JEXL

最新推荐文章于 2025-11-03 08:49:52 发布

原创最新推荐文章于 2025-11-03 08:49:52 发布 · 3.9k 阅读

1 ·

CC 4.0 BY-SA版权

文章标签：

#exception #string #n2 #class #testing #null

Java_Apache 专栏收录该内容

1 篇文章

订阅专栏

learning site

http://commons.apache.org/jexl/

Expression calculate

JexlContext defined the vars' context

ExpressionFactory creates the Expression to use.

check the following example to check how to calculate 2 expression belows

"3+2" and "n1+n2+2"

FormulaCalculator.java

package JEXL; import java.util.HashMap; import java.util.Map; import org.apache.commons.jexl.Expression; import org.apache.commons.jexl.ExpressionFactory; import org.apache.commons.jexl.JexlContext; /** * * JEXL test, this Util class is used for testing the Formula Calculator * * @author shangyang * */ public class FormulaCalculator { String _formula; JexlContext _jexlContext; Map _varMap; public FormulaCalculator(){ _jexlContext = new JexlContext(){ public Map getVars() { // TODO Auto-generated method stub return _varMap; } public void setVars(Map vars) { // TODO Auto-generated method stub _varMap.clear(); _varMap.putAll( vars ); } }; } public void setFormula(String formula) throws Exception{ validateFormula( formula ); _formula = formula; } // set the values to the variable of the expression public void setVars(Map<String, Number> vars){ _varMap = vars; } public Number calculate() throws Exception{ Expression e = ExpressionFactory.createExpression( _formula ); return (Number) e.evaluate( _jexlContext ); } private void validateFormula( String formula ) throws Exception{ // FIXME: implementation } }

FormulaCalculatorTest.java

package JEXL; import java.util.HashMap; import java.util.Map; import junit.framework.TestCase; import org.junit.Assert; public class FormulaCalculatorTest extends TestCase{ public void testCalculate() throws Exception{ String formula = "3+2"; FormulaCalculator cal = new FormulaCalculator(); cal.setFormula(formula); cal.setVars(null); Number n = cal.calculate(); Assert.assertEquals( 5, Integer.parseInt( n.toString() )); String formula2 = "n1+n2+3"; cal.setFormula(formula2); Map<String, Number> mapVars = new HashMap<String, Number>(); mapVars.put( "n1", 2); mapVars.put( "n2", 3); cal.setFormula( formula2); cal.setVars( mapVars); Number n2 = cal.calculate(); Assert.assertEquals(8, Integer.parseInt( n2.toString() )); } }