v2.13.0: upgrade to java 8 and dependencies

Note

from 2.13.x upgrade to Java 8 🚀
If you need Java 6 support, use version 2.12.x

This version contains no new features or bug fix but upgradation of java 8 and dependencies/plugins.

Change Log

• upgrade source to java 8
• upgrade dependencies/plugins
  • resolved the problem caused by low version javassist(#388 by @howardliu-cn)

Java API Doc

https://alibaba.github.io/transmittable-thread-local/apidocs/2.13.0/index.html

Maven dependency

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>transmittable-thread-local</artifactId>
    <version>2.13.0</version>
</dependency>