GZIPInputStream的bug

关于GZIPInputStream的bug，在jdk的最新版本上竟然还没解决这个问题。用到gzip的需要注意了：

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4691425

问题描述：

在使用GZIPInputStream对gizp文件进行读取的时候，使用read方法，方法返回-1，表示该文件读取真正的结束，但是实际却并不是这样。


这些文件在windowsxp用win-rar解压或者linux上zcat aaa.gz命令进行解压后，是可以获得文件的全部内容的。但是在使用GZIPInputStream却不行。

这个bug是java在读取gzip文件的时候，还没有读取完毕，过早的返回-1，造成有部分文件没有读取完毕。

不过好在已经有人解决这个问题了，下面是解决的方法：

package x.y.z;

import java.io.InputStream;
import java.io.PushbackInputStream;
import java.io.IOException;

public
class MultiMemberGZIPInputStream extends GZIPInputStream {

    public MultiMemberGZIPInputStream(InputStream in, int size) throws IOException
    {
        // Wrap the stream in a PushbackInputStream…
        super(new PushbackInputStream(in, size), size);
        this.size=size;
    }

    public MultiMemberGZIPInputStream(InputStream in) throws IOException
    {
        // Wrap the stream in a PushbackInputStream…
        super(new PushbackInputStream(in, 1024));
        this.size=-1;
    }

    private MultiMemberGZIPInputStream(MultiMemberGZIPInputStream parent) throws IOException
    {
        super(parent.in);
        this.size=-1;
        this.parent=parent.parent==null ? parent : parent.parent;
        this.parent.child=this;
    }

    private MultiMemberGZIPInputStream(MultiMemberGZIPInputStream parent, int size) throws IOException
    {
        super(parent.in, size);
        this.size=size;
        this.parent=parent.parent==null ? parent : parent.parent;
        this.parent.child=this;
    }

    private MultiMemberGZIPInputStream parent;
    private MultiMemberGZIPInputStream child;
    private int size;
    private boolean eos;

    public int read(byte[] inputBuffer, int inputBufferOffset, int inputBufferLen) throws IOException {

        if (eos) { return -1;}
        if (this.child!=null)
            return this.child.read(inputBuffer, inputBufferOffset, inputBufferLen);

        int charsRead=super.read(inputBuffer, inputBufferOffset, inputBufferLen);
        if (charsRead==-1)
        {
            // Push any remaining buffered data back onto the stream
            // If the stream is then not empty, use it to construct
            // a new instance of this class and delegate this and any
            // future calls to it…
            int n = inf.getRemaining() – 8;
            if (n > 0)
            {
                // More than 8 bytes remaining in deflater
                // First 8 are gzip trailer. Add the rest to
                // any un-read data…
                ((PushbackInputStream)this.in).unread(buf, len-n, n);
            }
            else
            {
                // Nothing in the buffer. We need to know whether or not
                // there is unread data available in the underlying stream
                // since the base class will not handle an empty file.
                // Read a byte to see if there is data and if so,
                // push it back onto the stream…
                byte[] b=new byte[1];
                int ret=in.read(b,0,1);
                if (ret==-1)
                {
                    eos=true;
                    return -1;
                }
                else
                    ((PushbackInputStream)this.in).unread(b, 0, 1);
            }

            MultiMemberGZIPInputStream child;
            if (this.size==-1)
                child=new MultiMemberGZIPInputStream(this);
            else
                child=new MultiMemberGZIPInputStream(this, this.size);
            return child.read(inputBuffer, inputBufferOffset, inputBufferLen);
        }
        else
            return charsRead;
    }

}

重写了GZIPInputStream这个类。然后你在使用的时候直接引入MultiMemberGZIPInputStream这个类，并调用即可。

例如：

  BufferedReader     bufferedReader = new BufferedReader(new InputStreamReader(new MultiMemberGZIPInputStream(new FileInputStream(gzFile)),

评论

4 楼 流氓24# 2013-05-22  

知道了，强转些就好了

3 楼 流氓24# 2013-05-22  

inf.getRemaining() – 8;  是什么啊，为什么跌进来就报错。

2 楼 小白茶1112 2013-04-22  

多谢大神，帮了大忙

1 楼 Williams_Glee 2012-11-21