1 java.lang.String getInitParameter(java.lang.String name)  根据参数名获取参数值
2 java.util.Enumeration getInitParameterNames()    获取所有参数
3 ServletContext getServletContext()     得到servlet上下文对象
4 java.lang.String getServletName()       得到servlet的名称

1  <servlet>
2     <servlet-name>ConfigDemo</servlet-name>
3     <servlet-class>gz.itcast.f_config.ConfigDemo</servlet-class>
4     <!-- 初始参数： 这些参数会在加载web应用的时候，封装到ServletConfig对象中 -->
5     <init-param>
6         <param-name>path</param-name>
7         <param-value>e:/b.txt</param-value>
8     </init-param>
9   </servlet>

public class ConfigDemo extends HttpServlet {/*** 以下两段代码GenericServlet已经写了，我们无需编写！！*//*private ServletConfig config;*//***  1）tomcat服务器把这些参数会在加载web应用的时候，封装到ServletConfig对象中 *  2）tomcat服务器调用init方法传入ServletConfig对象*//*@Overridepublic void init(ServletConfig config) throws ServletException {this.config = config;}*/public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {/*** 读取servlet的初始参数*/String path = this.getServletConfig().getInitParameter("path");File file = new File(path);//读取内容BufferedReader br = new BufferedReader(new FileReader(file));String str = null;while( (str=br.readLine())!=null ){System.out.println(str);}
}

java.lang.String getContextPath()   --得到当前web应用的路径java.lang.String getInitParameter(java.lang.String name)  --得到web应用的初始化参数
java.util.Enumeration getInitParameterNames()  void setAttribute(java.lang.String name, java.lang.Object object) --域对象有关的方法
java.lang.Object getAttribute(java.lang.String name)
void removeAttribute(java.lang.String name)  RequestDispatcher getRequestDispatcher(java.lang.String path)   --转发（类似于重定向）java.lang.String getRealPath(java.lang.String path)     --得到web应用的资源文件
java.io.InputStream getResourceAsStream(java.lang.String path)  

<context-param><param-name>AAA</param-name><param-value>AAA's value</param-value>
</context-param>

public class ContextDemo2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//得到SErvletContext对象ServletContext context = this.getServletContext();System.out.println("参数"+context.getInitParameter("AAA"));Enumeration<String> enums = context.getInitParameterNames();while(enums.hasMoreElements()){String paramName = enums.nextElement();String paramValue  =context.getInitParameter(paramName);System.out.println(paramName+"="+paramValue);}//尝试得到ConfigDemo中的servlet参数String path = this.getServletConfig().getInitParameter("path");System.out.println("path="+path);}}