https://ant.apache.org/: master POM (The Apache Software Foundation) 
/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.tools.ant.taskdefs.optional;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;
import java.nio.charset.Charset;
import java.nio.file.Files;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.types.FileSet;
import org.apache.tools.ant.types.RegularExpression;
import org.apache.tools.ant.types.Resource;
import org.apache.tools.ant.types.ResourceCollection;
import org.apache.tools.ant.types.Substitution;
import org.apache.tools.ant.types.resources.FileProvider;
import org.apache.tools.ant.types.resources.Union;
import org.apache.tools.ant.util.FileUtils;
import org.apache.tools.ant.util.regexp.Regexp;
import org.apache.tools.ant.util.regexp.RegexpUtil;


Performs regular expression string replacements in a text
file.  The input file(s) must be able to be properly processed by
a Reader instance.  That is, they must be text only, no binary.
The syntax of the regular expression depends on the implementation that
you choose to use. The system property ant.regexp.regexpimpl
will be the classname of the implementation that will be used (the default
is org.apache.tools.ant.util.regexp.JakartaOroRegexp and
requires the Jakarta Oro Package).

Available implementations:
  org.apache.tools.ant.util.regexp.Jdk14RegexpRegexp (default)
       Uses Java's built-in regular expression package
  org.apache.tools.ant.util.regexp.JakartaOroRegexp
       Requires  the jakarta-oro package
  org.apache.tools.ant.util.regexp.JakartaRegexpRegexp
       Requires the jakarta-regexp package
Usage:
  Call Syntax:
    <replaceregexp file="file"
                   match="pattern"
                   replace="pattern"
                   flags="options"?
                   byline="true|false"? >
      regexp?
      substitution?
      fileset*
    </replaceregexp>
   NOTE: You must have either the file attribute specified, or at least one fileset subelement
   to operation on.  You may not have the file attribute specified if you nest fileset elements
   inside this task.  Also, you cannot specify both match and a regular expression subelement at
   the same time, nor can you specify the replace attribute and the substitution subelement at
   the same time.
  Attributes:
    file    --> A single file to operation on (mutually exclusive
                   with the fileset subelements)
    match   --> The Regular expression to match
    replace --> The Expression replacement string
    flags   --> The options to give to the replacement
                g = Substitute all occurrences. default is to replace only the first one
                i = Case insensitive match
    byline  --> Should this file be processed a single line at a time (default is false)
                "true" indicates to perform replacement on a line by line basis
                "false" indicates to perform replacement on the whole file at once.
 Example:
    The following call could be used to replace an old property name in a ".properties"
    file with a new name.  In the replace attribute, you can refer to any part of the
    match expression in parenthesis using backslash followed by a number like '\1'.
    <replaceregexp file="test.properties"
                   match="MyProperty=(.*)"
                   replace="NewProperty=\1"
                   byline="true" />



/**
 * Performs regular expression string replacements in a text
 * file.  The input file(s) must be able to be properly processed by
 * a Reader instance.  That is, they must be text only, no binary.
 *
 * The syntax of the regular expression depends on the implementation that
 * you choose to use. The system property <code>ant.regexp.regexpimpl</code>
 * will be the classname of the implementation that will be used (the default
 * is <code>org.apache.tools.ant.util.regexp.JakartaOroRegexp</code> and
 * requires the Jakarta Oro Package).
 *
 * <pre>
 * Available implementations:
 *
 *   org.apache.tools.ant.util.regexp.Jdk14RegexpRegexp (default)
 *        Uses Java's built-in regular expression package
 *
 *   org.apache.tools.ant.util.regexp.JakartaOroRegexp
 *        Requires  the jakarta-oro package
 *
 *   org.apache.tools.ant.util.regexp.JakartaRegexpRegexp
 *        Requires the jakarta-regexp package
 *
 * Usage:
 *
 *   Call Syntax:
 *
 *     &lt;replaceregexp file="file"
 *                    match="pattern"
 *                    replace="pattern"
 *                    flags="options"?
 *                    byline="true|false"? &gt;
 *       regexp?
 *       substitution?
 *       fileset*
 *     &lt;/replaceregexp&gt;
 *
 *    NOTE: You must have either the file attribute specified, or at least one fileset subelement
 *    to operation on.  You may not have the file attribute specified if you nest fileset elements
 *    inside this task.  Also, you cannot specify both match and a regular expression subelement at
 *    the same time, nor can you specify the replace attribute and the substitution subelement at
 *    the same time.
 *
 *   Attributes:
 *
 *     file    --&gt; A single file to operation on (mutually exclusive
 *                    with the fileset subelements)
 *     match   --&gt; The Regular expression to match
 *     replace --&gt; The Expression replacement string
 *     flags   --&gt; The options to give to the replacement
 *                 g = Substitute all occurrences. default is to replace only the first one
 *                 i = Case insensitive match
 *
 *     byline  --&gt; Should this file be processed a single line at a time (default is false)
 *                 "true" indicates to perform replacement on a line by line basis
 *                 "false" indicates to perform replacement on the whole file at once.
 *
 *  Example:
 *
 *     The following call could be used to replace an old property name in a ".properties"
 *     file with a new name.  In the replace attribute, you can refer to any part of the
 *     match expression in parenthesis using backslash followed by a number like '\1'.
 *
 *     &lt;replaceregexp file="test.properties"
 *                    match="MyProperty=(.*)"
 *                    replace="NewProperty=\1"
 *                    byline="true" /&gt;
 *
 * </pre>
 *
 */
public class ReplaceRegExp extends Task {

