Java tutorial
/* * * Copyright (c) 2004 John Dennis Casey * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to * deal in the Software without restriction, including without limitation the * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or * sell copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER * DEALINGS IN THE SOFTWARE. * */ /* Created on Mar 26, 2004 */ package org.codehaus.marmalade.el.commonsEl; import org.apache.commons.el.ExpressionEvaluatorImpl; import org.codehaus.marmalade.el.AbstractExpressionEvaluator; import org.codehaus.marmalade.el.ExpressionEvaluationException; import org.codehaus.marmalade.util.Reflector; import org.codehaus.marmalade.util.ReflectorException; import javax.servlet.jsp.el.ELException; import javax.servlet.jsp.el.FunctionMapper; import javax.servlet.jsp.el.VariableResolver; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.util.Arrays; import java.util.Map; import java.util.TreeMap; import java.util.regex.Pattern; /** * @author jdcasey */ public class CommonsElExpressionEvaluator extends AbstractExpressionEvaluator { public static final String BOOLEAN_PATTERN = "true|false"; private static final String DIGIT_STRING_PATTERN = "[0-9]+"; private static final String POSITIVE_NEGATIVE_PATTERN = "[-+]?"; public static final String ROUND_NUMBER_PATTERN = POSITIVE_NEGATIVE_PATTERN + DIGIT_STRING_PATTERN; public static final String FRACTIONAL_NUMBER_PATTERN = POSITIVE_NEGATIVE_PATTERN + DIGIT_STRING_PATTERN + "." + DIGIT_STRING_PATTERN; private ExpressionEvaluatorImpl elImpl = new ExpressionEvaluatorImpl(true); private Reflector reflector = new Reflector(); public CommonsElExpressionEvaluator() { } public Object doEval(String expression, Map context, Class expectedType) throws ExpressionEvaluationException { Class realExpectedType = expectedType; if (expectedType.equals(Object.class)) { // try to figure out what we can intelligently do to interpret this value. if (expression.matches(BOOLEAN_PATTERN)) { realExpectedType = Boolean.class; } else if (expression.matches(ROUND_NUMBER_PATTERN)) { realExpectedType = Long.class; } else if (expression.matches(FRACTIONAL_NUMBER_PATTERN)) { realExpectedType = Double.class; } } Object result = eval(expression, context, realExpectedType); return result; } public Object assign(Object targetObject, String propertyName, Object value) throws ExpressionEvaluationException { Object result = null; if (targetObject == null) { throw new ExpressionEvaluationException("Cannot set property on null target."); } else if ((propertyName == null) || (propertyName.length() < 1)) { throw new ExpressionEvaluationException("Cannot set empty property."); } else { Object target = targetObject; String property = propertyName; int lastDot = property.lastIndexOf('.'); if (lastDot > -1) { String expr = "${target." + property.substring(0, lastDot) + "}"; Map ctx = new TreeMap(); ctx.put("target", target); target = eval(expr, ctx, Object.class); property = property.substring(lastDot + 1); } result = set(target, property, value); } return result; } private Object set(Object target, String property, Object value) throws ExpressionEvaluationException { Object result = null; try { Method method = findMethod(target, property, value); if (method != null) { result = method.invoke(target, new Object[] { value }); } else { Field field = target.getClass().getField(property); int fieldModifiers = field.getModifiers(); if (Modifier.isPublic(fieldModifiers) && !Modifier.isFinal(fieldModifiers) && field.getType().isAssignableFrom(value.getClass())) { field.set(target, value); result = value; } else { throw new ExpressionEvaluationException( "Cannot set property: \'" + property + "\' on target: " + target); } } } catch (IllegalArgumentException e) { throw new ExpressionEvaluationException("Error assigning value to property field.", e); } catch (IllegalAccessException e) { throw new ExpressionEvaluationException("Error assigning value to property field.", e); } catch (SecurityException e) { throw new ExpressionEvaluationException("Error assigning value to property field.", e); } catch (NoSuchFieldException e) { throw new ExpressionEvaluationException("Property not found: \'" + property + "\' on target: " + target, e); } catch (InvocationTargetException e) { throw new ExpressionEvaluationException("Error assigning value via property method.", e); } return result; } private Method findMethod(Object target, String property, Object value) { StringBuffer propNameBuffer = new StringBuffer(property.length() + 3); propNameBuffer.append("set").append(Character.toUpperCase(property.charAt(0))) .append(property.substring(1)); String methodName = propNameBuffer.toString(); Class targetClass = target.getClass(); Method method = null; if (value != null) { Class[] paramClasses = { value.getClass() }; try { method = reflector.getMethod(targetClass, methodName, paramClasses); method = targetClass.getMethod(methodName, paramClasses); } catch (NoSuchMethodException e) { // Ignore and return null, so we can move on to try field property access. } catch (ReflectorException e) { // Ignore and return null. } } else { try { method = reflector.getMethod(targetClass, methodName, new Class[0]); } catch (ReflectorException e) { // Ignore and return null. } } return method; } private Object eval(String expression, Map context, Class expectedReturnType) throws ExpressionEvaluationException { try { Object result = elImpl.evaluate(expression, expectedReturnType, new ElVarResolver(context), new ElFuncMapper()); if ((result != null) && !expectedReturnType.isAssignableFrom(result.getClass())) { throw new ExpressionEvaluationException( "Result of evaluation is not of type " + expectedReturnType.getName()); } else { return result; } } catch (ELException e) { throw new ExpressionEvaluationException(expression, e); } } private static final class ElVarResolver implements VariableResolver { private Map context; ElVarResolver(Map context) { this.context = context; } public Object resolveVariable(String name) throws ELException { return context.get(name); } } private static final class ElFuncMapper implements FunctionMapper { ElFuncMapper() { } public Method resolveFunction(String arg0, String arg1) { return null; } } }