Resolve error "org.springframework.beans.factory.BeanCreationException: Error creating bean with name Hello': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Method must not be null"

I think every Spring beginner will face this issue.Have no clues,Code seems like perfect.Tried all possible ways to resolve it? 

see below!

Reason: Its because of using different versions of the spring jars in the project.

Resolution:

 Clean the libraries/jars added to the project.Remove all the libraries from the class path.Then add the libraries into the project from the same version of Spring.

You can find the libraries in the Spring website  

http://www.springsource.org/download

Make sure that all the libraries added in the project are from the same spring version/release.

Stacktrace:

Nested in org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.beans.factory.config.PropertyPlaceholderConfigurer#0': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: Method must not be null:
java.lang.IllegalArgumentException: Method must not be null
    at org.springframework.util.Assert.notNull(Assert.java:112)
    at org.springframework.core.BridgeMethodResolver.findBridgedMethod(BridgeMethodResolver.java:63)
    at org.springframework.beans.GenericTypeAwarePropertyDescriptor.<init>(GenericTypeAwarePropertyDescriptor.java:58)
    at org.springframework.beans.CachedIntrospectionResults.<init>(CachedIntrospectionResults.java:250)
    at org.springframework.beans.CachedIntrospectionResults.forClass(CachedIntrospectionResults.java:144)
    at org.springframework.beans.BeanWrapperImpl.getCachedIntrospectionResults(BeanWrapperImpl.java:252)
    at org.springframework.beans.BeanWrapperImpl.getPropertyDescriptorInternal(BeanWrapperImpl.java:282)
    at org.springframework.beans.BeanWrapperImpl.isWritableProperty(BeanWrapperImpl.java:333)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1247)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
    at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:515)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:362)
    at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45)