spring-boot-devtools支持开发过程中的热加载报错的问题

前提：用的spring-boot-devtools支持开发过程中的热加载

问题：开发的过程中如果您修改了代码，项目进行了热加载，自动启动，会报以下错误：

1. 2019-01-23 14:34:38.511- [restartedMain]- [ERROR]- [o.s.boot.SpringApplication]- [Application startup failed]- 
2. org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'initActiveRecordPlugin' defined in class path resource [com/gistone/config/ActiveRecordPluginConfig.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.jfinal.plugin.activerecord.ActiveRecordPlugin]: Factory method 'initActiveRecordPlugin' threw exception; nested exception is java.lang.IllegalArgumentException: Config already exists: main
3. at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:599)
4. at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1173)
5. at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1067)
6. at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513)
7. at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
8. at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
9. at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
10. at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
11. at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
12. at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761)
13. at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:866)
14. at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542)
15. at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
16. at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737)
17. at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370)
18. at org.springframework.boot.SpringApplication.run(SpringApplication.java:314)
19. at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162)
20. at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151)
21. at com.gistone.SpringBootSampleApplication.main(SpringBootSampleApplication.java:27)
22. at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
23. at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
24. at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
25. at java.lang.reflect.Method.invoke(Unknown Source)
26. at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49)
27. Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.jfinal.plugin.activerecord.ActiveRecordPlugin]: Factory method 'initActiveRecordPlugin' threw exception; nested exception is java.lang.IllegalArgumentException: Config already exists: main
28. at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:189)
29. at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:588)
30. ... 23 common frames omitted
31. Caused by: java.lang.IllegalArgumentException: Config already exists: main
32. at com.jfinal.plugin.activerecord.DbKit.addConfig(DbKit.java:63)
33. at com.jfinal.plugin.activerecord.ActiveRecordPlugin.start(ActiveRecordPlugin.java:227)
34. at com.gistone.config.ActiveRecordPluginConfig.initActiveRecordPlugin(ActiveRecordPluginConfig.java:47)
35. at com.gistone.config.ActiveRecordPluginConfig$EnhancerBySpringCGLIB$ac4f4599.CGLIB$initActiveRecordPlugin$0()
36. at com.gistone.config.ActiveRecordPluginConfig$EnhancerBySpringCGLIB$ac4f4599$FastClassBySpringCGLIB$d1faec4e.invoke()
37. at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:228)
38. at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:356)
39. at com.gistone.config.ActiveRecordPluginConfig$EnhancerBySpringCGLIB$ac4f4599.initActiveRecordPlugin()
40. at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
41. at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
42. at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
43. at java.lang.reflect.Method.invoke(Unknown Source)
44. at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:162)
45. ... 24 common frames omitted

愿因就是以下两行代码：

1. druidPlugin.start();
2. arp.start();

解决方案：

在src/main/resources/目录下创建文件夹META-INF，在该文件夹下创建文件spring-devtools.properties

内容如下，只有一行：

1. restart.include.thirdparty=/jfinal-3.5.jar

到这里就万事大吉了，that's all~

备注：具体底层的原因，一些细节我也不是很清楚，欢迎大牛补充，再附一下另一个分享地址，或许能对您起到帮助作用