e1036. getting and setting initialization parameters for a servlet.txt

这里面包含了一百多个JAVA源文件

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.