Daniel Ferber's Technical Tavern

Time to unslop human spec writing

Sun, 27 Sep 2026 00:00:00 +0000

We blame AI for writing slop specs. But the worst spec slop I’ve seen in my career was written by humans.

Long before LLMs, I was reading requirements like this:

“The system shall allow the user to be able to add an item to the set of items.”

“The system shall not allow an unauthenticated user to fail to be prevented from accessing non-public resources.”

“The system shall block registration of customers whose tax ID already exists and allow registration of customers that already exist, updating the previous record.”

More or less Portable WebLogic 12c on Windows

Sun, 21 Aug 2022 00:00:00 +0000

This article appeared first at techtavern.wordpress.com.

(or, “Oracle SOA Suite” from “Quick Start installation”, as stated in the overworded documentation from Oracle)

(or version 12.2.1.4 of WebLogic)

Yes, it is possible to create a more or less portable installation the WebLogic 12c. This installation will work afterwards without administration privileges. And may run with other JVMs (even non “certified” ones as Adopt Open JDK). The installation might be moved to other directories or computers where one does not own administration privileges.

Copying all DBeaver configuration from one computer to another

Wed, 21 Apr 2021 00:00:00 +0000

This article appeared first at techtavern.wordpress.com.

This article explains how to copy your current DBeaver connection from one computer to another.

Instead of installing all drivers again and instead of creating your connections from scratch, it is actually very simple to copy the DBeaver configuration from one computer to another.

First, discover where the configuration is stored on the source computer. You can check this easily the the Preferences: Menu -> Preferences -> Worspace. Check the path shown at “Show full workspace path:”.

Moving from AppEngine and taking your data with you

Wed, 03 Mar 2021 00:00:00 +0000

This article appeared first at techtavern.wordpress.com.

AppEngine and its companion Datastore have been of great value for our application. Nevertheless, time has come to move to another cloud, which also means to face the annoying fact that all our data is stored within a closed, isolated, black box within Googles infrastructure and accessible only through Googles proprietary AppEngine API.

This article explains how we managed to download all data from Datastore and prepared it for another cloud.

Choosing a Gradle Java Webstart/JNLP Plugin

Sat, 11 Mar 2017 00:00:00 +0000

While developing a JavaFX application distributed with Webstart, I had to choose a Gradle plugin in order to package the application. Unfortunately, Gradle does not support Webstart out of the box. After experiencing several available plugins, I decided for the gradle-jnlp-plugin from Tobias Schulte, hosted at Github.

His gradle-jnlp-plugin creates a webstart distribution for a JavaSE application as required by the webstart specification. It creates the jnlp file and compresses/signs the jar files. The directory created by the plugin may then be uploaded to your static web server or embedded into your war file.

Using the gradle-jnlp-plugin – part 1

Sat, 11 Mar 2017 00:00:00 +0000

This collection of articles describe the gradle-jnlp-plugin from Tobias Schulte, hosted at Github.

The plugin produces a webstart distribution for a JavaSE application as required by the webstart specification. It creates the jnlp file and compresses/signs the jar files. The directory created by the plugin may then be uploaded to your static web server or embedded into your war file.

Using the gradle-jnlp-plugin – part 2

Sat, 11 Mar 2017 00:00:00 +0000

This collection of articles describe the gradle-jnlp-plugin from Tobias Schulte, hosted at Github.

Datanucleus fails for Google AppEngine on Netbeans 8

Sat, 15 Oct 2016 00:00:00 +0000

This article explain how to prevent Datanucleus Enhancer failure when developing for Google AppEngine on Netbeans 8.

This article originally appeared on https://techtavern.wordpress.com

The cause

The Google AppEngine plugin for Netbeans from Gaelyk does not work with Google AppEngine Java SDK 40 and later.

The workaroud

While developing, use AppEngine Java SDK 37 (latest available version thar worked for me on Netbeans). You may download it from Maven Repository (see this link), as it is no longer available at Google Appengine site. When building the release version, compile against the latest AppEngine Java SDK.

Unit tests for Objectify entities and DAOs

Wed, 14 Sep 2016 00:00:00 +0000

This article explains how to write unit tests (with junit) for Objectify entities and DAOs.

Google Cloud Platform describes how to write unit tests for Google DataStore. A small adaptation enables the same solution for Objectify.

The documentation suggest creating a LocalServiceTestHelper to be initialized in a @Before/setUp() method and disposed in a @After/tearDown() method.

