Ant example source code file (ANTLR.java)

This example Ant source code file (ANTLR.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Ant tags/keywords

antlr, antlr, bufferedreader, buildexception, buildexception, commandlinejava, compiling, execute, file, file, io, setting, string, string, unable

The ANTLR.java source code

/*
 *  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
 *
 *      http://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.ByteArrayOutputStream;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import org.apache.tools.ant.AntClassLoader;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.taskdefs.Execute;
import org.apache.tools.ant.taskdefs.LogOutputStream;
import org.apache.tools.ant.taskdefs.PumpStreamHandler;
import org.apache.tools.ant.taskdefs.condition.Os;
import org.apache.tools.ant.types.Commandline;
import org.apache.tools.ant.types.CommandlineJava;
import org.apache.tools.ant.types.Path;
import org.apache.tools.ant.util.JavaEnvUtils;
import org.apache.tools.ant.util.LoaderUtils;
import org.apache.tools.ant.util.TeeOutputStream;
import org.apache.tools.ant.util.FileUtils;

/**
 *  Invokes the ANTLR Translator generator on a grammar file.
 *
 */
public class ANTLR extends Task {

    private CommandlineJava commandline = new CommandlineJava();

    /** the file to process */
    private File targetFile;

    /** where to output the result */
    private File outputDirectory;

    /** an optional super grammar file */
    private File superGrammar;

    /** optional flag to enable html output */
    private boolean html;

    /** optional flag to print out a diagnostic file */
    private boolean diagnostic;

    /** optional flag to add trace methods */
    private boolean trace;

    /** optional flag to add trace methods to the parser only */
    private boolean traceParser;

    /** optional flag to add trace methods to the lexer only */
    private boolean traceLexer;

    /** optional flag to add trace methods to the tree walker only */
    private boolean traceTreeWalker;

    /** working directory */
    private File workingdir = null;

    /** captures ANTLR's output */
    private ByteArrayOutputStream bos = new ByteArrayOutputStream();

    /** The debug attribute */
    private boolean debug;


    /** Instance of a utility class to use for file operations. */
    private static final FileUtils FILE_UTILS = FileUtils.getFileUtils();

    /** Constructor for ANTLR task. */
    public ANTLR() {
        commandline.setVm(JavaEnvUtils.getJreExecutable("java"));
        commandline.setClassname("antlr.Tool");
    }

    /**
     * The grammar file to process.
     * @param target the gramer file
     */
    public void setTarget(File target) {
        log("Setting target to: " + target.toString(), Project.MSG_VERBOSE);
        this.targetFile = target;
    }

    /**
     * The directory to write the generated files to.
     * @param outputDirectory the output directory
     */
    public void setOutputdirectory(File outputDirectory) {
        log("Setting output directory to: " + outputDirectory.toString(), Project.MSG_VERBOSE);
        this.outputDirectory = outputDirectory;
    }

    /**
     * Sets an optional super grammar file.
     * Use setGlib(File superGrammar) instead.
     * @param superGrammar the super grammar filename
     * @deprecated  since ant 1.6
     */
    public void setGlib(String superGrammar) {
        String sg = null;
        if (Os.isFamily("dos")) {
            sg = superGrammar.replace('\\', '/');
        } else {
            sg = superGrammar;
        }
        setGlib(FILE_UTILS.resolveFile(getProject().getBaseDir(), sg));
    }
    /**
     * Sets an optional super grammar file
     * @param superGrammar the super grammar file
     * @since ant 1.6
     */
    public void setGlib(File superGrammar) {
        this.superGrammar = superGrammar;
    }
    /**
     * Sets a flag to enable ParseView debugging
     * @param enable a <code>boolean value
     */
    public void setDebug(boolean enable) {
        this.debug = enable;
    }

    /**
     * If true, emit html
     * @param enable a <code>boolean value
     */
    public void setHtml(boolean enable) {
        html = enable;
    }

    /**
     * Sets a flag to emit diagnostic text
     * @param enable a <code>boolean value
     */
    public void setDiagnostic(boolean enable) {
        diagnostic = enable;
    }

