org.apache.oro.text

Class MatchActionProcessor

java.lang.Object

org.apache.oro.text.MatchActionProcessor

public final class MatchActionProcessor
extends java.lang.Object

The MatchActionProcessor class provides AWK-like line by line filtering of a text stream, pattern action pair association, and field splitting based on a registered separator. However, the class can be used with any compatible PatternMatcher/PatternCompiler implementations and need not use the AWK matching classes in org.apache.oro.text.awk. In fact, the default matcher and compiler used by the class are Perl5Matcher and Perl5Compiler from org.apache.oro.text.regex.

To completely understand how to use MatchActionProcessor, you should first look at MatchAction and MatchActionInfo. A MatchActionProcessor is first initialized with the desired PatternCompiler and PatternMatcher instances to use to compile patterns and perform matches. Then, optionally, a field separator may be registered with setFieldSeparator() Finally, as many pattern action pairs as desired are registerd with addAction() before processing the input with processMatches(). Pattern action pairs are processed in the order they were registered.

The look of added actions can closely mirror that of AWK when anonymous classes are used. Here's an example of how you might use MatchActionProcessor to extract only the second column of a semicolon delimited file:

 import java.io.*;

 import org.apache.oro.text.*;
 import org.apache.oro.text.regex.*;

 public final class semicolon {

  public static final void main(String[] args) {
    MatchActionProcessor processor = new MatchActionProcessor();

    try {
      processor.setFieldSeparator(";");
      // Using a null pattern means to perform the action for every line.
      processor.addAction(null, new MatchAction() {
        public void processMatch(MatchActionInfo info) {
            // We assume the second column exists
          info.output.println(info.fields.elementAt(1));
        }
     });
   } catch(MalformedPatternException e) {
     e.printStackTrace();
     System.exit(1);
   }

   try {
      processor.processMatches(System.in, System.out);
   } catch(IOException e) {
     e.printStackTrace();
     System.exit(1);
   }
  }
}
 

You can redirect the following sample input to stdin to test the code:

 1;Trenton;New Jersey
 2;Annapolis;Maryland
 3;Austin;Texas
 4;Richmond;Virginia
 5;Harrisburg;Pennsylvania
 6;Honolulu;Hawaii
 7;Santa Fe;New Mexico
 

Since:

1.0

Version:

2.0.8

See Also:

MatchAction, MatchActionInfo

Constructor Summary

Constructors

Constructor and Description
MatchActionProcessor() Default constructor for MatchActionProcessor.
MatchActionProcessor(PatternCompiler compiler, PatternMatcher matcher) Creates a new MatchActionProcessor instance initialized with the specified pattern compiler and matcher.

Method Summary

Modifier and Type	Method and Description
void	addAction(java.lang.String pattern) Binds a patten to the default action.
void	addAction(java.lang.String pattern, int options) Binds a patten to the default action, providing options to be used to compile the pattern.
void	addAction(java.lang.String pattern, int options, MatchAction action) Registers a pattern action pair, providing options to be used to compile the pattern.
void	addAction(java.lang.String pattern, MatchAction action) Registers a pattern action pair.
void	processMatches(java.io.InputStream input, java.io.OutputStream output) This method reads the provided input one line at a time using the platform standart character encoding and for every registered pattern that is contained in the line it executes the associated MatchAction's processMatch() method.
void	processMatches(java.io.InputStream input, java.io.OutputStream output, java.lang.String encoding) This method reads the provided input one line at a time and for every registered pattern that is contained in the line it executes the associated MatchAction's processMatch() method.
void	processMatches(java.io.Reader input, java.io.Writer output) This method reads the provided input one line at a time and for every registered pattern that is contained in the line it executes the associated MatchAction's processMatch() method.
void	setFieldSeparator(java.lang.String separator) Sets the field separator to use when splitting a line into fields.
void	setFieldSeparator(java.lang.String separator, int options) Sets the field separator to use when splitting a line into fields.

Methods inherited from class java.lang.Object

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

Constructor Detail

MatchActionProcessor

public MatchActionProcessor(PatternCompiler compiler,
                            PatternMatcher matcher)

Creates a new MatchActionProcessor instance initialized with the specified pattern compiler and matcher. The field separator is set to null by default, which means that matched lines will not be split into separate fields unless the field separator is set with setFieldSeparator().

Parameters:

compiler - The PatternCompiler to use to compile registered patterns.

matcher - The PatternMatcher to use when searching for matches.

MatchActionProcessor

public MatchActionProcessor()

Default constructor for MatchActionProcessor. Same as calling

MatchActionProcessor(new Perl5Compiler(), new Perl5Matcher());

Method Detail

addAction

public void addAction(java.lang.String pattern,
                      int options,
                      MatchAction action)
               throws MalformedPatternException

Registers a pattern action pair, providing options to be used to compile the pattern. If a pattern is null, the action is performed for every line of input.

