上一次的降级过程中差不多曾经跑起来90%了，这周一下班解决完一点小问题，服务曾经失常跑起来了，于是再拿着一些其余的服务测试了一下，又发现了一些其余的报错，所以持续。
14. DiscoveryEnabledServer Not Found
次要问题还是 eureka 中没有了 ribbon 相干的依赖。
Caused by: java.lang.NoClassDefFoundError: com/netflix/niws/loadbalancer/DiscoveryEnabledServer at java.lang.Class.getDeclaredMethods0(Native Method) ~[?:?] at java.lang.Class.privateGetDeclaredMethods(Class.java:3167) ~[?:?] at java.lang.Class.getDeclaredMethods(Class.java:2310) ~[?:?] at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:467) ~[spring-core-5.3.23.jar:5.3.23] at org.springframework.util.ReflectionUtils.doWithLocalMethods(ReflectionUtils.java:321) ~[spring-core-5.3.23.jar:5.3.23]解决方案：手动引入相干依赖包。
<dependency> <groupId>com.netflix.ribbon</groupId> <artifactId>ribbon-loadbalancer</artifactId> <version>2.7.18</version></dependency><dependency> <groupId>com.netflix.ribbon</groupId> <artifactId>ribbon-eureka</artifactId> <version>2.7.18</version></dependency><dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-ribbon</artifactId> <version>2.2.10.RELEASE</version></dependency>15. 中间件循环依赖
仍然是循环依赖报错，之前没留神看代码，简略的设置了一下为提早初始化，认真一看发现代码这样写的，你细品。
而后启动报错：
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'cachesEndpoint' defined in class path resource [org/springframework/boot/actuate/autoconfigure/cache/CachesEndpointAutoConfiguration.class]: Unsatisfied dependency expressed through method 'cachesEndpoint' parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Requested bean is currently in creation: Is there an unresolvable circular reference?16. CacheMetricsRegistrarConfiguration 报错
因为在解决 15 的问题一开始是设置为提早初始化，而后启动发现依然报错。
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.actuate.autoconfigure.metrics.cache.CacheMetricsRegistrarConfiguration': Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.autoconfigure.metrics.cache.CacheMetricsRegistrarConfiguration]: Constructor threw exception; nested exception is java.lang.StackOverflowError解决方案：去掉 Autowired 注入，15和16的问题全副解决。
17. kafka-clients 版本和 spring-kafka 不兼容
降级后默认spring-kafka是2.8.10版本，KafkaTemplate 报错找不到类，起因在于本地kafka-clients应用的是 2.3.0 版本。
Caused by: java.lang.IllegalStateException: Failed to introspect Class [org.springframework.kafka.core.KafkaTemplate] from ClassLoader [jdk.internal.loader.ClassLoaders$AppClassLoader@9e89d68]Caused by: java.lang.NoClassDefFoundError: org/apache/kafka/clients/consumer/ConsumerGroupMetadata解决方案：kafka-clients降级到兼容版本 3.0.2 ，这个版本是 spring-cloud-dependency 中依赖的版本。
18. swagger启动报错
这个报错是因为新版本 Spring Boot 将 Spring MVC 默认门路匹配策略由AntPathMatcher改成了PathPatternParser，这个报错在我这里是WARN，而且十分荫蔽，须要认真查找。
[WARN] [2022.11.08 16:17:39.963] [10.135.0.95] [] [main] [org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext()] - Exception encountered during context initialization - cancelling refresh attempt: org.springframework.context.ApplicationContextException: Failed to start bean 'documentationPluginsBootstrapper'; nested exception is java.lang.NullPointerException解决方案：配置成原来的AntPathMatcher，增加配置spring.mvc.pathmatch.matching-strategy= ANT_PATH_MATCHER
这个报错信息是一行 WARN 日志，十分难找，另外起因是依据网上信息搜寻定位到的，这个报错信息我真的服了。
19. spring-session依赖报错
启动报错信息：
