Ibatis error: Error parsing XPath '/sqlMap/insert'. Cause: java.util.NoSuchElementException

If IBatis is throwing following exception then apart from usual suspects of correct dtd declaration in sql-map-config xml and sql-map xml files, one should also look at the insert sql definition in sql-map xml.

com.ibatis.common.xml.NodeletException: Error parsing XML. Cause: java.lang.RuntimeException: Error parsing XPath '/sqlMapConfig/sqlMap'. Cause: com.ibatis.common.xml.NodeletException: Error parsing XML. Cause: java.lang.RuntimeException: Error parsing XPath '/sqlMap/insert'. Cause: java.util.NoSuchElementException

I had something like this in my insert query xml definition:
INSERT INTO TEST_T (ACCT_ID) VALUES (#acctId)

above mentioned sql statement throws com.ibatis.common.xml.NodeletException which is difficult to figure out.

In my case, error is due to not having closing hash (#) with acctId

If i change the insert statement to following then things work again, notice the closing # in #acctId#

INSERT INTO TEST_T (ACCT_ID) VALUES (#acctId#)

Hope that this is of some use to others who get this error.

150 is the limit of human brain!

This article from July/August 2009 issue of IEEE Security & Privacy states that based on research, it has been found that 150 is the limit of human brain to recognize other people, personally.

It has been this way forever and military formations also follow this rule and so do other tribes.

More can be read here.

How to fix Spring and MQ issue of Failed to convert property value of type [javax.naming.Reference] to required type [javax.jms.ConnectionFactory]

I ran into this exception and had to waste some hours to fix it. I was using Rational Application Developer 6 with Websphere MQ 5.3 to run a command line client. It should be valid for even higher versions of RAD and WMQ.

Exception is

org.springframework.beans.TypeMismatchException: Failed to convert property value of type [javax.naming.Reference] to required type [javax.jms.ConnectionFactory] for property 'targetConnectionFactory';

I hope that following will help others who run into this issue.

Steps you can take to solve this are:

1) Make sure that you have following jars in classpath:

* com.ibm.mq.jar
* com.ibm.mqbind.jar
* com.ibm.mqjms.jar
* ecutils.jar
* j2ee.jar
* messaging.jar
* messagingClient.jar
* messagingImpl.jar
* namingclient.jar

2) If above is there in classpath but you are still getting this error then check if you have conflicting version of jms related classes.

Sometimes, we have 2 different versions of jms.jar or jms related classes.

Make sure that you have right version of classes.

3) If you suspect class loading issue then use -verbose as a vm argument to see the classloading details.

See following article for RAD and JMS for more details.

Using Java to Crack Office 2007

Using Java to Crack Office 2007 is a good article by Ted Neward - it shows how you can read word 2007 using plain java - thanks to new OOXML

Finding out major mail servers of the world

This article is great about how to identify the mail servers, out there in the wild.

What is interesting is to look at mail server responses...

Physiological Basis of Yoga

Yoga is known to have done wonders for people. This article goes into some details to explain the physiological basis for this.

Code Quality: Coupling, Afferent and Efferent and Code Quality

All Software Projects deviate from their original design, as the time goes by. This is specially true
as code base gets bigger and new developers join in.

Maintaining the intention of design and keep things manageable, becomes tougher and tougher.

To handle this kind of situation, we need some support from Tools to properly understand
the coupling of code, their complexity and their test coverage. Without this information,
it is nearly impossible to know the cost of change in system.

Thankfully, we have JDepend which can help us deal with these kind of issues. It gives
us a measure of afferent (how many packages depend on you) and efferent coupling (how many
packages you depend on), Abstactedness, Instability.

Do read this article to know more about it.

Good news is that you can integrate this into your eclipse workspace too, via an eclipse plugin.

Savour the historic moment of Triump of Determination and Will Power in Perth Cricket Test Match Jan 2008

Most of Indians felt cheated and humiliated by the end of Sydney Cricket Test Match in India's tour of Australia in Jan 2008.

Aussies got Mike Proctor - Match Referee from ICC to ban Harbhajan for 3 Test Matches. Indian team revolted and BCCI wilted under pressure. BCCI threatened to call of tour unless Bhajji was absolved of racial slur and Steve Bucknor (ever the nemesis of India) was relieved from umpiring in coming matches. ICC blinked and removed Bucknor off the tour and postponed Bhajji's hearing after the test series is over.

BCCI allowed the tour to go on and game was on for Perth,WACA. All pundits said that Shaun Tait and Lee would demolish INDIA but at the end of 4th day, 19 Jan 2008, India emerged victorious by defeating Aussie by 72 runs.

