java 文件下载实例

简单的来说 Java 文件下载主要分四步

1.设置文件ContentType类型

2.设置文件头

3.通过response获取ServletOutputStream对象(out)

4.写到输出流(out)中

同时需要俩个jar包 commons-fileupload.jar和commons-io.jar

    Java代码   
    
  

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.context.ServletContextAware;
import javax.servlet.ServletContext;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
@Controller
public class FileController implements ServletContextAware{
//Spring这里是通过实现ServletContextAware接口来注入ServletContext对象
private ServletContext servletContext;
@RequestMapping("file/download")
public void fileDownload(HttpServletResponse response){
//获取网站部署路径(通过ServletContext对象)，用于确定下载文件位置，从而实现下载
String path = servletContext.getRealPath("/");
//1.设置文件ContentType类型，这样设置，会自动判断下载文件类型
response.setContentType("multipart/form-data");
//2.设置文件头：最后一个参数是设置下载文件名(假如我们叫a.pdf)
response.setHeader("Content-Disposition", "attachment;fileName="+"a.pdf");
ServletOutputStream out;
//通过文件路径获得File对象(假如此路径中有一个download.pdf文件)
File file = new File(path + "download/" + "download.pdf");
try {
FileInputStream inputStream = new FileInputStream(file);
//3.通过response获取ServletOutputStream对象(out)
out = response.getOutputStream();
int b = 0;
byte[] buffer = new byte[512];
while (b != -1){
b = inputStream.read(buffer);
//4.写到输出流(out)中
out.write(buffer,0,b);
}
inputStream.close();
out.close();
out.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void setServletContext(ServletContext servletContext) {
this.servletContext = servletContext;
}
}

 
    
  
    public HttpServletResponse download(String path, HttpServletResponse response) {
         try {
             // path是指欲下载的文件的路径。
            File file = new File(path);
             // 取得文件名。
            String filename = file.getName();
             // 取得文件的后缀名。
            String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();

             // 以流的形式下载文件。
            InputStream fis = new BufferedInputStream(new FileInputStream(path));
             byte[] buffer = new byte[fis.available()];
             fis.read(buffer);
             fis.close();
             // 清空response
            response.reset();
             // 设置response的Header
            response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));
             response.addHeader("Content-Length", "" + file.length());
             OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
             response.setContentType("application/octet-stream");
             toClient.write(buffer);
             toClient.flush();
             toClient.close();
         } catch (IOException ex) {
             ex.printStackTrace();
         }
         return response;
     }

     public void downloadLocal(HttpServletResponse response) throws FileNotFoundException {
         // 下载本地文件
        String fileName = "Operator.doc".toString(); // 文件的默认保存名
         // 读到流中
        InputStream inStream = new FileInputStream("c:/Operator.doc");// 文件的存放路径
         // 设置输出的格式
        response.reset();
         response.setContentType("bin");
         response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
         // 循环取出流中的数据
        byte[] b = new byte[100];
         int len;
         try {
             while ((len = inStream.read(b)) > 0)
                 response.getOutputStream().write(b, 0, len);
             inStream.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     public void downloadNet(HttpServletResponse response) throws MalformedURLException {
         // 下载网络文件
        int bytesum = 0;
         int byteread = 0;

         URL url = new URL("windine.blogdriver.com/logo.gif");

         try {
             URLConnection conn = url.openConnection();
             InputStream inStream = conn.getInputStream();
             FileOutputStream fs = new FileOutputStream("c:/abc.gif");

             byte[] buffer = new byte[1204];
             int length;
             while ((byteread = inStream.read(buffer)) != -1) {
                 bytesum += byteread;
                 System.out.println(bytesum);
                 fs.write(buffer, 0, byteread);
             }
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 
    
  

//支持在线打开文件的一种方式

 
     
   
    public void downLoad(String filePath, HttpServletResponse response, boolean isOnLine) throws Exception {
         File f = new File(filePath);
         if (!f.exists()) {
             response.sendError(404, "File not found!");
             return;
         }
         BufferedInputStream br = new BufferedInputStream(new FileInputStream(f));
         byte[] buf = new byte[1024];
         int len = 0;

         response.reset(); // 非常重要
        if (isOnLine) { // 在线打开方式
            URL u = new URL("file:///" + filePath);
             response.setContentType(u.openConnection().getContentType());
             response.setHeader("Content-Disposition", "inline; filename=" + f.getName());
             // 文件名应该编码成UTF-8
        } else { // 纯下载方式
            response.setContentType("application/x-msdownload");
             response.setHeader("Content-Disposition", "attachment; filename=" + f.getName());
         }
         OutputStream out = response.getOutputStream();
         while ((len = br.read(buf)) > 0)
             out.write(buf, 0, len);
         br.close();
         out.close();
     }

java 文件下载实例

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