如何将Bean注入自定义参数解析器？

Question

您好，我使用Spring Boot 1.3.2版本。我有一个自定义参数解析器，名称为ActiveCustomerArgumentResolver。一切都很好，resolveArgument方法工作正常，但是我无法初始化我的自定义arg的服务组件。解析器。生命周期流程有问题吗？这是我的代码：

import org.springframework.beans.factory.annotation.Autowired;
//other import statements

public class ActiveCustomerArgumentResolver implements HandlerMethodArgumentResolver {

@Autowired
private CustomerService customerService;

@Override
public boolean supportsParameter(MethodParameter parameter) {
    if (parameter.hasParameterAnnotation(ActiveCustomer.class) && parameter.getParameterType().equals(Customer.class))
        return true;
    else
        return false;
}

@Override
public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
    Principal userPrincipal = webRequest.getUserPrincipal();
    if (userPrincipal != null) {
        Long customerId = Long.parseLong(userPrincipal.getName()); 
        return customerService.getCustomerById(customerId).orNull(); //customerService is still NULL here, it keeps me getting NullPointerEx.
    } else {
        throw new IllegalArgumentException("No user principal is associated with the current request, yet parameter is annotated with @ActiveUser");
    }
}

}

Answer 1

让Spring通过为它创建解析器Component：

@Component
public class ActiveCustomerArgumentResolver implements HandlerMethodArgumentResolver {...}

然后将解析器注入您的解析器，WebConfig而不是简单地使用new，如下所示：

@EnableWebMvc
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    @Autowired private ActiveCustomerArgumentResolver activeCustomerArgumentResolver;

    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        argumentResolvers.add(activeCustomerArgumentResolver);
    }
}