Remove the source warning for JDK 8

[taojintianxia]

<java.version>1.8</java.version>

as set the java compiler version to 1.8, whenever compile the project by maven, will get the followings warnings :

[WARNING] 源值 8 已过时，将在未来发行版中删除
[WARNING] 目标值 8 已过时，将在未来发行版中删除
[WARNING] 要隐藏有关已过时选项的警告, 请使用 -Xlint:-options。

please fix this issue.