working on a Java Spring Boot application I am finding the following problem and I don't know if exist a pattern that can solve my problem.
I will try to explain my situation in details and how I am trying to solve this situation (with no concrete result at the moment).
I have this DTO class named ExcelTrendTabGeneralDTO:
public class ExcelTrendTabGeneralDTO {
private String excelDocumentName;
private String excelTabName;
private List<ExcelTabInterface> tabTrendList;
public ExcelTrendTabGeneralDTO() {
super();
}
public ExcelTrendTabGeneralDTO(String excelDocumentName, String excelTabName,
List<ExcelTabInterface> tabTrendList) {
super();
this.excelDocumentName = excelDocumentName;
this.excelTabName = excelTabName;
this.tabTrendList = tabTrendList;
}
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GETTER AND SETTER METHODS
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}
In this class there is the core of my problem. As you can see it contains this field:
private List<ExcelTabInterface> tabTrendList;
That, at the moment, I defined as an empty interface:
public interface ExcelTabInterface {
}
It is a list of ExcelTabInterface (that is an interface, now I explain why and what I am trying to do). At the beginning instead this ExcelTabInterface I had a specific concrete type (a class) but I replaced it with an interface because this list could contain different kind of objects instances of classes implementing this interface (this was my idea).
So for example I had a class like this (named CompVibrAndTempDTO):
@Description(value = "DTO for the \"Vibration Monitore\" Excel tab")
public class CompVibrAndTempDTO extends ExcelTabAbstractDTO implements ExcelTabInterface {
private String tempReadingPointA;
private String tempReadingPointB;
private String tempReadingPointC;
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CONSTRUCTOR AND GETTER AND SETTER METHODS
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}
Ok...the idea seems to work (I have not syntax error in my IDE).
And here the problem: then I have a repository class that uses JdbcTemplate to perform query on my database:
@Repository
public class ExcelRepositoryImpl implements ExcelRepository{
@Autowired
private JdbcTemplate jdbcTemplate;
@Override
//public List<CompVibrAndTempDTO> findCompVibrAndTempTab() {
public List<ExcelTabInterface> findCompVibrAndTempTab() {
String SELECT_COMP_VIBR_AND_TEMP_TAB = "SELECT * FROM TREND006";
List<ExcelTabInterface> resultList = jdbcTemplate.query(SELECT_COMP_VIBR_AND_TEMP_TAB, new CompVibrAndTempMapper());
return resultList;
}
}
So as you can see I am performing a SQL query expecting to retrieve a list of objects implementing my ExcelTabInterface interface. The problem is that to build these objects I use a custom mapper class named CompVibrAndTempMapper implementing the Spring RowMapper interface.
So this is my custom mapper class:
public class CompVibrAndTempMapper implements RowMapper<ExcelTabInterface>{
@Override
public CompVibrAndTempDTO mapRow(ResultSet rs, int rowNum) throws SQLException {
ExcelTabInterface compVibrAndTempDto = new CompVibrAndTempDTO();
SimpleDateFormat formatDateTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat formatDate = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat formatTime = new SimpleDateFormat("HH:mm:ss");
String dateStr = null;
String timeStr = null;
String dateFromDB = rs.getString("Time_Stamp");
try {
Date date = formatDateTime.parse(dateFromDB);
dateStr = formatDate.format(date);
timeStr = formatTime.format(date);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
compVibrAndTempDto.setDate(dateStr);
compVibrAndTempDto.setTime(timeStr);
compVibrAndTempDto.setTempReadingPointA(rs.getString("Sensor464DV"));
compVibrAndTempDto.setTempReadingPointB(rs.getString("Sensor465DV"));
compVibrAndTempDto.setTempReadingPointC(rs.getString("Sensor466DV"));
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return compVibrAndTempDto;
}
}
And here I have my problem. The problem is that it give me error on the setter methods because these methods are not defined in my interface (that is empty).
Ok I can insert these setter methods for my concrete DTO and I solve this error !!! BUT this partially nullifies my efforts to generalize my DTOs classes.
Because I have other DTOs classes implementing my ExcelTabInterface interface --> so I have to insert also the getter and setter methods of these others DTOs classes into my interface --> so I need to declare all the methods of a each DTOs into all my DTOs classes implementing ExcelTabInterface interface.
In theory I thing that a solution could be implement all the methods that I need to declare in the ExcelTabInterface interface in all my DTOs classes and implement as "do nothing" methods the mnethods that I have not to use but it seems to me pretty a mess.
What do you think about? Could be a viable solution or is it ugly as hell? Exist some patterns or something like this tha solve my problema in a neater way?
And why do you define
ExcelTabInterface compVibrAndTempDto = new CompVibrAndTempDTO();
just use
CompVibrAndTempDTO compVibrAndTempDto = new CompVibrAndTempDTO();
you need concrete class here and you have one.
new RowMapper<ExcelTabInterface>() {
@Override
public ExcelTabInterface mapRow(ResultSet rs, int rowNum) throws SQLException {
CompVibrAndTempDTO compVibrAndTempDTO = new CompVibrAndTempDTO();
compVibrAndTempDTO.setvalue("value");
return compVibrAndTempDTO ;
}
};