filter filter in servlet

The main role of the filter

• 1. Any system or website must determine whether the user is logged in.
• 2 , the network chat system or forum, the function is to filter the illegal text.
• 3. Unified solution coding

 

How to create a filter:

• 1. Generate a common class and implement the Filter interface (javax.servlet.Filter;) .
• 2. Rewrite the three methods in the interface: init , doFilter , destroy .
• 3 , and then configure the filter in web.xml .