servlet下载图片

梦里梦外; 2022-06-13 03:19 182阅读 0赞

### 点击下载的超链接 ###

package web;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class Main extends HttpServlet { 
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            response.setContentType("text/html;charset=utf-8");
            PrintWriter out = response.getWriter();
            out.println("<a href='/web/Servlet'>点击下载</a>");
        }
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
    
        }
    
    }

response.setContentType(“text/html;charset=utf-8”);可以解决显示在浏览器的乱码问题

--------------------

### 实现下载的servlet ###

package web;
    
    import java.io.*;
    import java.net.URLEncoder;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    /** * * @author Administrator *实现文件的下载 */
    public class Servlet extends HttpServlet { 
    
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            response.setContentType("text/html;charset=utf-8");
            //获得此servlet对象， 得到文件的路径
            String path = this.getServletContext().getRealPath("/WEB-INF/classes/图片.jpg");
    
            //创建字节输入流
            FileInputStream in = new FileInputStream(path);
            //得到下载的文件名
            String filename = path.substring(path.lastIndexOf("\\")+1);//找到最后的\然后取后面的文件名
            //设置文件编码
            filename = URLEncoder.encode(filename, "UTF-8"); //转成utf-8 ，返回String
    
            //创建字节输出流
            OutputStream out = response.getOutputStream(); //此方法获取输出流对象
    
    
            //告知客户端下载文件
            //启动下载
            //规定后缀名
            response.setHeader("content-disposition", "attachment;filename="+filename);
            response.setHeader("content-type","image/jpeg");
    
            //执行输出操作
            int len = 1;
            byte[] b = new byte[1024];
            while ((len=in.read(b))!=-1){
                out.write(b,0,len);
                //out.write(len);与上面的区别
            }
            out.close();
            in.close();
        }
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request, response);
        }
    }

知识补充：  
lastIndexOf(子串） 子串在主串最后的位置  
substring（下标位置） 截取从下标位置开始之后的字符串