您好,登錄后才能下訂單哦!
這篇文章主要介紹Spring BPP中怎樣創(chuàng)建動(dòng)態(tài)代理Bean,文中介紹的非常詳細(xì),具有一定的參考價(jià)值,感興趣的小伙伴們一定要看完!
v一、前言
本文章所講并沒(méi)有基于Aspectj,而是直接通過(guò)Cglib以及ProxyFactoryBean去創(chuàng)建代理Bean。通過(guò)下面的例子,可以看出Cglib方式創(chuàng)建的代理Bean和ProxyFactoryBean創(chuàng)建的代理Bean的區(qū)別。
v二、基本測(cè)試代碼
測(cè)試實(shí)體類,在BPP中創(chuàng)建BppTestDepBean類型的代理Bean。
@Component public static class BppTestBean { @Autowired private BppTestDepBean depBean; public void test1() { depBean.testDep(); } public void test2() { depBean.testDep(); } @TestMethod public void test3() { depBean.testDep(); } } @Component public static class BppTestDepBean { public void testDep() { System.out.println("HEHE"); } } @Target(ElementType.METHOD) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface TestMethod { }
測(cè)試類
@RunWith(SpringRunner.class) @SpringBootTest public class BppTest { @Autowired private BppTestBean bppTestBean; @Test public void test() { bppTestBean.test1(); bppTestBean.test2(); bppTestBean.test3(); } }
v三、使用Cglib創(chuàng)建代理Bean
public class ProxyBpp1 implements BeanPostProcessor { private static final Logger LOGGER = LoggerFactory.getLogger(ProxyBpp1.class); @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { if (bean instanceof BppTestBean) { Enhancer enhancer = new Enhancer(); enhancer.setSuperclass(bean.getClass()); //標(biāo)識(shí)Spring-generated proxies enhancer.setInterfaces(new Class[]{SpringProxy.class}); //設(shè)置增強(qiáng) enhancer.setCallback((MethodInterceptor) (target, method, args, methodProxy) -> { if ("test1".equals(method.getName())) { LOGGER.info("ProxyBpp1 開始執(zhí)行..."); Object result = methodProxy.invokeSuper(target, args); LOGGER.info("ProxyBpp1 結(jié)束執(zhí)行..."); return result; } return method.invoke(target, args); }); return enhancer.create(); } return bean; } }
主要是代理 BppTestBean的test1方法。其實(shí)這種方式創(chuàng)建的代理Bean使用問(wèn)題的,@Autowired字段沒(méi)有注入進(jìn)來(lái),所以會(huì)有出現(xiàn)NPE。methodProxy.invokeSuper(target, args)
,這一行代碼是有問(wèn)題的,targe是代理類對(duì)象,而真實(shí)的對(duì)象是postProcessBeforeInitialization(Object bean, String beanName)
中的bean對(duì)象,此時(shí)bean對(duì)象@Autowired字段已經(jīng)注入了。所以可以將methodProxy.invokeSuper(target, args)
修改為method.invoke(bean, args)
解決無(wú)法注入@Autowired字段的問(wèn)題。
v四、使用ProxyFactoryBean創(chuàng)建代理Bean
public class ProxyBpp2 implements BeanPostProcessor { private static final Logger LOGGER = LoggerFactory.getLogger(ProxyBpp2.class); @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { if (bean instanceof BppTestBean) { ProxyFactoryBean pfb = new ProxyFactoryBean(); pfb.setTarget(bean); pfb.setAutodetectInterfaces(false); NameMatchMethodPointcutAdvisor advisor = new NameMatchMethodPointcutAdvisor(); advisor.addMethodName("test1"); advisor.setAdvice((MethodInterceptor) invocation -> { LOGGER.info("ProxyBpp2 開始執(zhí)行..."); Object result = invocation.getMethod().invoke(invocation.getThis(), invocation.getArguments()); LOGGER.info("ProxyBpp2 結(jié)束執(zhí)行..."); return result; }); pfb.addAdvisor(advisor); return pfb.getObject(); } return bean; } }
使用ProxyFactoryBean創(chuàng)建代理Bean的時(shí)候,一定要一個(gè)targe對(duì)象的。Advisor在切入的時(shí)候,會(huì)逐個(gè)執(zhí)行Advice。invocation.getThis()