    private File file;
    private String flags;
    private boolean byline;
    private Union resources;
    private RegularExpression regex;
    private Substitution subs;

    private static final FileUtils FILE_UTILS = FileUtils.getFileUtils();

    private boolean preserveLastModified = false;

    
Encoding to assume for the files

/**
     * Encoding to assume for the files
     */
    private String encoding = null;

    
Default Constructor  
/** Default Constructor  */
    public ReplaceRegExp() {
        super();
        this.file = null;
        this.flags = "";
        this.byline = false;

        this.regex = null;
        this.subs = null;
    }

    
file for which the regular expression should be replaced;
required unless a nested fileset is supplied.

Params:
  • file – The file for which the reg exp should be replaced.
/**
     * file for which the regular expression should be replaced;
     * required unless a nested fileset is supplied.
     *
     * @param file The file for which the reg exp should be replaced.
     */
    public void setFile(File file) {
        this.file = file;
    }

    
the regular expression pattern to match in the file(s);
required if no nested <regexp> is used

Params:
  • match – the match attribute.
/**
     * the regular expression pattern to match in the file(s);
     * required if no nested &lt;regexp&gt; is used
     *
     * @param match the match attribute.
     */
    public void setMatch(String match) {
        if (regex != null) {
            throw new BuildException("Only one regular expression is allowed");
        }

        regex = new RegularExpression();
        regex.setPattern(match);
    }

    
The substitution pattern to place in the file(s) in place
of the regular expression.
Required if no nested <substitution> is used

Params:
  • replace – the replace attribute
/**
     * The substitution pattern to place in the file(s) in place
     * of the regular expression.
     * Required if no nested &lt;substitution&gt; is used
     *
     * @param replace the replace attribute
     */

    public void setReplace(String replace) {
        if (subs != null) {
            throw new BuildException(
                "Only one substitution expression is allowed");
        }

        subs = new Substitution();
        subs.setExpression(replace);
    }

    
The flags to use when matching the regular expression.  For more
information, consult the Perl5 syntax.

    
 
  • g : Global replacement.  Replace all occurrences found
    • 
 
  • i : Case Insensitive.  Do not consider case in the match
    • 
 
  • m : Multiline.  Treat the string as multiple lines of input,
        using "^" and "$" as the start or end of any line, respectively,
        rather than start or end of string.
    • 
 
  • s : Singleline.  Treat the string as a single line of input, using
       "." to match any character, including a newline, which normally,
       it would not match.
    • 



Params:
  • flags – the flags attribute
/**
     * The flags to use when matching the regular expression.  For more
     * information, consult the Perl5 syntax.
     * <ul>
     *  <li>g : Global replacement.  Replace all occurrences found</li>
     *  <li>i : Case Insensitive.  Do not consider case in the match</li>
     *  <li>m : Multiline.  Treat the string as multiple lines of input,
     *         using "^" and "$" as the start or end of any line, respectively,
     *         rather than start or end of string.</li>
     *  <li>s : Singleline.  Treat the string as a single line of input, using
     *        "." to match any character, including a newline, which normally,
     *        it would not match.</li>
     * </ul>
     *
     * @param flags the flags attribute
     */
    public void setFlags(String flags) {
        this.flags = flags;
    }

    
Process the file(s) one line at a time, executing the replacement
on one line at a time.  This is useful if you
want to only replace the first occurrence of a regular expression on
each line, which is not easy to do when processing the file as a whole.
Defaults to false.

Params:
  • byline – the byline attribute as a string
Deprecated:since 1.6.x.
            Use setByLine(boolean).
/**
     * Process the file(s) one line at a time, executing the replacement
     * on one line at a time.  This is useful if you
     * want to only replace the first occurrence of a regular expression on
     * each line, which is not easy to do when processing the file as a whole.
     * Defaults to <i>false</i>.
     *
     * @param byline the byline attribute as a string
     * @deprecated since 1.6.x.
     *             Use setByLine(boolean).
     */
    @Deprecated
    public void setByLine(String byline) {
        this.byline = Boolean.parseBoolean(byline);
    }

    
Process the file(s) one line at a time, executing the replacement
on one line at a time.  This is useful if you
want to only replace the first occurrence of a regular expression on
each line, which is not easy to do when processing the file as a whole.
Defaults to false.

