如何在java中下载没有内存问题的大文件 [英] how to download large files without memory issues in java

问题描述

当我尝试从服务器下载260MB的大文件时，我收到此错误： java.lang.OutOfMemoryError：Java堆空间。我确定我的堆大小小于252MB。有没有什么办法可以在不增加堆大小的情况下下载大文件？

When I am trying to download a large file which is of 260MB from server, I get this error: java.lang.OutOfMemoryError: Java heap space. I am sure my heap size is less than 252MB. Is there any way I can download large files without increasing heap size?

如何在不出现此问题的情况下下载大文件？我的代码如下：

How I can download large files without getting this issue? My code is given below:

String path= "C:/temp.zip";   
response.addHeader("Content-Disposition", "attachment; filename=\"test.zip\""); 
byte[] buf = new byte[1024];   
try {   

             File file = new File(path);   
             long length = file.length();   
             BufferedInputStream in = new BufferedInputStream(new FileInputStream(file));   
             ServletOutputStream out = response.getOutputStream();   

             while ((in != null) && ((length = in.read(buf)) != -1)) {   
             out.write(buf, 0, (int) length);   
             }   
             in.close();   
             out.close();

推荐答案

有两个地方我可以看到你可能潜在的建立内存使用：

There are 2 places where I can see you could potentially be building up memory usage:

1. 在读取输入文件的缓冲区中。


2. 在缓冲区中写入输出流（HTTPOutputStream？）

对于＃1我建议直接从文件中读取 FileInputStream 没有 BufferedInputStream 。首先尝试这一点，看看它是否能解决您的问题。 ie：

For #1 I would suggest reading directly from the file via FileInputStream without the BufferedInputStream. Try this first and see if it resolves your issue. ie:

FileInputStream in = new FileInputStream(file);   

而不是：

BufferedInputStream in = new BufferedInputStream(new FileInputStream(file));   

如果＃1无法解决问题，您可以尝试在这么多数据后定期刷新输出流编写（必要时减少块大小）：

If #1 does not resolve the issue, you could try periodically flushing the output stream after so much data is written (decrease chunk size if necessary):

ie：

try
{
    FileInputStream fileInputStream  = new FileInputStream(file);
    byte[] buf=new byte[8192];
    int bytesread = 0, bytesBuffered = 0;
    while( (bytesread = fileInputStream.read( buf )) > -1 ) {
        out.write( buf, 0, bytesread );
        bytesBuffered += bytesread;
        if (bytesBuffered > 1024 * 1024) { //flush after 1MB
            bytesBuffered = 0;
            out.flush();
        }
    }
}
finally {
    if (out != null) {
        out.flush();
    }
}

这篇关于如何在java中下载没有内存问题的大文件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！