servlet_3

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