java web-mysql cannot set up transactions (teacher Fang Lixun’s course)

java webmysql transaction

Dear masters, take a look at Teacher Fang’s javaWEB to set the isolation level. I am using 5.7.16. The command is as follows. Why can’t I change it? Is it a version problem?
I am still a novice. Please explain it to me. ,Thank you

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Whether the root account is logged in to MySQL

set session|global transaction isolation level read uncommitted;
Set the current session or global isolation level. If there is no restriction, set the isolation level for the next (unstarted) transaction;