AWG Blogs

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    7 months ago
  • JSF vs Struts 2 - JSF was designed in part by the authors of Struts to create a "Struts" that did a more accurate implementation of MVC (Struts is technically "Model 2") a...
    8 months ago
  • XML Beans vs JAXB - Seems XML Beans is superior: JAXB provides support for the XML schema specification, but handles only a subset of it; XMLBeans supports all of it. Also, by...
    1 year ago
  • Algorithms and OOP - In addition to DCI, "generic programming" as well as the move to functional programming appears to add nuance to the OOP notion of joining behavior with da...
    1 year ago
  • Flyweight vs Singleton - Implementations seems to be virtually identical, differing only in style, where the flyweight object is created and held by associated objects (containers:...
    1 year ago
  • init-param vs context-param - see http://javahash.com/difference-between-servlet-init-and-context-parameter/ for background. Gist: context-param variables are global and accessible thro...
    1 year ago
  • rbenv vs RVM - RVM is responsible not only for changing Ruby versions, but for installing rubies and managing gemsets, as well. ...Along with rbenv [to manage ruby versi...
    2 years ago

Tuesday, March 20, 2018

Create keypair for Tomcat SSL and import same to Java keystore

Create the keypair:
keytool -genkeypair -alias tomcat -keyalg RSA -keysize 2048 -keystore tomcat-keystore.jks -validity 730

Export the certificate:
keytool -export -alias tomcat -file tomcat-keystore.cer -keystore tomcat-keystore.jks

Import to Java keystore:
keytool -import -alias tomcat -file tomcat-keystore.cer -keystore C:\jdk1.7.0_51\jre\lib\security\cacerts

Add it to Tomcat's server.xml:

    <Connector SSLEnabled="true" acceptCount="100" clientAuth="false"
disableUploadTimeout="true" enableLookups="false" maxThreads="25"
    port="8443" keystoreFile="/path/to/tomcat-keystore.jks" keystorePass="password"
    protocol="org.apache.coyote.http11.Http11NioProtocol" scheme="https"
    secure="true" sslProtocol="TLS" />

Now you can avoid errors in java programs like:

sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target; nested exception is javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed...

References:
https://dzone.com/articles/setting-ssl-tomcat-5-minutes
https://stackoverflow.com/a/7812567/1714485

Wednesday, May 31, 2017

Creating a multi-column constraint where one column has nulls

To create a multi-column unique constraint on a table where the new column will have nulls initially
need to ensure that the index associated with the unique constraint is non-unique. This can be done
using 'DEFERRABLE' in the constraint command or by creating a non-unique index first and
referring to it with a USING INDEX __ in the constraint command:

select name from v$database;

Alter table MYSCHEMA.MY_TABLE add MY_COLUMN  varchar2(250);

comment on column MY_TABLE.MY_COLUMN is 'a column description';

ALTER TABLE MYSCHEMA.MY_TABLE ADD CONSTRAINT XYZ1_MY_TABLE UNIQUE (ANOTHER_COLUMN, MY_COLUMN) DEFERRABLE NOVALIDATE;

commit;

-- ROLLBACK
(paste the below rollback commands in sql developer worksheet run as script and click commit)
ALTER TABLE MYSCHEMA.MY_TABLE DROP CONSTRAINT XYZ1_MY_TABLE;

Alter table MYSCHEMA.MY_TABLE drop column MY_COLUMN;

--verify column, constraint and associated index is deleted:
select index_name,index_type, uniqueness, visibility from dba_indexes where table_name='MY_TABLE' order by index_name;

select * from dba_constraints where table_name='MY_TABLE';


Sunday, April 23, 2017

Git rebase interactive to move feature to release

The scenario was similar to http://stackoverflow.com/questions/6594881/git-merge-only-the-changes-made-on-the-branch?noredirect=1&lq=1
where dev/master was in the middle, getting merged into continuously be various teams and their feature branches. Periodically a release branch is created and devs are stuck with the dilemma of having to merge a feature branch into both dev and release.

