SpringBoot-“this.peopleService”為空？

我對 Spring Boot 有點陌生，我正在嘗試創建 model/repo/service/serviceImp/controller 型別的架構。

在我嘗試發出這個獲取請求后：

http://localhost:8080/api/v1/people/name?name=steve

我收到了這個錯誤（我在 DB 中創建了幾個人）：

"java.lang.NullPointerException: Cannot invoke \"com.project.Springbootbackend.service.PeopleService.findAllByName(String)\" because \"this.peopleService\" is null\r\n\tat com.project.Springbootbackend.controller.PeopleController.findAllByName(PeopleController.java:24)

這是我的代碼：人（物體）

@Entity
public class People {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @Column(name = "name")
    private String name;

    @Column(name = "surname")
    private String surname;

    @Column(name = "email")
    private String email;
...
//constructor   get/set

人員控制器

@RestController
@RequestMapping("/api/v1/people")
@RequiredArgsConstructor
public class PeopleController {

    private PeopleService peopleService;

    @GetMapping("/name")
    public ResponseEntity<List<People>> findAllByName(@RequestParam String name) {

        return ResponseEntity.ok().body(peopleService.findAllByName(name));
    }
}

人報

public interface PeopleRepository extends JpaRepository<People, Integer> {
    List<People> findAllByName(String name);
}

人事服務

public interface PeopleService {
    List<People> findAllByName(String name);

}

人事服務小鬼

@RequiredArgsConstructor
@Service
public class PeopleServiceImp implements PeopleService {

    PeopleRepository peopleRepository;

    @Override
    public List findAllByName(String name) {
        return (List) ResponseEntity.ok(peopleRepository.findAllByName(name));
    }

}

提前謝謝各位。

*解決方案：

物體、服務和存盤庫是相同的。ServiceImp 和控制器更改如下：

控制器：

@RestController
@RequestMapping("/api/v1/people")
public class PeopleController {

    private PeopleService peopleService;

    public PeopleController(PeopleService peopleService) {
        this.peopleService = peopleService;
    }

    @GetMapping("/name")
    public ResponseEntity<List<People>> findAllByName(@RequestParam String name) {

        return ResponseEntity.ok().body(peopleService.findAllByName(name));
    }
}

服務小鬼

@Service
public class PeopleServiceImp implements PeopleService {

    private PeopleRepository peopleRepository;

    public PeopleServiceImp(PeopleRepository peopleRepository) {
        this.peopleRepository = peopleRepository;
    }

    @Override
    public List<People> findAllByName(String name) {
        List<People> people = peopleRepository.findAllByName(name);
        return people;
    }

}

uj5u.com熱心網友回復：

您的建構式不會注入服務，因為RequiredArgsConstructor（請參閱鏈接）需要特殊處理。因此，使用final：

@RestController
@RequestMapping("/api/v1/people")
@RequiredArgsConstructor
public class PeopleController {

    private final PeopleService peopleService;

    @GetMapping("/name")
    public ResponseEntity<List<People>> findAllByName(@RequestParam String name) {

        return ResponseEntity.ok().body(peopleService.findAllByName(name));
    }
}

同樣在這里：

@RequiredArgsConstructor
@Service
public class PeopleServiceImp implements PeopleService {

    private final PeopleRepository peopleRepository;

    @Override
    public List findAllByName(String name) {
        return (List) ResponseEntity.ok(peopleRepository.findAllByName(name));
    }

}

附加提示，使用型別串列：

@Override
public List<People> findAllByName(String name) {
    return ResponseEntity.ok(peopleRepository.findAllByName(name));
}

uj5u.com熱心網友回復：

試試這樣：

@Autowired
private PeopleService peopleService;

@Autowired
private PeopleRepository peopleRepository;

您還需要在應用程式的主類中添加@SpringBootApplication注解。

像這樣的東西：

@SpringBootApplication
class PeopleApplication {
public static void main(String[] args) {
...

看看這篇關于 Spring 中自動依賴注入的文章： https ://www.baeldung.com/spring-autowire

uj5u.com熱心網友回復：

您錯過了控制器中的自動裝配注釋以注入可能this.peopleService為空的服務。

@Autowired
private PeopleService peopleService;

您還需要在 serviceimpl 類中進行自動裝配

@Autowired
private PeopleRepository peopleRepository;

標籤：爪哇 弹簧靴

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