Parameters:

pattern - The pattern to bind to an action.

options - The compilation options to use for the pattern.

action - The action to associate with the pattern.

Throws:

MalformedPatternException - If the pattern cannot be compiled.

addAction

public void addAction(java.lang.String pattern,
                      int options)
               throws MalformedPatternException

Binds a patten to the default action, providing options to be used to compile the pattern. The default action is to simply print the matched line to the output. If a pattern is null, the action is performed for every line of input.

Parameters:

pattern - The pattern to bind to an action.

options - The compilation options to use for the pattern.

Throws:

MalformedPatternException - If the pattern cannot be compiled.

addAction

public void addAction(java.lang.String pattern)
               throws MalformedPatternException

Binds a patten to the default action. The default action is to simply print the matched line to the output. If a pattern is null, the action is performed for every line of input.

Parameters:

pattern - The pattern to bind to an action.

Throws:

MalformedPatternException - If the pattern cannot be compiled.

addAction

public void addAction(java.lang.String pattern,
                      MatchAction action)
               throws MalformedPatternException

Registers a pattern action pair. If a pattern is null, the action is performed for every line of input.

Parameters:

pattern - The pattern to bind to an action.

action - The action to associate with the pattern.

Throws:

MalformedPatternException - If the pattern cannot be compiled.

setFieldSeparator

public void setFieldSeparator(java.lang.String separator,
                              int options)
                       throws MalformedPatternException

Sets the field separator to use when splitting a line into fields. If the field separator is never set, or set to null, matched input lines are not split into fields.

Parameters:

separator - A regular expression defining the field separator.

options - The options to use when compiling the separator.

Throws:

MalformedPatternException - If the separator cannot be compiled.

setFieldSeparator

public void setFieldSeparator(java.lang.String separator)
                       throws MalformedPatternException

Sets the field separator to use when splitting a line into fields. If the field separator is never set, or set to null, matched input lines are not split into fields.

Parameters:

separator - A regular expression defining the field separator.

Throws:

MalformedPatternException - If the separator cannot be compiled.

processMatches

public void processMatches(java.io.InputStream input,
                           java.io.OutputStream output,
                           java.lang.String encoding)
                    throws java.io.IOException

This method reads the provided input one line at a time and for every registered pattern that is contained in the line it executes the associated MatchAction's processMatch() method. If a field separator has been defined with setFieldSeparator(), the fields member of the MatchActionInfo instance passed to the processMatch() method is set to a Vector of Strings containing the split fields of the line. Otherwise the fields member is set to null. If no match was performed to invoke the action (i.e., a null pattern was registered), then the match member is set to null. Otherwise, the match member will contain the result of the match.

The input stream, having been exhausted, is closed right before the method terminates and the output stream is flushed.

Parameters:

input - The input stream from which to read lines.

output - Where to send output.

encoding - The character encoding of the InputStream source. If you also want to define an output character encoding, you should use processMatches(Reader, Writer) and specify the encodings when creating the Reader and Writer sources and sinks.

Throws:

java.io.IOException - If an error occurs while reading input or writing output.

See Also:

MatchActionInfo

processMatches

public void processMatches(java.io.InputStream input,
                           java.io.OutputStream output)
                    throws java.io.IOException

This method reads the provided input one line at a time using the platform standart character encoding and for every registered pattern that is contained in the line it executes the associated MatchAction's processMatch() method. If a field separator has been defined with setFieldSeparator(), the fields member of the MatchActionInfo instance passed to the processMatch() method is set to a Vector of Strings containing the split fields of the line. Otherwise the fields member is set to null. If no match was performed to invoke the action (i.e., a null pattern was registered), then the match member is set to null. Otherwise, the match member will contain the result of the match.

The input stream, having been exhausted, is closed right before the method terminates and the output stream is flushed.

Parameters:

input - The input stream from which to read lines.

output - Where to send output.

Throws:

java.io.IOException - If an error occurs while reading input or writing output.

See Also:

MatchActionInfo

processMatches

public void processMatches(java.io.Reader input,
                           java.io.Writer output)
                    throws java.io.IOException

This method reads the provided input one line at a time and for every registered pattern that is contained in the line it executes the associated MatchAction's processMatch() method. If a field separator has been defined with setFieldSeparator(), the fields member of the MatchActionInfo instance passed to the processMatch() method is set to a Vector of Strings containing the split fields of the line. Otherwise the fields member is set to null. If no match was performed to invoke the action (i.e., a null pattern was registered), then the match member is set to null. Otherwise, the match member will contain the result of the match.

The input stream, having been exhausted, is closed right before the method terminates and the output stream is flushed.

Parameters:

input - The input stream from which to read lines.

output - Where to send output.

Throws:

java.io.IOException - If an error occurs while reading input or writing output.

See Also:

MatchActionInfo