JAVA applications using JSSE (Java Secure Socket Extension) can’t connect to servers with self-signed or untrusted certificates by default. Maven for example is not able to download required dependencies from a nexus server, if that uses a self-signed certificate or the certificate authority is not recognized. If you try to connect to a server of that kind a security ValidatorException will be thrown:

Error transferring file: sun.security.validator.ValidatorException:
PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException:
unable to find valid certification path to requested target