          A release1
         /
    D---E---F---G development
            \
             H---I---J feature_for_release1

So, as a proof of concept what I have done is show how feature_for_release1 could be attached onto release1 without including F.

I first created a staging branch off release1:

 MINGW64 /c/Work/testing/my_try_git (release1)
$ git checkout -b stage-release1-feature
Switched to a new branch 'stage-release1-feature'

Then merged in feature-for-release1:
 git merge feature-for-release1

At this point I printed the log and did a rebase interactive:
 MINGW64 /c/Work/testing/my_try_git (stage-release1-feature)
$  git log --pretty=oneline --graph
* 14b50fed8999aa785e7333a239b532c3f1fe11e0 file added for release1
* b6a8a66b8bd64de49b666d0e627e68de76747ac4 files changed for release1
*   e3ee2edbbfbb2ef629170309d5e35cad6181f4d6 Merge pull request #1 from awgtek/feature-for-release2
|\
| * cd091e9f75d8580c34c9a73c0f30aef616816a7f adding changes for release 2
|/
* eb95ed7111130064272be69957644223212d9981 Remove 322
* fde83b085873139a22cef07f069b46e98eeb0fe9 asdflkasjf;dsak
* 7a5797b379afca819f1e5a92bc122e41bbed52ab add all the octa t filesfrom2
* 05d0d336001842e6b4fec2206e6616363b8d9dbe adding redoctober
* 485cdfcd1fdcd5106518a9f19406a1243c91c555 add all the octocat txt files
* 81d5a2cb15e40752c8bf7aba7ffde6728ebfbdb6 add cute octaot story

MINGW64 /c/Work/testing/my_try_git (stage-release1-feature)
$ git rebase -i  eb95ed7111130064272be69957644223212d9981
In the editor was shown:

As can be seen, I am rebasing to eb95ed which corresponds to point E on the above diagram. I am also dropping cd091e9 from the replaying of this sequence of commits (top to bottom) onto the staging branch which is being rebased to the point just before eb95ed.

When I saved the file, it got an error:

error: could not apply b6a8a66... files changed for release1

When you have resolved this problem, run "git rebase --continue".
If you prefer to skip this patch, run "git rebase --skip" instead.
To check out the original branch and stop rebasing, run "git rebase --abort".
Could not apply b6a8a66b8bd64de49b666d0e627e68de76747ac4... files changed for release1

This was because one of the files committed in the dropped commit was also changed in a subsequent kept commit. So I had to edit the offending file remove all the merge conflicts, do a git add, and a git rebase --continue. After which the rebase was completed.

 MINGW64 /c/Work/testing/my_try_git (stage-release1-feature)
$  git log --pretty=oneline --graph
* 752d1871b4e8632a1daf8fe7579884f08dfa0b17 file added for release1
* faa4e3ba142bc00015bdba7c2988e02319cbfaab files changed for release1
* eb95ed7111130064272be69957644223212d9981 Remove 322
* fde83b085873139a22cef07f069b46e98eeb0fe9 asdflkasjf;dsak
* 7a5797b379afca819f1e5a92bc122e41bbed52ab add all the octa t filesfrom2
* 05d0d336001842e6b4fec2206e6616363b8d9dbe adding redoctober
* 485cdfcd1fdcd5106518a9f19406a1243c91c555 add all the octocat txt files
* 81d5a2cb15e40752c8bf7aba7ffde6728ebfbdb6 add cute octaot story

I could  then push stage-release1-feature to github and merge it into release. see here.

Saturday, July 23, 2016

Enabling Debugging in Eclipse for Tomcat Installation

When using the option "Use Tomcat installation (takes control of Tomcat installation), to enable debugging from Eclipse, you may need to adjust the VM arguments of the launch configuration as follows:

Double click the Tomcat server in the Servers tab, then click "Open launch configuration"
In the Arguments tab append the following line to the VM arguments text box:
 -agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=n

Then restart the server.