I have collected some of the best videos and writings about this match and here they are:

1) Ishant Sharma removed Ponting in both the innings and the way he did on day 4 was amazing
Ishant Sharma's heroics which removed Ponting on day 4

2) Without Warne, McGrath, Langer and Hayden - Aussie are weaker than ever
Australia's cracks finally exposed

3) Once again, India stopped Oz from creating the world record of 17 consecutive test matches - Last time, it was in KOLKATA 2001
India-Oz cricket rivalry revived

4) Watch awesome highlights here.


Awesome victory.... Satyamev Jayate.... (Truth prevails, against all odds)

Cookies and Firefox

It is bit mysterious the way FF stores cookies. It stores them in cookies.txt in Documents&Settings/User-Name/ApplicationData/Mozilla/Firefox/Profiles folder.

A Sample looks like this:

# HTTP Cookie File
# http://www.netscape.com/newsref/std/cookie_spec.html
# This is a generated file! Do not edit.
# To delete cookies, use the Cookie Manager.

.blogger.com TRUE / FALSE 1199862536 __utmz 150635877.

At times, we need Javascript to create cookies and manage them - more so when you are working with AJAX. So, refer to this article by PPK. It is useful.

Nasty Firefox 2/1.x ActiveX Error

Ever since I upgraded my FF to 2.0.x, I was getting nasty ActiveX Error which goes like this:

"active x error:
could not create the control {00000000-0000-0000-0000-000000000000}. Check that is has been installed on your computer and that this page correctly references it"

Fortunately, this tip saved my day. All it took to fix the errors was to update the npmozax.dll.

Anyone can download this from dlldump.com.

It is tough to be a Great Programmer

This article, called Law of Leaky Abstractions, by Joel is worth reading.

He articulates the issue very well.

Most Interesting Stuff is here...

The law of leaky abstractions means that whenever somebody comes up with a wizzy new code-generation tool that is supposed to make us all ever-so-efficient, you hear a lot of people saying "learn how to do it manually first, then use the wizzy tool to save time." Code generation tools which pretend to abstract out something, like all abstractions, leak, and the only way to deal with the leaks competently is to learn about how the abstractions work and what they are abstracting. So the abstractions save us time working, but they don't save us time learning.

And all this means that paradoxically, even as we have higher and higher level programming tools with better and better abstractions, becoming a proficient programmer is getting harder and harder.

Ten years ago, we might have imagined that new programming paradigms would have made programming easier by now. Indeed, the abstractions we've created over the years do allow us to deal with new orders of complexity in software development that we didn't have to deal with ten or fifteen years ago, like GUI programming and network programming. And while these great tools, like modern OO forms-based languages, let us get a lot of work done incredibly quickly, suddenly one day we need to figure out a problem where the abstraction leaked, and it takes 2 weeks. And when you need to hire a programmer to do mostly VB programming, it's not good enough to hire a VB programmer, because they will get completely stuck in tar every time the VB abstraction leaks.

The Law of Leaky Abstractions is dragging us down.

Very good video of REC Trichy - Reminiscence

Very good video of REC Trichy - Reminiscence is available at google.

Eyes will become moist for sure and heart will ache once again for glory days....

Check it here.

All Dostoevsky said was 'we shall be with Christ.'

This article gave me some good idea about Dostoevsky's experiences in his early years.

Most revealing paragraph is:

As for Dostoevsky himself, though tortured by fear, he nevertheless held fast to that "philosophy" which the pervert Freud detested. As one of Dostoevsky's fellow conspirators on the scaffold recalled: "All Dostoevsky said was 'we shall be with Christ.'" Yes, Dostoevsky had Christian faith. Holy Bible faith. Hebrews Chapter 11 faith. In his moment of greatest fear the image of a waiting Christ sustained him, preserved his sanity. To the pervert Freud, this faith shackles man. But to the condemned man, the man facing his own grave, this faith is liberating.

Of course, history records that shortly after Dostoevsky uttered his famous words, just as the rifles were due to fire upon the first three, a reprieve was granted.

Garbage Collection and JVM Tuning

Most of the large scale J2EE Applications need some JVM tuning to perform reasonably.

I had a miserable time in 2003 while trying to tune JVM on Red Hat Linux 7.3 with JBoss.

Since then, I keep a note of GC Notes and following articles are worth sharing with all.

How we solved our GC Problem?

A Collection of JVM options

Brief Note about MD5, Hash, Checksum and Digest

Recently, I became bit curious about checking the integrity of downloaded files from net and had to read up about MD5, Hash, Checksum et al.

