How to Modify jar File

# 1. unpack
mkdir <name> && cd <name>
unzip <name>.jar

# 2. add or modify class files

# 3.1 pack
jar cvf xxx.jar ./
# 3.2 pack with manifest file
jar cvfm xxx.jar ./META-INF/MANIFEST.MF ./

Reference

如何修改jar包中的内容