A solution to issue 'Invalid byte 1 of 1-byte UTF-8 sequence'

I got an issue which informed me an error occurred when starting to Tomcat, below is the error message:

'Invalid byte 1 of 1-byte UTF-8 sequence' in admin.xml

刚开始我感觉很奇怪，因为xml文件的开始的第一句话是<?xml version="1.0" encoding="UTF-8"?>，字符编码明显是UTF-8的，为什么还报字符编码的问题呢？后来我用editplus打开xml文件，然后另存为，在保存的时候选择字符为UTF-8，结果问题解决了。