java文件下载代码实例（单文件下载和多文件打包下载）

public String oneFileDownload(HttpServletRequest request,HttpServletResponse response){
    //针对需求需要与需求沟通下载文件传递参数
    //目前demo文件名是文件的hashCode值+后缀名的方式命名，可以默认该hashCode值为文件唯一id
    String fileName = request.getParameter("fileName");
    if(StringUtils.isBlank(fileName)){
      return "文件名为空";
    }
    String filePath = request.getSession().getServletContext().getRealPath("/convert")+File.separator+fileName;//目前文件默认在该文件夹下，后续变动需修改
    File downloadFile = new File(filePath);
    if(downloadFile.exists()){
      OutputStream out = null;
      FileInputStream fis = null;
      BufferedInputStream bis = null;
      try {
        if(downloadFile.isDirectory()){
          return "路径错误仅指向文件夹";
        }
        out = response.getOutputStream();// 创建页面返回方式为输出流，弹出下载框
        fis = new FileInputStream(downloadFile);
        bis = new BufferedInputStream(fis);
        response.setContentType("application/pdf; charset=UTF-8");//设置编码字符
        response.setHeader("Content-disposition", "attachment;filename=" + fileName);
        byte[] bt = new byte[2048];
        int size = 0;
        while((size=bis.read(bt)) != -1){
          out.write(bt, 0, size);
        }

      } catch (Exception e) {
        e.printStackTrace();
      }finally {
        try {
          //关闭流
          out.flush();
          if(out != null){
            out.close();
          }
          if(bis != null){
            bis.close();
          }
          if(fis != null){
            fis.close();
          }
        } catch (Exception e2) {
          e2.printStackTrace();
        }

      }
      return "下载成功";
    }else{
      
      return "文件不存在！";  
    }

  }

public String zipDownload(HttpServletRequest request,HttpServletResponse response) throws IOException{
    
    String sourceFilePath = request.getSession().getServletContext().getRealPath("/convert");//文件路径
    String destinFilePath = request.getSession().getServletContext().getRealPath("/fileZip");
    String fileName = FileUtil.zipFiles(sourceFilePath, destinFilePath);
    File file = new File(destinFilePath+File.separator+fileName);
    response.setHeader("Content-disposition", "attachment;filename=" + fileName);
    if(file.exists()){
      FileInputStream fis = null;
      BufferedInputStream bis = null;
      OutputStream out = response.getOutputStream();
      try {
        fis = new FileInputStream(file);
        bis = new BufferedInputStream(fis);
        byte[] bufs = new byte[1024 * 10];
        int read = 0;
        while ((read = bis.read(bufs, 0, 1024 * 10)) != -1) {
          out.write(bufs, 0, read);
        }
      } catch (FileNotFoundException e) {
        e.printStackTrace();
      }finally {
        if(bis != null){
          bis.close();
        }
        if(out!=null){
          out.close();
        }
        File zipFile = new File(destinFilePath+File.separator+fileName);
        if(zipFile.exists()){
          zipFile.delete();
        }
      }
    }else{
      return "文件压缩失败";
    }
    return "下载成功";
  }

public String zipDownloadRelativePath(HttpServletRequest request,HttpServletResponse response) {
    String msg ="";//下载提示信息
    String root = request.getSession().getServletContext().getRealPath("/convert");//文件路径
    Vector<File> fileVector = new Vector<File>();//定义容器装载文件
    File file = new File(root);
    File [] subFile = file.listFiles();
    //判断文件性质并取文件
    for(int i = 0; i<subFile.length; i++){
      if(!subFile[i].isDirectory()){//不是文件夹并且不为空
        fileVector.add(subFile[i]);//装载文件
      }else{//是文件夹,再次递归遍历文件夹里面的文件
        File [] files = subFile[i].listFiles();
        Vector v = FileUtil.getPathAllFiles(subFile[i],new Vector<File>());
        fileVector.addAll(v);//把迭代的文件装到容器中
      }
    }
    //设置文件下载名称
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
    String fileName = dateFormat.format(new Date())+".zip";
    response.setHeader("Content-disposition", "attachment;filename=" + fileName);//如果有中文需要转码
    //定义相关流
    //用于浏览器下载响应
    OutputStream out = null;
    //用于读压缩好的文件
    BufferedInputStream bis = null;//用缓存性能会好一些
    //用于压缩文件
    ZipOutputStream zos = null;
    //创建一个空的zip文件
    String zipBasePath = request.getSession().getServletContext().getRealPath("/fileZip");
    String zipFilePath = zipBasePath+File.separator+fileName;
    File zipFile = new File(zipFilePath);
    try {
      if(!zipFile.exists()){//不存在创建一个新的
        zipFile.createNewFile();
      }
      out = response.getOutputStream();
      //创建文件输出流
      zos = new ZipOutputStream(new FileOutputStream(zipFile));
      //循环文件，一个一个按顺序压缩
      for(int i = 0;i< fileVector.size();i++){
        System.out.println(fileVector.get(i).getName()+"大小为："+fileVector.get(i).length());
        FileUtil.zipFileFun(fileVector.get(i),root,zos);
      }
      //压缩完成以后必须要在此处执行关闭 否则下载文件会有问题
      if(zos != null){
        zos.closeEntry();
        zos.close();
        }
      byte[] bt = new byte[10*1024];
      int size = 0;
      bis = new BufferedInputStream(new FileInputStream(zipFilePath),10*1024);
      while((size=bis.read(bt,0,10*1024)) != -1){//没有读完
        out.write(bt,0,size);
      }
      
