[ http://issues.apache.org/jira/browse/JCR-320?page=comments#action_12366603 ]
Jukka Zitting commented on JCR-320: ----------------------------------- The current hashCode() implementation is based on a discussion we had in April 2005, see http://thread.gmane.org/gmane.comp.apache.jackrabbit.devel/1561 (starting a few messages down the thread). There are valid arguments for many different implementations, but once we implement equals() the Object contract requires that hashCode() is also implemented at least in some way. Returning a constant was considered the best alternative. > From an api design point of view we can dump Value equals and hashcode No, we can't. :-) The JCR API explicitly says that Value.equals() must be implemented in a specific way. See the javadoc link for details. > And Jukka I will get down to providing you with a patch and testcases. It > might take some time though... Thanks! I'm not decided if this is a serious enough breach of the JCR API to be a critical issue for the 1.0 release. If it is, then I can participate in getting this fixed, otherwise there is no need to hurry. > BinaryValue equals fails for two objects with two different byte arrays that > contain the same bytes. > ---------------------------------------------------------------------------------------------------- > > Key: JCR-320 > URL: http://issues.apache.org/jira/browse/JCR-320 > Project: Jackrabbit > Type: Bug > Components: core > Versions: 0.9 > Reporter: Piyush Purang > Priority: Minor > > http://svn.apache.org/repos/asf/incubator/jackrabbit/trunk/jackrabbit/src/main/java/org/apache/jackrabbit/value/BinaryValue.java > Here is the present implementation > public boolean equals(Object obj) { > if (this == obj) { > return true; > } > if (obj instanceof BinaryValue) { > BinaryValue other = (BinaryValue) obj; > if (text == other.text && stream == other.stream > && streamData == other.streamData) { > return true; > } > // stream, streamData and text are mutually exclusive, > // i.e. only one of them can be non-null > if (stream != null) { > return stream.equals(other.stream); > } else if (streamData != null) { > return streamData.equals(other.streamData); > } else { > return text.equals(other.text); > } > } > return false; > } > Here are the problems with the present implementation > 1. streamData.equals(other.streamData ) will fail miserably. > 2. too many return statements! I guess no one ran a checkstyle on it. > 3. return stream.equals(other.stream); will always be false unless both have > been created with the same InputStream! > I wrote some testcases in SetValueBinaryTest > public void testBinaryValueEquals() throws Exception { > BinaryValue binaryValue1 = null; > BinaryValue binaryValue2 = null; > // initialize some binary value > data = createRandomString(10).getBytes(); > binaryValue1 = (BinaryValue) > superuser.getValueFactory().createValue(new ByteArrayInputStream(data)); > binaryValue2 = (BinaryValue) superuser.getValueFactory > ().createValue(new ByteArrayInputStream(data)); > //ideallly setup a test harness that tests all the cases as defined > by the contract in Object.equals() > assertTrue( binaryValue1.equals(binaryValue2)); > assertTrue( binaryValue1.equals(binaryValue1)); > assertFalse( binaryValue1.equals(null)); > } > public void testBinaryValueEquals2() throws Exception { > String str = createRandomString(10); > BinaryValue binaryValue1 = new BinaryValue(str.getBytes()); > BinaryValue binaryValue2 = new BinaryValue(str.getBytes()); > assertTrue( binaryValue1.equals(binaryValue2)); > assertTrue( binaryValue1.equals(binaryValue1)); > assertFalse( binaryValue1.equals(null)); > } > > public void testBinaryValueEquals3() throws Exception { > String str1 = "Some string xyz"; > String str2 = new StringBuffer().append("Some string xyz").toString(); > BinaryValue binaryValue1 = new BinaryValue(str1); > BinaryValue binaryValue2 = new BinaryValue(str2); > assertTrue( binaryValue1.equals(binaryValue2)); > assertTrue( binaryValue1.equals(binaryValue1)); > assertFalse( binaryValue1.equals(null)); > } > They were written quickly but with the present implementation the first two > fail at the very first assert* statement which for stream I can understand > (as we are basically propogating InputStream's equals contract) but for byte > arrays I can't agree with this behaviour unless it is so intended. It behaves > the best when BinaryVlaue wraps a string i.e. testBinaryValueEquals3() > passes without trouble. > I propose a new implementation where I am not very convinced with the > behaviour when we have streams being wrapped. If it should fail for the > streams then we should change the documentation for the method. As for making > it work right when streams are involved .. well the streams will have to be > read and compared. > > public boolean equals(Object obj) { > boolean result = false; > if (this == obj) { > result = true; > } else if (obj instanceof BinaryValue) { > BinaryValue other = (BinaryValue) obj; > // only one of text, stream and streamData are set at any given > point > if (text != null) { > result = text.equals(other.text); > } else if (stream != null) { > result = stream.equals(other.stream); > } else if (streamData != null) { > result = Arrays.equals(streamData, other.streamData); > } else { > // all values are null; test that the other object (which > could be us) > // also has everything set to null! > result = (other.text == null && other.stream == null > && other.streamData == null); > } > } > return result; > } > This implementation of course fails at the first assert* of the first test > method testBinaryValueEquals (It will pass the other two assert*s). > And if this new implementation doesn't fit the bill and an alternative isn't > needed then just skip implementing equals. > One more thought running through my mind is - if text, stream and data are > mutually exclusive why don't we have different classes for each of them? (Try > and wrap a stringValue into a binary value...) > I have also noticed that the hashCodes all return 0's throughtout the > package. In the case that the hashCode can't keep up with the contract of > equal I would propose throwing an UnsupportedOpertaionException. And if not > then declare it in the BasValue as it will be inherited (unless this leads > the QA tools to report infringement of the rule that when you define equals > you need to redefine hashCode - checkstyle does that). > The value package doesn't have any tests for it.. or did I miss them? -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