After calling helper.setUp(), initialize the objectify framework by calling ObjectifyService.begin(). Store the returned closable so you can dispose Objectify at the end of your test.

Displaying PDF documents on Netbeans RCP

Thu, 14 Jan 2016 00:00:00 +0000

This article explains how to display PDF documents on Netbeans RCP, using JasperReports libraries.

This article appeared first at techtavern.wordpress.com.

The proposed solution uses a TopComponent instance in editor mode to display each PDF document. It assumes that there is a JasperPrint object that represents a page-oriented document that can be viewed, printed or exported to other formats. The TopComponent will use a JRViewer to render the PDF document. The JRViewer handles scrolling, zooming, paging and even printing and saving as PDF, Excel and other formats.

HttpURLConnection and GET query parameters

Mon, 30 Nov 2015 00:00:00 +0000

I regret that JAVA SE still lacks any decent native HTTP client framework! Simple use cases like GET requests with query parameters require handcrafted coding with HttpURLConnection.

This article appeared first at <techtavern.wordpress.com>.

HttpURLConnection misses methods to set query parameters. There is no URI builder facility as found on Apache HTTP Client. You are on your own.

Therefore, I wrote the applyParameter method that takes care of GET query parameters.

Comparing your Oracle databases

Mon, 26 Oct 2015 00:00:00 +0000

This article suggests an approach to compare your development, test and production databases using SQL scripts executed from a Servlet.

This article appeared first on techtavern.wordpress.com

Create a Servlet that produces following SQL statements as a text report: (replace **** with a proper value applicable to your database).

Tables, sequences and views: SELECT OBJECT_TYPE, OBJECT_NAME, STATUS FROM ALL_OBJECTS WHERE OWNER = ‘****’ ORDER BY OBJECT_TYPE, OBJECT_NAME
Columns of each table: SELECT TABLE_NAME, COLUMN_NAME, QUALIFIED_COL_NAME, DATA_TYPE, DATA_LENGTH, DATA_PRECISION, DATA_SCALE, NULLABLE, CHARACTER_SET_NAME, CHAR_COL_DECL_LENGTH, CHAR_LENGTH, CHAR_USED FROM ALL_TAB_COLS WHERE OWNER = ‘****’ ORDER BY TABLE_NAME, COLUMN_NAME
Constrains of each table: SELECT TABLE_NAME, CONSTRAINT_NAME, CONSTRAINT_TYPE, STATUS, SEARCH_CONDITION, R_CONSTRAINT_NAME, DELETE_RULE, DEFERRABLE, DEFERRED, VALIDATED, GENERATED FROM ALL_CONSTRAINTS WHERE OWNER = ‘****’ ORDER BY TABLE_NAME, CONSTRAINT_NAME
Sequences: SELECT SEQUENCE_NAME, INCREMENT_BY, MIN_VALUE, MAX_VALUE, CACHE_SIZE, CYCLE_FLAG, ORDER_FLAG FROM ALL_SEQUENCES WHERE SEQUENCE_OWNER = ‘****’ ORDER BY SEQUENCE_NAME

For security reasons, you may prefer to output them into the application log.

Update licence header without plugin

Mon, 26 Oct 2015 00:00:00 +0000

This article explains how to update license header for your java source files without any tool. It works for Notepad++, Netbeans and Eclipse and does not require installing any additional plugin.

This article appeared first at techtavern.wordpress.com.

Option 1: Using Notepad++

Open Notepad++ and navigate to Search->Find ind Files. Fill the dialog as shown below.

Find what: \A(.*?^package){1}
Replace with: /\\r\n \ (line 1)\r\n \* (line 2).\r\n \*/\r\npackage
Directory: The root directory of your source code.
Filters: *.java
Activate “Regular expression” and “. maches newline”.

Netbeans RCP: increasing JVM memory settings

Tue, 20 Oct 2015 00:00:00 +0000

This article explains how to increase memory limits for your Netbeans RCP application when using Ant to create a ZIP package or a Windows installer.

This article appeared originally at techtavern.wordpress.com.

Introduction

Both ZIP package and Windows installer contain an executable that reads JVM and bootstrap settings from the etc/application_name.conf file. This file is copied from the laucher configuration template at netbeans-installation\harness\etc\app.conf. The default options contains all command line parameters passed to the executable. JVM parameters are prefixed by “-J”.

Calling Objectify within DeferredTask

Mon, 19 Oct 2015 00:00:00 +0000

This article explains how to call Objectify within a DeferredTask on Google App Engine push queue.

