Spring使用BeanPostProcessor实现AB测试

第一步：

创建要实现AB测试的接口、实现类、controller

@RoutingSwitch("hello.switch")
public interface HelloService {

    @RoutingSwitch("B")
    String sayHello();
    @RoutingSwitch("A")
    String sayHi();
}

@Service
public class HelloServiceImplV1 implements HelloService {

    @Override
    public String sayHello() {
        String helloV1= "hello from V1";
        System.out.println("hello from V1");
        return helloV1;
    }

    @Override
    public String sayHi() {
        String hiV1= "hi from V1";
        System.out.println("hi from V1");
        return hiV1;
    }
}

@Service
public class HelloServiceImplV2 implements HelloService {
    @Override
    public String sayHello() {
        String helloV2 = "hello from V2";
        System.out.println("hello from V2");
        return helloV2;
    }

    @Override
    public String sayHi() {
        String hiV2 = "hi from V2";
        System.out.println("hi from V2");
        return hiV2;
    }
}

@RestController
@RequestMapping("/test")
public class HelloControllerV2 {
    @RoutingInject
    private HelloService helloService;

    @GetMapping("/hello")
    public String sayHello() {
       return helloService.sayHello();
    }

    @GetMapping("/hi")
    public String sayHi() {
        return helloService.sayHi();
    }
}

第二步：

创建RoutingBeanPostProcessor类实现接口BeanPostProcessor。注册controller的bean时，对使用@RoutingInject注解的接口，创建动态代理类实现类。在使用该接口时，通过invoke方法创建接口实现类。

对接口设置动态代理类注解：

@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface RoutingInject {
}

开关设置注解：

@Target({ElementType.FIELD, ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface RoutingSwitch {
    String value();
}

bean初始化后，对使用RoutingInject的注解类，进行处理后置处理

@Component
public class RoutingBeanPostProcessor implements BeanPostProcessor {
    @Autowired
    private ApplicationContext applicationContext;

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        Class clazz = bean.getClass();
        Field[] fields = clazz.getDeclaredFields();
        for (Field f : fields) {
            if(f.isAnnotationPresent(RoutingInject.class)) {
                if(!f.getType().isInterface()) {
                    throw new BeanCreationException("RoutingInject field must be declared as an interface:" + "@Class" + clazz.getName());
                }
                try {
                    this.handleRoutingInjected(f, bean, f.getType());
                } catch (IllegalAccessException e) {
                    throw new BeanCreationException("Exception thrown when handleAutowiredRouting", e);
                }
            }
        }
        return null;
    }

    private void handleRoutingInjected(Field field, Object bean, Class type) throws IllegalAccessException {
        Map<String, Object> candidates = applicationContext.getBeansOfType(type);
        field.setAccessible(true);
        if(candidates.size() == 1) {
            field.set(bean, candidates.entrySet().iterator().next());
        }else if(candidates.size() == 2) {
            Object proxy = RoutingBeanProxyFactory.createProxy(type, candidates);
            field.set(bean, proxy);
        }else{
            throw new IllegalAccessException("Find more bean 2 bean for type: " + type);
        }
    }
}

代理工程实现类：

public class RoutingBeanProxyFactory {
    public static Object createProxy(Class targetClass, Map<String, Object> beans) {
        ProxyFactory proxyFactory = new ProxyFactory();
        proxyFactory.setInterfaces(new Class[]{targetClass});
        proxyFactory.addAdvice(new VersionRoutingMethodInterceptor(targetClass, beans));
        return proxyFactory.getProxy();
    }

    static class VersionRoutingMethodInterceptor implements MethodInterceptor {
        private String classSwitch;
        private Object beanSwitchOn;
        private Object beanSwitchOff;

        public VersionRoutingMethodInterceptor(Class targetClass, Map<String, Object> beans) {
            String interfaceName = StringUtils.uncapitalize(targetClass.getSimpleName());
            if(targetClass.isAnnotationPresent(RoutingSwitch.class)) {
                this.classSwitch = ((RoutingSwitch) targetClass.getAnnotation(RoutingSwitch.class)).value();
            }
            this.beanSwitchOn = beans.get(this.buildBeanName(interfaceName, true));
            this.beanSwitchOff = beans.get(this.buildBeanName(interfaceName, false));
        }

        private String buildBeanName(String interfaceName, boolean isSwitchOn) {
            return interfaceName + "Impl" + (isSwitchOn ? "V2" : "V1");
        }

        @Override
        public Object invoke(MethodInvocation invocation) throws Throwable {
            Method method = invocation.getMethod();
            String switchName = this.classSwitch;
            if(method.isAnnotationPresent(RoutingSwitch.class)) {
                switchName = method.getAnnotation(RoutingSwitch.class).value();
            }

            if(StringUtils.isBlank(switchName)) {
                throw new IllegalStateException("RoutingSwitch's value is blank, method:" + method.getName());
            }
            return invocation.getMethod().invoke(getTargetName(switchName), invocation.getArguments());
        }

        public Object getTargetName(String switchName) {
            boolean switchOn;
            if(RoutingVersion.A.name().equals(switchName)) {
                switchOn = false;
            }else{
                switchOn = true;
            }

            return switchOn ? beanSwitchOn : beanSwitchOff;
        }
    }

    enum RoutingVersion{
        A,B
    }
}

第三步：

测试接口正常