java - mybatis 查询慢 然后结果就出不来了，一般超过3s就不行了

Answer 1

First extract the sql statement and run it directly in the database to see if the sql statement query is slow.
If so, you need to optimize the sql and establish relevant indexes;
If not, check the number of connections configuration of tomcat;

Answer 2

LZ, are you sure whether it is caused by slow SQL query or your JAVA business code?

Use EXPLAIN analysis for slow query SQL analysis
Business code can be tracked by adding log printing date and other methods