背景
微服務項目要整合合併,結果各種踩坑
問題描述
合併後的項目啓動應用報錯類型不一致,堆棧如下:
2020-07-02 11:32:04,008 ERROR [main] org.springframework.boot.SpringApplication:: Application startup failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'CNGetPakgOverDistanceHandler': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'stringRedisTemplate' is expected to be of type 'org.springframework.data.redis.core.StringRedisTemplate' but was actually of type 'org.springframework.data.redis.core.RedisTemplate'
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:321) ~[spring-context-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1269) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:551) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:481) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:312) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:308) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.17.RELEASE.jar:1.5.17.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) ~[spring-boot-1.5.17.RELEASE.jar:1.5.17.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) ~[spring-boot-1.5.17.RELEASE.jar:1.5.17.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) ~[spring-boot-1.5.17.RELEASE.jar:1.5.17.RELEASE]
at com.dianwoba.wireless.fundamental.boot.WirelessSpringApplication.run(WirelessSpringApplication.java:16) ~[wireless-fundamental-1.0.0-20191205.115817-28.jar:1.0.0-SNAPSHOT]
at com.dianwoba.order.foul.Application.main(Application.java:20) ~[classes/:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_131]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_131]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_131]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_131]
at com.intellij.rt.execution.CommandLineWrapper.main(CommandLineWrapper.java:64) ~[?:?]
Caused by: org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'stringRedisTemplate' is expected to be of type 'org.springframework.data.redis.core.StringRedisTemplate' but was actually of type 'org.springframework.data.redis.core.RedisTemplate'
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:384) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:522) ~[spring-context-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:496) ~[spring-context-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:627) ~[spring-context-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:171) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87) ~[spring-beans-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:318) ~[spring-context-4.3.20.RELEASE.jar:4.3.20.RELEASE]
... 21 more
查看發現項目中使用的自定義的redis模板定義,代碼如下CacheConfig:
@Bean
public RedisTemplate<String, String> stringRedisTemplate(RedisConnectionFactory redisConnectionFactory) {
RedisTemplate<String, String> template = new RedisTemplate<>();
template.setConnectionFactory(redisConnectionFactory);
template.setDefaultSerializer(template.getStringSerializer());
StringRedisSerializer serializer = new StringRedisSerializer();
template.setValueSerializer(serializer);
template.setHashValueSerializer(serializer);
return template;
}
這他丫的原服務怎麼啓動的?難道RedisTemplate<String, String>與StringRedisTemplate類型兼容?不會,不然我們的異常就不會報出來了。於是我切回原master分支。應用竟然啓動的賊流暢。小朋友,你是不是有很多問號?我有。
問題分析
spring注入類型兼容規則是什麼?
spring通過Resource註解注入類型匹配注入問題。兩個注入什麼樣類型的數據spring會自動兼容?沒錯跟java的父子類型轉換一樣,子類型可以注入到定義爲父類型的字段,但是父類型不能自動注入到定義爲子類型的字段。相關源碼如下:
- 構建注入元數據含元素ResourceElement,構造器中校驗類型,如果Resource註解指定了類型的情況時
- 獲取要注入到屬性的bean
// 內部類:org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.ResourceElement
// 該元素重寫了getResourceToInject方法,即獲取用來要注入到field字段的bean
protected Object getResourceToInject(Object target, String requestingBeanName) {
return (this.lazyLookup ? buildLazyResourceProxy(this, requestingBeanName) :
getResource(this, requestingBeanName));
}
// 1. 首先從jndi工廠中按照名稱查找,名稱優先級(Resource註解配置):lookup->mappedName->name
// 2. 其次從resourceFactory(beanFactory)中獲取bean
protected Object getResource(LookupElement element, String requestingBeanName) throws BeansException {
if (StringUtils.hasLength(element.mappedName)) {
return this.jndiFactory.getBean(element.mappedName, element.lookupType);
}
if (this.alwaysUseJndiLookup) {
return this.jndiFactory.getBean(element.name, element.lookupType);
}
if (this.resourceFactory == null) {
throw new NoSuchBeanDefinitionException(element.lookupType,
"No resource factory configured - specify the 'resourceFactory' property");
}
return autowireResource(this.resourceFactory, element, requestingBeanName);
}
- 從工廠中獲取要注入的bean(即CNGetPakgOverDistanceHandler父類DwdElemeOverDistanceCheckHandler所依賴的StringRedisTemplate)(doGetBean)。TypeConverterDelegate中對類型轉換並判斷是否匹配通過:ClassUtils.isAssignableValue(requiredType, convertedValue)方法判斷
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
try {
// 如果需要的話進行類型轉換:TypeConverterSupport.convertIfNecessary
return getTypeConverter().convertIfNecessary(bean, requiredType);
}
catch (TypeMismatchException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
此場景下顯然RedisTemplate不是StringRedisTemplate的子。拋出類型不匹配異常
爲什麼合併前項目可以啓動成功?