This article appeared first on techtavern.wordpress.com

Objectify Wiki presents a clear explanation how to user ObjectifyFilter to get or inject a Objectify instance into your servlet. However there is no word using Objectify within push queues.

Solution 1: Create task with worker URLs that are mapped to your servlet

Let ObjectifyFilter inject the Objectify instance. It your responsibility to encode and handle parameters and to secure your URLs.

Google App Engine Java SDK advices

Thu, 08 Oct 2015 00:00:00 +0000

It would have been nice if I knew this beforehand about Google App Engine Java SDK

This article originally appeared on https://techtavern.wordpress.com

GAE infrastructure is a kind of Java 7 platform. You may compile your code using the current Java 8 SDK, as long as source code version is set to Java 7. You may deploy and run your application locally with Java 8, too.

However, when deploying to Google infrastructure, there are some pitfalls.

Netbeans RCP: Asking before exiting the application

Sun, 23 Aug 2015 00:00:00 +0000

This article explains how to present a confirmation dialog asking if the user really wants to close the application.

This article was originally published on techtavern.wordpress.com.

The following solution registers a callable via @OnStop annotation. The callable is an opportunity to cancel closing the application by returning false.


import java.util.concurrent.Callable;
import org.openide.DialogDisplayer;
import org.openide.NotifyDescriptor;
import org.openide.modules.OnStop;

@OnStop
public class ApplicationOnStop implements Callable&amp;lt;Boolean&amp;gt; {
@Override
 public Boolean call() throws Exception {
 NotifyDescriptor d = new NotifyDescriptor.Confirmation("Close application?", NotifyDescriptor.YES_NO_OPTION)
 return DialogDisplayer.getDefault().notify(d) == NotifyDescriptor.YES_OPTION; 
 } 
}

SLF4J on Netbeans RCP Applications

Sun, 26 Jul 2015 00:00:00 +0000

This article explains how to configure SLF4J logging framework for your Netbeans RCP modules.

This article was originally published on techtavern.wordpress.com

Netbeans RCP favors Java standards for a small memory footprint and to spare us from learning new APIs. For example, Netbeans uses java.util.logging instead of creating its own logging API. However, most developers prefer leaner logger APIs like SLF4J.

Context

It happens that Netbeans kept only the API and replaced most of the java.util.logging original implementation. The startup module replaces the log manager. A custom handler writes messages into the platform messages file using a custom pattern. Another handler repeats messages on the platform messages TopComponent.

Netbeans RCP: external layer.xml

Thu, 02 Jul 2015 00:00:00 +0000

A Netbeans RCP application might benefit from an additional layer.xml file stored outside of application bundles. A network directory or a http server may provide some layer.xml with centralized or corporated configuration or user profiles, maintained the network administrator.

This article was first published at techtavern.wordpress.com

There are two solutions to add an additional layer.xml file to your application. Both solutions are provided by Netbeans RCP Toys at github.

LayerProvider

Register a LayerProvider using the @ServiceProvider(service = LayerProvider.class) annotation. The platform calls all LayerProvider.registerLayers(Collection<? super URL>) to populate the collection with URLs to additional layer files. This URL may refer a local file or a remote over HTTP. As this method is called early, your application might not yet know the URL. For example, it does not work for command line argument as they have not been parsed then LayerProvider.registerLayers() is called. This approach is file as long as your URLs are declared as static constants.

SLF4J on Java Google App Engine

Fri, 05 Dec 2014 00:00:00 +0000

This article suggest a recipe to configure SLF4J on Google App Engine for Java.

This article was first published at techtavern.wordpress.com

Google App Engine for Java offers a restricted Java 6 API, which includes just the cumbersome Java Utils Logging. Fortunately, SLF4J works as well. The recipe is the standard one. Nearly no configuration is required.

Just add following SLF4J libraries into the applications WEB-INF/lib directory: slfj4-api-1.7.7.jar and slf4j-jdk14-1.7.7.jar (version number may vary). This will redirect all your SLF4J logging statements to the Java Utils Logging controlled by the App Engine.

View TopComponents with icons on Netbeans RCP

Wed, 03 Dec 2014 00:00:00 +0000

This article explains an approach to enable tabs with icons to ‘view’ TopComponents.

This article appeared first on techtavern.wordpress.com

The Problem

A typical Netbeans RCP application always displays TopComponents with ‘editor’ mode with their icon and their title, even if the tab runs out of space. Here is an example:

Tabs of editor TopComponents

TopComponents with other modes are displayed as ‘views’. Their tabs are extremely simplistic: they never show their icon and their title is shortened or even omitted in case of less space. Here is an example:

Copying from Git to Clearcase

Sun, 23 Nov 2014 00:00:00 +0000

This article is about my recent open source project, git-to-clearcase.

