SqlSessionFactory sqlSessionFactory = null;
    
        static { 
            try { 
                //使用Mybatis第一步 ：获取sqlSessionFactory对象
                String resource = "mybatis-config.xml";
                InputStream inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) { 
                e.printStackTrace();
            }
        }
    
        //既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例.
        // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。
        public static SqlSession getSqlSession(){ 
            return sqlSessionFactory.openSession();
        }
    }
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### 编写代码 ###

*  实体类
 *  Dao接口
    
        public interface UserDao { 
            public List<User> getUserList();
        }
        123
 *  接口实现类 （由原来的UserDaoImpl转变为一个Mapper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="com.kuang.dao.UserDao">
            <select id="getUserList" resultType="com.kuang.pojo.User">
            select * from USER
          </select>
        </mapper>
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 *  测试
    
    **注意点：**
    
    org.apache.ibatis.binding.BindingException: Type interface com.kuang.dao.UserDao is not known to the MapperRegistry.
    
    **MapperRegistry是什么?**
    
    核心配置文件中注册mappers
    
     *  junit测试
        
            @Test
                public void test(){ 
            
                    //1.获取SqlSession对象
                    SqlSession sqlSession = MybatisUtils.getSqlSession();
                    //2.执行SQL
                    // 方式一：getMapper
                    UserDao userDao = sqlSession.getMapper(UserDao.class);
                    List<User> userList = userDao.getUserList();
                    for (User user : userList) { 
                        System.out.println(user);
                    }
            
                    //关闭sqlSession
                    sqlSession.close();
                }
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**可能会遇到的问题：**

1.  配置文件没有注册
2.  绑定接口错误
3.  方法名不对
4.  返回类型不对
5.  Maven导出资源问题

**来自狂神说**