Question

一个web项目web.xml的配置中<context-param>配置是起什么作用的

Answer 1

在任一个 servlet 或 filter 中使用：
@Override
public void init(ServletConfig config) throws ServletException {
String paramValue1 = config.getServletContext().getInitParameter("ParamName1");
}

//or
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String paramValue1 = this.getServletContext().getInitParameter("ParamName1");
...
}
...
}
另外，配置在servlet中的init－param的用法为:
<servlet>
<servlet-name>A Servlet</servlet-name>
<servlet-class>com.controller.TestServlet</servlet-class>
<init-param>
<description>This is an init parameter example</description>
<param-name>InitParam1</param-name>
<param-value>init param value</param-value>
</init-param>
</servlet>

@Override
public void init(ServletConfig config) throws ServletException {
String initParam1 = config.getInitParameter("InitParam1");
}

//or
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String initParam1 = getServletConfig().getInitParameter("InitParam1");
...
}

比较一下：
getServletContext().getInitParameter();
getServletConfig().getInitParameter();

Answer 2

传递 参数！