启动SpringBoot项目的时候控制台输出的log如下
2020-11-20 18:52:26.864 WARN o.s.b.w.s.c.AnnotationConfigServletWebServerApplicationContext - Exception encountered during context initialization - cancelling refresh attempt: org.springframework.context.ApplicationContextException: Failed to start bean 'documentationPluginsBootstrapper'; nested exception is com.google.common.util.concurrent.ExecutionError: java.lang.NoSuchMethodError: com.google.common.collect.FluentIterable.concat(Ljava/lang/Iterable;Ljava/lang/Iterable;)Lcom/google/common/collect/FluentIterable; 2020-11-20 18:52:26.866 INFO o.s.j.e.a.AnnotationMBeanExporter - Unregistering JMX-exposed beans on shutdown 2020-11-20 18:52:26.867 INFO o.s.j.e.a.AnnotationMBeanExporter - Unregistering JMX-exposed beans 2020-11-20 18:52:26.886 WARN c.n.c.sources.URLConfigurationSource - No URLs will be polled as dynamic configuration sources. 2020-11-20 18:52:26.886 INFO c.n.c.sources.URLConfigurationSource - To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath. 2020-11-20 18:52:26.905 INFO o.s.a.r.l.SimpleMessageListenerContainer - Shutdown ignored - container is not active already 2020-11-20 18:52:26.910 INFO o.a.catalina.core.StandardService - Stopping service [Tomcat] 2020-11-20 18:52:26.927 WARN o.a.c.loader.WebappClassLoaderBase - The web application [ROOT] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread: java.lang.Object.wait(Native Method) java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144) com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:43) Process finished with exit code 1
根据以前解决错误的思路，往往都是看最后一个报错的日志，例如：
but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread
但是、我找了半天都没找到什么原因。还以为是我写的程序存在内存泄漏呢，就去用JVM相关的技术去排错，排了半天也没发现问题。
后来实在没办法了，就继续一步一步的往上翻看日志，找到了一句：
Failed to start bean 'documentationPluginsBootstrapper' nested exception is com.google.common.util.concurrent.ExecutionError: java.lang.NoSuchMethodError: com.google.common.collect.FluentIterable.concat(Ljava/lang/Iterable;Ljava/lang/Iterable;)Lcom/google/common/collect/FluentIterable;
去百度一搜，果然是这个的问题。
出现这个问题的原因就是：当前项目的guava版本与之不匹配。
去查看了下项目里的guava的版本和swagger中的guava的版本：
果然是版本不同。
解决办法
修改成和swagger相同的guava版本即可：
<!-- <dependency> <groupId>com.google.guava</groupId> <artifactId>guava</artifactId> <version>19.0</version> </dependency>--> <dependency> <groupId>com.google.guava</groupId> <artifactId>guava</artifactId> <version>20.0</version> </dependency>