打斷點發現注入的StringRedisTemplate實例根本不是我們自定義配置CacheConfig中定義的bean。而是springboot自動配置中定義的StringRedisTemplate bean。
RedisAutoConfiguration配置類
@Configuration
protected static class RedisConfiguration {
...
@Bean
@ConditionalOnMissingBean(StringRedisTemplate.class)
public StringRedisTemplate stringRedisTemplate(
RedisConnectionFactory redisConnectionFactory)
throws UnknownHostException {
StringRedisTemplate template = new StringRedisTemplate();
template.setConnectionFactory(redisConnectionFactory);
return template;
}
}
兩個Configuration註解的配置類優先級是什麼?
Application(springboot的source類)優先級如下(其他bean優先級相同):
成員內部類或接口->ComponentScans->Import->ImportResource->Application自身Bean註解的方法->Application的接口->ImportResource
那麼也就是說org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration(Application的Import階段,由SpringBootApplication註解繼承的父註解EnableAutoConfiguration導入)的優先級應該是低於我們自定義CacheConfig
簡單說一下EnableAutoConfigurationImportSelector的處理流程,它會從spring工廠中加載EnableAutoConfiguration的實現類進行import導入。自動配置文件根據spring-autoconfigure-metadata元數據配置進行排序、過濾,然後再執行導入。
- Configuration配置類採集至ConfigurationClassParser.configurationClasses
- ConfigurationClassBeanDefinitionReader遍歷讀取ConfigurationClassParser.configurationClasses緩存中配置類將bean定義註冊至工廠
ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForConfigurationClass加載配置類中的bean定義,我們看下beanMethod方式的bean定義的處理邏輯:loadBeanDefinitionsForBeanMethod
- 判斷Conditional忽略bean定義
- 獲取bean定義的別名,讀取bean註解的name屬性,如果沒有則默認爲方法名稱
- 判斷是否被已存在的bean定義重寫。如果是ConfigurationClassBeanDefinition、ScannedGenericBeanDefinition、bean定義的角色大於ROLE_APPLICATION,則允許重寫
- 註冊bean定義至工廠registerBeanDefinition。獲取已存在的bean定義,如果不允許重寫bean定義則拋出異常(默認允許)。
小結
- 第一我們的自定義的bean優先級高於springboot自動配置的bean。
- 第二springboot自動配置的redis bean不會生效,條件判斷ConditionalOnMissingBean是註冊bean階段的條件(loadBeanDefinitionsForBeanMethod);會直接跳過,事實也證明是如此,見下圖斷點已經走到(即跳過了bean註冊):
所以不論如何都應該是自定義的cacheConfig中的redis bean生效纔對,也就是一定會報錯
爲什麼合併前工廠中是springboot自動配置的redis bean?
