import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;
import javax.servlet.http.HttpServletResponse;
import org.springframework.util.StringUtils;

 
/**
 * 文件下載
 */
public class FileLoad {

    /**
     * 使用response返回文件流
     */
    public void loadFile(String filePath, HttpServletResponse response) {
        // 聲明工具類
        BufferedInputStream in = null;
        BufferedOutputStream out = null;

        try {
            // 若路徑為空
            if (StringUtils.isEmpty(filePath)) {
                
 
throw new Exception("invalid filepath of null.");
            }

            // 沒找到文件
            File file = new File(filePath);
            if (!file.exists()) {
                throw new Exception("file not exist in path [" + filePath + "]");
            }

            // 獲取文件名
            String fileName = file.getName();

            
 
// 輸出文件流到瀏覽器
            in = new BufferedInputStream(new FileInputStream(filePath));
            out = new BufferedOutputStream(response.getOutputStream());
            response.setContentType("application/x-download;charset=utf-8");
            response.setHeader("Content-disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));

            byte[] buffer = new byte[8192];
            int count = 0;
            while ((count = in.read(buffer, 0, 8192)) != -1) {
                out.write(buffer, 0, count);
            }

            out.flush();
            file = null;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            closeStream(in, out);
        }
    }

    /**
     * 關閉輸入輸出流
     */
    public void closeStream(InputStream in, OutputStream out) {
        if (null != in) {
            try {
                in.close();
            } catch (IOException e) {
                // e.printStackTrace();
            }
        }
        if (null != out) {
            try {
                out.close();
            } catch (IOException e) {
                // e.printStackTrace();
            }
        }
    }

}

HttpServletResponse實現文件下載