source: release-kits/shared/ant-tasks/orans/GetPropertyValue.java@ 16927

import org.apache.tools.ant.*;
import org.apache.tools.ant.taskdefs.*;
import java.util.*;
import java.io.*;
import java.util.regex.*;

/**
 * Gets looks up a property in a properties file and returns its value
 */
public class GetPropertyValue extends Task {

    private File propertiesFile = null;
    private String propertyName = null;
    private String outputProperty = null;
    

    /**
     * for testing

    public static void main( String[] args ) {

        GetPropertyValue gpv = new GetPropertyValue();
        gpv.setPropertiesFile( new File(args[0]) );
        gpv.setPropertyName( args[1] );
        gpv.setOutputProperty( args[2] );
        gpv.execute();

    }
     */

    public void execute() {

        if ( propertiesFile == null ) {
            throw new BuildException( "Error - No properties file specified !!" );
        }

        if ( propertyName == null ) {
            throw new BuildException( "Error - No property name specified !!" );
        }

        if ( outputProperty == null ) {
            throw new BuildException( "Error - No output property specified !!" );
        }

        //compile the regex we're looking for
        //System.err.println( "compile the regex we're looking for" );
        String regex = "^" + propertyName.replaceAll("\\.","\\\\.") + "[:=]\\s*(.*)$";
        //System.err.println( "regex: " + regex );
        Pattern wantedLine = Pattern.compile( regex );

        //create the input stream
        //System.err.println( "create the input stream" );
        BufferedReader in = null;
        try {
            in = new BufferedReader(new FileReader( propertiesFile ));
        } catch ( Exception e ) {
            throw new BuildException( "Error - couldn't open the properties file " + propertiesFile );
        }

        //System.err.println( "pass over the file" );
        //pass over the file
        String line, value = null;

        try {
            
            boolean found = false;
            while ( (line = in.readLine()) != null && !found ) {

                Matcher matcher = wantedLine.matcher( line );
                if ( matcher.matches() ) {
                    //found the property
                    //System.err.println( "found the property" );
                    value = matcher.group(1);
                    value = value.replaceAll( "#.*", "" ).trim();
                    found = true;
                }


            }

            //close the input stream
            //System.err.println( "close the input stream" );
            in.close();

        } catch ( Exception e ) {
            throw new BuildException( "Error - couldn't read from the properties file" );
        }

        //set the property in ant
        if ( value != null ) {
            //System.err.println( "set the property in ant" );
            this.getProject().setProperty(outputProperty, value);
        }

        //System.err.println( "done" );

    }

   
    public void setPropertiesFile(File file) {
        this.propertiesFile = file;
    }

    public void setPropertyName(String name) {
        this.propertyName = name;
    }

    public void setOutputProperty(String property) {
        this.outputProperty = property;
    }

}