| /** |
| * 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.apex.malhar.lib.expression; |
| |
| import java.lang.reflect.Field; |
| import java.lang.reflect.Method; |
| import java.lang.reflect.Modifier; |
| import java.util.regex.Matcher; |
| import java.util.regex.Pattern; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import org.apache.apex.malhar.lib.util.KeyValPair; |
| |
| /** |
| * Defines how quasi-Java Expression should be parsed. |
| * |
| * @since 3.4.0 |
| */ |
| public class JavaExpressionParser implements Expression.ExpressionParser |
| { |
| private static final Logger logger = LoggerFactory.getLogger(JavaExpressionParser.class); |
| |
| private static final String GET = "get"; |
| private static final String IS = "is"; |
| |
| private final String variablePlaceholderPattern = "\\{(.*?)\\}"; |
| |
| private String exprObjPlaceholder; |
| private String codeObjPlaceholder; |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public String convertToCompilableExpression(String expression, Class<?> objectType, Class<?> returnType) |
| { |
| if (expression.startsWith(".")) { |
| expression = expression.substring(1); |
| } |
| |
| if (expression.isEmpty()) { |
| throw new IllegalArgumentException("The getter expression: \"" + expression + "\" is invalid."); |
| } |
| |
| Pattern entry = Pattern.compile(variablePlaceholderPattern); |
| Matcher matcher = entry.matcher(expression); |
| StringBuffer sb = new StringBuffer(); |
| |
| while (matcher.find()) { |
| if (matcher.groupCount() == 1) { |
| matcher.appendReplacement(sb, getObjectJavaExpression(matcher.group(1), objectType)); |
| } else { |
| throw new RuntimeException("Invalid expression: " + matcher.group()); |
| } |
| } |
| |
| matcher.appendTail(sb); |
| |
| if (sb.toString().equals(expression)) { |
| // This is a simple expression. No object placeholder. create proper expression. |
| if (!expression.startsWith(this.exprObjPlaceholder + ".")) { |
| expression = this.exprObjPlaceholder + "." + expression; |
| } |
| String tempExpr = getObjectJavaExpression(expression, objectType); |
| sb.setLength(0); |
| sb.append(tempExpr.replace("\\$", "$")); |
| } |
| |
| return "return ((" + returnType.getName().replace("$", "\\$") + ")(" + sb.toString() + "));"; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void setInputObjectPlaceholder(String exprObjPlaceholder, String codeObjPlaceholder) |
| { |
| this.exprObjPlaceholder = exprObjPlaceholder; |
| this.codeObjPlaceholder = codeObjPlaceholder; |
| } |
| |
| private String getObjectJavaExpression(String exp, Class objectType) |
| { |
| StringBuilder sb = new StringBuilder(); |
| |
| String[] split = exp.split("\\."); |
| Class<?> currentClassType = objectType; |
| |
| boolean first = true; |
| for (String field : split) { |
| if (first) { |
| first = false; |
| } else { |
| sb.append("."); |
| } |
| if (field.equals(exprObjPlaceholder)) { |
| // Replace with object type |
| sb.append("((").append(objectType.getName().replace("$", "\\$")).append(")").append("(") |
| .append(codeObjPlaceholder).append("))"); |
| currentClassType = objectType; |
| } else { |
| KeyValPair<String, ? extends Class<?>> getter = getGetterForVariable(field, currentClassType); |
| sb.append(getter.getKey()); |
| currentClassType = getter.getValue(); |
| } |
| } |
| |
| return sb.toString(); |
| } |
| |
| private KeyValPair<String, ? extends Class<?>> getGetterForVariable(String var, Class<?> inputClassType) |
| { |
| try { |
| final Field field = inputClassType.getField(var); |
| if (Modifier.isPublic(field.getModifiers())) { |
| return new KeyValPair<>(var, field.getType()); |
| } |
| logger.debug("Field {} is not publicly accessible. Proceeding to locate a getter method.", var); |
| } catch (NoSuchFieldException ex) { |
| logger.debug("{} does not have field {}. Proceeding to locate a getter method.", inputClassType.getName(), var); |
| } |
| |
| String[] methodAccessors = new String[]{GET, IS}; |
| |
| for (String m : methodAccessors) { |
| String methodName = m + var.substring(0, 1).toUpperCase() + var.substring(1); |
| try { |
| Method method = inputClassType.getMethod(methodName); |
| if (Modifier.isPublic(method.getModifiers())) { |
| return new KeyValPair<>(methodName + "()", method.getReturnType()); |
| } |
| logger.debug("Method {} of {} is not accessible. Proceeding to locate another getter method.", methodName, |
| inputClassType.getName()); |
| } catch (NoSuchMethodException ex) { |
| logger.debug("{} does not have method {}. Proceeding to locate another getter method", inputClassType.getName(), |
| methodName); |
| } |
| } |
| |
| return new KeyValPair<>(var, inputClassType); |
| } |
| |
| } |