就是在通過(guò)ProxyFactoryBean創(chuàng)建代理Bean的時(shí)候傳入的target對(duì)象。由于target對(duì)象就是postProcessBeforeInitialization(Object bean, String beanName)
中的bean對(duì)象,所以@Autowired字段也已經(jīng)注入進(jìn)來(lái)了。
v五、@Autowired注解何時(shí)被處理
想必大家都知道@Autowired字段的處理也是通過(guò)一個(gè)BPP,不過(guò)這個(gè)BPP比我們平常使用的要高級(jí)一些,它就是InstantiationAwareBeanPostProcessor。這個(gè)BPP可以實(shí)現(xiàn)Bean的創(chuàng)建、屬性的注入和解析(比如@Autowired、@Value、@Resource等等),大家可以參考一下CommonAnnotationBeanPostProcessor(處理JSR-250相關(guān)注解),AutowiredAnnotationBeanPostProcessor(處理@Autowired、@Value、@Inject相關(guān)注解)。
InstantiationAwareBeanPostProcessor中有一個(gè)如下的方法,AutowiredAnnotationBeanPostProcessor就是覆蓋這個(gè)方法實(shí)現(xiàn)了帶有相關(guān)注解屬性的自動(dòng)注入。
@Nullable default PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) throws BeansException { return null; }
@Override public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) { InjectionMetadata metadata = findAutowiringMetadata(beanName, bean.getClass(), pvs); try { metadata.inject(bean, beanName, pvs); } catch (BeanCreationException ex) { throw ex; } catch (Throwable ex) { throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", ex); } return pvs; }
InstantiationAwareBeanPostProcessor的postProcessProperties方法實(shí)在Spring AbstractAutowireCapableBeanFactory的populateBean方法中被調(diào)用。在AbstractAutowireCapableBeanFactory的doCreateBan中有如下代碼。
// Initialize the bean instance. Object exposedObject = bean;# try { populateBean(beanName, mbd, instanceWrapper); exposedObject = initializeBean(beanName, exposedObject, mbd); }
也就是先進(jìn)行了Bean的屬性填充,然后進(jìn)行Bean的初始化工作。initializeBean方法中主要做了四件事。
1、invokeAwareMethods
2、applyBeanPostProcessorsBeforeInitialization
3、invokeInitMethods
4、applyBeanPostProcessorsAfterInitialization
其中2和4就是分別調(diào)用的普通的BPP中的postProcessBeforeInitialization方法和postProcessAfterInitialization方法。
這就是為什么在BPP中創(chuàng)建代理Bean的時(shí)候,對(duì)應(yīng)的目標(biāo)Bean相關(guān)的@Autowired字段已經(jīng)注入的原因了。
v六、InstantiationAwareBeanPostProcessor方式創(chuàng)建動(dòng)態(tài)代理Bean
InstantiationAwareBeanPostProcessor接口中有個(gè)postProcessBeforeInstantiation方法,可以讓我們自己去實(shí)例化Bean。通過(guò)查看AbstractAutowireCapableBeanFactory,方法調(diào)用:createBean方法 -> resolveBeforeInstantiation方法 -> applyBeanPostProcessorsBeforeInstantiation方法 ->InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation方法,如果最終返回一個(gè)非null的實(shí)例,那么就不會(huì)再執(zhí)行doCreateBean方法。這就意味著不會(huì)有Bean屬性的填充和初始化的流程了,但是可以借助AbstractAutowireCapableBeanFactory幫助我們實(shí)現(xiàn)。
public <T> T postProcess(T object) { if (object == null) { return null; } T result; try { // 使用容器autowireBeanFactory標(biāo)準(zhǔn)依賴注入方法autowireBean()處理 object對(duì)象的依賴注入 this.autowireBeanFactory.autowireBean(object); // 使用容器autowireBeanFactory標(biāo)準(zhǔn)初始化方法initializeBean()初始化對(duì)象 object result = (T) this.autowireBeanFactory.initializeBean(object, object.toString()); } catch (RuntimeException e) { Class<?> type = object.getClass(); throw new RuntimeException( "Could not postProcess " + object + " of type " + type, e); } return result; }
