为什么 Spring MVC 响应一个404并报告“在 DispatcherServlet 中找不到带 URI [ ... ]的 HTTP 请求映射”?

我正在编写一个部署在 Tomcat 上的 Spring MVC 应用程序

public class Application extends AbstractAnnotationConfigDispatcherServletInitializer {
protected Class<?>[] getRootConfigClasses() {
return new Class<?>[] { };
}
protected Class<?>[] getServletConfigClasses() {
return new Class<?>[] { SpringServletConfig.class };
}
protected String[] getServletMappings() {
return new String[] { "/*" };
}
}

SpringServletConfig在哪里

@Configuration
@ComponentScan("com.example.controllers")
@EnableWebMvc
public class SpringServletConfig {
@Bean
public InternalResourceViewResolver resolver() {
InternalResourceViewResolver vr = new InternalResourceViewResolver();
vr.setPrefix("/WEB-INF/jsps/");
vr.setSuffix(".jsp");
return vr;
}
}

最后,在包 com.example.controllers中有一个 @Controller

@Controller
public class ExampleController {
@RequestMapping(path = "/home", method = RequestMethod.GET)
public String example() {
return "index";
}
}

我的应用程序的上下文名称是 Example

http://localhost:8080/Example/home

应用程序使用 HTTP Status 404进行响应,并记录以下内容

WARN  o.s.web.servlet.PageNotFound - No mapping found for HTTP request with URI `[/Example/WEB-INF/jsps/index.jsp]` in `DispatcherServlet` with name 'dispatcher'

我在 /WEB-INF/jsps/index.jsp有一个 JSP 资源,我希望 Spring MVC 使用我的控制器来处理请求并转发到 JSP,那么为什么它响应一个404?


这意味着对于有关此警告消息的问题,这是一个规范的帖子。

95800 次浏览

Your standard Spring MVC application will serve all requests through a DispatcherServlet that you've registered with your Servlet container.

The DispatcherServlet looks at its ApplicationContext and, if available, the ApplicationContext registered with a ContextLoaderListener for special beans it needs to setup its request serving logic. These beans are described in the documentation.

Arguably the most important, beans of type HandlerMapping map

incoming requests to handlers and a list of pre- and post-processors (handler interceptors) based on some criteria the details of which vary by HandlerMapping implementation. The most popular implementation supports annotated controllers but other implementations exists as well.

The javadoc of HandlerMapping further describes how implementations must behave.

The DispatcherServlet finds all beans of this type and registers them in some order (can be customized). While serving a request, the DispatcherServlet loops through these HandlerMapping objects and tests each of them with getHandler to find one that can handle the incoming request, represented as the standard HttpServletRequest. As of 4.3.x, if it doesn't find any, it logs the warning that you see

No mapping found for HTTP request with URI [/some/path] in DispatcherServlet with name SomeName

and either throws a NoHandlerFoundException or immediately commits the response with a 404 Not Found status code.

Why didn't the DispatcherServlet find a HandlerMapping that could handle my request?

The most common HandlerMapping implementation is RequestMappingHandlerMapping, which handles registering @Controller beans as handlers (really their @RequestMapping annotated methods). You can either declare a bean of this type yourself (with @Bean or <bean> or other mechanism) or you can use the built-in options. These are:

  1. Annotate your @Configuration class with @EnableWebMvc.
  2. Declare a <mvc:annotation-driven /> member in your XML configuration.

As the link above describes, both of these will register a RequestMappingHandlerMapping bean (and a bunch of other stuff). However, a HandlerMapping isn't very useful without a handler. RequestMappingHandlerMapping expects some @Controller beans so you need to declare those too, through @Bean methods in a Java configuration or <bean> declarations in an XML configuration or through component scanning of @Controller annotated classes in either. Make sure these beans are present.

If you're getting the warning message and a 404 and you've configured all of the above correctly, then you're sending your request to the wrong URI, one that isn't handled by a detected @RequestMapping annotated handler method.

The spring-webmvc library offers other built-in HandlerMapping implementations. For example, BeanNameUrlHandlerMapping maps

from URLs to beans with names that start with a slash ("/")

and you can always write your own. Obviously, you'll have to make sure the request you're sending matches at least one of the registered HandlerMapping object's handlers.

If you don't implicitly or explicitly register any HandlerMapping beans (or if detectAllHandlerMappings is true), the DispatcherServlet registers some detectAllHandlerMappings0. These are defined in detectAllHandlerMappings1 in the same package as the DispatcherServlet class. They are BeanNameUrlHandlerMapping and detectAllHandlerMappings2 (which is similar to RequestMappingHandlerMapping but deprecated).