    /**
     * If true, enables all tracing.
     * @param enable a <code>boolean value
     */
    public void setTrace(boolean enable) {
        trace = enable;
    }

    /**
     * If true, enables parser tracing.
     * @param enable a <code>boolean value
     */
    public void setTraceParser(boolean enable) {
        traceParser = enable;
    }

    /**
     * If true, enables lexer tracing.
     * @param enable a <code>boolean value
     */
    public void setTraceLexer(boolean enable) {
        traceLexer = enable;
    }

    /**
     * Sets a flag to allow the user to enable tree walker tracing
     * @param enable a <code>boolean value
     */
    public void setTraceTreeWalker(boolean enable) {
        traceTreeWalker = enable;
    }

    // we are forced to fork ANTLR since there is a call
    // to System.exit() and there is nothing we can do
    // right now to avoid this. :-( (SBa)
    // I'm not removing this method to keep backward compatibility
    /**
     * @ant.attribute ignore="true"
     * @param s a <code>boolean value
     */
    public void setFork(boolean s) {
        //this.fork = s;
    }

    /**
     * The working directory of the process
     * @param d the working directory
     */
    public void setDir(File d) {
        this.workingdir = d;
    }

    /**
     * Adds a classpath to be set
     * because a directory might be given for Antlr debug.
     * @return a path to be configured
     */
    public Path createClasspath() {
        return commandline.createClasspath(getProject()).createPath();
    }

    /**
     * Adds a new JVM argument.
     * @return  create a new JVM argument so that any argument can be passed to the JVM.
     * @see #setFork(boolean)
     */
    public Commandline.Argument createJvmarg() {
        return commandline.createVmArgument();
    }

    /**
     * Adds the jars or directories containing Antlr
     * this should make the forked JVM work without having to
     * specify it directly.
     * @throws BuildException on error
     */
    public void init() throws BuildException {
        addClasspathEntry("/antlr/ANTLRGrammarParseBehavior.class");
    }

    /**
     * Search for the given resource and add the directory or archive
     * that contains it to the classpath.
     *
     * <p>Doesn't work for archives in JDK 1.1 as the URL returned by
     * getResource doesn't contain the name of the archive.</p>
     * @param resource the resource name to search for
     */
    protected void addClasspathEntry(String resource) {
        /*
         * pre Ant 1.6 this method used to call getClass().getResource
         * while Ant 1.6 will call ClassLoader.getResource().
         *
         * The difference is that Class.getResource expects a leading
         * slash for "absolute" resources and will strip it before
         * delegating to ClassLoader.getResource - so we now have to
         * emulate Class's behavior.
         */
        if (resource.startsWith("/")) {
            resource = resource.substring(1);
        } else {
            resource = "org/apache/tools/ant/taskdefs/optional/"
                + resource;
        }

        File f = LoaderUtils.getResourceSource(getClass().getClassLoader(),
                                               resource);
        if (f != null) {
            log("Found " + f.getAbsolutePath(), Project.MSG_DEBUG);
            createClasspath().setLocation(f);
        } else {
            log("Couldn\'t find " + resource, Project.MSG_VERBOSE);
        }
    }

    /**
     * Execute the task.
     * @throws BuildException on error
     */
    public void execute() throws BuildException {
        validateAttributes();

        //TODO: use ANTLR to parse the grammar file to do this.
        File generatedFile = getGeneratedFile();
        boolean targetIsOutOfDate =
            targetFile.lastModified() > generatedFile.lastModified();
        boolean superGrammarIsOutOfDate  = superGrammar != null
                && (superGrammar.lastModified() > generatedFile.lastModified());
        if (targetIsOutOfDate || superGrammarIsOutOfDate) {
            if (targetIsOutOfDate) {
                log("Compiling " + targetFile + " as it is newer than "
                    + generatedFile, Project.MSG_VERBOSE);
            } else if (superGrammarIsOutOfDate) {
                log("Compiling " + targetFile + " as " + superGrammar
                    + " is newer than " + generatedFile, Project.MSG_VERBOSE);
            }
            populateAttributes();
            commandline.createArgument().setValue(targetFile.toString());

            log(commandline.describeCommand(), Project.MSG_VERBOSE);
            int err = run(commandline.getCommandline());
            if (err != 0) {
                throw new BuildException("ANTLR returned: " + err, getLocation());
            } else {
                String output = bos.toString();
                if (output.indexOf("error:") > -1) {
                    throw new BuildException("ANTLR signaled an error: "
                                             + output, getLocation());
                }
            }
        } else {
            log("Skipped grammar file. Generated file " + generatedFile
                + " is newer.", Project.MSG_VERBOSE);
        }
    }

