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SpringBoot 项目中不管是在哪个类上使用 @EnableWebMvc 注解，都将导致所有URL访问时返回 404 错误；
看到一篇文章：“Spring4 @EnableWebMvc 纯注解启动”，但还没有在 Spring MVC 项目上尝试过。
另外参考文章：“解析@EnableWebMvc 、WebMvcConfigurationSupport和WebMvcConfigurationAdapter”中说的：
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在spring-boot+spring mvc 的项目中，有些时候我们需要自己配置一些项目的设置，就会涉及到这三个，那么，他们之间有什么关系呢？
首先，@EnableWebMvc=WebMvcConfigurationSupport，使用了@EnableWebMvc注解等于扩展了WebMvcConfigurationSupport但是没有重写任何方法。
所以有以下几种使用方式：
@EnableWebMvc+extends WebMvcConfigurationAdapter，在扩展的类中重写父类的方法即可，这种方式会屏蔽springboot的@EnableAutoConfiguration中的设置
extends WebMvcConfigurationSupport，在扩展的类中重写父类的方法即可，这种方式会屏蔽springboot的@EnableAutoConfiguration中的设置
extends WebMvcConfigurationAdapter，在扩展的类中重写父类的方法即可，这种方式依旧使用springboot的@EnableAutoConfiguration中的设置
具体哪种方法适合，看个人对于项目的需求和要把控的程度
在WebMvcConfigurationSupport（@EnableWebMvc）和@EnableAutoConfiguration这两种方式都有一些默认的设定
而WebMvcConfigurationAdapter则是一个abstract class
具体如何类内如何进行个性化的设置，可以参考以下文章：
Spring Boot：定制HTTP消息转换器
EnableWebMvc官方文档
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难道是因为我的项目中使用了“@EnableAutoConfiguration”，@EnableWebMvc和@EnableAutoConfiguration 这两种方式有冲突吗？
注释掉 @EnableAutoConfiguration ，使用 @EnableWebMvc，得到以下错误：
javax.servlet.ServletException: Could not resolve view with name 'loginback' in servlet with name 'dispatcherServlet'
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1266) ~[spring-webmvc-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1041) ~[spring-webmvc-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:984) ~[spring-webmvc-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) ~[spring-webmvc-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) ~[javax.servlet-api-3.1.0.jar:3.1.0]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) ~[javax.servlet-api-3.1.0.jar:3.1.0]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55) ~[spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:110) ~[spring-boot-actuator-1.5.9.RELEASE.jar:1.5.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:106) ~[spring-boot-actuator-1.5.9.RELEASE.jar:1.5.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.23.jar:8.5.23]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_121]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_121]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.23.jar:8.5.23]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]Could not resolve view with name 'loginback' in servlet with name 'dispatcherServlet'
感觉是视图模板没有找到，于是在入口类（带有 @SpringBootApplication 注解的类）中添加以下代码，指定视图模板位置：
/**
* 配置JSP视图解析器
* 如果没有配置视图解析器。Spring会使用BeanNameViewResolver，通过查找ID与逻辑视图名称匹配且实现了View接口的beans
*
* @return
*/
@Bean
public InternalResourceViewResolver setupViewResolver() {
InternalResourceViewResolver resolver = new InternalResourceViewResolver();
/** 设置视图路径的前缀 */
resolver.setPrefix("/WEB-INF/jsp/");
/** 设置视图路径的后缀 */
resolver.setSuffix(".jsp");
return resolver;
}再次重启项目，一切正常了。
总结
使用 @EnableWebMvc 注解，需要以编程的方式指定视图文件相关配置；
使用 @EnableAutoConfiguration 注解，会读取 application.properties 或 application.yml 文件中的配置。