上圖代碼,可以幫組我們實(shí)現(xiàn)非Spring容器Bean自動(dòng)注入和初始化的功能。使用過(guò)Spring security同學(xué)都知道,內(nèi)部也是用了這個(gè)方式解決對(duì)象中的屬性注入問(wèn)題。如果你閱讀了Spring security的源碼,你會(huì)發(fā)現(xiàn)很多對(duì)象,比如WebSecurity、ProviderManager、各個(gè)安全Filter等,這些對(duì)象的創(chuàng)建并不是通過(guò)bean定義的形式被容器發(fā)現(xiàn)和注冊(cè)進(jìn)入spring容器的,而是直接new出來(lái)的。Spring security提供的AutowireBeanFactoryObjectPostProcessor這個(gè)工具類可以使這些對(duì)象具有容器bean同樣的生命周期,也能注入相應(yīng)的依賴,從而進(jìn)入準(zhǔn)備好被使用的狀態(tài)。
使用Cglib在InstantiationAwareBeanPostProcessor 中創(chuàng)建動(dòng)態(tài)代理Bean。
public class ProxyBpp3 implements InstantiationAwareBeanPostProcessor { private static final Logger LOGGER = LoggerFactory.getLogger(ProxyBpp3.class); private final AutowireCapableBeanFactory autowireBeanFactory; ProxyBpp3(AutowireCapableBeanFactory autowireBeanFactory) { this.autowireBeanFactory = autowireBeanFactory; } @Override public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException { if (beanClass.equals(BppConfig.BppTestBean.class)) { Enhancer enhancer = new Enhancer(); enhancer.setSuperclass(beanClass); //標(biāo)識(shí)Spring-generated proxies enhancer.setInterfaces(new Class[]{SpringProxy.class}); //設(shè)置增強(qiáng) enhancer.setCallback((MethodInterceptor) (target, method, args, methodProxy) -> { if ("test1".equals(method.getName())) { LOGGER.info("ProxyBpp3 開始執(zhí)行..."); Object result = methodProxy.invokeSuper(target, args); LOGGER.info("ProxyBpp3 結(jié)束執(zhí)行..."); return result; } return methodProxy.invokeSuper(target, args); }); return this.postProcess(enhancer.create()); } return null; } ... }
使用ProxyFactoryBean在InstantiationAwareBeanPostProcessor 中創(chuàng)建動(dòng)態(tài)代理Bean。
public class ProxyBpp4 implements InstantiationAwareBeanPostProcessor { private static final Logger LOGGER = LoggerFactory.getLogger(ProxyBpp4.class); private final AutowireCapableBeanFactory autowireBeanFactory; ProxyBpp4(AutowireCapableBeanFactory autowireBeanFactory) { this.autowireBeanFactory = autowireBeanFactory; } @Override public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException { if (beanClass.equals(BppConfig.BppTestBean.class)) { ProxyFactoryBean pfb = new ProxyFactoryBean(); pfb.setTarget(this.postProcess(BeanUtils.instantiateClass(beanClass))); pfb.setAutodetectInterfaces(false); NameMatchMethodPointcutAdvisor advisor = new NameMatchMethodPointcutAdvisor(); advisor.addMethodName("test1"); advisor.setAdvice((MethodInterceptor) invocation -> { LOGGER.info("ProxyBpp4 開始執(zhí)行..."); Object result = invocation.getMethod().invoke(invocation.getThis(), invocation.getArguments()); LOGGER.info("ProxyBpp4 結(jié)束執(zhí)行..."); return result; }); pfb.addAdvisor(advisor); return pfb.getObject(); } return null; } ... }
上述向兩種方式,注意,實(shí)例化bean后主動(dòng)通過(guò)postProcess方法借助AbstractAutowireCapableBeanFactory完成對(duì)象相關(guān)屬性的注入以及對(duì)象的初始化流程。
以上是“Spring BPP中怎樣創(chuàng)建動(dòng)態(tài)代理Bean”這篇文章的所有內(nèi)容,感謝各位的閱讀!希望分享的內(nèi)容對(duì)大家有幫助,更多相關(guān)知識(shí),歡迎關(guān)注億速云行業(yè)資訊頻道!
免責(zé)聲明:本站發(fā)布的內(nèi)容(圖片、視頻和文字)以原創(chuàng)、轉(zhuǎn)載和分享為主,文章觀點(diǎn)不代表本網(wǎng)站立場(chǎng),如果涉及侵權(quán)請(qǐng)聯(lián)系站長(zhǎng)郵箱:is@yisu.com進(jìn)行舉報(bào),并提供相關(guān)證據(jù),一經(jīng)查實(shí),將立刻刪除涉嫌侵權(quán)內(nèi)容。