I started off with wikipedia and google search; both of these gave me a bunch of info which I have summarized here for a quick intro.

What is "Hash"?
---------------
The term "hash" apparently comes by way of analogy with its standard meaning in
the physical world, to "chop and mix."

In the SHA-1 algorithm, for example, the domain is "flattened" and "chopped" into "words"
which are then "mixed" with one another using carefully chosen mathematical functions.


Hash Function
----------------
A hash function (or hash algorithm) is a way of creating a small digital "fingerprint"
from any kind of data.

The function chops and mixes the data to create the fingerprint, often called a hash
value.

The hash value is commonly represented as a short string of random-looking letters
and numbers (Binary data written in hexadecimal notation).

A good hash function is one that yields few hash collisions in expected input domains.
In hash tables and data processing, collisions inhibit the distinguishing of data,
making records more costly to find.


Error Detection - Use of Hash Function and Redundancy Check
-------------------------------------------------------------------------
Using a hash function to detect errors in transmission is straightforward.

The hash function is computed for the data at the sender, and the value of this hash is
sent with the data. The hash function is performed again at the receiving end, and if
the hash values do not match, an error has occurred at some point during the transmission.
This is called a redundancy check.

Checksum
---------------
This article is about checksums calculated using addition.

The term "checksum" is sometimes used in a more general sense to refer to any kind of
redundancy check.

A checksum is a form of redundancy check, a very simple measure for protecting the integrity
of data by detecting errors in data that is sent through space (telecommunications) or time (storage).

It works by adding up the basic components of a message, typically the asserted bits, and
storing the resulting value.

Later, anyone can perform the same operation on the data, compare the result to
the authentic checksum, and (assuming that the sums match) conclude that the
message was probably not corrupted.

The simplest form of checksum, which simply adds up the asserted bits in the data,
cannot detect a number of types of errors. In particular, such a checksum is not changed by:

* reordering of the bytes in the message
* inserting or deleting zero-valued bytes
* multiple errors which sum to zero

More sophisticated types of redundancy check, including Fletcher's checksum, Adler-32, and
cyclic redundancy checks (CRCs), are designed to address these weaknesses by considering not only the value of each byte but also its position.

The cost of the ability to detect more types of errors is the increased complexity of computing
the checksum.

These types of redundancy check are useful in detecting accidental modification such as corruption to stored data or errors in a communication channel. However, they provide no security against a malicious agent as their simple mathematical structure makes them trivial to circumvent.

To provide this level of integrity, the use of a cryptographic hash function, such as SHA-256,
is necessary. (Collisions have been found in the popular MD5 algorithm and finding collisions in SHA-1 seems possible, but there is no evidence as of 2005 that SHA-256 suffers similar weaknesses.)

On Unix, there is a tool called "cksum" that generates both a 32 bit CRC and a byte count for
any given input file.

CRC
----
A cyclic redundancy check (CRC) is a type of hash function used to produce a checksum
a small, fixed number of bits against a block of data, such as a packet of network traffic or
a block of a computer file. The checksum is used to detect errors after transmission or storage.

A CRC is computed and appended before transmission or storage, and verified afterwards by recipient to confirm that no changes occurred on transit. CRCs are popular because they are simple to implement in binary hardware, are easy to analyze mathematically, and are particularly good at detecting common errors caused by noise in transmission channels.

Hashes are "digests", not "encryption"
-------------------------------------
Encryption transforms data from a cleartext to ciphertext and back (given the right keys),
and the two texts should roughly correspond to each other in size: big cleartext yields
big ciphertext, and so on. "Encryption" is a two-way operation.

Hashes, on the other hand, compile a stream of data into a small digest
(a summarized form: think "Reader's Digest"), and it's strictly a one way operation. All hashes of the same type have the same size no matter how big the inputs are:

We'll note here that though hashes and digests are often informally called "checksums",
they really aren't. True checksums, such as a Cyclic Redundancy Check are designed to
catch data-transmission errors and not deliberate attempts at tampering with data.

Cipher
---------
A cipher is an algorithm for performing encryption (and the reverse, decryption)
A series of well-defined steps that can be followed as a procedure. An alternative term is encipherment

Excellent References:
-----------------------
1) An Illustrated Guide to Cryptographic Hashes


2) What is a Digital Signature

IO Redirection in Java

A Casual Google search led me to this interesting Java TechTips which talks about redirecting IO to a file as we normally do on command prompt

java test >myfile

Same thing can be achieved by using PrintWriter cleverly.

