這可能是你的攔截器類
這可能是你的配置類，用於加載攔截器
一切看起來絲毫沒有問題
不過一運行起來就報空指針異常
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1013) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:461) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:384) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:394) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:253) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:348) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:173) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.17.jar:9.0.17]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_231]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_231]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.17.jar:9.0.17]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_231]
Caused by: java.lang.NullPointerException: null
at com.example.springdata.filter.LoginInterceptor.preHandle(LoginInterceptor.java:25) ~[classes/:na]
at org.springframework.web.servlet.HandlerExecutionChain.applyPreHandle(HandlerExecutionChain.java:136) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1033) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
... 26 common frames omitted
這是爲什麼呢
原來攔截器加載的時間點在springcontext之前
所以在攔截器中注入自然爲null
因此，我們必須在配置類加載的同時加載攔截器
我們這樣做
我們在springcontext時就把攔截器加入io容器
記得，把攔截器類的@Component註解去掉
不然會報以下錯誤
Description:
The bean 'loginInterceptor', defined in class path resource [com/example/springdata/config/WebConfigurer.class], could not be registered. A bean with that name has already been defined in file [C:\Users\kingback\IdeaProjects\spring-data\target\classes\com\example\springdata\filter\LoginInterceptor.class] and overriding is disabled.
Action:
Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true
Process finished with exit code 1
OK，現在可以了
覺得有用的話點個贊把！