What does the servlet <load-on-startup> value signify

user_98044 0
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I am getting a bit confused here. In our application we are having a few servlets defined. Here is the excerpt from the web.xml for one of the servlets:

<servlet>
    <servlet-name>AxisServlet</servlet-name>
    <display-name>Apache-Axis Servlet</display-name>
    <servlet-class>com.foo.framework.axis2.http.FrameworkServlet</servlet-class>
    <load-on-startup>0</load-on-startup>
</servlet>

As per my understanding the value for the <load-on-startup> has to be a positive integer in order for it to get loaded automatically. I looked up on google but the responses I came across only added to my confusion.

jakarta-ee web.xml servlets
11 Answers

Resin 3.0 documents this behavior:

load-on-startup can specify an (optional) integer value. If the value is 0 or greater, it indicates an order for servlets to be loaded, servlets with higher numbers get loaded after servlets with lower numbers.

The JSP 3.1 spec (JSR 340) says this on page 14-160:

The element load-on-startup indicates that this servlet should be loaded (instantiated and have its init() called) on the startup of the Web application. The element content of this element must be an integer indicating the order in which the servlet should be loaded. If the value is a negative integer, or the element is not present, the container is free to load the servlet whenever it chooses. If the value is a positive integer or 0, the container must load and initialize the servlet as the application is deployed. The container must guarantee that servlets marked with lower integers are loaded before servlets marked with higher integers. The container may choose the order of loading of servlets with the same load-on-startup value.

You probably want to check not only the JSR, but also the documentation for your web container. There may be differences

user_577520

It indicates that the servlet won't be started until a request tries to access it.

If load-on-startup is greater than or equal to zero then when the container starts it will start that servlet in ascending order of the load on startup value you put there (ie 0, 1 then 2 then 5 then 10 and so on).

cletus_183930

Servlet Life Cycle

The lifecycle of a servlet is controlled by the container in which the servlet has been deployed. When a request is mapped to a servlet, the container performs the following steps.

  1. If an instance of the servlet does not exist, the web container:

    a. Loads the servlet class

    b. Creates an instance of the servlet class

    c. Initializes the servlet instance by calling the init method (initialization is covered in Creating and Initializing a Servlet)

  2. The container invokes the service method, passing request and response objects. Service methods are discussed in Writing Service Methods.

A 0 value on load-on-startup means that point 1 is executed when a request comes to that servlet. Other values means that point 1 is executed at container startup.

DirtyAffairs_275070

yes it can have same value....the reason for giving numbers to load-on-startup is to define a sequence for server to load all the servlet. servlet with 0 load-on-startup value will load first and servlet with value 1 will load after that.

if two servlets will have the same value for load-on-startup than it will be loaded how they are declared in the web.xml from top to bottom. the servlet which comes first in the web.xml will be loaded first and the other will be loaded after that.

user_5570340
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