Debugging

Spring MVC will log handlers registered through RequestMappingHandlerMapping. For example, a @Controller like

@Controller
public class ExampleController {
@RequestMapping(path = "/example", method = RequestMethod.GET, headers = "X-Custom")
public String example() {
return "example-view-name";
}
}

will log the following at INFO level

Mapped "{[/example],methods=[GET],headers=[X-Custom]}" onto public java.lang.String com.spring.servlet.ExampleController.example()

This describes the mapping registered. When you see the warning that no handler was found, compare the URI in the message to the mapping listed here. All the restrictions specified in the @RequestMapping must match for Spring MVC to select the handler.

Other HandlerMapping implementations log their own statements that should hint to their mappings and their corresponding handlers.

Similarly, enable Spring logging at DEBUG level to see which beans Spring registers. It should report which annotated classes it finds, which packages it scans, and which beans it initializes. If the ones you expected aren't present, then review your ApplicationContext configuration.

Other common mistakes

A DispatcherServlet is just a typical Java EE Servlet. You register it with your typical <web.xml> <servlet-class> and <servlet-mapping> declaration, or directly through ServletContext#addServlet in a WebApplicationInitializer, or with whatever mechanism Spring boot uses. As such, you must rely on the Servlet0 logic specified in the Servlet1, see Chapter 12. See also

With that in mind, a common mistake is to register the DispatcherServlet with a url mapping of /*, returning a view name from a @RequestMapping handler method, and expecting a JSP to be rendered. For example, consider a handler method like

@RequestMapping(path = "/example", method = RequestMethod.GET)
public String example() {
return "example-view-name";
}

with an InternalResourceViewResolver

@Bean
public InternalResourceViewResolver resolver() {
InternalResourceViewResolver vr = new InternalResourceViewResolver();
vr.setPrefix("/WEB-INF/jsps/");
vr.setSuffix(".jsp");
return vr;
}

you might expect the request to be forwarded to a JSP resource at the path /WEB-INF/jsps/example-view-name.jsp. This won't happen. Instead, assuming a context name of Example, the DisaptcherServlet will report

No mapping found for HTTP request with URI [/Example/WEB-INF/jsps/example-view-name.jsp] in DispatcherServlet with name 'dispatcher'

Because the DispatcherServlet is mapped to /* and /* matches everything (except exact matches, which have higher priority), the DispatcherServlet would be chosen to handle the forward from the JstlView (returned by the InternalResourceViewResolver). In almost every case, the DispatcherServlet will not be configured to handle such a request.

Instead, in this simplistic case, you should register the DispatcherServlet to /, marking it as the default servlet. The default servlet is the last match for a request. This will allow your typical servlet container to chose an internal Servlet implementation, mapped to *.jsp, to handle the JSP resource (for example, Tomcat has JspServlet), before trying with the default servlet.

That's what you're seeing in your example.

I came across another reason for the same error. This could also be due to the class files not generated for your controller.java file. As a result of which the the dispatcher servlet mentioned in web.xml is unable to map it to the appropriate method in the controller class.

@Controller
Class Controller{
@RequestMapping(value="/abc.html")//abc is the requesting page
public void method()
{.....}
}

In eclipse under Project->select clean ->Build Project.Do give a check if the class file has been generated for the controller file under builds in your workspace.

I resolved my issue when in addition to described before:`

@Bean
public InternalResourceViewResolver resolver() {
InternalResourceViewResolver vr = new InternalResourceViewResolver();
vr.setPrefix("/WEB-INF/jsps/");
vr.setSuffix(".jsp");
return vr;
}

added tomcat-embed-jasper:

<dependency>
<groupId>org.apache.tomcat.embed</groupId>
<artifactId>tomcat-embed-jasper</artifactId>
<scope>provided</scope>
</dependency>

` from: JSP file not rendering in Spring Boot web application

In my case, I was following the Interceptors Spring documentation for version 5.1.2 (while using Spring Boot v2.0.4.RELEASE) and the WebConfig class had the annotation @EnableWebMvc, which seemed to be conflicting with something else in my application that was preventing my static assets from being resolved correctly (i.e. no CSS or JS files were being returned to the client).

After trying a lot of different things, I tried removing the @EnableWebMvc and it worked!

Edit: Here's the reference documentation that says you should remove the @EnableWebMvc annotation

Apparently in my case at least, I'm already configuring my Spring application (although not by using web.xml or any other static file, it's definitely programmatically), so it was a conflict there.

For me, I found that my target classes were generated in a folder pattern not same as source. This is possibly in eclipse I add folders for containing my controllers and not add them as packages. So I ended up defining incorrect path in spring config.

