Custom Queries with JPA

JPA를 이용한 커스텀 쿼리 작성법에 대해 정리하였습니다.

 

 

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< Custom Queries with JPA >

Based on how the method is named, Spring Data JPA will automatically generate the “implementation” of the method when your application is compiled. 

The naming of the method declarations is extremely important here. The rules for the method names are detailed in the Spring documentation

 

JPA Query Methods :: Spring Data JPA

 

Example)

public interface PersonRepository extends CrudRepository<Person, Integer> {
  // this declaration is all we need!
  List<Person> findByEyeColor(String eyeColor); 
}

@GetMapping("/people/search")
public List<Person> searchPeople(
  @RequestParam(name = "eyeColor", required = false) String eyeColor
) {
  if (eyeColor != null) {
    return this.personRepository.findByEyeColor(eyeColor)
  } else {
    return new ArrayList<>();
  }
}

: This capability is extremely powerful, as it allows developers to create complex queries without even writing the code for them!

 

 

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< Advanced Custom Queries >

You can get even more advanced using And queries

 

List<Person> findByEyeColorAndAgeLessThan(String eyeColor, Integer age);

@GetMapping("/people/search")
public List<Person> searchPeople(
  @RequestParam(name = "eyeColor", required = false) String eyeColor,
  @RequestParam(name = "maxAge", required = false) Integer maxAge 
) {
  if (eyeColor != null && maxAge != null) {
    return this.personRepository.findByEyeColorAndAgeLessThan(eyeColor, maxAge);
  } else if (eyeColor != null) {
    return this.personRepository.findByEyeColor(eyeColor);
  } else if (maxAge != null) {
    return this.personRepository.findByAgeLessThan(maxAge);
  } else {
    return new ArrayList<>();
  }
}