如何返回所有保存在数据库中的联系人

Question

我创建了一个联系人保存应用程序。我无法返回所有保存在DB中的联系人，查询没有返回唯一的结果：2

我的控制器

public ModelAndView getAllContacts() {
    ModelAndView mav = new ModelAndView("getAllUser.jsp");
    User user = userda.getAllContacts();
    mav.addObject(user);
    return mav;

我的JPA存储库

@Query(value ="SELECT * from USER", nativeQuery = true)
User getAllContacts();

型号等级

@Entity(name = "USER")
@Table(name = "USER")
public class User {
    @Id
    private long id;
    private String name;
    public String toString() {
        return "Person Name is " + " : " + name + " and " + " Mobile Number is " + " : " + id;
    }
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

Answer 1

您的回购假设只有一个条目User getAllContacts();。你加载了所有联系人，你需要一个用户列表。。。List<User> getAllContacts()

提示：您的回购也可以继承CRUD回购。你有一些现成的方法。

Answer 2

您可以获得联系人列表，例如

public List<Contact> getAllContact(){
}

在我的情况下，我得到了图书实体

Book.java

@Entity
@Table(name = "books")
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String bookname;
    @OneToOne(cascade = CascadeType.ALL)
    @JsonManagedReference
    private Author author;
}

BookDao.java

public interface BookDao extends CrudRepository<Book, Integer> {
    public Book findById(int id);
}

BookService.java

@Component
public class BookService {
    @Autowired
    private BookRepository bookRepository;
    //get all lists
    public List<Book> getAllBooks(){
        List<Book> list = (List<Book>) this.bookRepository.findAll();
        return list;
    }
    //get book by id
    public Book getBookById(int id){
        Book book = this.bookRepository.findById(id);
        return book;
    }
}

BookController.java

@RestController
// @RequestMapping("/books")
public class BookController {
    @Autowired
    private BookService bookService;
    //get all books handler
    @GetMapping("/books")
    public List<Book> getBook(){
       List<Book> list =  this.bookService.getAllBooks();
    }
}