Class ContentCoding
- java.lang.Object
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- uk.ac.starlink.util.ContentCoding
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public abstract class ContentCoding extends java.lang.Object
Defines a policy for Content Codings used in HTTP connections. An instance of this class is used to prepare requests and decode responses for some HTTP-based communications in this package. It controls whether HTTP-level content codings are used; typically this means transparent gzip compression of the HTTP response stream where negotiation indicates it is allowed.Two static instances
NONE
andGZIP
are provided. It should be completely safe to use either of these in any context, since an instance of this class represents only an indication to an HTTP server that a particular coding scheme is supported by the client. A service is therefore always at liberty to ignore this hint/request and provide and unencoded response if, for instance, it does not support the requested compression scheme. Good practice for use of this class is therefore probably to use GZIP where the response is expected to be large and reasonably compressible (a long VOTable is a good example), and NONE where the response is expected to be short or, especially, not very gzippable (for instance noisy binary floating point data, or a byte stream that has already been compressed).The provided instances also include some logging functionality; information about how many bytes (and where applicable the level of compression) is logged for bytestreams read through these instances. The logging level for this information is currently CONFIG.
- See Also:
- RFC 2616 secs 3.5, 14.3, 14.11
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Field Summary
Fields Modifier and Type Field Description static java.lang.String
ACCEPT_ENCODING
Name of HTTP request header to request coded response ("Accept-Encoding").static java.lang.String
CONTENT_ENCODING
Name of HTTP response header to mark coded response ("Content-Encoding").static ContentCoding
GZIP
Gzip encoding is requested.static ContentCoding
NONE
No encoding is requested.
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Constructor Summary
Constructors Modifier Constructor Description protected
ContentCoding()
Constructor.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description abstract java.io.InputStream
getErrorStream(java.net.URLConnection conn)
Returns the error stream response from the given connection, which was prepared using this object'sprepareRequest
method.abstract java.io.InputStream
getInputStream(java.net.URLConnection conn)
Returns the input stream response from the given connection, which was prepared using this object'sprepareRequest
method.java.net.URLConnection
openConnection(java.net.URL url)
Convenience method to open a new connection prepared in accordance with this object's encoding policy.java.io.InputStream
openStream(java.net.URL url)
Convenience method to return a byte stream from a given URL in accordance with this object's encoding policy.abstract void
prepareRequest(java.net.URLConnection conn)
Sets up request headers for the given connection.
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Field Detail
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NONE
public static final ContentCoding NONE
No encoding is requested.
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GZIP
public static final ContentCoding GZIP
Gzip encoding is requested.
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ACCEPT_ENCODING
public static final java.lang.String ACCEPT_ENCODING
Name of HTTP request header to request coded response ("Accept-Encoding").- See Also:
- Constant Field Values
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CONTENT_ENCODING
public static final java.lang.String CONTENT_ENCODING
Name of HTTP response header to mark coded response ("Content-Encoding").- See Also:
- Constant Field Values
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Method Detail
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prepareRequest
public abstract void prepareRequest(java.net.URLConnection conn)
Sets up request headers for the given connection. The connection must not have yet been connected.- Parameters:
conn
- unconnected connection
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getInputStream
public abstract java.io.InputStream getInputStream(java.net.URLConnection conn) throws java.io.IOException
Returns the input stream response from the given connection, which was prepared using this object'sprepareRequest
method. Any required decoding will have been done transparently.- Parameters:
conn
- connection- Returns:
- stream decoded as required
- Throws:
java.io.IOException
- See Also:
URLConnection.getInputStream()
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getErrorStream
public abstract java.io.InputStream getErrorStream(java.net.URLConnection conn) throws java.io.IOException
Returns the error stream response from the given connection, which was prepared using this object'sprepareRequest
method. Any required decoding will have been done transparently.- Parameters:
conn
- connection- Returns:
- stream decoded as required
- Throws:
java.io.IOException
- See Also:
URLConnection.getInputStream()
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openConnection
public java.net.URLConnection openConnection(java.net.URL url) throws java.io.IOException
Convenience method to open a new connection prepared in accordance with this object's encoding policy. Opens the connection and callsprepareRequest
.- Parameters:
url
- target URL- Returns:
- prepared connection
- Throws:
java.io.IOException
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openStream
public java.io.InputStream openStream(java.net.URL url) throws java.io.IOException
Convenience method to return a byte stream from a given URL in accordance with this object's encoding policy. Opens the connection, prepares the request, and decodes the result.- Parameters:
url
- target URL- Returns:
- unencoded stream from the URL
- Throws:
java.io.IOException
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