一、response
* 功能：设置响应消息
1. 设置响应行
1. 格式：HTTP/1.1 200 ok
2. 设置状态码：setStatus(int sc)
2. 设置响应头：setHeader(String name, String value)
3. 设置响应体：
* 使用步骤：
1. 获取输出流
* 字符输出流：PrintWriter getWriter()
* 字节输出流：ServletOutputStream getOutputStream()
2. 使用输出流，将数据输出到客户端浏览器二、response重定向
1. 完成重定向
* 重定向：资源跳转的方式
* 代码实现：
//1. 设置状态码为302
response.setStatus(302);
//2.设置响应头location
response.setHeader("location","/day15/responseDemo2");
//简单的重定向方法
response.sendRedirect("/day15/responseDemo2");
* 重定向的特点:redirect
1. 地址栏发生变化
2. 重定向可以访问其他站点(服务器)的资源
3. 重定向是两次请求。不能使用request对象来共享数据
* 转发的特点：forward
1. 转发地址栏路径不变
2. 转发只能访问当前服务器下的资源
3. 转发是一次请求，可以使用request对象来共享数据
* forward 和 redirect 区别
---------------------------------------
package cn.itcast.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 重定向
*/
@WebServlet("/responseDemo1")
public class ResponseDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("demo1........");
//访问/responseDemo1，会自动跳转到/responseDemo2资源
/* //1. 设置状态码为302
response.setStatus(302);
//2.设置响应头location
response.setHeader("location","/day15/responseDemo2");*/
request.setAttribute("msg","response");
//动态获取虚拟目录
String contextPath = request.getContextPath();
//简单的重定向方法
response.sendRedirect(contextPath+"/responseDemo2");
//response.sendRedirect("http://www.itcast.cn");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
------------------------------
package cn.itcast.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/responseDemo2")
public class ResponseDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("demo2222222........");
Object msg = request.getAttribute("msg");
System.out.println(msg);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}路径写法：
1. 路径分类
1. 相对路径：通过相对路径不可以确定唯一资源
* 如：./index.html
* 不以/开头，以.开头路径
* 规则：找到当前资源和目标资源之间的相对位置关系
* ./：当前目录
* ../:后退一级目录
2. 绝对路径：通过绝对路径可以确定唯一资源
* 如：http://localhost/day15/responseDemo2 /day15/responseDemo2
* 以/开头的路径
* 规则：判断定义的路径是给谁用的？判断请求将来从哪儿发出
* 给客户端浏览器使用：需要加虚拟目录(项目的访问路径)
* 建议虚拟目录动态获取：request.getContextPath()
* <a> , <form> 重定向...
* 给服务器使用：不需要加虚拟目录
* 转发路径三、服务器输出数据到浏览器
1、服务器输出字符数据到浏览器
* 步骤：
1. 获取字符输出流
2. 输出数据
* 注意：
* 乱码问题：
1. PrintWriter pw = response.getWriter();获取的流的默认编码是ISO-8859-1
2. 设置该流的默认编码
3. 告诉浏览器响应体使用的编码
//简单的形式，设置编码，是在获取流之前设置：
response.setContentType("text/html;charset=utf-8");
----------------------------
package cn.itcast.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
@WebServlet("/responseDemo4")
public class ResponseDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取流对象之前，设置流的默认编码：ISO-8859-1 设置为：GBK
// response.setCharacterEncoding("utf-8");
//告诉浏览器，服务器发送的消息体数据的编码。建议浏览器使用该编码解码
//response.setHeader("content-type","text/html;charset=utf-8");
//简单的形式，设置编码
response.setContentType("text/html;charset=utf-8");
//1.获取字符输出流
PrintWriter pw = response.getWriter();
//2.输出数据
//pw.write("<h1>hello response</h1>");
pw.write("你好啊啊啊 response");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}2、服务器输出字节数据到浏览器
* 步骤：
1. 获取字节输出流
2. 输出数据
------------------------------
package cn.itcast.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/responseDemo5")
public class ResponseDemo5 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
//1.获取字节输出流
ServletOutputStream sos = response.getOutputStream();
//2.输出数据
sos.write("你好".getBytes("utf-8"));
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}3、验证码
1. 本质：图片
2. 目的：防止恶意表单注册
--------------------------------
package cn.itcast.web.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 100;
int height = 50;
//1.创建一对象，在内存中图片(验证码图片对象)
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
//2.美化图片
//2.1 填充背景色
Graphics g = image.getGraphics();//画笔对象
g.setColor(Color.PINK);//设置画笔颜色
g.fillRect(0,0,width,height);
//2.2画边框
g.setColor(Color.BLUE);
g.drawRect(0,0,width - 1,height - 1);
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
//生成随机角标
Random ran = new Random();
for (int i = 1; i <= 4; i++) {
int index = ran.nextInt(str.length());
//获取字符
char ch = str.charAt(index);//随机字符
//2.3写验证码
g.drawString(ch+"",width/5*i,height/2);
}
//2.4画干扰线
g.setColor(Color.GREEN);
//随机生成坐标点
for (int i = 0; i < 10; i++) {
int x1 = ran.nextInt(width);
int x2 = ran.nextInt(width);
int y1 = ran.nextInt(height);
int y2 = ran.nextInt(height);
g.drawLine(x1,y1,x2,y2);
}
//3.将图片输出到页面展示
ImageIO.write(image,"jpg",response.getOutputStream());
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
--------------------------------
