mybatis学习笔记

1.mybatis的入门案例

1.1添加依赖

<dependencies>
    <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.11</version>
    </dependency>
    <!--mybatis的核心依赖-->
    <dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.5</version>
    </dependency>
    </dependencies>

1.2配置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>
    <environments default="development">
    <environment id="development">
    <transactionManager type="JDBC"/>
    <dataSource type="POOLED">
    //8版本com.mysql.cj.jdbc.Driver 5版本com.mysql.jdbc.Driver
    <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost:3307/mybatis?useSSL=false&amp;serverTimezone=UTC&amp;rewriteBatchedStatements=true"/>
    <property name="username" value="root"/>
    <property name="password" value="root"/>
    </dataSource>
    </environment>
    </environments>
    <mappers>
    // 在resource下创建UserMapper.xml文件,写sql代码
    <mapper resource="UserMapper.xml"/>
    </mappers>
    </configuration>

1.3 在resource下创建UserMapper.xml文件,写sql代码

<?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和id在测试中是sqlSession.selectOne中的第一个参数,
    // 格式为：
    // namespace名.id名
    // User user = (User) sqlSession.selectOne("com.pojo.User.selectUser", 1);
    <mapper namespace="com.pojo.User">
    <select id="selectUser" resultType="com.pojo.User">
    select * from user where id=#{id}
    </select>
    </mapper>

1.3创建实体类

public class User {
    private Integer id;
    private String username;

    public User() {
    }

    public User(Integer id, String username) {
        this.id = id;
        this.username = username;
    }

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    @Override
    public String toString() {
        return "User{" +
            "id=" + id +
            ", username='" + username + '\'' +
            '}';
    }
}

1.4测试

@Test
    public void test01() throws IOException {
        String resources = "mybatis.xml";
InputStream io = Resources.getResourceAsStream(resources);
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(io);
try(SqlSession sqlSession = sessionFactory.openSession()) {
    // com.pojo.User.selectUser是之前创建
    User user = (User) sqlSession.selectOne("com.pojo.User.selectUser", 1);
    System.out.println("user = " + user);
}
}

1.5基于接口绑定的方式

/**
* 基于接口绑定的方式(但是要注意原先pojoMapper.xml的路径要和接口类的路径保持一致)
* 1.新建数据访问层接口：pojoMapper
* 2.添加mapper中对应的操作方法
* 2.1.方法名与mapper中sql语句的id名相同
* 2.2.返回类型与mapper中resultType类型一致
* 2.3.mapper中sql的语句中的参数要在方法中声明且类型一致
* 3. mapper中的namespace="pojoMapper的全类限定名"
* 4.修改mybatis中的<mapper class="(pojoMapper的全类限定名)com.mapper.UserMapper"/>
*
* @throws IOException
*/
@Test
    public void test02() throws IOException {
    try(SqlSession sqlSession = sessionFactory.openSession()) {
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    User user = userMapper.selectUser(1);
    System.out.println("user = " + user);
}
}

1.6基于注解的方式

/**
* 基于注解的方式
*在pojomapper中添加注解
*  @Select(" select * from user where id=#{id}")
*    User selectUser(Integer id);
*/
@Test
    public void test03() {
    try(SqlSession sqlSession = sessionFactory.openSession()) {
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.selectUser(1);
        System.out.println("user = " + user);
    }
}

1.7简单的增删改查

User selectUser(Integer id);
Integer insertUser(User user);
Integer updateUser(User user);
Integer deleteUser(Integer id);

<select id="selectUser" resultType="com.pojo.User">
select * from user where id=#{id}
</select>
<insert id="insertUser" >
INSERT INTO `mybatis`.`user` ( `username`) VALUES (#{username})
</insert>


<update id="updateUser">
UPDATE `mybatis`.`user` SET `username` = #{username} WHERE `id` = #{id};

</update>
<delete id="deleteUser">
delete from user where id=#{id}
</delete>

/**
* 查询
*/
@Test
    public void test01(){
    System.out.println(userMapper.selectUser(1));
}
/**
* 插入
*/
@Test
    public void test02(){
    System.out.println(userMapper.insertUser(new User(null, "李四")));
}
/**
* 修改
*/
@Test
    public void test03(){
    System.out.println(userMapper.updateUser(new User(1,"小芳")));
}
/**
* 删除
*/
@Test
    public void test04(){
    System.out.println(userMapper.deleteUser(8));
}