1、示例
package com.test;
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.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
@WebServlet(name = "Servlet_5",urlPatterns = "/download")
public class Servlet_5 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//獲取請求參數
String filename = request.getParameter("filename");
//獲取文件類型
String mimeType = this.getServletContext().getMimeType(filename);
//設置響應類型
response.setContentType(mimeType);
//設置相應頭，如不設置該響應頭，凡是能被瀏覽器識別的如jpg、txt等格式會預覽，設置後會直接下載
response.setHeader("Content-Disposition","attachment;filename=" + filename);
//獲取文件的絕對路勁
String real = this.getServletContext().getRealPath("download/" + filename);
InputStream in = new FileInputStream(real);
ServletOutputStream servletOutputStream = response.getOutputStream();
int len = 0;
byte[]buff = new byte[1024];
while((len = in.read(buff))>0){
servletOutputStream.write(buff,0,len);
}
in.close();
}
}