what is the relationship between tomcat and jdk and web application?

Question

Here is the question I asked recently: org.apache.commons.codec.digest.Md5Crypt.md5Crypt function. exception occured under linux, but fine under windows

Although finally, I resolved it, but I'm still confused. What made this happen?

My jdk was 1.7, my tomcat was 7, my web application was compiled by jdk 1.7, version of commons-codec.jar was 1.10, then an exception was thrown.

java.lang.IllegalAccessError: tried to access method org.apache.commons.codec.digest.DigestUtils.getMd5Digest()Ljava/security/MessageDigest; from class org.apache.commons.codec.digest.Md5Crypt

When I changed my tomcat from 7 to 8, it worked fine. Why? What does tomcat do to applications?

Answer 1

I strongly suggest that the problem was not resolved because you used tomcat 8 instead of 7, but it was resolved because you had a conflict in your java build path meaning that you had two different versions of the commons-codec JAR at run time probably had one in your tomcat 7 lib folder.