System class has methods to let you set your own PrintWriter to it. - System.setOut()

As a point of interest, the JDK 1.3 implementation of java.lang.System has internal code of this form:

    FileOutputStream fdOut =
      new FileOutputStream(FileDescriptor.out);
  setOut0(new PrintStream(
      new BufferedOutputStream(fdOut, 128), true));

Check out this TechTips for more info about IO Redirection and Array Manipulation.

VI Editor Related Links

VI Lovers Home Page and Mastering the VI Editor are good links for VI Learning

Good FAQ on Changing Unix Shell

This entry is worth reading before making a switch from one unix shell to another shell

Web Security - Why SSL is not enough to protect Credit Card

I have been under the illusion that SSL is enough for Point to Point Security. 2 Articles from Monitoring Central have broken the illusion for good!

Does SSL protect you, or is it a condom that is open at both ends?
Read this article to understand the limitation that SSL does not really ensure the authenticity of both ends, automatically.

Excerpt:

What it does not do is actually secure any of the data that passes through the pipe, or really know where either end of the pipe actually is. What you can be sure of is that anything put into one end of the pipe is going to come out wherever the other end is.

But surely the data is fully protected? Yes, whilst the data is in the pipe it is protected. Now, assuming - and unfortunately that's what we have to do - that you know for sure where each end of the pipe is, and you are sure that each end is very secure, and you know for certain who is at each end, then you're OK. If any of those is not true then you do have a problem.

My data is SSL protected between the server, and me so why should I worry? Well no one at the server end really knows whom the data is from because they don't know what your identity is. They assume that data arriving through the pipe is right, and that your identity can be presumed from the data, not the other way around. Unfortunately there are hacker attacks that divert your link through their own site, where they can pretend to each end that they are the other entity without either end being the wiser. (This is called a man-in-the-middle attack using web site spoofing.)

Why SSL is not enough to secure your credit card details
There is no easy for Server to establish the identity of client and vice-versa. Sure, we do get padlock but most of the people would not bother to check the certificate if they are valid, genuine or fake.

Web Services - RPC Vs Document

For Beginners, RPC Style Vs Document Style would be confusing.

Mitch has done a good job of clarifying it in his article.

A Distinction has been made between Communication Pattern and Style.

Excerpt:

we turn to the two decisions for formatting the contents of a message's element.

The style, or binding style, decision controls how the elements just under the SOAP body are constructed. The two choices are:

• RPC: Add extra elements to simulate a method call. (Note that RPC is also a communication pattern.)
• Document: Just send the XML as is. There's also a variation called wrapped that is still specified as document.

Here's an example of an RPC-style message:

  0000000000
  000000000B

RPC relies on some rules. Observe that the root element is qualified with a namespace, but the two child elements use unqualified names. The root element is named after the operation: opName for a SOAP request, opNameResponse for a SOAP response. Each child is a parameter, or a return value named opNameReturn.

Now here's an example of a document-style message:

test



Observe that all elements are defined within the same namespace. With a document-style Web service, you're free to define the XML however you wish because all the XML is explicitly specified.

Next, we examine how binding style is specified in the WSDL. There actually is a style attribute in the element, which is the element's first child. Also, each nonempty has one or more child elements, into which style factors.

Table 1. How binding style is specified in a WSDL document

	RPC	Document
element	style="rpc"	style="document"
element(s)	Any number of elements, each containing a type attribute	Single element containing an element attribute; zero also allowed

A WSDL document provides the interface (a generic "list of methods") and a set of instructions that describe how the service is bound to a messaging protocol.

The WSDL 1.1 specification distinguishes two different binding styles, as follows:

* RPC Style: This style specifies that the contains an element with the name of the service method being invoked (the wrapper element). This element, in turn, contains an entry for each parameter and the return value of this method.

* Document Style: In this style, there is no wrapper element. Instead, the message parts appear directly under the element. There are no SOAP formatting rules for what the contains. The contains what the sender and receiver agreed on as an XML document.

Within those styles, you can also have an encoded use or a literal use:

* Encoded: In this use, each message part references an abstract type using the type attribute. The message is produced using an encoding specified by the encodingStyle attribute. The encoding most frequently used is SOAP Encoding, which is a set of serialization rules defined in SOAP 1.1. The rules specify how objects, structures, arrays, and object graphs should be serialized. In general, applications that use SOAP encoding focus on remote procedure calls, and likely use the RPC message style.

* Literal: In this use, each part references a concrete schema definition using either the element or type attribute. In other words, data is serialized according to a given schema. In practice, this schema is usually expressed using W3C XML Schema.

To summarize, the binding style/use combinations are:

* RPC/encoded
* RPC/literal
* Document/encoded
* Document/literal

Refer to this JDC Tip