在web.xml中我们配置的参数如下：

<servlet>
        <servlet-name>GetInitParameterServlet</servlet-name>
        <servlet-class>servlet.GetInitParameterServlet</servlet-class>

        <init-param>
            <param-name>username</param-name>
            <param-value>admin</param-value>
        </init-param>

        <init-param>
            <param-name>password</param-name>
            <param-value>123456</param-value>
        </init-param>
        
    </servlet>

    <servlet-mapping>
        <servlet-name>GetInitParameterServlet</servlet-name>
        <url-pattern>/servlet/GetInitParameterServlet</url-pattern>
    </servlet-mapping>

那么在Servlet中，我们如果需要获取初始化参数，就继承以下init方法，在这里调用如下方法进行获取：

@Override
    public void init() throws ServletException {
        String username = this.getInitParameter("username");
        String password = this.getInitParameter("password");
    }