ServletConfig对象

ServletConfig对象对应web.xml文件中的节点。当Tomcat初始化一个Servlet时，会将该Servlet的配置信息，封装到一个ServletConfig对象中。我们可以通过该对象读取节点中的配置信息
servletConfig.getInitParameter(“key”)
该方法可以读取web.xml文件中标签中标签中的配置信息。
servletConfig.getInitParameterNames()
该方法可以读取web.xml文件中当前标签中所有标签中的值。

   <servlet>
        <servlet-name>getConfigServlet</servlet-name>
        <servlet-class>com.itbaizhan.GetConfigServlet</servlet-class>
        <init-param>
            <param-name>key1</param-name>
            <param-value>renlong</param-value>
        </init-param>
        <init-param>
            <param-name>key2</param-name>
            <param-value>jiangyan</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>getConfigServlet</servlet-name>
        <url-pattern>/getconfig.do</url-pattern>
    </servlet-mapping>

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
/**
 * 使用ServletConfig读取Servlet配置信息
 */
public class GetConfigServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取ServletConfig对象
        ServletConfig servletConfig =this.getServletConfig();
        //获取配置信息
        Enumeration<String> initParameterNames = servletConfig.getInitParameterNames();
        PrintWriter printWriter = resp.getWriter();
        while (initParameterNames.hasMoreElements()){
            String name =initParameterNames.nextElement();
            String value = servletConfig.getInitParameter(name);
            printWriter.println(name+value);
        }
        printWriter.flush();
        printWriter.close();
    }
}