    } catch (Exception e) {
      e.printStackTrace();
    }finally {//关闭相关流
      try {
        //避免出异常时无法关闭
        if(zos != null){
          zos.closeEntry();
          zos.close();
          }
        
        if(bis != null){
          bis.close();
        }
        
        if(out != null){
          out.close();
        }
        if(zipFile.exists()){
          zipFile.delete();//删除
        }
      } catch (Exception e2) {
        System.out.println("流关闭出错！");
      }

    }
    return "下载成功";
  }

package com.hhwy.fileview.utils;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Vector;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;




public class FileUtil {
  /**
   * 把某个文件路径下面的文件包含文件夹压缩到一个文件下
   * @param file
   * @param rootPath 相对地址
   * @param zipoutputStream
   */
  public static void zipFileFun(File file,String rootPath,ZipOutputStream zipoutputStream){
    if(file.exists()){//文件存在才合法
      if(file.isFile()){
        //定义相关操作流
        FileInputStream fis = null;
        BufferedInputStream bis = null;
        try {
          //设置文件夹
          String relativeFilePath = file.getPath().replace(rootPath+File.separator, "");
          //创建输入流读取文件
          fis = new FileInputStream(file);
          bis = new BufferedInputStream(fis,10*1024);
          //将文件装入zip中，开始打包
          ZipEntry zipEntry;
          if(!relativeFilePath.contains("\\")){
            zipEntry = new ZipEntry(file.getName());//此处值不能重复，要唯一，否则同名文件会报错
          }else{
            zipEntry = new ZipEntry(relativeFilePath);//此处值不能重复，要唯一，否则同名文件会报错
          }
          zipoutputStream.putNextEntry(zipEntry);
          //开始写文件
          byte[] b = new byte[10*1024];
          int size = 0;
          while((size=bis.read(b,0,10*1024)) != -1){//没有读完
            zipoutputStream.write(b,0,size);
          }
        } catch (Exception e) {
          e.printStackTrace();
        }finally {
          try {
            //读完以后关闭相关流操作
            if(bis != null){
              bis.close();
            }
            if(fis != null){
              fis.close();
            }
          } catch (Exception e2) {
            System.out.println("流关闭错误！");
          }
        }
      }
//      else{//如果是文件夹
//        try {
//          File [] files = file.listFiles();//获取文件夹下的所有文件
//          for(File f : files){
//            zipFileFun(f,rootPath, zipoutputStream);
//          }
//        } catch (Exception e) {
//          e.printStackTrace();
//        }
//        
//      }
    }
  }
  
  /*
   * 获取某个文件夹下的所有文件
   */
  public static Vector<File> getPathAllFiles(File file,Vector<File> vector){
    if(file.isFile()){//如果是文件，直接装载
      System.out.println("在迭代函数中文件"+file.getName()+"大小为："+file.length());
      vector.add(file);
    }else{//文件夹
      File[] files = file.listFiles();
      for(File f : files){//递归
        if(f.isDirectory()){
          getPathAllFiles(f,vector);
        }else{
          System.out.println("在迭代函数中文件"+f.getName()+"大小为："+f.length());
          vector.add(f);
        }
      }
    }
    return vector;
  }
  
  /**
   * 压缩文件到指定文件夹
   * @param sourceFilePath 源地址
   * @param destinFilePath 目的地址
   */
  public static String zipFiles(String sourceFilePath,String destinFilePath){
    File sourceFile = new File(sourceFilePath);
    FileInputStream fis = null;
    BufferedInputStream bis = null;
    FileOutputStream fos = null;
    ZipOutputStream zos = null;
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
    String fileName = dateFormat.format(new Date())+".zip";
    String zipFilePath = destinFilePath+File.separator+fileName;
    if (sourceFile.exists() == false) {
      System.out.println("待压缩的文件目录：" + sourceFilePath + "不存在.");
    } else {
      try {
        File zipFile = new File(zipFilePath);
        if (zipFile.exists()) {
          System.out.println(zipFilePath + "目录下存在名字为:" + fileName + ".zip" + "打包文件.");
        } else {
          File[] sourceFiles = sourceFile.listFiles();
          if (null == sourceFiles || sourceFiles.length < 1) {
            System.out.println("待压缩的文件目录：" + sourceFilePath + "里面不存在文件，无需压缩.");
          } else {
            //读取sourceFile下的所有文件
            Vector<File> vector = FileUtil.getPathAllFiles(sourceFile, new Vector<File>()); 
            fos = new FileOutputStream(zipFile);
            zos = new ZipOutputStream(new BufferedOutputStream(fos));
            byte[] bufs = new byte[1024 * 10];
            
            for (int i = 0; i < vector.size(); i++) {
              // 创建ZIP实体，并添加进压缩包
              ZipEntry zipEntry = new ZipEntry(vector.get(i).getName());//文件不可重名，否则会报错
              zos.putNextEntry(zipEntry);
              // 读取待压缩的文件并写进压缩包里
              fis = new FileInputStream(vector.get(i));
              bis = new BufferedInputStream(fis, 1024 * 10);
              int read = 0;
              while ((read = bis.read(bufs, 0, 1024 * 10)) != -1) {
                zos.write(bufs, 0, read);
              }
            }
          }
        }
      } catch (FileNotFoundException e) {
        e.printStackTrace();
        throw new RuntimeException(e);
      } catch (IOException e) {
        e.printStackTrace();
        throw new RuntimeException(e);
      } finally {
        // 关闭流
        try {
          if (null != bis)
            bis.close();
          if (null != zos)
            zos.closeEntry();
            zos.close();
        } catch (IOException e) {
          e.printStackTrace();
          throw new RuntimeException(e);
        }
      }
    }
    return fileName;
  }
  
}