Servlet – Load on startup

The element ‘load-on-startup‘ is used to load the servlet. The ‘void init()‘ method of servlet gets executed when the server gets started. The element content of ‘load-on-startup’ is Integer.

• if the integer is negative:  The container loads servlet at any time.
• if the integer is 0 or positive: The servlet marked with lower integers are loaded before servlets marked with higher integers.

How to add element load-on-startup while mapping servlet?

The load-on-startup is the sub-attribute of servlet attribute in web.xml. We do mapping of servlet in web.xml file.

In XML file

XML

<servlet>
    <servlet-name>servletOne</servlet-name>
    <servlet-class>com.gfg.ServletOne</servlet-class>
    <load-on-startup>0</load-on-startup>
</servlet>

<servlet>
    <servlet-name>servletTwo</servlet-name>
    <servlet-class>com.gfg.ServletTwo</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

ServletOne load first then ServletTwo get load.

Servlet Code

servletOne.java

Java

package com.gfg;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class ServletOne extends HttpServlet
{
    public void init()
    {
        // this method will get execute
        // when the server get start
        System.out.println("ServletOne got called");
    }
}

servletTwo.java

Java

package com.gfg;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class ServletTwo extends HttpServlet
{
    public void init()
    {
         // this method will get execute
        // when the server get start
        System.out.println("ServletTwo got called");
    }
}

Note: the above code is server-side code it will not work on online IDE (it is only for the clarification of the topic).