渚漪Day14——JavaWeb 05【HTTPServletResponse】

3、HTTPServletResponse

web服务器接收到客户端的http请求，针对这个请求，分别创建一个代表请求的HTTPServletRequest对象，代表响应的HTTPServletResponse；

如果要获取客户端请求过来的参数：找HTTPServletRequest
如果要给客户端响应一些信息：找HTTPServletResponse

1.简单分类

1 负责向浏览器发送数据的方法

ServletOutputStream getOutputStream() throws IOException;
PrintWriter getWriter() throws IOException;

2 负责向浏览器发送响应头的方法

void setCharacterEncoding(String var1);

void setContentLength(int var1);

void setContentLengthLong(long var1);

void setContentType(String var1);

void setDateHeader(String var1, long var2);

void setHeader(String var1, String var2);

3 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;

int SC_OK = 200;

int SC_MULTIPLE_CHOICES = 300;

int SC_NOT_FOUND = 404;

int SC_SERVICE_UNAVAILABLE = 503;

2.常见应用

向浏览器输出消息
下载文件
1. 要获取下载文件路径
2. 下载的文件名是什么
3. 想办法让浏览器能够支持下载需要的东西
4. 获取下载文件的输入流
5. 创建缓冲区
6. 获得OutputStream对象
7. 写入缓冲区buffer
8. 输出数据到客户端

import javax.servlet.ServletContext;
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.IOException;

public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1. 要获取下载文件路径
        ServletContext context = getServletContext();
        String path ="E:\1.mp3";
        //2. 下载的文件名是什么
        String filename = path.substring(path.lastIndexOf("\") + 1);
        //3. 想办法让浏览器能够支持下载需要的东西
        resp.setHeader("Content-Disposition","attachment;filename="+filename);
        //4. 获取下载文件的输入流
        FileInputStream in = new FileInputStream(path);
        //5. 创建缓冲区
        int len=0;
        byte[] buffer = new byte[1024];
        //6. 获得OutputStream对象
        ServletOutputStream out = resp.getOutputStream();
        //7. 写入缓冲区buffer
        while((len=in.read(buffer))!=-1){
            out.write(buffer,0,len);
        }
        in.close();
        out.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}