关于GZIPInputStream的bug

http://cin-ie.iteye.com/blog/859822

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;publicclass 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);elsechild=new MultiMemberGZIPInputStream(this, this.size);return child.read(inputBuffer, inputBufferOffset, inputBufferLen);}elsereturn 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)),

http://blog.csdn.net/hwq1987/article/details/6279130

在解压gz文件时，如果直接用java.util.zip.GZIPInputStream来处理问题只能解压很少一部分内容，通过类MultiMemberGZIPInputStream 可以完全解压一个gz文件。

import java.io.IOException;import java.io.InputStream;import java.io.PushbackInputStream;import java.util.zip.GZIPInputStream;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);elsechild = new MultiMemberGZIPInputStream(this, this.size);return child.read(inputBuffer, inputBufferOffset, inputBufferLen);} elsereturn charsRead;}}

应用示例：

try {int nnumber;FileInputStream fin = new FileInputStream(gzPath);MultiMemberGZIPInputStream MmGz = new MultiMemberGZIPInputStream(fin);FileOutputStream fout = new FileOutputStream(topath);byte[] buf = new byte[1024];nnumber = MmGz.read(buf, 0, buf.length);while (nnumber != -1) {fout.write(buf, 0, nnumber);nnumber = MmGz.read(buf, 0, buf.length);}MmGz.close();fout.close();fin.close();} catch (Exception e) {e.printStackTrace();}

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