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From mattf-horton <...@git.apache.org>
Subject [GitHub] metron pull request #641: METRON-539: added HASH function for stellar.
Date Tue, 11 Jul 2017 22:57:48 GMT
Github user mattf-horton commented on a diff in the pull request:

    https://github.com/apache/metron/pull/641#discussion_r126829075
  
    --- Diff: metron-stellar/stellar-common/src/main/java/org/apache/metron/stellar/dsl/functions/HashFunctions.java
---
    @@ -0,0 +1,85 @@
    +/*
    + * 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.metron.stellar.dsl.functions;
    +
    +import com.google.common.io.BaseEncoding;
    +import org.apache.commons.lang3.SerializationUtils;
    +import org.apache.metron.stellar.dsl.BaseStellarFunction;
    +import org.apache.metron.stellar.dsl.Stellar;
    +
    +import java.io.Serializable;
    +import java.nio.charset.StandardCharsets;
    +import java.security.MessageDigest;
    +import java.security.NoSuchAlgorithmException;
    +import java.util.List;
    +
    +public class HashFunctions {
    +  @Stellar(
    +    name = "HASH",
    +    description = "Hashes a given value using the given hashing algorithm and returns
a hex encoded string. This function only hashes " +
    +      "strings and values that implement java.io.Serializable.",
    +    params = {
    +      "toHash - value to hash.",
    +      "hashType - A valid string representation of an algorithm supported by java.security.MessageDigest.",
    +    },
    +    returns = "A hex representation of a hashed value using the given hashing algorithm.
If either argument is " +
    +      "null then null will be returned. If the type of 'toHash' is neither a string nor
of type java.io.Serializable, " +
    +      "then null is returned."
    +  )
    +  public static class Hash extends BaseStellarFunction {
    +
    +    @Override
    +    public Object apply(final List<Object> args) {
    +      if (args == null || args.size() != 2) {
    +        throw new IllegalArgumentException("Invalid number of arguments: " + (args ==
null ? 0 : args.size()));
    +      }
    +
    +      final Object toHash = args.get(0);
    +      final Object hashType = args.get(1);
    +
    +      if (toHash == null || hashType == null) {
    +        return null;
    +      }
    +
    +      final MessageDigest messageDigest = getMessageDigest(hashType.toString());
    +
    +      if (toHash instanceof String) {
    +        return getHashAsHex(messageDigest, toHash.toString().getBytes(StandardCharsets.UTF_8));
    +      } else if (toHash instanceof Serializable) {
    +        final byte[] serialized = SerializationUtils.serialize((Serializable) toHash);
    +        return getHashAsHex(messageDigest, serialized);
    +      }
    +
    +      return null;
    +    }
    +
    +    private MessageDigest getMessageDigest(String hashType) {
    --- End diff --
    
    If we expose MessageDigest objects, that would be a good example of non-Serializable objects
it is reasonable to be unable to hash :-)


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