1.首先在xml文件中配置初始化参数
<context-param>
<param-name>url</param-name>
<param-value>jdbc:mysql://localhost:3306/mybatis</param-value>
</context-param>
2.在类中通过ServletContext的getInitParameter(“url”)方法获取初始化参数
ServletContext context = this.getServletContext();
String url = context.getInitParameter("url");
resp.getWriter().print(url);
3.在xml中注册当前类
<servlet>
<servlet-name>GetP</servlet-name>
<servlet-class>com.***.******</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>GetP</servlet-name>
<url-pattern>/getp</url-pattern>
</servlet-mapping>
4.启动tomcat进行测试