Welcome file and load on start up in detail

welcome-file-list tag gets define inside web.xml deployment descriptor file. This tag is responsible to load a file as soon as server starts up running.

Creation of Dynamic Web Project by default generates below web.xml having default content as mentioned in below screenshot.

Below is the sample webl.xml file having <welcome-file-list> tag:

<welcome-file-list> tag contains multiple <welcome-file> tags under which we can provide file with below extensions:

• index.html
• index.htm
• index.jsp

localhost:<port_number>/project_name will by default load index.jsp file as soon as server starts.
e.g. http://localhost:8082/ServletDemo/

load-on-startup

load-on-startup tag gets define inside web.xml deployment descriptor file. This tag is responsible to load a servlet as soon as server starts up running and call init() method at the same time.

Below is the sample webl.xml file having <load-on-startup> tag:

<servlet> tag contains <load-on-startup>, <servlet-name> and <servlet-class> tags.

We can define multiple <servlet> tags having unique values for <load-on-startup>, <servlet-name> and <servlet-class> tags.

<load-on-startup> tag can have positive, zero on negative value.

The servlet with the lowest integer value will get loaded first. For example, suppose we have three <load-on-startup> tags in web.xml with values of -3, 0 and 2, respectively. As mentioned earlier, the servlet having the lowest value of -3 will load first. After that, it will load 0 and then 2.