Java Community | Help. Code. Learn.•7mo ago

How could I simplify this

public interface Dao<K, S extends Key<K>> { void update(S item); void insert(S item); void delete(K key); S select(K key); List<S> selectAll(); } public interface Dao<K, T, S extends Key<K, T>> { void update(S item); void insert(S item); void delete(K key1, T key2); S select(K key1, T key2); List<S> selectAll(); } public interface Dao<K, T, I S extends Key<K, T, I>> { void update(S item); void insert(S item); void delete(K key1, T key2, I key3); S select(K key1, T key2, I key3); List<S> selectAll(); }

49 Replies

JavaBot•7mo ago

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Hey @userexit! Please use /close or the Close Post button above when your problem is solved. Please remember to follow the help guidelines. This post will be automatically closed after 300 minutes of inactivity.

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JavaBot•7mo ago

Please format your code to make it more readable. For java, it should look like this:

```java
public void foo() {
 
}
```

```java
public void foo() {
 
}
```

userexitOP•7mo ago

public interface Dao<K, S extends Key<K>> {
    void update(S item);
    void insert(S item);
    void delete(K key);
    S select(K key);
    List<S> selectAll();
}

public interface Dao<K, T, S extends Key<K, T>> {
    void update(S item);
    void insert(S item);
    void delete(K key1, T key2);
    S select(K key1, T key2);
    List<S> selectAll();
}

public interface Dao<K, T, I, S extends Key<K, T, I>> {
    void update(S item);
    void insert(S item);
    void delete(K key1, T key2, I key3);
    S select(K key1, T key2, I key3);
    List<S> selectAll();
}

public interface Dao<K, S extends Key<K>> {
    void update(S item);
    void insert(S item);
    void delete(K key);
    S select(K key);
    List<S> selectAll();
}

public interface Dao<K, T, S extends Key<K, T>> {
    void update(S item);
    void insert(S item);
    void delete(K key1, T key2);
    S select(K key1, T key2);
    List<S> selectAll();
}

public interface Dao<K, T, I, S extends Key<K, T, I>> {
    void update(S item);
    void insert(S item);
    void delete(K key1, T key2, I key3);
    S select(K key1, T key2, I key3);
    List<S> selectAll();
}

JavaBot•7mo ago

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userexitOP•7mo ago

dan1st•7mo ago

This is not valid syntax or actually why do you have all these 3 classes? Is the first one not enough? you could create a void delete(List<? extends K> keys); if you want a method for deleting multiple keys

userexitOP•7mo ago

public class StationsDto extends Key<Integer> {...}

public class StationsDao implements Dao<Integer, StationsDto> {
  void delete(Integer key) {...}
  void insert(StationsDto item) {...}
  ...
}

public class StationsDto extends Key<Integer> {...}

public class StationsDao implements Dao<Integer, StationsDto> {
  void delete(Integer key) {...}
  void insert(StationsDto item) {...}
  ...
}

and

public class StopsDto extends Key<Integer, Integer> {...}

public class StopsDao implements Dao<Integer, Integer, StopsDto> {
  void delete(Integer key1, Integer key2) {...}
  void insert(StopsDto item) {...}
  ...
}

public class StopsDto extends Key<Integer, Integer> {...}

public class StopsDao implements Dao<Integer, Integer, StopsDto> {
  void delete(Integer key1, Integer key2) {...}
  void insert(StopsDto item) {...}
  ...
}

I have a Stations table in my db that has a primary key that consists of 1 column whereas in Stops table the primary key is consisted of multiple columns

dan1st•7mo ago

In the first one, there's no need to override the methods in the 2., why do you want a delete method with multiple keys when you can pass a list (or at least a vararg)

userexitOP•7mo ago

why ?

dan1st•7mo ago

Because the methods are already present in the super interface so the child interface inherits them So why override it?

userexitOP•7mo ago

because my primary key for the Stops table is consisted of multiple columns, 2 in this case, both integers, so then I can do: String query = "DELETE FROM STOPS WHERE first_id = ? AND second_id = ?" ... its a class

dan1st•7mo ago

ah ok I overlooked that

userexitOP•7mo ago

StationsDto represents a station (data transfer object) StationsDao connects to the database and does CRUD

dan1st•7mo ago

In that case, make a class for the primary key or a record

public record StopsKey(int firstStopId, int secondStopId) {}

public record StopsKey(int firstStopId, int secondStopId) {}

and

public class StopsDao implements Dao<StopsKey, StopsDto> {
    ...
}

public class StopsDao implements Dao<StopsKey, StopsDto> {
    ...
}

userexitOP•7mo ago

and then I can use the version

public interface Dao<K, S extends Key<K>> {
    void update(S item);
    void insert(S item);
    void delete(K key);
    S select(K key);
    List<S> selectAll();
}

public interface Dao<K, S extends Key<K>> {
    void update(S item);
    void insert(S item);
    void delete(K key);
    S select(K key);
    List<S> selectAll();
}

