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，代表响应的一个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
负责向浏览器发送数据的方法：
ServletOutputStream getOutputStream() throws IOException; PrintWriter getWriter() throws IOException;
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 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;
2、下载文件
1.要获取下载文件的路径
2.下载的文件名是啥?
3.设置想办法让浏览器能够支持下载我们需要的东西
4.获取下载文件的输入流
5.创建缓冲区
6.获取OutputStream对象
7.将FileOutputStream流写入到buffer缓冲区
8.使用OutputStream将缓冲区中的数据输出到客户端!
FileServlet
package com.allen.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.IOException;
import java.net.URLEncoder;
public class FileServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1.要获取下载文件的路径
String realPath = "/Users/allen/IdeaProjects/javaweb-02-servlet/response/src/main/resources/1.jpg";
System.out.println("下载文件的路径：" + realPath);
//2.下载文件的名是啥？
String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
//3.设置想办法让浏览器能够支持（Content-Disposition）下载我们需要的东西，中文文件名URLRcoder.ercode编码，否则有可能乱码
resp.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
//4.获取下载文件的输入流
FileInputStream in = new FileInputStream(realPath);
//5.创建缓冲区
int len = 0;
byte[] buffer = new byte[1024];
//6.获取OutputStream对象
ServletOutputStream out = resp.getOutputStream();
//7.将FileOutputStream流写到buffer缓冲区，使用OutputStream缓冲区中的数据输出到客户端！
while((len = in.read(buffer)) > 0){
out.write(buffer, 0, len);
}
in.close();
out.close();
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
}web.xml
<servlet> <servlet-name>down</servlet-name> <servlet-class>com.allen.servlet.FileServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>down</servlet-name> <url-pattern>/down</url-pattern> </servlet-mapping>
测试：
