spring boot项目中使用spring-boot-devtools模块进行代码热部署，避免重新启动web项目

devtools模块，是为开发者服务的一个模块。主要的功能就是代码修改后一般在5秒之内就会自动重新加载至服务器，相当于restart成功。spring-boot提供的重新启动技术使用两个类加载器，一个类加载器用来加载那些不变的类（如第三方jar包提供的类），另外一个用来加载正在开发的代码类，你正在开发的类被加载进了一个重新启动类加载器中，当应用程序 重新启动时会抛弃掉之前的类加载器，然后重新创建一个重新启动的类加载器，所以使用DevTools工具模块重新部署代码是很快的。只要我们修改了classpath下任何文件只要保存Devtools模块都会重新启动应用程序。一、spring-boot-devtools模块是一个为开发者服务的模块，其中最重要的功能就是代码的热部署，只需在pom文件中加入如下依赖不需要任何其他的配置

<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
</dependencies>

二、加入如上的代码依赖我们使用启动web项目，然后修改一下代码可以看到后台重新编译运行了项目，而且结果也改变了

2017-10-15 17:14:58.619  INFO 1519 --- [       Thread-6] ConfigServletWebServerApplicationContext : Closing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@895709: startup date [Sun Oct 15 17:14:20 CST 2017]; root of context hierarchy
2017-10-15 17:14:58.624  WARN 1519 --- [       Thread-6] o.s.b.f.support.DisposableBeanAdapter    : Invocation of destroy method failed on bean with name 'classPathFileSystemWatcher': java.lang.NullPointerException
2017-10-15 17:14:58.625  INFO 1519 --- [       Thread-6] o.s.j.e.a.AnnotationMBeanExporter        : Unregistering JMX-exposed beans on shutdown

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/\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/  ___)| |_)| | | | | || (_| |  ) ) ) )
'  |____| .__|_| |_|_| |_\__, | / / / /
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:: Spring Boot ::  (v2.0.0.BUILD-SNAPSHOT)

2017-10-15 17:14:58.876  INFO 1519 --- [  restartedMain] ggauthority.v1.GgauthorityApplication    : Starting GgauthorityApplication on yaomingyangdeMacBook-Pro.local with PID 1519 (/Users/yaomingyang/Documents/IDE/workplace/ggauthority/target/classes started by yaomingyang in /Users/yaomingyang/Documents/IDE/workplace/ggauthority)
2017-10-15 17:14:58
4000
.877  INFO 1519 --- [  restartedMain] ggauthority.v1.GgauthorityApplication    : No active profile set, falling back to default profiles: default
2017-10-15 17:14:58.880  INFO 1519 --- [  restartedMain] ConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@2fc9f5: startup date [Sun Oct 15 17:14:58 CST 2017]; root of context hierarchy
2017-10-15 17:14:59.401  INFO 1519 --- [  restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8011 (http)
2017-10-15 17:14:59.402  INFO 1519 --- [  restartedMain] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2017-10-15 17:14:59.403  INFO 1519 --- [  restartedMain] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.23
2017-10-15 17:14:59.409  INFO 1519 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2017-10-15 17:14:59.410  INFO 1519 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 530 ms
2017-10-15 17:14:59.446  INFO 1519 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
2017-10-15 17:14:59.447  INFO 1519 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
2017-10-15 17:14:59.447  INFO 1519 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2017-10-15 17:14:59.447  INFO 1519 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2017-10-15 17:14:59.447  INFO 1519 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
2017-10-15 17:14:59.480  INFO 1519 --- [  restartedMain] org.mongodb.driver.cluster               : Cluster created with settings {hosts=[127.0.0.1:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500}
2017-10-15 17:14:59.547  INFO 1519 --- [127.0.0.1:27017] org.mongodb.driver.connection            : Opened connection [connectionId{localValue:2, serverValue:19}] to 127.0.0.1:27017
2017-10-15 17:14:59.548  INFO 1519 --- [127.0.0.1:27017] org.mongodb.driver.cluster               : Monitor thread successfully connected to server with description ServerDescription{address=127.0.0.1:27017, type=STANDALONE, state=CONNECTED, ok=true, version=ServerVersion{versionList=[3, 2, 11]}, minWireVersion=0, maxWireVersion=4, maxDocumentSize=16777216, roundTripTimeNanos=635614}
2017-10-15 17:14:59.678  INFO 1519 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@2fc9f5: startup date [Sun Oct 15 17:14:58 CST 2017]; root of context hierarchy
2017-10-15 17:14:59.691  INFO 1519 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/users/list],methods=[GET || POST]}" onto public ggauthority.v1.user.entity.User ggauthority.v1.user.controller.UserController.list(java.lang.Long)
2017-10-15 17:14:59.691  INFO 1519 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/users/get_user/{user_id}],methods=[GET || POST]}" onto public java.util.Map<java.lang.String, java.lang.Object> ggauthority.v1.user.controller.UserController.get_user(java.lang.Long)
2017-10-15 17:14:59.696  INFO 1519 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2017-10-15 17:14:59.696  INFO 1519 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2017-10-15 17:14:59.708  INFO 1519 --- [  restartedMain] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-10-15 17:14:59.709  INFO 1519 --- [  restartedMain] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-10-15 17:14:59.727  INFO 1519 --- [  restartedMain] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-10-15 17:14:59.776  INFO 1519 --- [  restartedMain] o.s.b.d.a.OptionalLiveReloadServer       : LiveReload server is running on port 35729
2017-10-15 17:14:59.883  INFO 1519 --- [  restartedMain] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2017-10-15 17:14:59.904  INFO 1519 --- [  restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8011 (http)
2017-10-15 17:14:59.907  INFO 1519 --- [  restartedMain] ggauthority.v1.GgauthorityApplication    : Started GgauthorityApplication in 1.07 seconds (JVM running for 40.767)

三、当你更改不在classpath下的文件你可能想让你的应用程序重新启动或者只加载对应的文件，你可以使用spring.devtools.restart.additional-paths属性配置文件将对应的文件加载到devtools工具的检测范围之内，

spring.devtools.restart.exclude排除那个目录下不需要加载。

#添加那个目录的文件需要restartspring.devtools.restart.additional-paths=src/main/java#排除那个目录的文件不需要restartspring.devtools.restart.exclude=static/**,public/**

四、可以通过设置

spring.devtools.restart.enabled=false禁用devtools模块的功能。