好用的文件下载类

    /**
     * 首页下载使用说明
     * @throws Exception 
     */
    @RequestMapping(value="downfileDownload")
    public void downfileDownload(HttpServletResponse response) throws Exception{
        String filePath = String.valueOf(Thread.currentThread().getContextClassLoader().getResource("").getPath()+"../../")+"instruction.docx";
        FileDownload.fileDownload(response, filePath, "北京市高层建筑消防安全综合治理数据平台使用手册（支队、监督员、用户版）.docx");
    }

package com.fh.util;

import java.io.BufferedOutputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.http.HttpServletResponse;

/**
 * 下载文件
 * 创建时间：2014年12月23日
 * @version
 */
public class FileDownload {

    /**
     * @param response 
     * @param filePath        //文件完整路径(包括文件名和扩展名)
     * @param fileName        //下载后看到的文件名
     * @return  文件名
     */
    public static void fileDownload(final HttpServletResponse response, String filePath, String fileName) throws Exception{  
           
        byte[] data = FileUtil.toByteArray2(filePath);  
        fileName = URLEncoder.encode(fileName, "UTF-8");  
        response.reset();  
        response.setHeader("Content-Disposition", "attachment; filename="" + fileName + """);  
        response.addHeader("Content-Length", "" + data.length);  
        response.setContentType("application/octet-stream;charset=UTF-8");  
        OutputStream outputStream = new BufferedOutputStream(response.getOutputStream());  
        outputStream.write(data);  
        outputStream.flush();  
        outputStream.close();
        response.flushBuffer();
        
    } 

}

package com.fh.util;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;

/**    文件处理
*  创建人：FH Q313596790
 * 创建时间：2014年12月23日
 */
public class FileUtil {

    
    /**获取文件大小 返回 KB 保留3位小数  没有文件时返回0
     * @param filepath 文件完整路径，包括文件名
     * @return
     */
    public static Double getFilesize(String filepath){
        File backupath = new File(filepath);
        return Double.valueOf(backupath.length())/1000.000;
    }
    
    /**
     * 创建目录
     * @param destDirName目标目录名
     * @return 
     */
    public static Boolean createDir(String destDirName) {
        File dir = new File(destDirName);
        if(!dir.getParentFile().exists()){                //判断有没有父路径，就是判断文件整个路径是否存在
            return dir.getParentFile().mkdirs();        //不存在就全部创建
        }
        return false;
    }

    /**
     * 删除文件
     * @param filePathAndName
     *            String 文件路径及名称 如c:/fqf.txt
     * @param fileContent
     *            String
     * @return boolean
     */
    public static void delFile(String filePathAndName) {
        try {
            String filePath = filePathAndName;
            filePath = filePath.toString();
            java.io.File myDelFile = new java.io.File(filePath);
            myDelFile.delete();
        } catch (Exception e) {
            System.out.println("删除文件操作出错");
            e.printStackTrace();
        }
    }

    /**
     * 读取到字节数组0
     * @param filePath //路径
     * @throws IOException
     */
    public static byte[] getContent(String filePath) throws IOException {
        File file = new File(filePath);
        long fileSize = file.length();
        if (fileSize > Integer.MAX_VALUE) {
            System.out.println("file too big...");
            return null;
        }
        FileInputStream fi = new FileInputStream(file);
        byte[] buffer = new byte[(int) fileSize];
        int offset = 0;
        int numRead = 0;
        while (offset < buffer.length
                && (numRead = fi.read(buffer, offset, buffer.length - offset)) >= 0) {
            offset += numRead;
        }
        // 确保所有数据均被读取
        if (offset != buffer.length) {
            throw new IOException("Could not completely read file " + file.getName());
        }
        fi.close();
        return buffer;
    }

    /**
     * 读取到字节数组1
     * 
     * @param filePath
     * @return
     * @throws IOException
     */
    public static byte[] toByteArray(String filePath) throws IOException {

        File f = new File(filePath);
        if (!f.exists()) {
            throw new FileNotFoundException(filePath);
        }
        ByteArrayOutputStream bos = new ByteArrayOutputStream((int) f.length());
        BufferedInputStream in = null;
        try {
            in = new BufferedInputStream(new FileInputStream(f));
            int buf_size = 1024;
            byte[] buffer = new byte[buf_size];
            int len = 0;
            while (-1 != (len = in.read(buffer, 0, buf_size))) {
                bos.write(buffer, 0, len);
            }
            return bos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
            throw e;
        } finally {
            try {
                in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            bos.close();
        }
    }

    /**
     * 读取到字节数组2
     * 
     * @param filePath
     * @return
     * @throws IOException
     */
    public static byte[] toByteArray2(String filePath) throws IOException {
        File f = new File(filePath);
        if (!f.exists()) {
            throw new FileNotFoundException(filePath);
        }
        FileChannel channel = null;
        FileInputStream fs = null;
        try {
            fs = new FileInputStream(f);
            channel = fs.getChannel();
            ByteBuffer byteBuffer = ByteBuffer.allocate((int) channel.size());
            while ((channel.read(byteBuffer)) > 0) {
                // do nothing
                // System.out.println("reading");
            }
            return byteBuffer.array();
        } catch (IOException e) {
            e.printStackTrace();
            throw e;
        } finally {
            try {
                channel.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                fs.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Mapped File way MappedByteBuffer 可以在处理大文件时，提升性能
     * 
     * @param filename
     * @return
     * @throws IOException
     */
    public static byte[] toByteArray3(String filePath) throws IOException {

        FileChannel fc = null;
        RandomAccessFile rf = null;
        try {
            rf = new RandomAccessFile(filePath, "r");
            fc = rf.getChannel();
            MappedByteBuffer byteBuffer = fc.map(MapMode.READ_ONLY, 0,
                    fc.size()).load();
            //System.out.println(byteBuffer.isLoaded());
            byte[] result = new byte[(int) fc.size()];
            if (byteBuffer.remaining() > 0) {
                // System.out.println("remain");
                byteBuffer.get(result, 0, byteBuffer.remaining());
            }
            return result;
        } catch (IOException e) {
            e.printStackTrace();
            throw e;
        } finally {
            try {
                rf.close();
                fc.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}