ServletContext

	介绍

	提供的功能

	servlet中获取servletcontext实例

	servletcontext接口的方法
	

package com.fgy;

import java.io.IOException;

import java.net.MalformedURLException;

import java.net.URL;

import java.util.Enumeration;

import java.util.Set;

import javax.servlet.ServletConfig;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet(name="servlet",urlPatterns="/servlet",loadOnStartup=1)

public class InitParaServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Override

    public void init(ServletConfig config) throws ServletException {

        ServletContext context=config.getServletContext();

        System.out.println(context.getServerInfo());

        System.out.println(context.getMajorVersion());

        System.out.println(context.getMinorVersion());

        System.out.println(context.getServletContextName());

        System.out.println(context.getClassLoader());

        System.out.println(context.getVirtualServerName());

        Enumeration<String> names=context.getInitParameterNames();

        while (names.hasMoreElements()) {

            String name = names.nextElement();

            System.out.println(name+":"+context.getInitParameter(name));

        }

        try {

            URL url=context.getResource("/index.html");

            System.out.println(url);

        } catch (MalformedURLException e) {

            e.printStackTrace();

        }

        Set<String> paths=context.getResourcePaths("/");

        for (String path : paths) {

            System.out.println(path);

        }

        System.out.println(context.getRealPath("/"));

    }

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

//        ServletContext context1=getServletContext();

//        ServletContext context2=request.getServletContext();

    }

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

        doGet(request, response);

    }

}

请求分派-1

    请求分派概述

    RequestDispatcher接口

        获取实例方法

        实例提供的方法

    getServletContext().getRequestDispatcher("/index.html");

    request.getRequestDispatcher("index.html");

    上面这二者的区别，一个是相对于应用根目录，一个是相对于映射的servlet目录

    forward与include方法

package com.fgy;

import java.io.IOException;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet("/servlet6/test")

public class Servlet6 extends HttpServlet {

    private static final long serialVersionUID = 1L;

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

//        RequestDispatcher rd=getServletContext().getRequestDispatcher("/index.html");

//        System.out.println(rd);

        RequestDispatcher rd=request.getRequestDispatcher("index.html");

        rd.forward(request, response);

    }

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

        doGet(request, response);

    }

}

请求分派-2

    路径中查询字符串中的参数优先级

    前台重定向与后台转发的区别

    httpservletresponse.sendredirect

    浏览器地址栏会发生变化，发两次请求

    requestdispatcher.forward

    浏览器地址栏不发生变化，发一次请求

    数据共享