ServletConfig对象

A servlet configuration object used by a servlet container to pass information to a servlet during initialization.

servlet 容器使用的 servlet 配置对象，该对象在初始化期间将信息传递给 servlet。

ServletConfig接口提供的方法:

Method Summary
String	getInitParameter(String name)           Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist.
Enumeration	getInitParameterNames()           Returns the names of the servlet's initialization parameters as an Enumeration of String objects, or an empty Enumeration if the servlet has no initialization parameters.
ServletContext	getServletContext()           Returns a reference to the ServletContext in which the caller is executing.
String	getServletName()           Returns the name of this servlet instance.

代码演示:

package com.itheima.action;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ServeletDemo13
 */
public class ServletDemo13 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 0.获取ServletConfig对象
        ServletConfig config = getServletConfig();
        // 1.根据指定参数名获取参数值
        String username = config.getInitParameter("username");
        String password = config.getInitParameter("password");
        System.out.println(username + " " + password);
        // 2.获取所有初始化参数名
        Enumeration<String> names = config.getInitParameterNames();
        while (names.hasMoreElements()) {
            String name = names.nextElement();
            // 根据已获得的参数名获取参数值
            String value = config.getInitParameter(name);
            System.out.println(name + "---" + value);
        }
        //    3.获取Servlet名称
        String servletName = config.getServletName();
        System.out.println(servletName);
        
        // 4.获取contextpath
        String contextPath = config.getServletContext().getContextPath();
        System.out.println(contextPath);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

web.xml相关配置如下:
　　

<servlet>
    <description></description>
    <display-name>ServletDemo13</display-name>
    <servlet-name>ServletDemo13</servlet-name>
    <servlet-class>com.itheima.action.ServletDemo13</servlet-class>
    <init-param>
        <param-name>username</param-name>
        <param-value>root</param-value>
    </init-param>
    <init-param>
        <param-name>password</param-name>
        <param-value>abc</param-value>
    </init-param>
  </servlet>
  <servlet-mapping>
    <servlet-name>ServletDemo13</servlet-name>
    <url-pattern>/ServletDemo13</url-pattern>
  </servlet-mapping>