Spring Cloud Gateway 使用Druid连接池引

原文链接：https://www.fank243.com/posts/kxdfsgao.html

启动项目时直接抛异常，堆栈信息如下

13:13:25 [org.springframework.boot.SpringApplication]-[ERROR] Application run failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'statViewServletRegistrationBean' defined in class path resource [com/alibaba/druid/spring/boot/autoconfigure/stat/DruidStatViewServletConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.web.servlet.ServletRegistrationBean]: Factory method 'statViewServletRegistrationBean' threw exception; nested exception is java.lang.NoClassDefFoundError: javax/servlet/http/HttpServlet
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:627) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:607) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1321) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1160) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:845) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:66) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:742) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:389) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:311) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1213) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1202) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
    at com.fank.blog.gateway.GatewayApplication.main(GatewayApplication.java:19) [classes/:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_181]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.1.6.RELEASE.jar:2.1.6.RELEASE]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.web.servlet.ServletRegistrationBean]: Factory method 'statViewServletRegistrationBean' threw exception; nested exception is java.lang.NoClassDefFoundError: javax/servlet/http/HttpServlet
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:622) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    ... 24 more
Caused by: java.lang.NoClassDefFoundError: javax/servlet/http/HttpServlet
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.8.0_181]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[?:1.8.0_181]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.8.0_181]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:467) ~[?:1.8.0_181]
    at java.net.URLClassLoader.access$100(URLClassLoader.java:73) ~[?:1.8.0_181]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:368) ~[?:1.8.0_181]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:362) ~[?:1.8.0_181]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_181]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:361) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_181]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_181]
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.8.0_181]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[?:1.8.0_181]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.8.0_181]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:467) ~[?:1.8.0_181]
    at java.net.URLClassLoader.access$100(URLClassLoader.java:73) ~[?:1.8.0_181]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:368) ~[?:1.8.0_181]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:362) ~[?:1.8.0_181]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_181]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:361) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_181]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_181]
    at com.alibaba.druid.spring.boot.autoconfigure.stat.DruidStatViewServletConfiguration.statViewServletRegistrationBean(DruidStatViewServletConfiguration.java:35) ~[druid-spring-boot-starter-1.1.10.jar:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_181]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:622) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    ... 24 more
Caused by: java.lang.ClassNotFoundException: javax.servlet.http.HttpServlet
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_181]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_181]
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.8.0_181]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[?:1.8.0_181]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.8.0_181]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:467) ~[?:1.8.0_181]
    at java.net.URLClassLoader.access$100(URLClassLoader.java:73) ~[?:1.8.0_181]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:368) ~[?:1.8.0_181]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:362) ~[?:1.8.0_181]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_181]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:361) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_181]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_181]
    at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.8.0_181]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[?:1.8.0_181]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[?:1.8.0_181]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:467) ~[?:1.8.0_181]
    at java.net.URLClassLoader.access$100(URLClassLoader.java:73) ~[?:1.8.0_181]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:368) ~[?:1.8.0_181]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:362) ~[?:1.8.0_181]
    at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_181]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:361) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_181]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[?:1.8.0_181]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_181]
    at com.alibaba.druid.spring.boot.autoconfigure.stat.DruidStatViewServletConfiguration.statViewServletRegistrationBean(DruidStatViewServletConfiguration.java:35) ~[druid-spring-boot-starter-1.1.10.jar:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_181]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:622) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    ... 24 more
Disconnected from the target VM, address: '127.0.0.1:61208', transport: 'socket'

刚开始以为是缺少jar包导致，就引入了对tomcat的启动依赖，发现依然无济于事

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-tomcat</artifactId>
</dependency>

后台仔细查看异常信息，发现一个关键的信息

at com.alibaba.druid.spring.boot.autoconfigure.stat.DruidStatViewServletConfiguration.statViewServletRegistrationBean(DruidStatViewServletConfiguration.java:35) ~[druid-spring-boot-starter-1.1.10.jar:?]

发现是druid-spring-boot-starter这个jar引起的，经过google搜索发现有两种方案可以解决，既换用别的连接池，另一种既升级版本。

于是将druid-spring-boot-starter升级到最新版本后问题解决了。

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.1.17</version>
</dependency>