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web.xml related configuration
Configure the default page, this forwarding mechanism will prevent you from seeing URL changes:
By default, web.xml is configured as a .jsp or .html file with index and default as the filename prefix. So as long as there is a file in your project directory with the same name as the file configured in the above figure, then when you access the web project, you will access this file by default.
For example, I create an index.jsp in the web project directory, and then access the web project on the browser:
Browser access:
As shown in the figure, you can see that the URL address has not changed, but it has accessed this index.jsp. Usually, when we visit a website domain name, we also visit such a default page, but the URL will not change. , which is what makes this forwarding mechanism special.
Configure the page to jump to after an http error status code occurs:
When a 404 error occurs, it jumps to the 404.html file in the root directory.
Configure the expiration time and ID name of the session:
ServletContext object initialization parameter configuration:
Multiple <context-param> tags can be configured, <param-name> the name of the configuration parameter, <param-value> the value of the configuration parameter, these two tags need to be configured within the <context-param> tag.