Params:
  • byline – the byline attribute
/**
     * Process the file(s) one line at a time, executing the replacement
     * on one line at a time.  This is useful if you
     * want to only replace the first occurrence of a regular expression on
     * each line, which is not easy to do when processing the file as a whole.
     * Defaults to <i>false</i>.
     *
     * @param byline the byline attribute
     */
    public void setByLine(boolean byline) {
        this.byline = byline;
    }

    
Specifies the encoding Ant expects the files to be in -
defaults to the platforms default encoding.

Params:
  • encoding – the encoding attribute
Since:Ant 1.6
/**
     * Specifies the encoding Ant expects the files to be in -
     * defaults to the platforms default encoding.
     *
     * @param encoding the encoding attribute
     * @since Ant 1.6
     */
    public void setEncoding(String encoding) {
        this.encoding = encoding;
    }

    
list files to apply the replacement to

Params:
  • set – the fileset element
/**
     * list files to apply the replacement to
     *
     * @param set the fileset element
     */
    public void addFileset(FileSet set) {
        addConfigured(set);
    }

    
Support arbitrary file system based resource collections.

Params:
  • rc – ResourceCollection
Since:Ant 1.8.0
/**
     * Support arbitrary file system based resource collections.
     *
     * @param rc ResourceCollection
     * @since Ant 1.8.0
     */
    public void addConfigured(ResourceCollection rc) {
        if (!rc.isFilesystemOnly()) {
            throw new BuildException("only filesystem resources are supported");
        }
        if (resources == null) {
            resources = new Union();
        }
        resources.add(rc);
    }

    
A regular expression.
You can use this element to refer to a previously
defined regular expression datatype instance

Returns:the regular expression object to be configured as an element
/**
     * A regular expression.
     * You can use this element to refer to a previously
     * defined regular expression datatype instance
     * @return the regular expression object to be configured as an element
     */
    public RegularExpression createRegexp() {
        if (regex != null) {
            throw new BuildException("Only one regular expression is allowed.");
        }

        regex = new RegularExpression();
        return regex;
    }


    
A substitution pattern.  You can use this element to refer to a previously
defined substitution pattern datatype instance.

Returns:the substitution pattern object to be configured as an element
/**
     * A substitution pattern.  You can use this element to refer to a previously
     * defined substitution pattern datatype instance.
     *
     * @return the substitution pattern object to be configured as an element
     */
    public Substitution createSubstitution() {
        if (subs != null) {
            throw new BuildException(
                "Only one substitution expression is allowed");
        }

        subs = new Substitution();
        return subs;
    }

    
Whether the file timestamp shall be preserved even if the file
is modified.

Params:
  • b – boolean
Since:Ant 1.8.0
/**
     * Whether the file timestamp shall be preserved even if the file
     * is modified.
     *
     * @param b boolean
     * @since Ant 1.8.0
     */
    public void setPreserveLastModified(boolean b) {
        preserveLastModified = b;
    }

    
Invoke a regular expression (r) on a string (input) using
substitutions (s) for a matching regex.

Params:
  • r – a regular expression
  • s – a Substitution
  • input – the string to do the replacement on
  • options – The options for the regular expression
Returns:the replacement result
/**
     * Invoke a regular expression (r) on a string (input) using
     * substitutions (s) for a matching regex.
     *
     * @param r a regular expression
     * @param s a Substitution
     * @param input the string to do the replacement on
     * @param options The options for the regular expression
     * @return the replacement result
     */
    protected String doReplace(RegularExpression r,
                               Substitution s,
                               String input,
                               int options) {
        String res = input;
        Regexp regexp = r.getRegexp(getProject());

        if (regexp.matches(input, options)) {
            log("Found match; substituting", Project.MSG_DEBUG);
            res = regexp.substitute(input, s.getExpression(getProject()),
                                    options);
        }

        return res;
    }

    
Perform the replacement on a file

Params:
  • f – the file to perform the replacement on
  • options – the regular expressions options
Throws:
/**
     * Perform the replacement on a file
     *
     * @param f the file to perform the replacement on
     * @param options the regular expressions options
     * @exception IOException if an error occurs
     */
    protected void doReplace(File f, int options)
         throws IOException {
        File temp = FILE_UTILS.createTempFile("replace", ".txt", null, true, true);
        try {
            boolean changes = false;