There are many old-fashioned IT business that still believe on Clearcase as their software configuration management.

I experienced that Clearcase imposes an extremely complex versioning model, is poorly supported on major IDEs and lacks some elementary features, like simple file undelete. Everything is complicated and slow on Clearcase and crashes happen frequently. Even worse, Clearcase completely fails to support some modern trends, like agile development, lean infrastructure, incremental design and refactoring.

Netbeans Platform: excluding locales from zip and installer distribution

Tue, 03 Jun 2014 00:00:00 +0000

This article explains how to prevent Netbeans RCP from packaging unwanted locales into the zip distribution and installers.

This article originally appeared on https://techtavern.wordpress.com

Current situation:

The default Netbeans RCP build always includes all localization jars from the harness directory: Russian, Chinese, Japanese and Brazilian Portuguese.
Netbeans project properties and branding properties lack configuration to select bundled languages.
The build templates did not foresee features to exclude locales.

Problem:

Annoying long build times. Proportional to the number of jars, build time increases by five if all default languages are included.
Larger distributable artifact size. Localization jars take about 500kB.

Solution:

Netbeans Ant build is reasonably organized by build templates. And Ant allows overriding targets inherited from templates.
We override the build-zip target. This target generates the .zip distribution artifact, which also serves a input for the installer.

The modified script:

The original build-zip target (netbeans 8.0) is found in the harness directory of your Netbeans installation. We place an adapted copy into the build.xml of your application root directory, thus overriding the behavior of the original target. The red lines were added to prevent adding localization for Russian, Chinese and Japanese.

Google AppEngine on Netbeans 8

Tue, 13 May 2014 00:00:00 +0000

Even though Google does not officially support Netbeans IDE, it is still possible to develop Google App Engine applications with Netbeans 8.

This article originally appeared on https://techtavern.wordpress.com

There has been a Netbeans plugin for Google App Engine hosted at Kenai, which seems to have been left on its own since June 2009. Fortunately, the project was forked by Gaelyk and who updated the plugin for Netbeans 7.4. I was pleased to confirm that his plugin also works for Netbeans 8.0 and for Google App Engine 1.9.x. And I assure that it work better than that dumb Eclipse Web Tools Platform.

Git Ignore file for Netbeans RCP projects

Sun, 11 May 2014 00:00:00 +0000

This article suggest a .gitignore file for GIT repositories that keep Netbeans RCP suite and module projects.

For short:

nbproject/private/
build/
dist/

As explained:

nbproject/private/ Matches the local, per-user configuration directories, which are suite/nbproject/private for suites and module/nbproject/private for module projects.
build/ Matches the module/build and suite/build directories. Modules store their compiled classes within the module/build directory. Suites write shareable artifacts into the module/build directory.
dist/ Matches the suite/dist directories, where suites store distributable artifacts like installation programs and java webstart.

If you prefer Eclipse EGit, then add following lines:

Ant task to remove signature from jar file

Tue, 01 Apr 2014 00:00:00 +0000

This article suggest an Ant macro that removes the publisher signature from an java .jar file, also known as to ‘unsign’ a jar.


 <macrodef name="unsignjar">
 <attribute name="jarFile" />
 <sequential>
 <jar update="yes"
 jarfile="@{jarFile}.tmp">
 <zipfileset src="@{jarFile}">
 <include name="**"/>
 <exclude name="META-INF/*.SF"/>
 <exclude name="META-INF/*.DSA"/>
 <exclude name="META-INF/*.RSA"/>
 </zipfileset>
 </jar>
 <move file="@{jarFile}.tmp" 
 tofile="@{jarFile}"
 overwrite="true" />
 </sequential>
 </macrodef>

An example how to call the macro.

Portable Java 8 JDK on Windows

Tue, 25 Mar 2014 00:00:00 +0000

Yes, it is possible to extract the Java 8 JDK without administration privileges (a portable Java 8 JDK), although Oracle only provides an installer for windows. This recipe also works for Java 7.

Recipe for JDK 8 (update 93 and newer)

Prerequisite: Install 7-Zip file archiver (or its portable alternative).