My target class was generating classes under app and I was referring to com.happy.app

<context:annotation-config />
<context:component-scan
base-package="com.happy.app"></context:component-scan>

I added packages (not folders) for com.happy.app and moved the files from folders to packages in eclipse and it resolved the issue.

Clean your server. Maybe delete the server and add the project once again and Run.

  1. Stop the Tomcat server

  2. Right click the server and select "Clean"

  3. Right click server again and select "Clean Tomcat Work Directory"

In my case, I was playing around with import of secondary java config files into a main java config file. While making secondary config files, I had changed the name of the main config class, but I had failed to update the name in web.xml. So, every time that I had restarted my tomcat server, I was not seeing mapping handlers noted in the Eclipse IDE console, and when I tried to navigate to my home page I was seeing this error:

Nov 1, 2019 11:00:01 PM org.springframework.web.servlet.PageNotFound noHandlerFound WARNING: No mapping found for HTTP request with URI [/webapp/home/index] in DispatcherServlet with name 'dispatcher'

The fix was to update the web.xml file so that the old name "WebConfig" would be instead "MainConfig", simply renaming it to reflect the latest name of the main java config file (where "MainConfig" is arbitrary and the words "Web" and "Main" used here are not a syntax requirement). MainConfig was important, because it was the file that did the component scan for "WebController", my spring mvc controller class that handles my web requests.

@ComponentScan(basePackageClasses={WebController.class})

web.xml had this:

<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>
com.lionheart.fourthed.config.WebConfig
</param-value>
</init-param>

web.xml file now has:

<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>
com.lionheart.fourthed.config.MainConfig
</param-value>
</init-param>

Now I am seeing the mapping in the console window:

INFO: Mapped "{[/home/index],methods=[GET]}" onto public org.springframework.web.servlet.ModelAndView com.lionheart.fourthed.controller.WebController.gotoIndex()

And my web page is loading again.

I had same problem as **No mapping found for HTTP request with URI [/some/path] in DispatcherServlet with name SomeName**

After I analyzed for 2 to 4 days I found out the root cause. Class files was not generated after I run the project. I clicked the project tab.

Project-->CloseProject-->OpenProject-->Clean-->Build project

Class files for source code have been generated. It solved my problem. To check whether class files have been generated or not, Please check the Build folder in your project folder.

Try to amend your code with the following change on your config file. Java config is used instead of application.properties. Do not forget to enable configuration in configureDefaultServletHandling method.

WebMvcConfigurerAdapter class is deprecated, so we use WebMvcConfigurer interface.

@Configuration
@EnableWebMvc
@ComponentScan
public class WebConfig implements WebMvcConfigurer {


@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
registry.jsp("/WEB-INF/views/", ".jsp");
}


@Override
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
configurer.enable();
}
}

I use gradle, your should have the following dependencies in pom.xml:

dependencies {


compile group: 'org.springframework.boot', name: 'spring-boot-starter-web', version: '2.3.0.RELEASE'
compile group: 'org.apache.tomcat.embed', name: 'tomcat-embed-jasper', version: '9.0.35'
}

So the problem can be as simple as an additional space in the path of the project. Make sure that there is no space in the path which took me quite some time to solve.

In my case, I had created Config.java (class) and also config.xml and mapping was done partially in both of them. And since config.java uses @Configuration annotation , it was considered priority. And was not considering config.xml. If anyone gets in trouble like this , just delete config.java with annotation and try to keep config.xml , it works fine.

For me, the issue was hidden in the web.xml file.

Inside the servlet tag, you'll find:

<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/todo-servlet.xml</param-value>
</init-param>

Make sure that in the <param-value> you have kept the correct location of the dispatcher servlet (aka Front Controller).

I had kept an incorrect location, hence I was able to view the homepage but all other pages were giving HTTP 404 error.

In my case using a tutorial for SpringBoot(2.7.3) RestController, startup failed with java.lang.ClassNotFoundException: javax.validation.ParameterNameProvider

I thought that Spring REST does not use WebMvc so I removed 'spring-boot-starter-web' and that resolved the startup problem. However, POST requests failed with the '404 Not Found' issue described here and spent several hours experimenting with

  • server.servlet.context-path
  • @RestController vs @Controller etc, and
  • SecurityConfig options

I finally resolved the 404 issue by

  • restoring dependency 'spring-boot-starter-web'
  • adding dependency javax.validation validation-api and after undoing my 101 debug hacks it worked.

Very painful because even with root logger at DEBUG, there were no server-side logs to help.