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package org.codehaus.plexus.util;
import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
import java.util.HashMap;
import java.util.Map;
A FilterReader which interpolates keyword values into a character stream. Keywords are recognized when enclosed
between starting and ending delimiter strings. The keywords themselves, and their values, are fetched from a Map
supplied to the constructor.
When a possible keyword token is recognized (by detecting the starting and ending token delimiters):
- if the enclosed string is found in the keyword Map, the delimiters and the keyword are effectively replaced by
the keyword's value;
- if the enclosed string is found in the keyword Map, but its value has zero length, then the token (delimiters and
keyword) is effectively removed from the character stream;
- if the enclosed string is not found in the keyword Map, then no substitution is made; the token text is
passed through unaltered.
See Also: - s
/**
* A FilterReader which interpolates keyword values into a character stream. Keywords are recognized when enclosed
* between starting and ending delimiter strings. The keywords themselves, and their values, are fetched from a Map
* supplied to the constructor.
* <p>
* When a possible keyword token is recognized (by detecting the starting and ending token delimiters):
* </p>
* <ul>
* <li>if the enclosed string is found in the keyword Map, the delimiters and the keyword are effectively replaced by
* the keyword's value;</li>
* <li>if the enclosed string is found in the keyword Map, but its value has zero length, then the token (delimiters and
* keyword) is effectively removed from the character stream;</li>
* <li>if the enclosed string is <em>not</em> found in the keyword Map, then no substitution is made; the token text is
* passed through unaltered.</li>
* </ul>
*
* @see LineOrientedInterpolatingReader s
*/
public class InterpolationFilterReader
extends FilterReader
{
replacement text from a token /** replacement text from a token */
private String replaceData = null;
Index into replacement data /** Index into replacement data */
private int replaceIndex = -1;
Index into previous data /** Index into previous data */
private int previousIndex = -1;
Hashtable to hold the replacee-replacer pairs (String to String). /** Hashtable to hold the replacee-replacer pairs (String to String). */
private Map<?, Object> variables = new HashMap<Object, Object>();
Character marking the beginning of a token. /** Character marking the beginning of a token. */
private String beginToken;
Character marking the end of a token. /** Character marking the end of a token. */
private String endToken;
Length of begin token. /** Length of begin token. */
private int beginTokenLength;
Length of end token. /** Length of end token. */
private int endTokenLength;
Default begin token. /** Default begin token. */
private static final String DEFAULT_BEGIN_TOKEN = "${";
Default end token. /** Default end token. */
private static final String DEFAULT_END_TOKEN = "}";
Construct a Reader to interpolate values enclosed between the given delimiter tokens.
Params: - in – a Reader to be wrapped for interpolation.
- variables – name/value pairs to be interpolated into the character stream.
- beginToken – an interpolation target begins with this.
- endToken – an interpolation target ends with this.
/**
* Construct a Reader to interpolate values enclosed between the given delimiter tokens.
*
* @param in a Reader to be wrapped for interpolation.
* @param variables name/value pairs to be interpolated into the character stream.
* @param beginToken an interpolation target begins with this.
* @param endToken an interpolation target ends with this.
*/
public InterpolationFilterReader( Reader in, Map<?, Object> variables, String beginToken, String endToken )
{
super( in );
this.variables = variables;
this.beginToken = beginToken;
this.endToken = endToken;
beginTokenLength = beginToken.length();
endTokenLength = endToken.length();
}
Construct a Reader using the default interpolation delimiter tokens "${" and "}".
Params: - in – a Reader to be wrapped for interpolation.
- variables – name/value pairs to be interpolated into the character stream.
/**
* Construct a Reader using the default interpolation delimiter tokens "${" and "}".
*
* @param in a Reader to be wrapped for interpolation.
* @param variables name/value pairs to be interpolated into the character stream.
*/
public InterpolationFilterReader( Reader in, Map<String, Object> variables )
{
this( in, variables, DEFAULT_BEGIN_TOKEN, DEFAULT_END_TOKEN );
}
Skips characters. This method will block until some characters are available, an I/O error occurs, or the end of
the stream is reached.
Params: - n – The number of characters to skip
Throws: - IllegalArgumentException – If
n
is negative. - IOException – If an I/O error occurs
Returns: the number of characters actually skipped
/**
* Skips characters. This method will block until some characters are available, an I/O error occurs, or the end of
* the stream is reached.
