Allocate exception for servlet - Web Programming in JAVA

Question

I am very new to JAVA but I have some experience in web programming. I am creating simple jsp pages and using @RequestMapping for page views. But I am facing an exception, I have googled BUT nothing found goods which solved my problem. Here is the exception with full stack trace :

SEVERE: Allocate exception for servlet [WebAppGraph] java.lang.ClassNotFoundException: com.WebAppGraph.app at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1269) at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1104) at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:508) at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:489) at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:119) at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1041) at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:770) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:133) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:625) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:498) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:796) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1372) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745)

A sample of my code :

indexController.java

package com.WebAppGraph.app;

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

@Controller
public class indexController {

    @RequestMapping("/")
    public String home() {
        return "index.jsp";
    }

    @RequestMapping("/test.html")
    public String test() {
        return "test.jsp";
    }

}

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>WebAppGraph</servlet-name>
        <servlet-class>
            com.WebAppGraph.app
        </servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>WebAppGraph</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

WebAppGraph-servlet.xml

<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    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
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

    <context:component-scan base-package="com.WebAppGraph.app"></context:component-scan>

</beans>

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.WebAppGraph.app</groupId>
    <artifactId>WebAppGraph</artifactId>
    <packaging>war</packaging>
    <version>1.0</version>
    <name>WebAppGraph 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-webmvc -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>4.3.10.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.0.1</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>
    <build>
        <finalName>WebAppGraph</finalName>
    </build>
</project>

File Structures:

When I try to run my program it opens the index.jsp page, BUT the second page only open when I write localhost:9000/WebAppGraph/test.jsp BUT when I write localhost:9000/WebAppGraph/test.html it doesn't show me the test.jsp and instead shows me the exception I posted above. Any idea how to solve this ?

Answer 1

For your servlet mapping you can do something like this in web.xml:

<servlet>
    <servlet-name>WebAppGraph</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/WebAppGraph-servlet.xml</param-value>
    </init-param>
</servlet>

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet-mapping>
    <servlet-name>WebAppGraph</servlet-name>
    <url-pattern>*.html</url-pattern>
    <url-pattern>/</url-pattern>
</servlet-mapping>

Answer 2

You need to try a spring-mvc hello world tutorial. Your class name is com.WebAppGraph.app.indexController not com.WebAppGraph.app and if you are going to put it in the web.xml <Servlet> tag it needs to extend javax.servlet.Servlet. What you have is a spring bean annotated as a spring MVC controller not a Servlet. You want to put the spring MVC dispatch servlet in the XML:

<servlet>
    <servlet-name>Controller</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>Controller</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

And then inject the Controller annotation with a context scan in your spring xml (which you are already doing)

Answer 3

Change the value of the servlet-class tag in web.xml file. You can change as the following (As most of us use DispatcherServlet as servlet-class):

<servlet>
    <servlet-name>WebAppGraph</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

An additional thing, If you use default configuration of spring, then you need to remove .jsp from the returned string of controller function as like:

@RequestMapping("/")
public String home() {
    return "index";
}

@RequestMapping("/test.html")
public String test() {
    return "test";
}