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
/*
分析：
点击超链接或者图片，需要换一张
1.给超链接和图片绑定单击事件
2.重新设置图片的src属性值
*/
window.onload = function(){
//1.获取图片对象
var img = document.getElementById("checkCode");
//2.绑定单击事件
img.onclick = function(){
//加时间戳
var date = new Date().getTime();
img.src = "/day15/checkCodeServlet?"+date;
}
}
</script>
</head>
<body>
<img id="checkCode" src="/day15/checkCodeServlet" />
<a id="change" href="https://zhishitu.com">看不清换一张？</a>
</body>
</html>四、ServletContext对象
1. 概念
代表整个web应用，可以和程序的容器(服务器)来通信2. 获取
1. 通过request对象获取
request.getServletContext();
2. 通过HttpServlet获取
this.getServletContext();
----------------------------------
package cn.itcast.web.servletcontext;
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;
import java.io.IOException;
@WebServlet("/servletContextDemo1")
public class ServletContextDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext对象获取：
1. 通过request对象获取
request.getServletContext();
2. 通过HttpServlet获取
this.getServletContext();
*/
//1. 通过request对象获取
ServletContext context1 = request.getServletContext();
//2. 通过HttpServlet获取
ServletContext context2 = this.getServletContext();
System.out.println(context1);
System.out.println(context2);
System.out.println(context1 == context2);//true
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}3. 功能
1. 获取MIME类型：
* MIME类型:在互联网通信过程中定义的一种文件数据类型
* 格式： 大类型/小类型 text/html image/jpeg
* 获取：String getMimeType(String file)
-----------------------------
package cn.itcast.web.servletcontext;
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;
import java.io.IOException;
@WebServlet("/servletContextDemo2")
public class ServletContextDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext功能：
1. 获取MIME类型：
* MIME类型:在互联网通信过程中定义的一种文件数据类型
* 格式： 大类型/小类型 text/html image/jpeg
* 获取：String getMimeType(String file)
2. 域对象：共享数据
3. 获取文件的真实(服务器)路径
*/
//2. 通过HttpServlet获取
ServletContext context = this.getServletContext();
//3. 定义文件名称
String filename = "a.jpg";//image/jpeg
//4.获取MIME类型
String mimeType = context.getMimeType(filename);
System.out.println(mimeType);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
2. 域对象：共享数据
1. setAttribute(String name,Object value)
2. getAttribute(String name)
3. removeAttribute(String name)
* ServletContext对象范围：所有用户所有请求的数据
-----------------------------
package cn.itcast.web.servletcontext;
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;
import java.io.IOException;
@WebServlet("/servletContextDemo3")
public class ServletContextDemo3 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext功能：
1. 获取MIME类型：
2. 域对象：共享数据
3. 获取文件的真实(服务器)路径
*/
//2. 通过HttpServlet获取
ServletContext context = this.getServletContext();
//设置数据
context.setAttribute("msg","haha");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
-----------------------------
package cn.itcast.web.servletcontext;
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;
import java.io.IOException;
@WebServlet("/servletContextDemo4")
public class ServletContextDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext功能：
1. 获取MIME类型：
2. 域对象：共享数据
3. 获取文件的真实(服务器)路径
*/
//2. 通过HttpServlet获取
ServletContext context = this.getServletContext();
//获取数据
Object msg = context.getAttribute("msg");
System.out.println(msg);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
3. 获取文件的真实(服务器)路径
1. 方法：String getRealPath(String path)
String b = context.getRealPath("/b.txt");//web目录下资源访问
System.out.println(b);
String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问
System.out.println(c);
String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问
System.out.println(a);
-----------------------------
package cn.itcast.web.servletcontext;
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;
import java.io.File;
import java.io.IOException;
@WebServlet("/servletContextDemo5")
public class ServletContextDemo5 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
ServletContext功能：
1. 获取MIME类型：
2. 域对象：共享数据
3. 获取文件的真实(服务器)路径
*/
// 通过HttpServlet获取
ServletContext context = this.getServletContext();
// 获取文件的服务器路径
String b = context.getRealPath("/b.txt");//web目录下资源访问
System.out.println(b);
// File file = new File(realPath);
String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问
System.out.println(c);
String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问
System.out.println(a);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}