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From: chinmaykolhatkar <git@git.apache.org>
To: dev@apex.incubator.apache.org
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References: <git-pr-209-incubator-apex-malhar@git.apache.org>
In-Reply-To: <git-pr-209-incubator-apex-malhar@git.apache.org>
Subject: [GitHub] incubator-apex-malhar pull request: APEXMALHAR-2010 Add
 Tranform o...
Content-Type: text/plain
Message-Id: <20160321062627.5DE04DFB7D@git1-us-west.apache.org>
Date: Mon, 21 Mar 2016 06:26:27 +0000 (UTC)

Github user chinmaykolhatkar commented on a diff in the pull request:

    https://github.com/apache/incubator-apex-malhar/pull/209#discussion_r56785568
  
    --- Diff: library/src/main/java/com/datatorrent/lib/expression/JavaExpressionParser.java ---
    @@ -0,0 +1,179 @@
    +/**
    + * 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 com.datatorrent.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 com.datatorrent.lib.util.KeyValPair;
    +
    +/**
    + * Defines how quasi-Java Expression should be parsed.
    + */
    +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 String variablePlaceholderPattern = "\\{(.*?)\\}";
    +
    +  private String exprObjPlaceholder;
    +  private String codeObjPlaceholder;
    +
    +  public JavaExpressionParser()
    +  {
    +    // Fro kryo serialization.
    +  }
    +
    +  /**
    +   * {@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) {
    +        try {
    +          matcher.appendReplacement(sb, getObjectJavaExpression(matcher.group(1), objectType));
    +        } catch (NoSuchFieldException e) {
    +          throw new RuntimeException("Failed to parse the operand: " + matcher.group(1), e);
    +        }
    +      } 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("$.")) {
    +        expression = "$." + expression;
    +      }
    +      try {
    +        String tempExpr = getObjectJavaExpression(expression, objectType);
    +        sb.setLength(0);
    +        sb.append(tempExpr.replace("\\$", "$"));
    +      } catch (NoSuchFieldException e) {
    +        throw new RuntimeException("Failed to create expression.", e);
    +      }
    +    }
    +
    +    return "return ((" + returnType.getName().replace("$", "\\$") + ")" + sb.toString() + ");";
    +  }
    +
    +  /**
    +   * {@inheritDoc}
    +   */
    +  @Override public void setInputObjectPlaceholder(String exprObjPlaceholder, String codeObjPlaceholder)
    +  {
    +    this.exprObjPlaceholder = exprObjPlaceholder;
    +    this.codeObjPlaceholder = codeObjPlaceholder;
    +  }
    +
    +  private String getObjectJavaExpression(String exp, Class objectType) throws NoSuchFieldException
    --- End diff --
    
    This is removed.


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