` and if I have another table that needs for example 4 columns as pk i just make a new record everytime ? @dan1st | Daniel sounds like a good solution to me

dan1st•7mo ago

yes yeah btw you can also use records for your DTOs if you want to

userexitOP•7mo ago

but can you override equals and hashcode in a record ?

dan1st•7mo ago

yes but it gives you a good equals/hashCode with all components by default So in most cases, you don't have to override it

userexitOP•7mo ago

well the only problem is how do I setup the interface now to accept StopsKey, StopsDto

public interface Dao<K, S extends Key<K>> {
    void update(S item);
    void insert(S item);
    void delete(K key);
    S select(K key);
    List<S> selectAll();
}

public interface Dao<K, S extends Key<K>> {
    void update(S item);
    void insert(S item);
    void delete(K key);
    S select(K key);
    List<S> selectAll();
}

or should I make StopsPK extends Key of some sort ?

dan1st•7mo ago

wouldn't that need to be the DTO?

userexitOP•7mo ago

userexitOP•7mo ago

but like what do I put in something<T>

dan1st•7mo ago

Why? just do <T,S> unless Key has something important and if it's an interface, records can implement interfaces

userexitOP•7mo ago

no it s just a record itself lol

dan1st•7mo ago

userexitOP•7mo ago

if u do

dan1st•7mo ago

Is there any reason to not just use Dao<T,S>?

userexitOP•7mo ago

Dao<T, S> ur not making sure that T is a key of some sort to S if u do

dan1st•7mo ago

userexitOP•7mo ago

Dao<T, S extends something<T>> ur making sure S extends Key<T>

dan1st•7mo ago

yeah you can make an interface for that

userexitOP•7mo ago

empty interface > ?

dan1st•7mo ago

either empty or with a K getKey() method your choice that's if you want all your DTOs to have a getKey method in common

userexitOP•7mo ago

you meant this ?

dan1st•7mo ago

What's Key?

userexitOP•7mo ago

empty interface in the end i just made a StationsPK to keep a main program structure

dan1st•7mo ago

I thought about

public interface Dto<K>{
  //if you want to, not necessary
  //K getKey();
}
public interface Dao<K,T implements Dto<K>>{}

public record StationsDto(Integer key, WhateverOtherParameters youHave) implements Dto<Integer>{}
public class StationsDao implements Dao<Integer, StationsDto>{}


public record StopKey(Integer firstStationId, Integer secondStationId){}
public record StopDto(StopKey key, OtherParameters here) implements Dto<StopKey>{}
public class StopDao implements Dao<StopKey, StopDto>{}

public interface Dto<K>{
  //if you want to, not necessary
  //K getKey();
}
public interface Dao<K,T implements Dto<K>>{}

public record StationsDto(Integer key, WhateverOtherParameters youHave) implements Dto<Integer>{}
public class StationsDao implements Dao<Integer, StationsDto>{}


public record StopKey(Integer firstStationId, Integer secondStationId){}
public record StopDto(StopKey key, OtherParameters here) implements Dto<StopKey>{}
public class StopDao implements Dao<StopKey, StopDto>{}

but what you did looks ok as well

userexitOP•7mo ago

can i return its parent ?

JavaBot•7mo ago

💤 Post marked as dormant

This post has been inactive for over 300 minutes, thus, it has been archived. If your question was not answered yet, feel free to re-open this post or create a new one. In case your post is not getting any attention, you can try to use /help ping. Warning: abusing this will result in moderative actions taken against you.

dan1st•7mo ago

userexitOP•7mo ago

nvm was a dumb question of the moment it was 9 am for me

userexitOP•7mo ago

dan1st•7mo ago

So you no longer have that question?

userexitOP•7mo ago

yeah no longer

dan1st•7mo ago

Is that late (i.e. before going to bed) or early (after waking up)? xd (yes that message is sarcastic)

JavaBot•7mo ago

💤 Post marked as dormant

This post has been inactive for over 300 minutes, thus, it has been archived. If your question was not answered yet, feel free to re-open this post or create a new one. In case your post is not getting any attention, you can try to use /help ping. Warning: abusing this will result in moderative actions taken against you.

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How could I simplify this