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| mqjeff |
 Posted: Thu Sep 10, 2015 6:06 am Post subject: |
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Joined: 25 Jun 2008
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The issues with Byte are why the MQ API uses the byte primitive instead of the Byte class... 
There are various ways to convert a byte[] into a hex string, including printf options....
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| tczielke |
| Posted: Thu Sep 10, 2015 6:06 am Post subject: |
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Joined: 08 Jul 2010
Posts: 939
Location: Illinois, USA
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| mqjeff wrote: |
| tczielke wrote: |
It looks like in Java there isn't a primitive type that corresponds to the unsigned char in C. The closest one I see is the byte, like you mentioned which is the following:
byte 8 bits -128 - +127
So if a Java application is trying to display individual bytes in the MsgId using a byte primitive, it looks like it would show a negative number for any byte >= 80.
A little deficient on the Java side to me, if that is the case. |
Again, the MQ Java API (not the JMS API) says that the MsgID and CorrelID are byte arrays - byte[]. And, yeah, a Java byte is an 8 bit byte, not anything bigger. But unsigned, so you get 0-254, not -128 to +127. |
In both of the Java books that I use ("Java in a Nutshell" and "Head First Java"), the Java primitive of byte is defined with a range of -128 - +127. That is what I was referring to.
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| tczielke |
| Posted: Thu Sep 10, 2015 6:14 am Post subject: |
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Joined: 08 Jul 2010
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| fjb_saper wrote: |
Even more deficient in java is the decode function of Byte, Integer, etc...
It only accepts positive values...
So if you have a byte that's above 7F you get a number format exception...
The answer is use the Integer.decode function and cast to byte...
For extracting the hex string you can use shift and bit masks so that you never have a value over 15...
Have fun |
I did run across a similar issue with the MQOptions java program in the MH06 supportpac, when I wanted to take an input 4 byte hex number and convert it to an integer primitive. Java is a little quirky that way, but part of it is probably me just getting used to the language.
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| bruce2359 |
| Posted: Thu Sep 10, 2015 10:58 am Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9399
Location: US: west coast, almost. Otherwise, enroute.
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| mqjeff wrote: |
| tczielke wrote: |
It looks like in Java there isn't a primitive type that corresponds to the unsigned char in C. The closest one I see is the byte, like you mentioned which is the following:
byte 8 bits -128 - +127
So if a Java application is trying to display individual bytes in the MsgId using a byte primitive, it looks like it would show a negative number for any byte >= 80.
A little deficient on the Java side to me, if that is the case. |
Again, the MQ Java API (not the JMS API) says that the MsgID and CorrelID are byte arrays - byte[]. And, yeah, a Java byte is an 8 bit byte, not anything bigger. But unsigned, so you get 0-254, not -128 to +127. |
An MQBYTE is just a string of bits, neither signed nor unsigned.
A Java primitive data type byte is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive).
Incompatible. Whose oversight is that?
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| smdavies99 |
| Posted: Thu Sep 10, 2015 9:43 pm Post subject: |
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Jedi Council
Joined: 10 Feb 2003
Posts: 6076
Location: Somewhere over the Rainbow this side of Never-never land.
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| bruce2359 wrote: |
| mqjeff wrote: |
Again, the MQ Java API (not the JMS API) says that the MsgID and CorrelID are byte arrays - byte[]. And, yeah, a Java byte is an 8 bit byte, not anything bigger. But unsigned, so you get 0-255, not -128 to +127. |
An MQBYTE is just a string of bits, neither signed nor unsigned.
A Java primitive data type byte is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive).
Incompatible. Whose oversight is that? |
My guess is that MQBYTE predates Java which was added to MQ around V5 (might be wrong there though)
For those of us who cross ourselves when we have to work with the spawn of the devil (Java) using MQBYTE in C/C++ represents no problem at all.
Even in other languages it is no problem. As I said, Java is ....
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| tczielke |
| Posted: Fri Sep 11, 2015 4:32 am Post subject: |
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This is just a limitation of the Java language, as far as I know. The only 8 bit primitive that they give you to work with is the byte primitive, and it has a range of -128 - +127. In fact, all their integer primitives (byte, short, int, long) assume a sign. Not sure why they didn't see the need to also support unsigned integer primitives.
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Last edited by tczielke on Fri Sep 11, 2015 7:23 am; edited 1 time in total |
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| mqjeff |
| Posted: Fri Sep 11, 2015 4:48 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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just because they assume a sign doesn't mean you have to treat it as a sign bit.
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| fjb_saper |
| Posted: Fri Sep 11, 2015 7:14 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20696
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| mqjeff wrote: |
| just because they assume a sign doesn't mean you have to treat it as a sign bit. |
No but it means that the class does not provide you with the default manipulation objects for an unsigned content and that you have to do some of that manipulation yourself... or build a workaround...
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| mqjeff |
| Posted: Fri Sep 11, 2015 7:30 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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| fjb_saper wrote: |
| mqjeff wrote: |
| just because they assume a sign doesn't mean you have to treat it as a sign bit. |
No but it means that the class does not provide you with the default manipulation objects for an unsigned content and that you have to do some of that manipulation yourself... or build a workaround... |
If you want to do anything other than what amounts to memcopy into an unsigned byte.
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