Here is a screenshot:

Saturday, March 5, 2016

Two-way authentication with Tomcat

Start by creating a private key, cert, and keystore using openssl then convert to jks using Java's keytool so it can be used in Tomcat:
MyOwnPC+Joe@MyOwnPC ~/temp
$ openssl req -new -x509 -key serverprivatekey.pem -out servercert.pem -days 1095
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:.
State or Province Name (full name) [Some-State]:.
Locality Name (eg, city) []:.
Organization Name (eg, company) [Internet Widgits Pty Ltd]:.
Organizational Unit Name (eg, section) []:.
Common Name (e.g. server FQDN or YOUR name) []:myownpc
Email Address []:.

MyOwnPC+Joe@MyOwnPC ~/temp
$ ls
servercert.pem  serverprivatekey.pem

MyOwnPC+Joe@MyOwnPC ~/temp
$ openssl pkcs12 -export -out serverkeystore.pkcs12 -in servercert.pem -inkey serverprivatekey.pem -name myownpc -passout pass:changeit

MyOwnPC+Joe@MyOwnPC ~/temp
$ ls
servercert.pem  serverkeystore.pkcs12  serverprivatekey.pem

MyOwnPC+Joe@MyOwnPC ~/temp
$ keytool -importkeystore -alias myownpc -srckeystore serverkeystore.pkcs12 -srcstoretype PKCS12 -destkeystore keystore.jks -deststoretype JKS
Enter destination keystore password:  changeit
Re-enter new password: changeit
Enter source keystore password:  changeit

MyOwnPC+Joe@MyOwnPC ~/temp
$ ls
keystore.jks  servercert.pem  serverkeystore.pkcs12  serverprivatekey.pem

MyOwnPC+Joe@MyOwnPC ~/temp
$ cp keystore.jks ../certs
Add (or modify) so that Tomcat's conf/server.xml contains reference to the new keystore:
    <Connector port="8443" protocol="org.apache.coyote.http11.Http11Protocol"
               maxThreads="150" SSLEnabled="true" scheme="https" secure="true"
        keystoreFile="C:/cygwin64/home/Joe/certs/keystore.jks" keystorePass="changeit"
               clientAuth="false" sslProtocol="TLS" />
Restart Tomcat. Then browse to https://myownpc:8443/someapp. Accept the certificate browser warnings and verify that the presented certificate's details contains 'myownpc' as the 'issued for'. Also you can check using the following keytool command to ensure 'myownpc' is an alias for the imported cert: keytool -list -v -keystore keystore.jks Now create a client certificate and add it to the keystore used by tomcat:

MyOwnPC+Joe@MyOwnPC ~/temp
$ openssl genrsa -out clientprivatekey.pem 2048                                 Generating RSA private key, 2048 bit long modulus
.......................+++
.............+++
e is 65537 (0x10001)

MyOwnPC+Joe@MyOwnPC ~/temp
$ openssl req -new -x509 -key clientprivatekey.pem -out clientcert.pem -days 365
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:.
State or Province Name (full name) [Some-State]:.
Locality Name (eg, city) []:.
Organization Name (eg, company) [Internet Widgits Pty Ltd]:.
Organizational Unit Name (eg, section) []:.
Common Name (e.g. server FQDN or YOUR name) []:joe
Email Address []:.

