The Java Developers Almanac 1.4


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Home > List of Packages > javax.servlet  [11 examples]

e1036. Getting and Setting Initialization Parameters for a Servlet

The servlet container supports the ability to store startup and configuration information for a servlet. After the container instantiates the servlet, it makes this information available to the servlet instance. This example demonstrates a servlet that retrieves some initialization parameters in its init() method:
    // See also e1035 The Quintessential Servlet
    
    // This method is called by the servlet container just before this servlet
    // is put into service.
    public void init() throws ServletException {
        getServletContext().log("getinit init");
        // Get the value of an initialization parameter
        String value = getServletConfig().getInitParameter("param1");
    
        // Get all available intialization parameters
        java.util.Enumeration enum = getServletConfig().getInitParameterNames();
        for (; enum.hasMoreElements(); ) {
            // Get the name of the init parameter
            String name = (String)enum.nextElement();
    
            // Get the value of the init parameter
            value = getServletConfig().getInitParameter(name);
        }
    
    
        // The int parameters can also be retrieved using the servlet context
        value = getServletContext().getInitParameter("param1");
    }
The initialization parameters for the servlet are specified in the deployment descriptor (i.e., web.xml file). Here is an example of a deployment descriptor that specifies two initialization parameters:
    <web-app>
        <servlet>
            <servlet-name>MyServletName</servlet-name>
            <servlet-class>com.mycompany.MyServlet</servlet-class>
    
            <init-param>
                <param-name> param1 </param-name>
                <param-value> value1 </param-value>
            </init-param>
            <init-param>
                <param-name> param2 </param-name>
                <param-value> value2 </param-value>
            </init-param>
            ...
        </servlet>
        ...
    </web-app>
Note that the leading and trailing space around the parameter value is trimmed.

 Related Examples
e1035. The Quintessential Servlet
e1037. Returning an Image in a Servlet
e1038. Saving Data in a Servlet
e1039. Logging a Message in a Servlet


© 2002 Addison-Wesley.