            final Charset charset = encoding == null ? Charset.defaultCharset() : Charset.forName(encoding);
            try (InputStream is = Files.newInputStream(f.toPath());
                 OutputStream os = Files.newOutputStream(temp.toPath())) {
                Reader r = null;
                Writer w = null;
                try {
                    r = new InputStreamReader(is, charset);
                    w = new OutputStreamWriter(os, charset);
                    log("Replacing pattern '" + regex.getPattern(getProject())
                        + "' with '" + subs.getExpression(getProject())
                        + "' in '" + f.getPath() + "'" + (byline ? " by line" : "")
                        + (flags.isEmpty() ? "" : " with flags: '" + flags + "'")
                        + ".", Project.MSG_VERBOSE);

                    if (byline) {
                        r = new BufferedReader(r);
                        w = new BufferedWriter(w);

                        StringBuilder linebuf = new StringBuilder();
                        int c;
                        boolean hasCR = false;

                        do {
                            c = r.read();

                            if (c == '\r') {
                                if (hasCR) {
                                    // second CR -> EOL + possibly empty line
                                    changes |= replaceAndWrite(linebuf.toString(),
                                                               w, options);
                                    w.write('\r');

                                    linebuf = new StringBuilder();
                                    // hasCR is still true (for the second one)
                                } else {
                                    // first CR in this line
                                    hasCR = true;
                                }
                            } else if (c == '\n') {
                                // LF -> EOL
                                changes |= replaceAndWrite(linebuf.toString(),
                                                           w, options);
                                if (hasCR) {
                                    w.write('\r');
                                    hasCR = false;
                                }
                                w.write('\n');

                                linebuf = new StringBuilder();
                            } else { // any other char
                                if (hasCR || c < 0) {
                                    // Mac-style linebreak or EOF (or both)
                                    changes |= replaceAndWrite(linebuf.toString(),
                                                               w, options);
                                    if (hasCR) {
                                        w.write('\r');
                                        hasCR = false;
                                    }

                                    linebuf = new StringBuilder();
                                }

                                if (c >= 0) {
                                    linebuf.append((char) c);
                                }
                            }
                        } while (c >= 0);

                    } else {
                        changes = multilineReplace(r, w, options);
                    }
                } finally {
                    FileUtils.close(r);
                    FileUtils.close(w);
                }
            }
            if (changes) {
                log("File has changed; saving the updated file", Project.MSG_VERBOSE);
                try {
                    long origLastModified = f.lastModified();
                    FILE_UTILS.rename(temp, f);
                    if (preserveLastModified) {
                        FILE_UTILS.setFileLastModified(f, origLastModified);
                    }
                    temp = null;
                } catch (IOException e) {
                    throw new BuildException("Couldn't rename temporary file "
                                             + temp, e, getLocation());
                }
            } else {
                log("No change made", Project.MSG_DEBUG);
            }
        } finally {
            if (temp != null) {
                temp.delete();
            }
        }
    }

    
Execute the task

Throws:
  • BuildException – is there is a problem in the task execution.
/**
     * Execute the task
     *
     * @throws BuildException is there is a problem in the task execution.
     */
    @Override
    public void execute() throws BuildException {
        if (regex == null) {
            throw new BuildException("No expression to match.");
        }
        if (subs == null) {
            throw new BuildException("Nothing to replace expression with.");
        }

        if (file != null && resources != null) {
            throw new BuildException(
                "You cannot supply the 'file' attribute and resource collections at the same time.");
        }

        int options = RegexpUtil.asOptions(flags);

        if (file != null && file.exists()) {
            try {
                doReplace(file, options);
            } catch (IOException e) {
                log("An error occurred processing file: '"
                    + file.getAbsolutePath() + "': " + e.toString(),
                    Project.MSG_ERR);
            }
        } else if (file != null) {
            log("The following file is missing: '"
                + file.getAbsolutePath() + "'", Project.MSG_ERR);
        }

        if (resources != null) {
            for (Resource r : resources) {
                File f = r.as(FileProvider.class).getFile();

                if (f.exists()) {
                    try {
                        doReplace(f, options);
                    } catch (Exception e) {
                        log("An error occurred processing file: '"
                            + f.getAbsolutePath() + "': " + e.toString(),
                            Project.MSG_ERR);
                    }
                } else {
                    log("The following file is missing: '"
                        + f.getAbsolutePath() + "'", Project.MSG_ERR);
                }
            }
        }
    }

    private boolean multilineReplace(Reader r, Writer w, int options)
        throws IOException {
        return replaceAndWrite(FileUtils.safeReadFully(r), w, options);
    }

    private boolean replaceAndWrite(String s, Writer w, int options)
        throws IOException {
        String res = doReplace(regex, subs, s, options);
        w.write(res);
        return !res.equals(s);
    }
}