    /**
     * A refactored method for populating all the command line arguments based
     * on the user-specified attributes.
     */
    private void populateAttributes() {
        commandline.createArgument().setValue("-o");
        commandline.createArgument().setValue(outputDirectory.toString());
        if (superGrammar != null) {
            commandline.createArgument().setValue("-glib");
            commandline.createArgument().setValue(superGrammar.toString());
        }
        if (html) {
            commandline.createArgument().setValue("-html");
        }
        if (diagnostic) {
            commandline.createArgument().setValue("-diagnostic");
        }
        if (trace) {
            commandline.createArgument().setValue("-trace");
        }
        if (traceParser) {
            commandline.createArgument().setValue("-traceParser");
        }
        if (traceLexer) {
            commandline.createArgument().setValue("-traceLexer");
        }
        if (traceTreeWalker) {
            if (is272()) {
                commandline.createArgument().setValue("-traceTreeParser");
            } else {
                commandline.createArgument().setValue("-traceTreeWalker");
            }
        }
        if (debug) {
            commandline.createArgument().setValue("-debug");
        }
    }

    private void validateAttributes() throws BuildException {
        if (targetFile == null || !targetFile.isFile()) {
            throw new BuildException("Invalid target: " + targetFile);
        }

        // if no output directory is specified, used the target's directory
        if (outputDirectory == null) {
            setOutputdirectory(new File(targetFile.getParent()));
        }
        if (!outputDirectory.isDirectory()) {
            throw new BuildException("Invalid output directory: " + outputDirectory);
        }
    }

    private File getGeneratedFile() throws BuildException {
        String generatedFileName = null;
        try {
            BufferedReader in = new BufferedReader(new FileReader(targetFile));
            String line;
            while ((line = in.readLine()) != null) {
                int extendsIndex = line.indexOf(" extends ");
                if (line.startsWith("class ") && extendsIndex > -1) {
                    generatedFileName = line.substring(6, extendsIndex).trim();
                    break;
                }
            }
            in.close();
        } catch (Exception e) {
            throw new BuildException("Unable to determine generated class", e);
        }
        if (generatedFileName == null) {
            throw new BuildException("Unable to determine generated class");
        }
        return new File(outputDirectory, generatedFileName
                        + (html ? ".html" : ".java"));
    }

    /** execute in a forked VM */
    private int run(String[] command) throws BuildException {
        PumpStreamHandler psh =
            new PumpStreamHandler(new LogOutputStream(this, Project.MSG_INFO),
                                  new TeeOutputStream(
                                                      new LogOutputStream(this,
                                                                          Project.MSG_WARN),
                                                      bos)
                                  );
        Execute exe = new Execute(psh, null);
        exe.setAntRun(getProject());
        if (workingdir != null) {
            exe.setWorkingDirectory(workingdir);
        }
        exe.setCommandline(command);
        try {
            return exe.execute();
        } catch (IOException e) {
            throw new BuildException(e, getLocation());
        } finally {
            FileUtils.close(bos);
        }
    }

    /**
     * Whether the antlr version is 2.7.2 (or higher).
     *
     * @return true if the version of Antlr present is 2.7.2 or later.
     * @since Ant 1.6
     */
    protected boolean is272() {
        AntClassLoader l = null;
        try {
            l = getProject().createClassLoader(commandline.getClasspath());
            l.loadClass("antlr.Version");
            return true;
        } catch (ClassNotFoundException e) {
            return false;
        } finally {
            if (l != null) {
                l.cleanup();
            }
        }
    }
}