This usually caused by outdated Java client.
Please check the Java version, web framework version, and OS version used to connect. Please make sure you are not using outdated version, and stay updated.
For example if your versions are Java version 7, web framework version Spring 3.1, and OS version windows 7.
Please update the Java version, because version 7 is no longer officially supported by Oracle (https://java.com/en/download/faq/java_7.xml). Other than that, Spring and OS version is also outdated. Using outdated platforms make your system vulnerable to security threats, which is not suitable environment for handling payments.