Download the Java 8 SDK for Windows from Oracle. You will get a file named like jdk-8u101-windows-x64.exe.
Open the downloaded file with 7-Zip, which will show a a list of files and folders.
Open folder ‘.rsrc’ (select and double click this folder within 7-Zip).
Open folder ‘1033’ (or the folder of greatest size).
Open folder ‘JAVA_CAB10’ (or the folder of greatest size).
Open file ‘111’ (or the folder of greatest size).
Open file ‘tools.zip’.
Extract its contents to a directory where own write permissions, for example: C:\Users\Daniel\Documents\jdk-8u102-x64. To prevent issues, I recommend a directory without spaces.
From within this directory, search for all .pack files and extract them using unpack2000.exe command line tool found in the bin subdirectory. Following windows prompt command does the trick when executed from within the extracted directory: for /r %i in (*.pack) do .\bin\unpack200.exe %i %~pi%~ni.jar

The downloaded .exe file also contains the JDK sources. Navigating through the folders ‘.rsrc’, ‘1033’, ‘JAVA_CAB9’, ‘110’.

Compiling your abstract syntax tree transformation with Netbeans IDE

Wed, 11 Dec 2013 00:00:00 +0000

This article explains how to configure the Netbeans IDE to recognize java code the uses compiler internal classes. These classes are not part of the standard JDK and are not recognized by IDEs such as Netbeans, which will refuse to compile the correct code.

The compiler internal classes are used mainly as a hack to define annotations that automatically generate code. The most significant example is the Project Lombok, which transparently generates getters, setters and other code bload. Under the hood, the “Pluggable Annotation Processing API” (JSR 269) provides a mechanism that exposes internal classes from the java compiler. These classes provide methods that allow us change the abstract syntax tree.

Smaller font sizes for Netbeans on Linux

Tue, 01 Oct 2013 00:00:00 +0000

This article describes an approach to launch Netbeans on Linux with smaller and narrower font sizes.

Modern desktop environments like KDE or Gnome suggest larger font sizes to enhance screen readability. However, Netbeans users might not be willing to waste precious space on views around the source code that matters. Here are some alternatives one might consider.

This article originally appeared on https://techtavern.wordpress.com

1) To customize window manager and themes

The Gnome desktop provides nice dialogs to customize GTK+ and Gnome decorations and font sizes. The KDE desktop offers the QT-GTK binding that applies KDE design on GTK/Gnome applications. While simple, this alternative applies to Netbeans and all other application, which might not be your intention.

Copy files by extension that keeps directory structure

Fri, 13 Sep 2013 00:00:00 +0000

Some more essential Linux knowledge, written down to document it.

Problem:

Copy only files by their type (or file extension), while preserving the directory structure.

Solution:

I would recommend using rsync that copies files recursively and allows filtering them by their file name. The challenge is configuring a set of filter rules.

Command line:

To copy everything: rsync -avim –include=’*/’ –include=’*.doc’ –exclude=’*’ /source /destination

Explained:

Copy recursively. Go down into directory structure.

Netbeans actions toolbar with local lookup context

Fri, 05 Jul 2013 00:00:00 +0000

This article talks about Netbeans and an action toolbar that is sensitive to a local selection lookup context. Actually, global selection context sensitive actions is powerful mechanism with a subtle limitation: everything happens globally. It is no use for a local actions menu or toolbar sensitive to a limited selection context restricted to a JPanel or TopComponent. Not surprisingly, the Netbeans Java IDE itself reinvents the wheel each time this requirement arises, for example, on the ‘variables’ and ‘breakpoint’ windows.

Simplest JTable icon cell renderer ever

Mon, 01 Jul 2013 00:00:00 +0000

While there are many examples of JTable cell renderers spread on the Internet, they lack a clear understanding about how they were proposed to work. This article presents and explains a minimal and correct cell renderer, extending the default cell renderer as supposed by the Java API. The example explains how to display icons instead of text.

Originally published at https://techtavern.wordpress.com.

For the hurried, first the code:


public class EnumIconCellRenderer extends DefaultTableCellRenderer {

private final Map<!--?, ImageIcon--> icones;

 public EnumIconCellRenderer(final Map<!--?, ImageIcon--> icones) {
 // Initialize data used to render cells.
 this.icones = icones;

 // Set properties that never change.
 this.setHorizontalAlignment(JLabel.CENTER);
 this.setVerticalAlignment(JLabel.CENTER);
 this.setText(null);
 }

 @Override
 protected void setValue(Object value) {
 // Set properties that change on individual cells.
 this.setIcon(icones.get(value));
 }
}

A cell renderer works like a rubber-stamp for each cell in the table. The renders uses a Swing component to draw the first cell, changes the contents of that cell renderer, and for each following row shifts the origin of the component to the new location, then re-draws it. The default cell renderer uses the convenient JLabel to stamp a potentially inconvenient toString() representation of data objects. Note that getTableCellRendererComponent() returns itself (the JLabel), but properly configured for an individual cell. Therefore, setting properties of the renderes itself actually configures the component returned by getTableCellRendererComponent().

