java.lang.ClassNotFoundException: org.springframework.core.io.Resource

There is a version conflict between jar/dependency please check all version of spring is same. if you use maven remove version of dependency and use Spring.io dependency.it handle version conflict. Add this in your pom

 <dependency>
            <groupId>io.spring.platform</groupId>
            <artifactId>platform-bom</artifactId>
            <version>2.0.1.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
  </dependency>

Right-Click on your project -> Properties -> Deployment Assembly.

On the Left-hand panel Click 'Add' and add the 'Project and External Dependencies'.

'Project and External Dependencies' will have all the spring related jars deployed along with your application

Make sure, following jar file included in your class path and lib folder.

spring-core-3.0.5.RELEASE.jar

if you are using maven, make sure you have included dependency for spring-core-3xxxxx.jar file

<dependency>
 <groupId>org.springframework</groupId>
 <artifactId>spring-core</artifactId>
 <version>${org.springframework.version}</version>
</dependency>

Note : Replace ${org.springframework.version} with version number.

org.springframework.core.io.Resource is part of spring-core-<version>.jar

But this lib is already in your lib folder. So I guess it is just a Deployment Problem. -- Try to clean your server and redeploy your application.