记录一下，简单的小错误，报错log，如下：

2022-05-11 21:13:08.188 ERROR 18568 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Circular view path [index]: would dispatch back to the current handler URL [/index] again. Check your ViewResolver setup! (Hint: This may be the result of an unspecified view, due to default view name generation.)] with root cause

javax.servlet.ServletException: Circular view path [index]: would dispatch back to the current handler URL [/index] again. Check your ViewResolver setup! (Hint: This may be the result of an unspecified view, due to default view name generation.)
	at org.springframework.web.servlet.view.InternalResourceView.prepareForRendering(InternalResourceView.java:210) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:148) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1401) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1145) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1084) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:655) ~[tomcat-embed-core-9.0.62.jar:4.0.FR]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.19.jar:5.3.19]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.62.jar:4.0.FR]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.19.jar:5.3.19]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.19.jar:5.3.19]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.19.jar:5.3.19]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.19.jar:5.3.19]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.19.jar:5.3.19]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.19.jar:5.3.19]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) ~[tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:890) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1743) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.62.jar:9.0.62]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_311]

解决办法：

package com.trf.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * @author 小小唐
 * @Date 2022/5/11-星期三-0:57
 */
@Controller
public class MyController {
    @RequestMapping({"/","/index"})
    public String toIndex(Model model){
        model.addAttribute("msg","hello,shiro");
        return "index";
    }
}

package com.trf.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * @author 小小唐
 * @Date 2022/5/11-星期三-0:57
 */
@Controller
public class MyController {
    @RequestMapping({"/","/index"})
    @ResponseBody
    public String toIndex(Model model){
        model.addAttribute("msg","hello,shiro");
        return "index";
    }
}

原因是，我们没有添加@ResponseBody注解对我们的字符进行转换从而使得我们的页面报500错误

添加之后，运行成功！