*
* @param n The number of characters to skip
* @return the number of characters actually skipped
* @exception IllegalArgumentException If <code>n</code> is negative.
* @exception IOException If an I/O error occurs
*/
public long skip( long n )
throws IOException
{
if ( n < 0L )
{
throw new IllegalArgumentException( "skip value is negative" );
}
for ( long i = 0; i < n; i++ )
{
if ( read() == -1 )
{
return i;
}
}
return n;
}
Reads characters into a portion of an array. This method will block until some input is available, an I/O error
occurs, or the end of the stream is reached.
Params: - cbuf – Destination buffer to write characters to. Must not be
null
. - off – Offset at which to start storing characters.
- len – Maximum number of characters to read.
Throws: - IOException – If an I/O error occurs
Returns: the number of characters read, or -1 if the end of the stream has been reached
/**
* Reads characters into a portion of an array. This method will block until some input is available, an I/O error
* occurs, or the end of the stream is reached.
*
* @param cbuf Destination buffer to write characters to. Must not be <code>null</code>.
* @param off Offset at which to start storing characters.
* @param len Maximum number of characters to read.
* @return the number of characters read, or -1 if the end of the stream has been reached
* @exception IOException If an I/O error occurs
*/
public int read( char cbuf[], int off, int len )
throws IOException
{
for ( int i = 0; i < len; i++ )
{
int ch = read();
if ( ch == -1 )
{
if ( i == 0 )
{
return -1;
}
else
{
return i;
}
}
cbuf[off + i] = (char) ch;
}
return len;
}
Returns the next character in the filtered stream, replacing tokens from the original stream.
Throws: - IOException – if the underlying stream throws an IOException during reading
Returns: the next character in the resulting stream, or -1 if the end of the resulting stream has been reached
/**
* Returns the next character in the filtered stream, replacing tokens from the original stream.
*
* @return the next character in the resulting stream, or -1 if the end of the resulting stream has been reached
* @exception IOException if the underlying stream throws an IOException during reading
*/
public int read()
throws IOException
{
if ( replaceIndex != -1 && replaceIndex < replaceData.length() )
{
int ch = replaceData.charAt( replaceIndex++ );
if ( replaceIndex >= replaceData.length() )
{
replaceIndex = -1;
}
return ch;
}
int ch;
if ( previousIndex != -1 && previousIndex < endTokenLength )
{
ch = endToken.charAt( previousIndex++ );
}
else
{
ch = in.read();
}
if ( ch == beginToken.charAt( 0 ) )
{
StringBuilder key = new StringBuilder();
int beginTokenMatchPos = 1;
do
{
if ( previousIndex != -1 && previousIndex < endTokenLength )
{
ch = endToken.charAt( previousIndex++ );
}
else
{
ch = in.read();
}
if ( ch != -1 )
{
key.append( (char) ch );
if ( ( beginTokenMatchPos < beginTokenLength )
&& ( ch != beginToken.charAt( beginTokenMatchPos++ ) ) )
{
ch = -1; // not really EOF but to trigger code below
break;
}
}
else
{
break;
}
}
while ( ch != endToken.charAt( 0 ) );
// now test endToken
if ( ch != -1 && endTokenLength > 1 )
{
int endTokenMatchPos = 1;
do
{
if ( previousIndex != -1 && previousIndex < endTokenLength )
{
ch = endToken.charAt( previousIndex++ );
}
else
{
ch = in.read();
}
if ( ch != -1 )
{
key.append( (char) ch );
if ( ch != endToken.charAt( endTokenMatchPos++ ) )
{
ch = -1; // not really EOF but to trigger code below
break;
}
}
else
{
break;
}
}
while ( endTokenMatchPos < endTokenLength );
}
// There is nothing left to read so we have the situation where the begin/end token
// are in fact the same and as there is nothing left to read we have got ourselves
// end of a token boundary so let it pass through.
if ( ch == -1 )
{
replaceData = key.toString();
replaceIndex = 0;
return beginToken.charAt( 0 );
}
String variableKey = key.substring( beginTokenLength - 1, key.length() - endTokenLength );
Object o = variables.get( variableKey );
if ( o != null )
{
String value = o.toString();
if ( value.length() != 0 )
{
replaceData = value;
replaceIndex = 0;
}
return read();
}
else
{
previousIndex = 0;
replaceData = key.substring( 0, key.length() - endTokenLength );
replaceIndex = 0;
return beginToken.charAt( 0 );
}
}
return ch;
}
}