spring文件下载

package com.util;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.util.FileCopyUtils;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

/**
 * 文件下载
 * 调用入口写在BaseController里面
 * Created by zyb on 2017/5/3.
 */
public class DownloadFile {

    /**
     * 下载文件
     *
     * @param filePath 文件物理路径
     * @param fileName 文件名带后缀(为null或空字符串时，获取文件真实名称)
     * @return ResponseEntity
     */
    public static ResponseEntity<byte[]> downloadResponse(String filePath, String fileName) {
        try {
            filePath = new String(filePath.getBytes("ISO8859-1"), "UTF-8");
            if (fileName != null)
                fileName = new String(fileName.getBytes("ISO8859-1"), "UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        byte[] res = new byte[0];
        File file = new File(filePath);
        if (file.exists() && !file.isDirectory()) {
            try {
                res = FileCopyUtils.copyToByteArray(file);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if (fileName == null || fileName.length() == 0) {
            fileName = file.getName();
        }
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes())
                .getRequest();
        String header = request.getHeader("User-Agent").toUpperCase();
        HttpStatus status = HttpStatus.CREATED;
        try {
            if (header.contains("MSIE") || header.contains("TRIDENT") || header.contains("EDGE")) {
                fileName = URLEncoder.encode(fileName, "UTF-8");
                fileName = fileName.replace("+", "%20");    // IE下载文件名空格变+号问题
                status = HttpStatus.OK;
            } else {
                fileName = new String(fileName.getBytes("UTF-8"), "ISO8859-1");
            }
        } catch (UnsupportedEncodingException ignored) {
            ignored.printStackTrace();
        }
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        headers.setContentDispositionFormData("attachment", fileName);
        headers.setContentLength(res.length);
        return new ResponseEntity<byte[]>(res, headers, status);
    }
}