Creating a generic mongo repository in spring boot

I want to create a generic mongo repository and just pass the document and use it, instead of creating multiple repositories for each document.

So far this is what I thought about:

@NoRepositoryBean
public interface GenericRepository<T, String> extends MongoRepository<T,String> {
 T findById(ObjectId id);
}


@RestController
@RequestMapping("/endpoint")
public class Controller {

    @Autowired
    public GenericRepository<DocumentClass, String> repository;

    @GetMapping("/")
    public List<DocumentClass> all(){
        return repository.findAll();
    }

}

I'm not sure this is the correct way of doing so because I'm getting a lot of errors.

Try it like this…

@NoRepositoryBean
public interface GenericRepository< T,  ID > extends MongoRepository< T, ID >{ 
@Override
public T findById( ID id );
@Override    
public List< T > findAll();
...
}

…Then given some entity…

public class SomeEntity{ 
private final String id;
private final String someField;
public SomeEntity( String id, String someField ){ 
this.id = id;
this.someField = someField;
}
public String getId( ){ return this.id; }
...   
}

…A concrete implementation could be like…

public class SomeEntityRepository implements GenericRepository< SomeEntity, String >{ 
...
@Override
public SomeEntity findById( String id ){ /* Your implementation goes here */  }
@Override    
public List< SomeEntity > findAll(){ /* Your implementation goes here */ }
...
}

Here's a demonstration of how that would be used…

    /* Given */
SomeEntity anNtt = new SomeEntity( "foo", "bar" );
MongoRepository< SomeEntity, String > repo = new SomeEntityRepository( ) ;
repo.save( anNtt );
out.printf( "Saved entity:%1$35s%n", anNtt );
/* Manual (i.e., non-Spring) dependency injection */
Controller ctrlR = new Controller( repo );
/* When */
List< SomeEntity > allNtts = ctrlR.all( );
SomeEntity oneNtt = ctrlR.one( anNtt.getId( ) );
/* Then */
out.printf( "Found exactly 1? %1$20s%n", allNtts.size( ) == 1 );
out.printf( "Found exactly %1$20s%n", allNtts.size( ) );
out.printf( "Found entity.equals( Saved entity )? %1$20s%n", allNtts.get( 0 ).equals( anNtt ) && oneNtt.equals( anNtt ) );
out.printf( "Found entity: %1$35s%n", oneNtt );
}

Click the green Start button at the top of the demo to run it…

Saved entity: SomeEntity [id=foo, someField=bar]
Found exactly 1?                 true
Found exactly                    1
Found entity.equals( Saved entity )?                 true
Found entity:  SomeEntity [id=foo, someField=bar]