Crazy Idea


test blog
October 27, 2016, 11:27 am
Filed under: Uncategorized

test blog by email



java.lang.VerifyError in a tomcat 7.x webapp
April 25, 2012, 11:46 pm
Filed under: Uncategorized | Tags: , , ,

Ahoy there! 

I have a webapp(built using maven 3.0.3) deployed into Tomcat 7.0.23. After I log into the app, I get this error

javax.servlet.ServletException: java.lang.VerifyError: (class: org/apache/jsp/ChLogin_jsp, method: _jspService signature: (Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponse;)V) Inconsistent stack height 0 != 1

Just to be sure, the WAR/web-inf/lib folder does not contain either servlet/jsp/jstl libraries. I also don’t precompile any of the JSP files.

Here’s the sequence 

1) user goes to login.jsp page using a GET request . This works just fine

2) user enters credentials and submits it to jsp2 using a POST request

3) java.lang.VerifyError happens when jsp2 constructor is being invoked by the servlet engine.

What is the problem ? what should I be checking for ?

Just so you know, this webapp works just fine if I deploy it into Tomcat 5.5 (I just have to add jstl to the dependencies)

Thank you,



How to view certificate(s) details of a LDAP server?
March 20, 2008, 6:32 pm
Filed under: 1 | Tags: , , ,

hi there,

if I connect to a https server, I can click on the icon(status bar) and find out which certificate(SSL/TLS) is installed on the server.

How can I do the same with a LDAP server ? Which (free/opensource) client can show me the certificate information to the connected LDAP server ?

I googled for any clues — Not much help. Found some source code on novell’s site :

http://developer.novell.com/documentation/samplecode/jldap_sample/index.htm

Do users have any tips/favorite clients that they use which has such features ?

Even if you have some source code that might do the trick (java/C++/C), will work for me.

Thank you very much for the info.

BR,
~A



Jdbc : Why doesn’t Oracle’s driver support READ_UNCOMMITTED ?
September 7, 2007, 6:56 pm
Filed under: Uncategorized

hi lazy Web,

I tried to change the Transaction Isolation level to see what my unit test(spring/hibernate/dbUnit) was doing.

Class.forName(“oracle.jdbc.driver.OracleDriver”);
Connection conn = java.sql.DriverManager.getConnection(url, user, password);
if (null != conn) {
System.out.printf(“%s%n”, conn.getTransactionIsolation());
conn.setTransactionIsolation(Connection.TRANSACTION_READ_UNCOMMITTED);
}

and got the following exception

2
Exception in thread “main” java.sql.SQLException: READ_COMMITTED and SERIALIZABLE are the only valid transaction levels
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:208)
at oracle.jdbc.driver.PhysicalConnection.setTransactionIsolation(PhysicalConnection.java:1678)
at JdbcTest.main(JdbcTest.java:17)

So, why doesn’t Oracle JDBC driver let me do dirty reads ?

Does anyone out there know of a tool (java or otherwise) that can let me do this ? I have TOAD : does TOAD support a way to do this ? How about ruby/Python tools ? I’m on windows XP. So, it would help me if you could refer  me to windows specific OR cross-platform tools.

Thank you for any pointers,



openJDK/Java 7 : RFE
August 30, 2007, 12:20 am
Filed under: Uncategorized

Hi There,

Not sure if someone at sun/JCP or those who know how JCP works is listening.

On Windows/Win32, for over 10 years, we’ve had an API called DebugBreak(). At runtime, when the the program calls this function, the OS will prompt the user to activate a (specified) Debugger. For most purposes, this debugger is usually the developer’s IDE like Visual CC++ or Borland C++. If the application has debug symbols and the debugger has the associated sources, then the developer can debug with full source!

When I moved from the Windows to the java world, I’ve been yearning for something like this.  I read (http://today.java.net/pub/a/today/2007/08/09/looking-ahead-to-java-7.html) that it appears that Jdk 7 is currently slated for spring 2009. Given that we have enough time, I’m wondering if there’s enough time to add something like DebugBreak(). I know that not all OS have support to do that. What would it take to do it on Windows where the majority of Java developers live ?



Java Swing Vs VB 4.0
July 17, 2007, 5:14 pm
Filed under: Uncategorized

Java’s weak point has been its Rich client programming capabilities . Especially, the ease of use for building applications.

I used to develop for the Windows environment before doing Java. I used Borland C++, VC++ and VB. Whenever, people boasted about Java GUI apps, I always felt nostalgic about my windows IDEs and how easy it was to build a GUI.

I saw this link from http://www.jroller.com/MasterMark/entry/java_users_group_cologne_ide
talking about an IDE shootout. He talks about Netbeans Matisse Swing GUI toolkit/framework/wizard that helps people build GUIs in Java and how he feels “Hey, we’ve reached parity with VB at a last! That’s great.” Followed
immediately by the thought “Wow, that only took a decade. Meh.”