MyOwnPC+Joe@MyOwnPC ~/temp
$ ls
clientcert.pem        keystore.jks    serverkeystore.pkcs12
clientprivatekey.pem  servercert.pem  serverprivatekey.pem

MyOwnPC+Joe@MyOwnPC ~/temp
$ openssl pkcs12 -export -out clientkeystore.pkcs12 -in clientcert.pem -inkey clientprivatekey.pem -name joe -passout pass:changeit

MyOwnPC+Joe@MyOwnPC ~/temp
$ keytool -importkeystore -alias joe -srckeystore clientkeystore.pkcs12 -srcstoretype PKCS12 -destkeystore keystore.jks -deststoretype JKS
Enter destination keystore password:  changeit
Enter source keystore password:  changeit

MyOwnPC+Joe@MyOwnPC ~/temp
$ ls
clientcert.pem         keystore.jks           serverprivatekey.pem
clientkeystore.pkcs12  servercert.pem
clientprivatekey.pem   serverkeystore.pkcs12

MyOwnPC+Joe@MyOwnPC ~/temp
$ cp keystore.jks ../certs
Now modify the server.xml SSL connector, adding keyAlias, truststoreFile, and truststorePass attributes and set clientAuth to true:
    <Connector port="8443" protocol="org.apache.coyote.http11.Http11Protocol"
               maxThreads="150" SSLEnabled="true" scheme="https" secure="true"
        keystoreFile="C:/cygwin64/home/Joe/certs/keystore.jks" keystorePass="changeit"
               clientAuth="true" sslProtocol="TLS"
  keyAlias="myownpc" truststoreFile="C:/cygwin64/home/Joe/certs/keystore.jks"
  truststorePass="changeit"
 />
Restart Tomcat. Now loading the https page will give an error like
An error occurred during a connection to myownpc:8443. SSL peer cannot verify your certificate. (Error code: ssl_error_bad_cert_alert) 
So in Firefox, do Options, Advanced, View Certificates, Import and import the file clientkeystore.pkcs12 and enter the password when prompted. Try loading the page again and Firefox should present you with the option to use the certificate you imported; accept and load the page.

Refs: http://venkateshragi.blogspot.com/2013/04/two-way-ssl-authentication-on-tomcat.html main flow here. Correction, the truststoreFile was actually required for me.
http://www.cloudera.com/documentation/enterprise/5-3-x/topics/cm_sg_openssl_jks.html found correction to above blog, adding -name option to openssl exports.

Saturday, February 21, 2015

Eclipse Classpath Run Configurations being overwritten

Encountered a strange issue with eclipse (both Luna and Mars) on certain run configurations. What happened was when launching I would almost immediately (after some messages from loading classes) get "Error: Could not find or load [name of the class]" or in some other run configuration a java.lang.ClassNotFoundException and then a stack trace.

This would happen despite cleaning the project, recreating the run configuration, or running eclipse  with the -clean option. The project depended on another project to which I traced the unfound class. This told me that it was a classpath issue; however, the project was clearly listed in the Classpath tab of the run configuration. I even tried exporting the project to a jar and adding it to the local client project build path but that didn't work either.

I then decided to examine the running JVM process. I ran JConsole, attached to the failing process and opened the VM Summary tab. There were a huge number of VM arguments which I scrolled through to get to the Class path entry. The Class path entry had only one entry in it, a single jar file used by the application. There should have been more entries though. I then created a new run configuration using the reverse-engineered items from the output of wmic to get the full command line (see http://serverfault.com/questions/323795/display-complete-command-line-including-arguments-for-windows-process). I tried obtaining it from Process Explorer via save but it truncated it because it was very long I guess. The reverse configured run configuration also produced the same errors.

The I did a search for the single jar file that was assigned to the classpath in the long command line figuring it had to be set there somehow. Sure enough it was being assigned via the -Djava.class.path vm argument. Since the jar was already being loaded via the build path I removed the java.class.path argument -- and that resolved the error. Apparently, adding that argument was causing Eclipse to ignore the Classpath as shown in the Classpath tab of the run configuration. This would only happen though using that particular set of VM arguments. If I only added a few VM arguments in addition to the java.class.path argument Eclipse would run the config and no errors would result. Interestingly JConsole would show only the VM arguments other than java.class.path so apparently Eclipse cleans it up, perhaps recognizing whether the entry is needed or already is reflected in the run configuration classpath (update: this seems to indicate java.class.path is not settable; and I wasn't able to prove otherwise, i.e that it was settable, when using test projects and configurations with classpath tweaking by removing the default classpath and adding my own under "User entries").

