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Groovy example source code file (Script.java)

This example Groovy source code file (Script.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 - Groovy tags/keywords

binding, closure, compilationfailedexception, compilationfailedexception, groovyobjectsupport, groovyshell, io, ioexception, missingmethodexception, missingpropertyexception, missingpropertyexception, object, object, script, script

The Groovy Script.java source code

/*
 * Copyright 2003-2007 the original author or authors.
 *
 * Licensed 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 groovy.lang;

import org.codehaus.groovy.ast.expr.ArgumentListExpression;
import org.codehaus.groovy.control.CompilationFailedException;
import org.codehaus.groovy.runtime.DefaultGroovyMethods;
import org.codehaus.groovy.runtime.InvokerHelper;

import java.io.File;
import java.io.IOException;

/**
 * This object represents a Groovy script
 *
 * @author <a href="mailto:james@coredevelopers.net">James Strachan
 * @author Guillaume Laforge
 * @version $Revision: 20507 $
 */
public abstract class Script extends GroovyObjectSupport {
    private Binding binding;

    protected Script() {
        this(new Binding());
    }

    protected Script(Binding binding) {
        this.binding = binding;
    }

    public Binding getBinding() {
        return binding;
    }

    public void setBinding(Binding binding) {
        this.binding = binding;
    }

    public Object getProperty(String property) {
        try {
            return binding.getVariable(property);
        } catch (MissingPropertyException e) {
            return super.getProperty(property);
        }
    }

    public void setProperty(String property, Object newValue) {
        if ("binding".equals(property))
            setBinding((Binding) newValue);
        else if("metaClass".equals(property))
            setMetaClass((MetaClass)newValue);
        else
            binding.setVariable(property, newValue);
    }

    /**
     * Invoke a method (or closure in the binding) defined.
     *
     * @param name method to call
     * @param args arguments to pass to the method
     * @return value
     */
    public Object invokeMethod(String name, Object args) {
        try {
            return super.invokeMethod(name, args);
        }
        // if the method was not found in the current scope (the script's methods)
        // let's try to see if there's a method closure with the same name in the binding
        catch (MissingMethodException mme) {
            try {
                if (name.equals(mme.getMethod())) {
                    Object boundClosure = binding.getVariable(name);
                    if (boundClosure != null && boundClosure instanceof Closure) {
                        return ((Closure) boundClosure).call((Object[])args);
                    } else {
                        throw mme;
                    }
                } else {
                    throw mme;
                }
            } catch (MissingPropertyException mpe) {
                throw mme;
            }
        }
    }

    /**
     * The main instance method of a script which has variables in scope
     * as defined by the current {@link Binding} instance.
     */
    public abstract Object run();

    // println helper methods

    /**
     * Prints a newline to the current 'out' variable which should be a PrintWriter
     * or at least have a println() method defined on it.
     * If there is no 'out' property then print to standard out.
     */
    public void println() {
        Object object;

        try {
            object = getProperty("out");
        } catch (MissingPropertyException e) {
            System.out.println();
            return;
        }

        InvokerHelper.invokeMethod(object, "println", ArgumentListExpression.EMPTY_ARRAY);
    }

    /**
     * Prints the value to the current 'out' variable which should be a PrintWriter
     * or at least have a print() method defined on it.
     * If there is no 'out' property then print to standard out.
     */
    public void print(Object value) {
        Object object;

        try {
            object = getProperty("out");
        } catch (MissingPropertyException e) {
            DefaultGroovyMethods.print(System.out,value);
            return;
        }

        InvokerHelper.invokeMethod(object, "print", new Object[]{value});
    }

    /**
     * Prints the value and a newline to the current 'out' variable which should be a PrintWriter
     * or at least have a println() method defined on it.
     * If there is no 'out' property then print to standard out.
     */
    public void println(Object value) {
        Object object;

        try {
            object = getProperty("out");
        } catch (MissingPropertyException e) {
            DefaultGroovyMethods.println(System.out,value);
            return;
        }

        InvokerHelper.invokeMethod(object, "println", new Object[]{value});
    }

    /**
     * Prints a formatted string using the specified format string and argument.
     *
     * @param format the format to follow
     * @param value the value to be formatted
     */
    public void printf(String format, Object value) {
        Object object;

        try {
            object = getProperty("out");
        } catch (MissingPropertyException e) {
            DefaultGroovyMethods.printf(System.out, format, value);
            return;
        }

        InvokerHelper.invokeMethod(object, "printf", new Object[] { format, value });
    }

    /**
     * Prints a formatted string using the specified format string and arguments.
     *
     * @param format the format to follow
     * @param values an array of values to be formatted
     */
    public void printf(String format, Object[] values) {
        Object object;

        try {
            object = getProperty("out");
        } catch (MissingPropertyException e) {
            DefaultGroovyMethods.printf(System.out, format, values);
            return;
        }

        InvokerHelper.invokeMethod(object, "printf", new Object[] { format, values });
    }

    /**
     * A helper method to allow the dynamic evaluation of groovy expressions using this
     * scripts binding as the variable scope
     *
     * @param expression is the Groovy script expression to evaluate
     */
    public Object evaluate(String expression) throws CompilationFailedException {
        GroovyShell shell = new GroovyShell(getClass().getClassLoader(), binding);
        return shell.evaluate(expression);
    }

    /**
     * A helper method to allow the dynamic evaluation of groovy expressions using this
     * scripts binding as the variable scope
     *
     * @param file is the Groovy script to evaluate
     */
    public Object evaluate(File file) throws CompilationFailedException, IOException {
        GroovyShell shell = new GroovyShell(getClass().getClassLoader(), binding);
        return shell.evaluate(file);
    }

    /**
     * A helper method to allow scripts to be run taking command line arguments
     */
    public void run(File file, String[] arguments) throws CompilationFailedException, IOException {
        GroovyShell shell = new GroovyShell(getClass().getClassLoader(), binding);
        shell.run(file, arguments);
    }
}

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