n attempt was made to call a method that does not exist. The attempt was made from the following location: org.springframework.boot.autoconfigure.session.SessionAutoConfiguration$ServletSessionConfiguration.cookieSerializer(SessionAutoConfiguration.java:109)The following method did not exist: 'void org.springframework.session.web.http.DefaultCookieSerializer.setSameSite(java.lang.String)'The calling method's class, org.springframework.boot.autoconfigure.session.SessionAutoConfiguration$ServletSessionConfiguration, was loaded from the following location: jar:file:/Users/user/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.7.5/spring-boot-autoconfigure-2.7.5.jar!/org/springframework/boot/autoconfigure/session/SessionAutoConfiguration$ServletSessionConfiguration.classThe called method's class, org.springframework.session.web.http.DefaultCookieSerializer, is available from the following locations: jar:file:/Users/user/.m2/repository/org/springframework/session/spring-session/1.3.5.RELEASE/spring-session-1.3.5.RELEASE.jar!/org/springframework/session/web/http/DefaultCookieSerializer.classspring-session应用的是1.3.5.RELEASE，然而关上 Maven 仓库一看，这竟然是最新版本？而且还是 2019 年的版本？
其实并非如此，查找 Github 代码后发现是代码做了模块化拆分，新版本应该引入spring-session-core。
<dependency> <groupId>org.springframework.session</groupId> <artifactId>spring-session-core</artifactId> <version>2.7.0</version></dependency>20. spring-security版本兼容问题
在看到 SessionAutoConfiguration外面代码同时发现spring-security相干依赖代码产生了扭转。
解决方案：引入最新版本spring-security-web。
<dependency> <groupId>org.springframework.security</groupId> <artifactId>spring-security-web</artifactId> <version>5.7.4</version></dependency>21. RibbonLoadBalancerClient启动报错
报错信息：
org.springframework.retry.RetryException: Could not recover; nested exception is java.lang.AbstractMethodError: Receiver class org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient does not define or inherit an implementation of the resolved method abstract choose(Ljava/lang/String;Lorg/springframework/cloud/client/loadbalancer/Request;)Lorg/springframework/cloud/client/ServiceInstance; of interface org.springframework.cloud.client.loadbalancer.ServiceInstanceChooser.起因在于位于spring-cloud-commons外面的ServiceInstanceChooser#choose办法产生了扭转。
而咱们因为为了持续应用spring-cloud-netflix-ribbon包，引入的只能是更新到2021年的最新版本2.2.10.RELEASE，这个包最初更新工夫是 2021年11月份，所以这外面实现的依然是老的choose办法。
解决方案：应用同 package 名形式本人重写该类，choose 办法的逻辑其实是和原来传参 object 办法一样的，或者本人把包拉下来改代码从新打包。
22. MongoDB报错
spring-boot-autoconfigure新版本下MongoClientFactory构造函数产生扭转，以前的写法产生编译谬误。
以前的这种写法传参是MongoProperties。
return new MongoClientFactory(mongoProperties).createMongoClient(mongoClientOptions());当初的写法：
MongoClientSettingsBuilderCustomizer customizer = new MongoPropertiesClientSettingsBuilderCustomizer(mongoProperties, environment);return new MongoClientFactory(Lists.newArrayList(customizer)).createMongoClient(mongoClientOptions());另外一个问题是原来的createMongoClient传参是 MongoClientOptions，当初是 MongoClientSettings。
原来应用heartbeatFrequency、heartbeatConnectTimeout等等一些写法也不一样了，示意一下当初的写法：
MongoClientSettings.builder() .applyToServerSettings(builder -> builder.heartbeatFrequency(8000, TimeUnit.MILLISECONDS)) .applyToConnectionPoolSettings(builder -> builder.maxConnectionIdleTime(30000,TimeUnit.MILLISECONDS)) .applyToSocketSettings(builder -> builder.connectTimeout(30000,TimeUnit.MILLISECONDS)) .build();另外，如果应用到了 morphia 的话，这个改变就更大了，根本老代码没法用了，尝试了一下，改不动，临时放弃了。
总结
事件根本到这里就临时告一段落了，有一些老的代码改变太大，根本要废除重写了，临时搁置吧。