mybatis学习（1）配置遇到的问题及增删改查

• jdk1.8
• mysql5.7
• maven3.6.1
• idea

• maven仓库

    org.mybatis
    mybatis
    3.4.6

• GitHub release发行版

• SSM都是有配置文件的，对照官网学习 mybatis官网

1. 搭建环境

//创建一个父工程导入依赖，mybatis,mysql-connector.junit

        
            mysql
            mysql-connector-java
            5.1.47
        
        
        
            org.mybatis
            mybatis
            3.4.6
        
        
            junit
            junit
            4.12
        

    

2. 在父工程里面新建一个maven的module，配置核心资源配置文件pom.xml

3. 在官方文档找到配置语句，resource下面创建mybatis-config.xml文件，复制进去，修改好driver,url…

4. 利用官方文档写一个mybatis的工具类

public class myBatisUtil {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String resource = "org/mybatis/example/mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    public static SqlSession getSession() {
        return sqlSessionFactory.openSession();
    }
}

5. 编写实体类

public class User {
    private int id;
    private String name;
    private String pwd;

    public User() {
        
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }
}

6. 编写操作数据库的DAO层，包括接口和实现接口的 xml 文件

//要实现的接口
public interface UserDao {
    List getUserList();
}
//mapper.xml文件，相当于用配置的方式来实现接口




    
    
        select * from mybatis.user
    

7. 很重要的一步，在.config里面配置

8. junit编写测试类

public class UserDaoTest {
    @Test
    public void test() {
        SqlSession sqlSession= myBatisUtil.getSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List list=mapper.getUserList();

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

9. 出现的问题

• could not find xx.config 原因是在pom.xml下面写的资源过滤有问题

    
        
            src/main/java
            
                ***.xml
            
            true
        
    
    下面这段加上就会出问题
    //--------------
    
        
            src/main/resources
            
                ***.xml
            
            true
        
    
    //-------------

• org.apache.ibatis.exceptions.PersistenceException:

  Error querying database. Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

这个问题只需要把useSSL=true改成 useSSL=false就好了

• 对数据库mybatis.user的增删改查

• 注意的地方

  1. sqlsession用完需要关闭 sqlsession.close()

  2. 增删改的操作都需要提交事务sqlsession.commit()

//UserMapper接口的编写
public interface UserMapper {
    //查询全部用户
    List getUserList();

    //查询单个用户
    User getUserById(int id);

    //增加一个用户
    int addUser(User user);

    //修改用户信息
    int updateUser(User user);

    //删除一个用户
    int deleteUser(int id);

}

//对应UserMapper.xml配置文件的编写



    
        select * from mybatis.user
    

    
        SELECT * FROM mybatis.user WHERe id=#{id}
    

    
        INSERT into mybatis.user (id,name,pwd) VALUES (#{id},#{name},#{pwd})
    

    
        UPDATE mybatis.user set id=#{id},name=#{name},pwd=#{pwd} WHERe id=#{id}
    

    
        DELETE FROM mybatis.user WHERe id=#{id}
    

//测试类编写
public class UserDaoTest {
    @Test
    public void test() {
        SqlSession sqlSession= myBatisUtil.getSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List list=mapper.getUserList();

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

    @Test
    public void getUserById() {
        SqlSession sqlSession=myBatisUtil.getSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User userById = mapper.getUserById(3);
        System.out.println(userById);

        sqlSession.close();
    }

    @Test
    public void addUer() {
        SqlSession sqlSession = myBatisUtil.getSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        int res=userMapper.addUser(new User(4, "xpc", "00000000"));
        System.out.println("插入成功"+res);
        //增删改需要提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void updateUser() {
        SqlSession sqlSession = myBatisUtil.getSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res=mapper.updateUser(new User(2, "zhangsan", "aaa"));
        if (res>0) {
            System.out.println("修改成功"+res);
        }
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void deleteUser() {
        SqlSession sqlSession = myBatisUtil.getSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.deleteUser(2);
        if (res > 0) {
            System.out.println("删除成功" + res);
        }
        sqlSession.commit();
        sqlSession.close();
    }
}