public class User {
  private Integer id;
  private Message message;
}

public class Message {
  private Integer id;
  private String address;
  private String job;
}

@MappedTypes(Message.class)
@MappedJdbcTypes(JdbcType.VARCHAR)
public class MessageTypeHandler implements TypeHandler<Message> {
  @Override
  public void setParameter(PreparedStatement ps, int i, Message parameter, JdbcType jdbcType) throws SQLException {
    ps.setString(i, JSON.toJSONString(parameter));
  }

  @Override
  public Message getResult(ResultSet rs, String columnName) throws SQLException {
    return JSON.parseObject(rs.getString(columnName),Message.class);
  }

  @Override
  public Message getResult(ResultSet rs, int columnIndex) throws SQLException {
    return JSON.parseObject(rs.getString(columnIndex),Message.class);
  }

  @Override
  public Message getResult(CallableStatement cs, int columnIndex) throws SQLException {
    return null;
  }
}

  <typeHandlers>
    <typeHandler handler="org.mybatis.***.MessageTypeHandler"/>
  </typeHandlers>

  <insert id="insertUser">
      insert into user (id,message) values (#{id},#{message})
  </insert>

  <select id="getUser" parameterType="int" resultType="org.mybatis.***.mapper.User" >
    select id,message from user where id = #{id}
  </select>