eu.bandm.tools.util

Class ParameterExpander

java.lang.Object

eu.bandm.tools.util.ParameterExpander

public class ParameterExpander
extends Object

Processor for parameter substitution in character streams. Every recognized parameter reference in the input stream is expanded to a specified value in the output stream.

Parameter References

Parameters references are of the form ESC+'{'+ name+'}', where ESC is a configurable nonempty constant prefix string, and name is a valid Java identifier starting with a lower-case letter. Compounds may be structured by internal capitalization (camel case). The default prefix is "$". Examples: ${param}, ${anotherParam}.

If a parameter reference is recognized, and a value has been specified (via substitution or the command line), then the reference is removed from the character stream, and replaced by the value. References to unknown parameters and syntactic fragments that do not constitute a well-formed reference are left untouched.

Java identifiers that start with an upper case letter are reserved for intrinsic operations. The names of these are otherwise case-insensitive; for interoperability a form that uses only upper case is recommended.

Java identifiers that do not start with a letter are reserved for future use.

Command Line Instrinsics

When this class is run as a command line application, the following intrinsic parameters expand to pre-defined values:

NOW

ISO-8601 representation of the time when processing has started.

INPUTS

A space-separated list of all input file arguments.

SUBST

A space-separated list of name=value pairs of the defined parameters.

Conditional Sections

Arbitrary sections of input text may be included from or excluded in the output, depending on whether a parameter has a specified non-empty value.

IF name

Marks the beginning of a section that is only included if parameter name has a specified value that is not the empty string. The section extends until a matching ELSE or ENDIF reference, or until the end of input.

ELSE

Ends the current conditional section and starts a section that is only included in the opposite case, that is if the named parameter has no specified value or is set to the empty string. If there is no current conditional section, then an excluded section is started.

ENDIF

Ends the current conditional section. Enclosing conditional sections remain in effect. If there is no current conditional section, then nothing happens.

Conditional sections may be nested. Text is included if and only if there is no enclosing section that is being excluded.

Command Line Syntax

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ParameterExpander.Parameter

Field Summary

Fields

Modifier and Type	Field and Description
static String	ASSIGN
static char	CLOSE_BRACE
static String	DEFAULT_ENCODING
static String	DEFAULT_ESCAPE
static String	ENCODING_PROPERTY_NAME
static String	ESCAPE_PROPERTY_NAME
static ParameterExpander.Parameter	INPUTS
static int	MAX_VALUE_LENGTH
static ParameterExpander.Parameter	NOW
static char	OPEN_BRACE
static ParameterExpander.Parameter	SUBST

Constructor Summary

Constructors

Constructor and Description
ParameterExpander(String escape)

Method Summary

Modifier and Type	Method and Description
static String	getInputsValue(Collection<String> inputs)
static String	getNowValue()
String	getSubstValue()
static void	main(String[] args) Run an instance of this class as a command line tool.
static void	parseArgument(String arg, List<String> inputs, Map<ParameterExpander.Parameter,String> substitution)
void	process(Reader in, Writer out)
void	setPredefinedParameters(Collection<String> inputs)
Map<ParameterExpander.Parameter,String>	substitution()
protected static ParameterExpander.Parameter	systemParameter(String name)
void	unfoldRecursiveSubstitutions()
static ParameterExpander.Parameter	userParameter(String name)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ESCAPE_PROPERTY_NAME

public static final String ESCAPE_PROPERTY_NAME

See Also:

Constant Field Values

ENCODING_PROPERTY_NAME

public static final String ENCODING_PROPERTY_NAME

See Also:

Constant Field Values

DEFAULT_ESCAPE

public static final String DEFAULT_ESCAPE

See Also:

Constant Field Values

DEFAULT_ENCODING

public static final String DEFAULT_ENCODING

See Also:

Constant Field Values

OPEN_BRACE

public static final char OPEN_BRACE

See Also:

Constant Field Values

CLOSE_BRACE

public static final char CLOSE_BRACE

See Also:

Constant Field Values

ASSIGN

public static final String ASSIGN

See Also:

Constant Field Values

MAX_VALUE_LENGTH

public static final int MAX_VALUE_LENGTH

See Also:

Constant Field Values

NOW

public static final ParameterExpander.Parameter NOW

INPUTS

public static final ParameterExpander.Parameter INPUTS

SUBST

public static final ParameterExpander.Parameter SUBST

Constructor Detail

ParameterExpander

public ParameterExpander(String escape)

Method Detail

userParameter

public static ParameterExpander.Parameter userParameter(String name)

systemParameter

protected static ParameterExpander.Parameter systemParameter(String name)

substitution

public Map<ParameterExpander.Parameter,String> substitution()

process

public void process(Reader in,
                    Writer out)
             throws IOException

Throws:

IOException

main

public static void main(String[] args)
                 throws IOException

Run an instance of this class as a command line tool.

Every command line argument that contains the character '=' is assumed to be a parameter specifier of the form name+'='+value.

Command line arguments that do not contain the character '=' are assumed to be names of input files. All named files are processed in order, and the output is concatenated. If there is no named input file, then input is read from System.in. Output is always written to System.out.

The behavior can be configured via system properties:

eu.bandm.tools.util.ParameterExpander.encoding

The name of the encoding to use for input and output stream (default: "UTF-8").

eu.bandm.tools.util.ParameterExpander.escape

The nonempty escape prefix (default: "$").

Throws:

IOException

setPredefinedParameters

public void setPredefinedParameters(Collection<String> inputs)

parseArgument

public static void parseArgument(String arg,
                                 List<String> inputs,
                                 Map<ParameterExpander.Parameter,String> substitution)

getSubstValue

public String getSubstValue()

getNowValue

public static String getNowValue()

getInputsValue

public static String getInputsValue(Collection<String> inputs)

unfoldRecursiveSubstitutions

public void unfoldRecursiveSubstitutions()