73.【JavaWeb-01】（七）

4.读取资源文件:
(1).在java目录下新建properties
(2).在resource目录下新建properties
都被打包到了同一个路径下:classes,我们俗称这个路径为classpath
(3).切记我们赋值路径，复制的是out目录下的路径.

!--在build中配置resources-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
</build>

基本思路:
(1).设置getServletContext()
ServletContext servletContext = this.getServletContext();
(2).导入文件的相对目录
InputStream is = servletContext.getResourceAsStream("/WEB-INF/classes/Database.properties");
(3).进行流的加载
Properties properties = new Properties();
properties.load(is);
(4).通过键值对进行获取值
String username = properties.getProperty("username");
String password = properties.getProperty("password");
(6).打印输出
resp.getWriter().println(username+" "+password);
(7).配置web

package com.Jsxs.Servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
public class ServletDemo05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        InputStream is = servletContext.getResourceAsStream("/WEB-INF/classes/Database.properties");
        Properties properties = new Properties();
        properties.load(is);
        String username = properties.getProperty("username");
        String password = properties.getProperty("password");
        resp.getWriter().println(username+" "+password);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

web服务器接受到客户端的http请求，针对这个请求，分别创建一个代表响应的
HttpServletResponse对象，和一个代表请求HttpServletRequest的对象。
(1).如果要获取客户端请求过来的参数: 找httpServletRequest
(2).如果要给客户端相应一些信息: 找HttpServletResponse
1.简单分类:
负责向浏览器发送数据的方法:
(1).
Servletoutputstream getOutputStream() throw IOException;
(2).
Printwriter getwriter() throw IOException;
负责向浏览器发送响应头的方法:
void setContentLength(int var1);
void setContentLengthLong(long var1);
void setContentType(String var1);
void setBufferSize(int var1);
void setDateHeader(String var1, long var2);
void addDateHeader(String var1, long var2);
void setHeader(String var1, String var2);
void addHeader(String var1, String var2);
void setIntHeader(String var1, int var2);
void addIntHeader(String var1, int var2);
响应的状态码:
int SC_CONTINUE = 100;
int SC_SWITCHING_PROTOCOLS = 101;
int SC_OK = 200;
int SC_CREATED = 201;
int SC_ACCEPTED = 202;
int SC_NON_AUTHORITATIVE_INFORMATION = 203;
int SC_NO_CONTENT = 204;
int SC_RESET_CONTENT = 205;
int SC_PARTIAL_CONTENT = 206;
int SC_MULTIPLE_CHOICES = 300;
int SC_MOVED_PERMANENTLY = 301;
int SC_MOVED_TEMPORARILY = 302;
int SC_FOUND = 302;
int SC_SEE_OTHER = 303;
int SC_NOT_MODIFIED = 304;
int SC_USE_PROXY = 305;
int SC_TEMPORARY_REDIRECT = 307;
int SC_BAD_REQUEST = 400;
int SC_UNAUTHORIZED = 401;
int SC_PAYMENT_REQUIRED = 402;
int SC_FORBIDDEN = 403;
int SC_NOT_FOUND = 404;
int SC_METHOD_NOT_ALLOWED = 405;
int SC_NOT_ACCEPTABLE = 406;
int SC_PROXY_AUTHENTICATION_REQUIRED = 407;
int SC_REQUEST_TIMEOUT = 408;
int SC_CONFLICT = 409;
int SC_GONE = 410;
int SC_LENGTH_REQUIRED = 411;
int SC_PRECONDITION_FAILED = 412;
int SC_REQUEST_ENTITY_TOO_LARGE = 413;
int SC_REQUEST_URI_TOO_LONG = 414;
int SC_UNSUPPORTED_MEDIA_TYPE = 415;
int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
int SC_EXPECTATION_FAILED = 417;
int SC_INTERNAL_SERVER_ERROR = 500;
int SC_NOT_IMPLEMENTED = 501;
int SC_BAD_GATEWAY = 502;
int SC_SERVICE_UNAVAILABLE = 503;
int SC_GATEWAY_TIMEOUT = 504;
int SC_HTTP_VERSION_NOT_SUPPORTED = 505;

resp.setHeader("content-Disposition","attachment;filename="+ URLEncoder.encode(fileName,"utf-8"));
1.向浏览器输出消息
2.下载文件:
(1).要知道下载文件的路径
(2).下载的文件名是啥?
(3).设置想办法让浏览器支持下载我们需要的东西
(4).获取下载文件的输入流
(5).获取输出流
(6).使用输出流将缓存区的数据输出到客户端.
(7).配置web的操作

package com.Jsxs.Servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URLEncoder;
public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        (1).要知道下载文件的路径
        String realPath = "E:\\Ideal源码\\FirstMaven\\Servelete03\\src\\main\\resources\\1.jpg";
//        (2).下载的文件名是啥?
        String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
//        (3).设置想办法让浏览器支持下载我们需要的东西
        resp.setHeader("content-Disposition","attachment;filename="+ URLEncoder.encode(fileName,"utf-8"));
//        (4).获取下载文件的输入流
        FileInputStream fileInputStream = new FileInputStream(realPath);
//        (5).设置缓冲区
        int count=0;
        byte[] bytes = new byte[1024];
//        (6).获取fillOutputStream输出流
        ServletOutputStream outputStream = resp.getOutputStream();
//        (7).将fillOutputStream流写入到缓存区，使用输出流将缓存区的数据输出到客户端.
        while ((count=(fileInputStream.read(bytes)))!=-1){
            outputStream.write(bytes,0,count);
        }
        outputStream.close();
        fileInputStream.close();
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

2.验证码功能:
(1).浏览器每秒刷新的操作:
resp.setHeader("refresh","3");

package com.Jsxs.Servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
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;
public class ImageServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//       让浏览器秒刷新一次
        resp.setHeader("refresh","3");
//        在内存中国创建一个图片
        BufferedImage bufferedImage = new BufferedImage(80, 20, BufferedImage.TYPE_INT_BGR);
//        得到图片
        Graphics2D graphics2D=(Graphics2D) bufferedImage.getGraphics();  //笔
//        设置图片的背景颜色
        graphics2D.setColor(new Color(224, 222, 222));
        graphics2D.fillRect(0,0,80,20);
//        给图片写入数据
        graphics2D.setColor(new Color(25, 132, 206));
        graphics2D.setFont(new Font("黑体",Font.BOLD,25));
        graphics2D.drawString(makeNum(),0,20);
//        告诉浏览器，这个方式用图片的方式打开
        resp.setContentType("image/jpg");
//        取消缓存
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("pragma","no-cache");
//        把图片写给浏览器
        ImageIO.write(bufferedImage,"jpg",resp.getOutputStream());
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
    private String makeNum(){
        Random random=new Random();
        String s = random.nextInt(9999999) + "";
        StringBuffer stringBuffer=new StringBuffer();
//        假如不足七位数就进行0填充
        for (int i = 0; i <7-s.length() ; i++) {
            stringBuffer.append("0");
        }
        s=stringBuffer.toString()+s;
        return s;
    }
}