spring MVC - mapping error [duplicate]

问题:

This question already has an answer here:

• Why does Spring MVC respond with a 404 and report “No mapping found for HTTP request with URI […] in DispatcherServlet”? 6 answers

I found similar questions asked here but I tried those answers and here I am after spending a day. I dont know what is wrong here I am stuck with my first spring mvc application. If anyone can help me then that will be highly appreciated. I am getting error 404- Not found. Console error - "No mapping found for HTTP request with URI [/FirstSpringMVC/welcome] in DispatcherServlet with name 'mvc-dispatcher'"

Here is my entire code.

pom.xml

    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.thomsontech</groupId>
  <artifactId>FirstSpringMVC</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>FirstSpringMVC Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.8.RELEASE</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.springframework/spring-aop -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aop</artifactId>
        <version>4.3.8.RELEASE</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>4.3.8.RELEASE</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/javax.servlet/jstl -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

  </dependencies>
  <build>
    <finalName>FirstSpringMVC</finalName>
  </build>
</project>

web.xml

        <!DOCTYPE web-app PUBLIC
     "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
     "http://java.sun.com/dtd/web-app_2_3.dtd" >

    <web-app>
      <display-name>Archetype Created Web Application</display-name>

      <servlet>
        <servlet-name>mvc-dispatcher</servlet-name>
            <servlet-class>
                 org.springframework.web.servlet.DispatcherServlet
            </servlet-class>
      </servlet>
      <servlet-mapping>
        <servlet-name>mvc-dispatcher</servlet-name>
            <url-pattern>/</url-pattern>
      </servlet-mapping>
    </web-app>

mvc-dispatcher-servlet.xml

    <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd"> 

        <bean id="HandlerMapping" class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping" />

        <context:component-scan base-package="com.thomsontech.controller" />

        <bean id="viewResolver"
            class="org.springframework.web.servlet.view.InternalResourceViewResolver" >
            <property name="prefix">
                <value>/WEB-INF/</value>
            </property>
            <property name="suffix">
                <value>.jsp</value>
            </property>
        </bean>

    </beans>

HelloWorldController.java

    package com.thomsontech.controller;

    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.servlet.ModelAndView;

    @Controller
    public class HelloWorldController {

        @RequestMapping("/welcome")
        public ModelAndView helloWorld() {

            ModelAndView model = new ModelAndView("HelloWorldPage");
            model.addObject("msg", "hello world");

            return model;
        }
    }

HelloWorldPage.jsp

        <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
    <html>
    <body>
        <h1>Spring MVC Hello World Example</h1>

        <h2>${msg}</h2>
    </body>
    </html>

回答1:

Well, have done below changes to your code to fix the 404 issue.

@Controller
public class HelloWorldController {

    @RequestMapping(value = {"/welcome","/"}, method = RequestMethod.GET)
    public ModelAndView helloWorld() {

        ModelAndView model = new ModelAndView("HelloWorldPage");
        model.addObject("msg", "hello world");

        return model;
    }

}

It is almost same as yours except it answers to the requests received on root page("/"). I've just added it to directly test the homepage.

I don't know the reason, the combination of @Controller and <context:component-scan base-package="com.thomsontech.controller" /> weren't creating the helloWorldController bean. So, I had to explicitly create bean by adding <bean id="helloWorldController" class="com.thomsontech.controller.HelloWorldController"></bean> in mvc-dispatcher-servlet.xml file. I also removed <bean id="HandlerMapping" class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping"/> from the same file as I couldn't see that bean being used anywhere.

So, your final mvc-dispatcher-servlet.xml would be :

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <context:component-scan base-package="com.thomsontech.controller" />

    <bean id="helloWorldController" class="com.thomsontech.controller.HelloWorldController"></bean>

    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix">
            <value>/WEB-INF/</value>
        </property>
        <property name="suffix">
            <value>.jsp</value>
        </property>
    </bean>

</beans>

In your web.xml, have added <load-on-startup>1</load-on-startup> to </servlet> tag, so as to load mvc-dispatcher servlet on startup. Also, you will have to upgrade of web-app version 2.3 as you are using jstl. JSTL doesn't works only with 2.4+ versions. However, this shouldn't stop you from testing 404 issue. ${msg} in HelloWorldPage jsp will not render "hello world" string returned by the HelloWorldController controller.

Your final web.xml would be :

<web-app>
    <display-name>Archetype Created Web Application</display-name>
    <servlet>
        <servlet-name>mvc-dispatcher</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>mvc-dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

After making these changes, do a cleanup of tomcat/jetty work directory followed by maven clean install and then run this app on the server.

Hope this helps and good luck!!