Security中如何在自定義過濾器(Filter)中注入Service方法？

Security中在自定義filter中注入Service方法

問題起源

最近做項目遇到一個問題：在spring security中自定義JwtLoginFilter繼承自UsernamePasswordAuthenticationFilter，進行登錄認證。在其中有一個我自己寫的構造函數，然後我想調用自己寫的Service來進行用戶名和密碼的驗證，所以就使用@Autowired的方法注入。但是在實際運行過程中卻遇到了這樣一個問題。

問題詳情

java.lang.RuntimeException: java.lang.NullPointerException
	at com.learn.wyg.filter.JwtLoginFilter.attemptAuthentication(JwtLoginFilter.java:89) ~[classes/:na]
	at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:212) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:92) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:77) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178) ~[spring-security-web-5.2.2.RELEASE.jar:5.2.2.RELEASE]
	at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:358) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:271) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1594) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_241]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_241]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.33.jar:9.0.33]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_241]
Caused by: java.lang.NullPointerException: null
	at com.learn.wyg.filter.JwtLoginFilter.attemptAuthentication(JwtLoginFilter.java:63) ~[classes/:na]
	... 47 common frames omitted

後來我以爲是mybatis調用出了問題，然後就去測試mybatis實現的service方法，它實際是可以運行成功的，我就發現這不是問題的根源所在。

解決辦法

1、上面說了，我在自己實現的JwtLoginFilter中實現了一個自己的構造函數，這就是問題的關鍵所在。
由於我自己寫了一個構造函數，所以在JwtLoginFilter進行初始化的時候還沒有注入這個service，所以就會發現無法調用該方法，在運行過程中如果沒有執行調用則不會報錯，如果執行了就是一個大坑。
所以我就把這個service放在了構造函數裏面，讓它隨着構造函數一起初始化。然後就解決了這個問題。
2、當然還有其他的解決方法，那就是不寫構造函數，只重寫他的方法，這樣就不會因爲初始化構造函數而沒有注入service，造成service無法調用。

參考：對我有啓發的一個CSDN論壇中的問題