假装Hystrix Fallback在启动时抛出bean错误

Question

我正在制作一个关于Feign和Hystrix的示例。没有虚假的后备属性，一切正常。但是，当我添加fallback属性并创建实现外部客户机接口的fallback类时，我得到了以下错误

 Description:

Field customerClient in com.feign.demo.controllers.CustomerController required a single bean, but 2 were found:
    - customerClientFallback: defined in file [../ApplicationFeign/target/classes/com/feign/demo/clients/fallback/CustomerClientFallback.class]
    - com.feign.demo.clients.CustomerClient: defined in null


Action:

Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

下面是我的虚拟客户端界面：

@FeignClient(name = "CUSTOMERSERVICE", fallback = CustomerClientFallback.class, primary = false)
@RequestMapping(value = "customer")
public interface CustomerClient {

    @RequestMapping(method = RequestMethod.GET, value = "/getAllCustomers")
    List<Customer> getAllCustomers();

    @RequestMapping(method = RequestMethod.PATCH, value = "/{customerId}", consumes = "application/json")
    Customer update(@PathVariable("customerId") long customerId, @RequestBody Customer customer);

    @RequestMapping(method = RequestMethod.GET, value = "/{customerId}")
    Customer getCustomerById(@PathVariable("customerId") long customerId);

    @RequestMapping(method = RequestMethod.POST, value = "/", consumes = "application/json")
    Customer saveCustomer(@RequestBody Customer customer);

}

CustomerClient回调实现：

@Component
public class CustomerClientFallback implements CustomerClient {

    @Override
    public List<Customer> getAllCustomers() {

        return new ArrayList<Customer>();
    }

    @Override
    public Customer update(long customerId, Customer customer) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Customer getCustomerById(long customerId) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Customer saveCustomer(Customer customer) {
        // TODO Auto-generated method stub
        return null;
    }

}

应用类别：

@SpringBootApplication
@EnableFeignClients
@EnableDiscoveryClient
@EnableHystrix
@EnableHystrixDashboard
public class ApplicationFeignApplication {

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

    }

}

Spring云版本：

Greenwich.SR1




<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
        </dependency>

贝娄是一个修改，但它不工作，以及。

@RestController
public class CustomerController {

    @Autowired
    private CustomerClient customerClient;

    @Autowired
    public CustomerController(@Qualifier("customerClientFallback") CustomerClient customerClient) {
        this.customerClient = customerClient;
    }

    @RequestMapping(path = "/getAllCustomers", method = RequestMethod.GET)
    public ResponseEntity<Object> getAllCustomers() {
        List<Customer> customers = customerClient.getAllCustomers();
        return new ResponseEntity<>(customers, HttpStatus.OK);

    }

    @RequestMapping(path = "/{customerId}", method = RequestMethod.GET)
    public ResponseEntity<Object> get(@PathVariable() long customerId) {
        try {
            Customer c = customerClient.getCustomerById(customerId);
            if (c != null) {
                return new ResponseEntity<>(c, HttpStatus.OK);
            } else {
                return ResponseEntity.status(HttpStatus.NOT_FOUND).body("Customer Not Found");
            }
        } catch (Exception e) {
            e.printStackTrace();
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(e.getMessage());
        }
    }

    @RequestMapping(path = "/{customerId}", method = RequestMethod.PATCH)
    public ResponseEntity<Object> UpdateCustomer(@PathVariable() Long customerId, @RequestBody Customer customer) {
        Customer c;
        try {
            c = customerClient.update(customerId, customer);
            if (c != null) {
                return new ResponseEntity<>(c, HttpStatus.OK);
            } else {
                return ResponseEntity.status(HttpStatus.NOT_FOUND).body("Customer Not Found");
            }
        } catch (Exception e) {
            e.printStackTrace();
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(e.getMessage());
        }
    }

    @RequestMapping(path = "", method = RequestMethod.POST)
    public ResponseEntity<Object> saveCustomer(@RequestBody Customer customer) {
        Customer c;
        try {
            c = customerClient.saveCustomer(customer);
            return new ResponseEntity<>(c, HttpStatus.OK);
        } catch (Exception e) {
            e.printStackTrace();
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(e.getMessage());
        }
    }
}

Answer 1

从字段中删除自动连接的注释，您已经在构造函数中注入了依赖项。

private CustomerClient customerClient;

@Autowired
public CustomerController(@Qualifier("customerClientFallback") CustomerClient customerClient) {
    this.customerClient = customerClient;
}

使用构造函数依赖项注入而不是字段注入也更安全——通过字段注入，任何人都可以在无效状态下创建类的实例。在构造函数中明确指定了依赖项，并且更容易测试代码（模拟依赖项并在构造函数中使用它们）

此外，当您用@RequestMapping注释接口或类时，即使您有@FeignClient注释，Spring也会注册一个处理程序。由于您有这个接口的实现，您应该删除它以避免任何不明确的映射问题。

像这样

@FeignClient(name = "CUSTOMERSERVICE", fallback = CustomerClientFallback.class, primary = false)
public interface CustomerClient {

    @RequestMapping(method = RequestMethod.GET, value = "/getAllCustomers")
    List<Customer> getAllCustomers();

    @RequestMapping(method = RequestMethod.PATCH, value = "/{customerId}", consumes = "application/json")
    Customer update(@PathVariable("customerId") long customerId, @RequestBody Customer customer);

    @RequestMapping(method = RequestMethod.GET, value = "/{customerId}")
    Customer getCustomerById(@PathVariable("customerId") long customerId);

    @RequestMapping(method = RequestMethod.POST, value = "/", consumes = "application/json")
    Customer saveCustomer(@RequestBody Customer customer);

}

Answer 2

这是Spring Cloud中的已知错误，请参阅：https://github.com/spring-cloud/spring-cloud-netflix/issues/2677

Answer 3

由于使用CustomerClient，似乎出现了问题。javacontroller类中的外部客户端。

请确保您正在添加限定符

@Autowired
private CustomerClient customerClient;

@Autowired
public CustomerController(@Qualifier("customerClientFallback") CustomerClient customerClient ) {
    this.customerClient= customerClient;
}

现在应该可以了。

我建议您研究FallBackFactory，以获得更强大的外部异常处理能力，