Question

我试图使用Spring-Boot编写一个非常基本的应用程序。我目前唯一想做的就是从SQL Server数据库中获取一些信息。

Application.java

@SpringBootApplication(scanBasePackageClasses = { MainView.class, Application.class })
@EnableJpaRepositories(basePackageClasses = CustomerRepository.class)
@EntityScan(basePackageClasses = Customer.class)
public class Application extends SpringBootServletInitializer {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }
}

Customerrepository.java

@Repository
public interface CustomerRepository extends JpaRepository<Customer, Integer> 
{

}

CustomerController.java

@Controller
@RequestMapping(path = "/customer")
public class CustomerController {

    @Autowired
    private CustomerRepository customerRepository;

    @GetMapping(path = "/all")
    public @ResponseBody Iterable<Customer> getAllCustomers() {
        return customerRepository.findAll();
    }
}

CustomersView.java

@Tag("customers-view")
@HtmlImport("src/views/customers/customers-view.html")
@Route(value = ApplicationConst.PAGE_CUSTOMERS, layout = MainView.class)
@PageTitle(ApplicationConst.TITLE_CUSTOMERS)
public class CustomersView extends PolymerTemplate<TemplateModel> {

    @Autowired
    CustomerRepository customerRepository;

    public CustomersView() {
        customerRepository.findAll();
    }

}

转到http://localhost:8080/customer可以很好地返回我数据库中的每个客户。

但是当我尝试在CustomersView.java中找到所有客户时，自动装配的CustomerRepository会返回nullpointerexception。

有人能指出我正确的方向吗？

Answer 1

尝试在构造函数中@Autowire Repository，如下所示：

@Tag("customers-view")
@HtmlImport("src/views/customers/customers-view.html")
@Route(value = ApplicationConst.PAGE_CUSTOMERS, layout = MainView.class)
@PageTitle(ApplicationConst.TITLE_CUSTOMERS)
public class CustomersView extends PolymerTemplate<TemplateModel> {

CustomerRepository customerRepository;

@Autowired
public CustomersView(CustomerRepository customerRepository) {
    this.costumerRepository = customerRepository;
    this.customerRepository.findAll();
}

}

这是因为在构造函数完成后插入了所有@ autowired-attributes。如果要在构造函数时注入@ autowired-attributes，则必须使用上面的方法。

Spring Repository nullpointerexception

1 个答案: