如果您對Spring Boot有一些經驗，或者對Spring MVC很熟悉。那么對于Spring構建的Web應用在啟動的時候，都會輸出當前應用創建的HTTP接口列表。
比如下面的這段日志：
2020-02-11 15:32:39.293 INFO 48395 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2020-02-11 15:32:39.482 INFO 48395 --- [ main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@7ff95560: startup date [Tue Feb 11 15:32:37 CST 2020]; root of context hierarchy
2020-02-11 15:32:39.568 INFO 48395 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/users/{id}],methods=[GET]}" onto public com.didispace.chapter26.User com.didispace.chapter26.UserController.getUser(java.lang.Long)
2020-02-11 15:32:39.569 INFO 48395 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/users/{id}],methods=[PUT]}" onto public java.lang.String com.didispace.chapter26.UserController.putUser(java.lang.Long,com.didispace.chapter26.User)
2020-02-11 15:32:39.570 INFO 48395 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/users/],methods=[GET]}" onto public java.util.List com.didispace.chapter26.UserController.getUserList()
2020-02-11 15:32:39.570 INFO 48395 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/users/],methods=[POST]}" onto public java.lang.String com.didispace.chapter26.UserController.postUser(com.didispace.chapter26.User)
2020-02-11 15:32:39.570 INFO 48395 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/users/{id}],methods=[DELETE]}" onto public java.lang.String com.didispace.chapter26.UserController.deleteUser(java.lang.Long)
2020-02-11 15:32:39.573 INFO 48395 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity> org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2020-02-11 15:32:39.573 INFO 48395 --- [ main] 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)
2020-02-11 15:32:39.590 INFO 48395 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2020-02-11 15:32:39.590 INFO 48395 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
這些日志接口信息是由org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping類在啟動的時候，通過掃描Spring MVC的@Controller、@RequestMapping等注解去發現應用提供的所有接口信息。然后在日志中打印，以方便開發者排查關于接口相關的啟動是否正確。
但是，足夠仔細的開發者可能已經發現，從Spring Boot 2.1.0版本開始，就不再打印這些信息了，完整的啟動日志變的非常少，以Spring Boot 2.x基礎教程：構建RESTful API與單元測試一文的例子為例，可以看到輸入內容如下：
2020-02-11 15:34:15.280 INFO 48784 --- [main] c.d.chapter26.Chapter26Application : Starting Chapter26Application on zhaiyongchaodeMacBook-Pro.local with PID 48784 (/Users/zhaiyongchao/Documents/git/github/SpringBoot-Learning/2.1.x/chapter2-6/target/classes started by zhaiyongchao in /Users/zhaiyongchao/Documents/git/github/SpringBoot-Learning/2.1.x)
2020-02-11 15:34:15.283 INFO 48784 --- [main] c.d.chapter26.Chapter26Application : No active profile set, falling back to default profiles: default
2020-02-11 15:34:16.556 INFO 48784 --- [main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2020-02-11 15:34:16.587 INFO 48784 --- [main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2020-02-11 15:34:16.588 INFO 48784 --- [main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.16]
2020-02-11 15:34:16.596 INFO 48784 --- [main] o.a.catalina.core.AprLifecycleListener : The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: [/Users/zhaiyongchao/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.]
2020-02-11 15:34:16.702 INFO 48784 --- [main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2020-02-11 15:34:16.702 INFO 48784 --- [main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1377 ms
2020-02-11 15:34:16.954 INFO 48784 --- [main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2020-02-11 15:34:17.187 INFO 48784 --- [main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2020-02-11 15:34:17.192 INFO 48784 --- [main] c.d.chapter26.Chapter26Application : Started Chapter26Application in 2.238 seconds (JVM running for 2.764)
找回日志中請求路徑列表
為什么在Spring Boot 2.1.x版本中不再打印請求路徑列表呢？
主要是由于從該版本開始，將這些日志的打印級別做了調整：從原來的INFO調整為TRACE。所以，當我們希望在應用啟動的時候打印這些信息的話，只需要在配置文件增增加對RequestMappingHandlerMapping類的打印級別設置即可，比如在application.properties中增加下面這行配置：
logging.level.org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping=trace
在增加了上面的配置之后重啟應用，便可以看到如下的日志打?。?/span>
2020-02-11 15:36:09.787 TRACE 49215 --- [main] s.w.s.m.m.a.RequestMappingHandlerMapping :
c.d.c.UserController:
{PUT /users/{id}}: putUser(Long,User)
{GET /users/{id}}: getUser(Long)
{POST /users/}: postUser(User)
{GET /users/}: getUserList()
{DELETE /users/{id}}: deleteUser(Long)
2020-02-11 15:36:09.791 TRACE 49215 --- [main] s.w.s.m.m.a.RequestMappingHandlerMapping :
o.s.b.a.w.s.e.BasicErrorController:
{ /error}: error(HttpServletRequest)
{ /error, produces [text/html]}: errorHtml(HttpServletRequest,HttpServletResponse)
2020-02-11 15:36:09.793 DEBUG 49215 --- [main] s.w.s.m.m.a.RequestMappingHandlerMapping : 7 mappings in 'requestMappingHandlerMapping'
可以看到在2.1.x版本之后，除了調整了日志級別之外，對于打印內容也做了調整。現在的打印內容根據接口創建的Controller類做了分類打印，這樣更有助于開發者根據自己編寫的Controller來查找初始化了那些HTTP接口。
注：本文轉載自“程序猿DD”，如有侵權，請聯系刪除！
