java - spring中条件注解的排序评估

Question

我有三个类，所有这些类都需要根据 @ConditionalOnExpression 注释启用/禁用。所有这些都位于单独的 .java 文件中。

例如:

@ConditionalOnExpression("#T(com.xxx.xxx.xxx.xxx.CxProperties).isAEnabled()}")
Class A{
}


@ConditionalOnExpression("#T(com.xxx.xxx.xxx.xxx.CxProperties).isBEnabled()}")
Class B{
}


@ConditionalOnExpression("#T(com.xxx.xxx.xxx.xxx.CxProperties).isCEnabled()}")
Class C{
}

现在我在另一个类中有一个 init 函数，它首先执行，并且我将启用/禁用值设置为类 CxProperties。注意:假设所有 setter 都是静态的

class setvalues{

        public void init(){
             /*Read config values from a file*/
             CxProperties.setAEnabled(true/false);
             CxProperties.setBEnabled(true/false);
             CxProperties.setCEnabled(true/false);
        }
}

现在，当根本未设置启用/禁用时，这些条件的评估发生在程序开始时(甚至在执行 init 之前)。

在 spring 中是否有任何可能的方法来命令对这些条件进行评估，例如在执行的某个点后评估此条件？

非常感谢任何指点。

Answer 1

我建议您不要为此使用 @ConditionalOnExpression 注释。

考虑使用@PreAuthorize。是的，它来自 spring-security。

这样，您可以保护每个服务在未启用的情况下不被使用，并动态切换其启用/禁用状态:

@SpringBootApplication
public class So44462763Application {

    public static void main(String[] args) {
        SpringApplication.run(So44462763Application.class, args);
    }

    @EnableWebSecurity
    @EnableGlobalMethodSecurity(prePostEnabled = true)  // <-- this is required for PreAuthorize annotation to work
    public static class SecurityConfiguration extends WebSecurityConfigurerAdapter {
        @Override
        protected void configure(HttpSecurity http) throws Exception {
            http.csrf().disable();
        }
    }

    interface CxProperties {
        boolean isServiceAEnabled();
        boolean isServiceBEnabled();
        boolean isServiceCEnabled();

        boolean enableService(String service);
        boolean disableService(String service);
    }

    @Component("cx")
    public static class CxPropertiesImpl implements CxProperties {
        private static final ConcurrentHashMap<String, Boolean> services = new ConcurrentHashMap<>(); //could be database/redis/property file/etc

        @PostConstruct
        private void init() {
            //services.put("serviceA", true); //initial population from property file/network resource/whatever
        }

        public boolean isServiceAEnabled() {
            return services.getOrDefault("serviceA", false);
        }

        public boolean isServiceBEnabled() {
            return services.getOrDefault("serviceB", false);
        }

        public boolean isServiceCEnabled() {
            return services.getOrDefault("serviceC", false);
        }
        //just a sample how you can dynamically control availability for each service
        @Override
        public boolean enableService(String service) {
            services.put(service, true);
            return services.getOrDefault(service, false);
        }

        @Override
        public boolean disableService(String service) {
            services.put(service, false);
            return services.getOrDefault(service, false);
        }
    }

    interface BusinessService {
        String doSomething();
    }

    @Service("serviceA")
    @PreAuthorize("@cx.serviceAEnabled")
    public static class ServiceA implements BusinessService {

        @Override
        public String doSomething() {
            return this.getClass().getSimpleName() + " doing some work";
        }
    }

    @Service("serviceB")
    @PreAuthorize("@cx.serviceBEnabled")
    public static class ServiceB implements BusinessService {

        @Override
        public String doSomething() {
            return this.getClass().getSimpleName() + " doing some work";
        }
    }

    @Service("serviceC")
    @PreAuthorize("@cx.serviceCEnabled")
    public static class ServiceC implements BusinessService {

        @Override
        public String doSomething() {
            return this.getClass().getSimpleName() + " doing some work";
        }
    }

    @RestController
    @RequestMapping("/api/work")
    public static class WorkApi {
        private static final Logger log = LoggerFactory.getLogger(WorkApi.class);

        private final List<BusinessService> businessServices;

        @Autowired
        public WorkApi(final List<BusinessService> businessServices) {
            this.businessServices = businessServices;
        }

        @GetMapping
        public String doWork() {
            final StringJoiner joiner = new StringJoiner(",");
            for (BusinessService service : businessServices) {
                try {
                    joiner.add(service.doSomething());
                } catch (AccessDeniedException e) {
                    log.warn("Service {} is disabled.", service);
                }
            }
            return joiner.toString();
        }
    }

    @RestController
    @RequestMapping("/api/control")
    public static class ControlApi {

        private final CxProperties cxProperties;

        @Autowired
        public ControlApi(final CxProperties cxProperties) {
            this.cxProperties = cxProperties;
        }

        @PostMapping("{service}/enable")
        public boolean enable(@PathVariable("service") String serviceName) {
            return cxProperties.enableService(serviceName);
        }

        @PostMapping("{service}/disable")
        public boolean disable(@PathVariable("service") String serviceName) {
            return cxProperties.disableService(serviceName);
        }
    }
}

这是一个示例用法:

$ curl -u user:123 -XGET 'localhost:8080/api/work'
$ curl -u user:123 -XPOST 'localhost:8080/api/control/serviceC/enable'
true% 
$ curl -u user:123 -XGET 'localhost:8080/api/work'                    
ServiceC doing some work%
$ curl -u user:123 -XPOST 'localhost:8080/api/control/serviceA/enable'
true%
$ curl -u user:123 -XGET 'localhost:8080/api/work'                    
ServiceA doing some work,ServiceC doing some work%

使用这种方法，即使不重新启动，您也可以控制服务的可访问性。

所有这些都可以在没有 spring-security 的情况下完成，但需要更多的手动工作，并且可能会稍微降低代码的整体可读性。