切回master分支運行斷點,依然是先走到自定義的redis bean,再走到springboot自動註冊redis bean,但是竟然沒有skip?那麼問題的原因漸漸浮現了,問題一定是在shouldSkip條件判斷這個階段
// OnBeanCondition.getMatchOutcome
if (metadata.isAnnotated(ConditionalOnMissingBean.class.getName())) {
BeanSearchSpec spec = new BeanSearchSpec(context, metadata,
ConditionalOnMissingBean.class);
// 如果找到bean則返回條件不通過noMatch。查找策略爲ALL,即所有
List<String> matching = getMatchingBeans(context, spec);
if (!matching.isEmpty()) {
return ConditionOutcome.noMatch(ConditionMessage
.forCondition(ConditionalOnMissingBean.class, spec)
.found("bean", "beans").items(Style.QUOTE, matching));
}
// 如果未找到bean則返回條件通過
matchMessage = matchMessage.andCondition(ConditionalOnMissingBean.class, spec)
.didNotFind("any beans").atAll();
}
return ConditionOutcome.match(matchMessage);
// 創建BeanSearchSpec
BeanSearchSpec(ConditionContext context, AnnotatedTypeMetadata metadata,
Class<?> annotationType) {
this.annotationType = annotationType;
MultiValueMap<String, Object> attributes = metadata
.getAllAnnotationAttributes(annotationType.getName(), true);
collect(attributes, "name", this.names);
collect(attributes, "value", this.types);
collect(attributes, "type", this.types);
collect(attributes, "annotation", this.annotations);
collect(attributes, "ignored", this.ignoredTypes);
collect(attributes, "ignoredType", this.ignoredTypes);
this.strategy = (SearchStrategy) metadata
.getAnnotationAttributes(annotationType.getName()).get("search");
BeanTypeDeductionException deductionException = null;
try {
if (this.types.isEmpty() && this.names.isEmpty()) {
addDeducedBeanType(context, metadata, this.types);
}
}
...
}
getMatchingBeans查找bean
如果查找策略SearchStrategy是PARENTS或者ANCESTORS,則使用工廠的父類查找。
如果工廠爲null則返回空集合,即ConditionalOnMissingBean條件通過
從工廠中獲取所有註解type屬性指定類型的beanNames(包含父子層級)。此時cacheConfig中定義的類型是RedisTemplate所以不屬於指定類型。父類不能轉讓成子類。type=StringRedisTemplate,工廠中目前僅存在:RedisTemplate
// BeanTypeRegistry
Set<String> getNamesForType(Class<?> type) {
updateTypesIfNecessary();
Set<String> matches = new LinkedHashSet<String>();
for (Map.Entry<String, Class<?>> entry : this.beanTypes.entrySet()) {
if (entry.getValue() != null && type.isAssignableFrom(entry.getValue())) {
matches.add(entry.getKey());
}
}
return matches;
}
從beanNames中移除條件註解ignoredTypes屬性指定的類型對應的beanName
從工廠中獲取所有註解annotation屬性指定類型的beanNames(包含父子層級)
從工廠中獲取註解name屬性指定相同名稱的bean(包含父子層級),調用工廠containsBean方法。沒有指定name所以,最終判斷條件通過繼續註冊bean,會覆蓋自定義的cacheConfig中的redis bean
爲什麼合併後工廠中不是springboot自動配置的redis bean?
由於合併的分支增加了下面的配置,所以導致此處springboot的自動配置miss。
@Bean
@Primary
public StringRedisTemplate stringRedisTemplate2(RedisConnectionFactory redisConnectionFactory) {
return new StringRedisTemplate(redisConnectionFactory);
}
問題總結
- 合併前,項目中沒有StringRedisTemplate類型的bean,所以自動配置的bean定義會覆蓋掉自定義bean定義。所以自定義的bean定義是錯的也沒有拋出異常
- 合併後,項目中存在StringRedisTemplate類型的bean配置,所以自動配置的bean定義不會覆蓋掉自定義bean定義。注入時根據名稱匹配注入,因爲自定義的配置類型是錯誤的RedisTemplate類型。於是拋出了異常