在MyBatis中使用接口映射的步骤详解

public interface UserMapper {
    @Select("SELECT * FROM users WHERE id = #{id}")
    User getUserById(Integer id);
    
    @Insert("INSERT INTO users(name, email) VALUES(#{name}, #{email})")
    @Options(useGeneratedKeys = true, keyProperty = "id")
    void insertUser(User user);
    
    @Update("UPDATE users SET name=#{name}, email=#{email} WHERE id=#{id}")
    void updateUser(User user);
    
    @Delete("DELETE FROM users WHERE id=#{id}")
    void deleteUser(Integer id);
}

<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"/>
                <property name="username" value="root"/>
                <property name="password" value="password"/>
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <mapper class="org.example.mapper.UserMapper"/>
    </mappers>
</configuration>

try (SqlSession session = sqlSessionFactory.openSession()) {
    UserMapper mapper = session.getMapper(UserMapper.class);
    
    // 使用mapper操作数据库
    User user = mapper.getUserById(1);
    System.out.println(user.getName());
    
    // 更多的数据库操作...
}

public <T> T getMapper(Class<T> type) {
    return configuration.<T>getMapper(type, this);
}

public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
    if (mapperProxyFactory == null) {
        throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
    }
    try {
        return mapperProxyFactory.newInstance(sqlSession);
    } catch (Exception e) {
        throw new BindingException("Error getting mapper instance. Cause: " + e, e);
    }
}

public T newInstance(SqlSession sqlSession) {
    final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface, methodCache);
    return newInstance(mapperProxy);
}

protected T newInstance(MapperProxy<T> mapperProxy) {
    return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[]{mapperInterface}, mapperProxy);
}

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    if (Object.class.equals(method.getDeclaringClass())) {
        return method.invoke(this, args);
    } else {
        final MapperMethod mapperMethod = cachedMapperMethod(method);
        return mapperMethod.execute(sqlSession, args);
    }
}