web中gzip,deflate的压缩与解压

一，对发送请求进行gzip,deflate压缩

1:gzip的情况

Sring url = "http://localhost/save";
PostMethod post = new PostMethod(url);
//请求体内容
String body = "sample";
//用gzip方式压缩请求体并赋给request
ByteArrayInputStream bis = new ByteArrayInputStream(body.getBytes());
ByteArrayOutputStream bos = new ByteArrayOutputStream();
GZIPOutputStream gos = new GZIPOutputStream(bos);
for (int c = bis.read(); c != -1; c = bis.read()) {
    gos.write(c);
}
gos.close();
InputStreamRequestEntity entity = new InputStreamRequestEntity(new ByteArrayInputStream(bos.toByteArray()), "text/html");
post.setRequestEntity(entity);
post.addRequestHeader("Content-Encoding", "gzip");

 

2:deflate的情况

Sring url = "http://localhost/save";
PostMethod post = new PostMethod(url);
//请求体内容
String body = "sample";
//用deflate方式压缩请求体并赋给request
ByteArrayInputStream bis = new ByteArrayInputStream(body.getBytes());
ByteArrayOutputStream bos = new ByteArrayOutputStream();
DeflaterOutputStream dos = new DeflaterOutputStream(bos);
for (int c = bis.read(); c != -1; c = bis.read()) {
    dos.write(c);
}
dos.close();
InputStreamRequestEntity entity = new InputStreamRequestEntity(new ByteArrayInputStream(bos.toByteArray()), "text/html");
post.setRequestEntity(entity);
post.addRequestHeader("Content-Encoding", "deflate");

 

二，在服务器端使用过滤器对压缩过的请求进行解压

新建一个filter继承UserAgentFilter.java,截取req,进行包装，接着继续执行别的filters

@Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException,
    ServletException {
    HttpServletRequest request = (HttpServletRequest) req;
    String ce = request.getHeader("Content-Encoding"); // gzip|deflate|inflate
    if (ce != null) {
        if (ce.indexOf("deflate") >= 0 || ce.indexOf("inflate") >= 0) {
	    // uncompress using inflate
	    request = new InflateRequestWrapper(request);
        } else if (ce.indexOf("gzip") >= 0) {
	    // uncompress using gzip
	    request = new GZipRequestWrapper(request);
        }
    }
    ......
    super.doFilter(request, res, chain);
    ......
}

 

下面是InflateRequestWrapper的内容，GZipRequestWrapper与之类似

public class InflateRequestWrapper extends HttpServletRequestWrapper {
    private BufferedServletInputStreamWrapper _stream;

    public InflateRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        _stream = new BufferedServletInputStreamWrapper(new InflaterInputStream(request.getInputStream()), request.getContentLength());
    }

    @Override
    public BufferedServletInputStreamWrapper getInputStream() {
        return _stream;
    }

    @Override
    public int getContentLength() {
        return _stream.getBytes().length;
    }
}

 

下面是BufferedServletInputStreamWrapper的内容

public class BufferedServletInputStreamWrapper extends ServletInputStream {

    private static final int DEFAULT_READ_BUFFER_SIZE = 1024;
    private final byte[] EMPTY_ARRAY = new byte[0];
    private ByteArrayInputStream _is;
    private byte[] _bytes;

    /**
     * takes in the actual input stream that we should be buffering
     */
    public BufferedServletInputStreamWrapper(InflaterInputStream stream, int length) throws IOException {
        _bytes = (length == 0) ? EMPTY_ARRAY : toBytes(stream, length);
        _is = new ByteArrayInputStream(_bytes);
    }

    @Override
    public int read() throws IOException {
        return _is.read();
    }

    @Override
    public int read(byte[] buf,
                    int off,
                    int len) {
        return _is.read(buf, off, len);
    }

    @Override
    public int read(byte[] buf) throws IOException {
        return _is.read(buf);
    }

    @Override
    public int available() {
        return _is.available();
    }

    /**
     * resets the wrapper's stream so that it can be re-read from the stream. if we're
     * using this somewhere were we expect it to be done again in the chain this should
     * be called after we're through so we can reset the data.
     */

    public void resetWrapper() {
        _is = new ByteArrayInputStream(_bytes);
    }

    public byte[] getBytes() {
        return _bytes;
    }

    private byte[] toBytes(InputStream is, int bufferSize) throws IOException {
        bufferSize = (bufferSize <= 0) ? DEFAULT_READ_BUFFER_SIZE : bufferSize;
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] buffer = new byte[bufferSize];
        int read = is.read(buffer);

        while (-1 != read) {
            bos.write(buffer, 0, read);
            read = is.read(buffer);
        }

        return bos.toByteArray();
    }
}

 

三，服务器对response进行压缩可参考jetty相关源码

 

四，java客户端对压缩过的返回值进行解压

1,gzip的情况

GZIPInputStream gzip = new GZIPInputStream(post.getResponseBodyAsStream());
StringBuffer out = new StringBuffer();
byte[] b = new byte[4096];
for (int n; (n = gzip.read(b)) != -1;) {
    out.append(new String(b, 0, n));
}
return out.toString();

 

2，deflate的情况

InflaterInputStream iis = new InflaterInputStream(post.getResponseBodyAsStream());
contentLength = (contentLength <= 0) ? 1024 : contentLength;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] buffer = new byte[contentLength];
int read = iis.read(buffer);

while (-1 != read) {
    bos.write(buffer, 0, read);
    read = iis.read(buffer);
}

byte[] _bytes = (contentLength == 0) ? EMPTY_ARRAY : bos.toByteArray();
ByteArrayInputStream _is = new ByteArrayInputStream(_bytes);

StringBuffer out = new StringBuffer();
byte[] b = new byte[4096];
for (int n; (n = _is.read(b)) != -1;) {
    out.append(new String(b, 0, n));
}
return out.toString();

 

评论

2 楼 zhoulei984623 2011-03-21  

youfengkai 写道

客户端如何判断，该针对gzip还是deflate来解压呢？

对返回的头信息里面加上相应的标记

1 楼 youfengkai 2011-03-21  

客户端如何判断，该针对gzip还是deflate来解压呢？