package javax.servlet;

import java.util.Enumeration;

public interface ServletConfig {
    // 获取当前 ServletName 信息
    String getServletName();
  
    // 获取当前 Web 应用 ServletContext 对象
    ServletContext getServletContext();
   
    // 获取当前 Servlet 指定初始化参数名值信息
    String getInitParameter(String var1);

    // 获取当前 Servlet 初始化参数名组成枚举
    Enumeration<String> getInitParameterNames();
}

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

public abstract class GenericServlet implements Servlet, ServletConfig, Serializable {

    private static final long serialVersionUID = 1L;

    private transient ServletConfig config;

    public GenericServlet() {
    }

    public void destroy() {
    }

   
   // 两个 init 方法设计较为巧妙
    public void init(ServletConfig config) throws ServletException {
        this.config = config;
        this.init();
    }
 
   // 避免实现类修改 导致 ServletConfig 赋值为空
    public void init() throws ServletException {
    }

  
    // 核心方法
    public abstract void service(ServletRequest var1, ServletResponse var2) throws ServletException, IOException;

 
}

目录

• ServletContext接口
• 1.概念
• 2.功能
• 1、获取Web应用程序的初始化参数
• 2、实现多个Servlet对象共享数据
• 3、读取Web应用下的资源文件
• ServletConfig接口
• 1.概念
• 2.ServletConfig的常用方法

ServletContext context = request.getServletContext();

ServletContext context = this.getServletContext();

     package cn.itcast.chapter04.servlet;
     import java.io.*;
     import java.util.*;
     import javax.servlet.*;
     import javax.servlet.http.*;
     public class TestServlet03 extends HttpServlet {
         public void doGet(HttpServletRequest request, 
                          HttpServletResponse response)
                 throws ServletException, IOException {
               response.setContentType("text/html;charset=utf-8");
               PrintWriter out = response.getWriter();
               // 得到ServletContext对象
              ServletContext context = this.getServletContext();
              // 得到包含所有初始化参数名的Enumeration对象
              Enumeration<String> paramNames = 
     context.getInitParameterNames();
               // 遍历所有的初始化参数名，得到相应的参数值，打印到控制台
              out.println("all the paramName and paramValue are 
                         following:");
               // 遍历所有的初始化参数名，得到相应的参数值并打印
              while (paramNames.hasMoreElements()) {
                 String name = paramNames.nextElement();
                 String value = context.getInitParameter(name);
                 out.println(name + ": " + value);
                   out.println("<br>");
              }
         }
         public void doPost(HttpServletRequest request, 
                           HttpServletResponse response)
                 throws ServletException, IOException {
               this.doGet(request, response);
         }
     }

          ServletContext context = this.getServletContext();
            // 通过setAttribute()方法设置属性值
           context.setAttribute("data", "this servlet save data");

     package cn.itcast.chapter04.servlet;
     import java.io.*;
     import java.util.Properties;
     import javax.servlet.*;
     import javax.servlet.http.*;
     public class TestServlet06 extends HttpServlet {
         public void doGet(HttpServletRequest request, 
                          HttpServletResponse response)
                 throws ServletException, IOException {
              response.setContentType("text/html;charset=utf-8");
             ServletContext context = this.getServletContext();
             PrintWriter out = response.getWriter();
             InputStream in = context
             .getResourceAsStream("/WEB-
                                 INF/classes/itcast.properties");
             Properties pros = new Properties();
             pros.load(in);
             out.println("Company=" + pros.getProperty("Company") + "
                      <br>");
             out.println("Address=" + pros.getProperty("Address") + "
                      <br>");    
     }
         public void doPost(HttpServletRequest request, 
                           HttpServletResponse response)
                 throws ServletException, IOException {
             this.doGet(request, response);
         }
     }

     package cn.itcast.chapter04.servlet;
     import java.io.*;
     import javax.servlet.*;
     import javax.servlet.http.*;
     public class TestServlet02 extends HttpServlet {
         protected void doGet(HttpServletRequest request,
                 HttpServletResponse response) throws ServletException, 
     IOException {
             PrintWriter out = response.getWriter();
              // 获得ServletConfig对象
             ServletConfig config = this.getServletConfig();
             // 获得参数名为encoding对应的参数值
             String param = config.getInitParameter("encoding");
              out.println("encoding="+param);
         }
         protected void doPost(HttpServletRequest request,
                 HttpServletResponse response) throws ServletException, 
     IOException {
             this.doGet(request, response);
         }
     }

• JavaWeb入门:ServletContext详解和应用
• 深入了解Java ServletContext
• Java ServletContext对象原理及功能解析
• Java ServletContext对象用法解析
• Java基于ServletContextListener实现UDP监听
• JavaWeb ServletContext基础与应用详细讲解