My guess regarding the error is that the replacing of the run configuration classpath with the value added to java.class.path vm argument is due to either 1) the vm argument list I was using was too long or 2) the vm argument list was corrupted somehow. This cause would be in addition to an existing eclipse state -- most likely the state of the plugins installed. The reason why is that some eclipse installations worked given the same set of vm arguments and all else being equal while other eclipse installations failed. It did so happen that when I uninstalled one custom plugin that did custom run configurations and reinstalled an earlier version of the plugin this solved the issue. However repeating the steps did not solve the issue on other eclipse installations so I could not pinpoint it to the plugin. It therefore must be a combination of plugin installation or absence of and the above faulty set of vm arguments containing the java.class.path entry...


refs:
http://www.javahotchocolate.com/tutorials/bad-output-folder.html

Friday, February 13, 2015

Creating a sequence diagram from a stack trace

Install AmaterasUML:
- download AmaterasUML from http://amateras.sourceforge.jp/cgi-bin/fswiki_en/wiki.cgi?page=AmaterasUML
- unzip AmaterasUML_1.3.4.zip
- copy the three jars to eclipse plugin folder, e.g. D:\App\eclipse-jee-luna-R-win32-x86_64\eclipse\plugins
- install Graphical Editing Framework eclipse plugin. It was already installed in mine, maybe through a dependency on BPMN2 Modeler or something else.
- restart eclipse
Get the stack trace
- in Eclipse put a breakpoint in some method you want to analyze via sequence diagram
- start debug 
- in the debug view right-click the Daemon Thread and click Copy Stack
- paste into text editor
Fix up stack trace
- remove unwanted lines including lines that end with "line: 1" or start with "Daemon Thread" or "owns:" leaving only the lines that start with entities to be added to the sequence diagram
- save the file e.g. D:\work\AmaterasPrepWork\MyStackTrace.txt
- create a second text file and paste into it the following awk script:
{
str = $0;\
sub(/^\t/, "", str);\
sub(/\(.*\./,".",str);\
sub(/\$.*\./,".",str);\
match(str, /(.*)\./, arr);\
sub(/^/, "at ", str);\
#print str;\
sub(/\([^\)]*\)/, "(", str);\
sub(/ line: /, arr[1]".java:", str);\
sub(/$/, ")", str);\
sub(/\t\)$/, ")", str);\
print str}
- save the file as e.g. D:\work\AmaterasPrepWork\AmaterasPrepProg.txt
- download gawk and run file e.g. gawk-3.1.6-1-setup.exe
- open a command prompt and cd to e.g. D:\work\AmaterasPrepWork
- execute the following commands:
D:\AmaterasPrepWork>set path=%path%;D:\Program Files (x86)\GnuWin32\bin
D:\AmaterasPrepWork>echo awk -f AmaterasPrepProg.txt MyStackTrace.txt ^> out.txt > run.bat
D:\AmaterasPrepWork>run.bat
Make sequence diagram in eclipse
- Do Window, Show View, AmaterasUML, Stack Trace Sample, OK
- paste the contents of D:\AmaterasPrepWork\out.txt into the window
- click the 'i' (image of lower case 'i') button in upper right-hand corner of the Stack Trace Sample view
- select a folder in your project as the destination of new sequence
- refresh the folder in eclipse
- open sequence.sqd
- do finishing touches. It appears e.g. that some entities weren't added and need to be added?? will check on this...
- save the file as MySequence.sqd or save sequence.sqd and refactor to another name because AmaterasUML uses sequence.sqd as the target file name evidently.


ref: