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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (APEXMALHAR-2010) Add transform operator
Date Fri, 18 Mar 2016 12:35:33 GMT

    [ https://issues.apache.org/jira/browse/APEXMALHAR-2010?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15201405#comment-15201405
] 

ASF GitHub Bot commented on APEXMALHAR-2010:
--------------------------------------------

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

    https://github.com/apache/incubator-apex-malhar/pull/209#discussion_r56649179
  
    --- 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
    +  {
    +    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 | SecurityException ex) {
    +      logger.debug("{} does not have field {}. Proceeding to locate a getter method.",
inputClassType.getName(), var);
    +    }
    +
    +    String methodName = GET + 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 | SecurityException ex) {
    --- End diff --
    
    Swallow only the required exception.  SecurityException  should not be.


> Add transform operator
> ----------------------
>
>                 Key: APEXMALHAR-2010
>                 URL: https://issues.apache.org/jira/browse/APEXMALHAR-2010
>             Project: Apache Apex Malhar
>          Issue Type: New Feature
>          Components: algorithms
>    Affects Versions: 3.4.0
>            Reporter: Chinmay Kolhatkar
>            Assignee: Chinmay Kolhatkar
>
> Add transform operator
> Details to be added soon once the mailing thread reaching conclusion:
> http://mail-archives.apache.org/mod_mbox/incubator-apex-dev/201603.mbox/%3CCABAipVZUdRGx5dS35bYPN46koLQU5gSLgbCeRH8aM_y9ANRU2w%40mail.gmail.com%3E



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