mybatis入门，CRUD，万能Map，模糊查询

第一个Mybatis程序

核心配置文件mybatis-config.xml

<?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/db4?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/dao/UserMapper.xml"/>
    </mappers>
</configuration>

编写mybatis工具类

public class MybatisUtils {
    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();
        }
    }

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

编写代码

• 实体类User

public class User {
    private int id;
    private String username;
    private String password;
}
//重写方法toString方法等

• Dao接口UserMapper.java

public interface UserMapper {
    List<User> getUserList();
}

• 接口实现类Mapper配置文件UserMapper.xml

<?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.dao.UserMapper">
  <select id="getUserList" resultType="com.pojo.User">
    select * from db4.user
  </select>
</mapper>

• test类

public class test {
    @Test
    public void test1(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = userMapper.getUserList();

        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }
}

• 约定大于配置

<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>

CRUD

• UserMapper.xml

<?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.dao.UserMapper">
    <select id="getUserList" resultType="com.pojo.User">
        select *
        from db4.user
    </select>

    <select id="getUserById" parameterType="int" resultType="com.pojo.User">
        select *
        from db4.user
        where id = #{id}
    </select>

    <select id="addUser" parameterType="com.pojo.User">
        insert into db4.user (id, username, password)
        values (#{id}, #{username}, #{password})
    </select>

    <select id="updateUser" parameterType="com.pojo.User">
        update db4.user
        set username = #{username},
            password = #{password}
        where id = #{id};
    </select>

    <select id="deleteUser" parameterType="int">
        delete
        from db4.user
        where id = #{id}
    </select>
</mapper>

• UserMapper.java

public interface UserMapper {
    List<User> getUserList();

    User getUserById(int id);

    void addUser(User user);

    void updateUser(User user);

    void deleteUser(int id);
}

• test.java

public class test {
    @Test
    public void getUserList_test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = userMapper.getUserList();

        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }

    @Test
    public void getUserById_test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.getUserById(1);
        System.out.println(user);
        sqlSession.close();
    }

    @Test
    public void addUser_test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
         userMapper.addUser(new User(66,"zhang", "7777"));
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void updateUser_test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.updateUser(new User(2,"oooo", "000000"));
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void deleteUser_test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.deleteUser(10);
        sqlSession.commit();
        sqlSession.close();
    }
}

万能的Map查询

• Map被用为构造器

User getUserByMapId(Map map);

<select id="getUserByMapId" parameterType="map" resultType="com.pojo.User">
    select *
    from db4.user
    where id = #{mapId}
</select>

@Test
public void getUserByMapId_test() {
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    Map<String, Object> map = new HashMap<>();
    map.put("mapId", 1);
    User user = userMapper.getUserByMapId(map);
    System.out.println(user);
    sqlSession.commit();
    sqlSession.close();
}

模糊查询怎么写

• java执行代码的时候，使用通配符% %

List<User> userlist = mapper.getUserLike("%张%")；

• 在sql拼接中使用通配符！

select * from db4.user where name like "%"#{value}"%"