Although he did not mention VB 4.0 in the above quote, it’s kinda assumed. So, when will a Java IDE going to be at parity or better than the current VB as far as GUI development capabilities go ?

Process Perfection

I still haven’t seen a single Java IDE have packaging tools like VB (Installshield lite/express). Granted Java has been better in terms of unit testing/coverage, etc but the (till now) missing “GUI building” functionality was costing it much. The fact that AJAX is making desktop apps envious and ruby/php/.NET/FLASH improving on Rich-Client functionality, there is little time to be lost if Java has to be contender for building Rich Client apps.

Europa from Eclipse is a good step in the direction. Idea is trying to keep everyone happy : it appears that they don’t share sun’s enthusiasm as far as Swing is concerned 🙂

Nice Interesting times…

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tags
June 22, 2007, 11:52 pm
Filed under: Uncategorized

Mark Watson, in today’s post on “Everything is Miscellaneous” book review  quotes

“Rigid tree-structured indexing allows parent/child associations but fails to allow general associations between objects. Example: multiple tags allow users to identify information the way they want to access it.

  • When applying tags indicating that an object belongs to a group, it is good to allow a numeric value. Example: Mary is a: manager (0.75), technical guru (0.9), good in meetings (0.25)

That is a cool idea! The sum of the individual components don’t quite add up to 1. Would be nice to see more examples of these!

Probably, del.icio.us should start having a new experimental site for doing it. Now that google also has a bookmarking site, it’s a good time to try this out!

 Related idea

I wish every enterprise had a tag/bookmarking site internally so that people could quickly  lookup what they were after! Wonder if google appliance has a way to search for tags ? But, in order to do that, people need to save some tags in each doc. What if they let people tag  the docs in the company implicitly and explicitly and then a user can search based on tags ?



interviewing techniques for java web developer
June 11, 2007, 10:46 pm
Filed under: Uncategorized

These days, an enterprise developer works on multiple source files

a) xml/XSL

b) java/C#

c) SQL

d) HTML

e) javascript(ECMAscript)

f) CSS

The xml itself can/will contain different grammars depending upon the payload (config, build, content, rules, etc). So, when someone interviews for a position, it is nice to give them a lot of code (say an eclipse/netbeans/idea project) and ask them to add a new feature to the code.

It’s NOT only important to know that the developer understands how to read existing code (like say quicksort/bubblesort/stringReverse) BUT also, how to add new code to existing code(http://tickletux.wordpress.com/2007/01/24/using-fizzbuzz-to-find-developers-who-grok-coding/). If a person can cross that chasm, then such a person can go to the next stage of interviewing.

It’s important to let the interviewee(candidate) do this for all the artifacts that they are expected to create/USE(java/xml, SQL etc). It’s also good to have some sample code available for them so that they can do copy/paste. This is so that the candidate does not fail just on syntax.

If, as Joel says, it takes smarts + “getting things done” attitude to succeed at his company, the above exercise should take care of “GETTING THINGS DONE”. I guess the puzzles and related questions go a long way at testing a person’s smarts ?

Comments ?

BR,

~A



Is anybody in production using Java 6
June 9, 2007, 1:10 am
Filed under: Uncategorized

hi All,

I was talking to someone who’s going to put into production a critical java/j2ee app beginning of next year. They are insisting on using Java 1.5 : I mentioned that Java 6 could give out of the box performance and monitoring improvements over Java 1.5. Also mentioned that my experience porting and production support of a java 1.4 app to java 1.5 was very pleasant. But they try to be conservative and try to be 1 version behind, just in case!!

So, do you know of any big important apps/companies that are in production today with Java 6 ? How did Java 6 far compared to Java 5 ?

Thanks,



Netbeans ISA http proxy server client module
May 4, 2007, 11:44 pm
Filed under: Uncategorized

HI LazyWeb

I downloaded the latest netbeans 6.0 M9 today. Took a lot of time — must be a popular download what with javascript and ruby support built into the IDE.

I noticed that netbeans has a decent MS ISA http proxy server client — I’ve tested various other tools and they cannot work well with MS ISA server.

It would be nice to extract the ISA Server client from netbeans and make it a library that other java developers can use .

jEdit can surely use it. I’ve had trouble getting across ISA server from jEdit. Thanks to fiddler proxy server, I was able to download some plugins on jedit but that was a very slow process.

Hopefully, when I get some time, I will try to get into the netbeans dev list and ask someone to point me to the right location so that I can create a library — assuming that it is OSS.

Eclipse also has a decent proxy client (mostly because I think they use IE to go around the ISA proxy server)

The ruby world has a plugin(gem) that is supposed to do it : rubysspi but I was NOT able to get it working so far.  I can’t get wget/curl to work with the ISA Server. It would be nice if I could have a highly performing local proxy server which can talk to ISA proxy server. That way, all my tools don’t need to point to ISA server but just the local proxy server(which can be seeded with the credentials).

Any hints ?