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Groovy example source code file (Eval.java)

This example Groovy source code file (Eval.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, binding, compilationfailedexception, eval, groovyshell, groovyshell, object, object, string, string

The Groovy Eval.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.util;

import org.codehaus.groovy.control.CompilationFailedException;

import groovy.lang.Binding;
import groovy.lang.GroovyShell;

/**
 * Allow easy integration from Groovy into Java through convenience methods. <br/>
* * This class is a simple helper on top of GroovyShell. You can use it to evaluate small * Groovy scripts that don't need large Binding objects. For example, this script * executes with no errors: * <pre> * assert 10 == Eval.me(' 2 * 4 + 2') * assert 10 == Eval.x(2, ' x * 4 + 2') * </pre> * * @see GroovyShell * * @author Dierk Koenig */ public class Eval { /** * Evaluates the specified String expression and returns the result. For example: * <pre> * assert 10 == Eval.me(' 2 * 4 + 2') * </pre> * @param expression the Groovy expression to evaluate * @return the result of the expression * @throws CompilationFailedException if expression is not valid Groovy */ public static Object me(final String expression) throws CompilationFailedException { return me(null, null, expression); } /** * Evaluates the specified String expression and makes the parameter available inside * the script, returning the result. For example, this code binds the 'x' variable: * <pre> * assert 10 == Eval.me('x', 2, ' x * 4 + 2') * </pre> * @param expression the Groovy expression to evaluate * @return the result of the expression * @throws CompilationFailedException if expression is not valid Groovy */ public static Object me(final String symbol, final Object object, final String expression) throws CompilationFailedException { Binding b = new Binding(); b.setVariable(symbol, object); GroovyShell sh = new GroovyShell(b); return sh.evaluate(expression); } /** * Evaluates the specified String expression and makes the parameter available inside * the script bound to a variable named 'x', returning the result. For example, this * code executes without failure: * <pre> * assert 10 == Eval.x(2, ' x * 4 + 2') * </pre> * @param expression the Groovy expression to evaluate * @return the result of the expression * @throws CompilationFailedException if expression is not valid Groovy */ public static Object x(final Object x, final String expression) throws CompilationFailedException { return me("x", x, expression); } /** * Evaluates the specified String expression and makes the first two parameters available inside * the script bound to variables named 'x' and 'y' respectively, returning the result. For example, * this code executes without failure: * <pre> * assert 10 == Eval.xy(2, 4, ' x * y + 2') * </pre> * @param expression the Groovy expression to evaluate * @return the result of the expression * @throws CompilationFailedException if expression is not valid Groovy */ public static Object xy(final Object x, final Object y, final String expression) throws CompilationFailedException { Binding b = new Binding(); b.setVariable("x", x); b.setVariable("y", y); GroovyShell sh = new GroovyShell(b); return sh.evaluate(expression); } /** * Evaluates the specified String expression and makes the first three parameters available inside * the script bound to variables named 'x', 'y', and 'z' respectively, returning the result. For * example, this code executes without failure: * <pre> * assert 10 == Eval.xyz(2, 4, 2, ' x * y + z') * </pre> * @param expression the Groovy expression to evaluate * @return the result of the expression * @throws CompilationFailedException if expression is not valid Groovy */ public static Object xyz(final Object x, final Object y, final Object z, final String expression) throws CompilationFailedException { Binding b = new Binding(); b.setVariable("x", x); b.setVariable("y", y); b.setVariable("z", z); GroovyShell sh = new GroovyShell(b); return sh.evaluate(expression); } }

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