MySQL, Scheduled Events and Amazon RDS

Tue, 25 Jun 2013 00:00:00 +0000

This article explains how to enable SQL database scheduled events for the Amazon Relational Database Service (RDS). By default, Amazon does not allow one to create (in other words, to schedule) events. Events are SQL code intended to execute periodically or in future. The solution is quite similar my last article. One needs to provide the ‘event_scheduler’ parameter set to “ON” or “1”. Parameters are set by creating a new parameter group (or editing an existing one) and assigning this parameter group to the database instance.

MySQL, Triggers and Amazon RDS

Mon, 17 Jun 2013 00:00:00 +0000

This article explains how to enable SQL database triggers for the Amazon Relational Database Service (RDS).

If one attempts to create a SQL database trigger, then the database server will complain a confusing and misleading message like: “ERROR 1419 (HY000) at line #: You do not have the SUPER privilege and binary logging is enabled (you might want to use the less safe log_bin_trust_function_creators variable)“.

It happens that Amazon decided to disable all user defined SQL code, as binary procedures could compromise the RDS architecture. And for this purpose, Amazon blocked granting the missing ‘SUPER’ privileges to any database user except the ‘rdsadmin’ user owned by Amazon itself.

Logging practices on running solver processes in Java

Wed, 24 Oct 2012 00:00:00 +0000

We implemented a java computer program that solves a certain mathematical problem. The program runs for a long time and produces a textual representation of the best solution found.

It was the opportunity to discover the importance of adopting two usually unnoticed components: the Simple Logging Facade for Java (SLF4J) and the Logback logging framework. By employing both components a step further than they were originally designed, we increased our coding, debugging, testing and validation productivity in means far away than expected for traditional logging. All benefits were nearly for free and required no additional coding.

SymmetricDS syncronizing two tables with different names

Sat, 14 Jul 2012 00:00:00 +0000

While working with our newly discovered SymmetricDS tool, I realized that their manual does not clearly state how to synchronize two databases if their table names do not match. That might happen while matching tables between databases of two different companies, each one with its own table name policies. Blame those Database Administrators!

Here is how I accomplished synchronized two tables with different names:

First, I did the usual configuration: I defined two node groups A and B, defined a link between those node groups, defined a channel and a router for each direction (A to B and B to A).

How SymmetricDS successfully replaced our complicated client-server architecture

Thu, 14 Jun 2012 00:00:00 +0000

With SymmetricDS , we avoided investing effort in designing, implementing and testing a complex, asynchronous communication protocol over web-service layer. Instead, we achieved a simple, intuitive interface that allowed us to deliver out solution within few days.

Our application started with a local standalone server that processes long running transactions. It naturally evolved to a distributed architecture. While benefits of the new architecture were clear to us and our customers, an issue arose : we would force our customers to enable their applications with boring and non intuitive web-services to communicate with our transaction server.

Eclipse Subversive does not frustrate me anymore… Now I use EGit!

Wed, 01 Feb 2012 00:00:00 +0000

A considerably time ago, I wrote down my frustration on using the Eclipse Subversive Plugin. At that time, I was annoyed just because refactoring did not work properly. Now, Subversive has gone worse.

SVN itself does a good job tracking history of moved and copied files, even if directories are moved or renamed. By 2009, the Subversive plugin stopped supporting this features and a simple directory rearrangements may now lead your local copy to an irreversible inconsistent state.

Firefox memory footprint

Thu, 10 Nov 2011 00:00:00 +0000

Firefox is releasing one new version after the other. And each new version, Mozilla claims to have enhanced memory usage to reduce the amount of resource required to load each page. Is that a valid claim?

As a curious computer engineer, I decided to install several legacy Firefox versions and compare the amount of memory required to load two greedy pages: http://www.gmail.com and http://www.spiegel.de.

Here are the results.

One observes that at Firefox 3.6, reading emails from gmail suddenly doubled memory usage. And from Firefox 4.0 on, it requires the triple of memory. I suspect that gmail also loads more content on newer versions since Firefox enhanced javascript support.

ILOG OPL syntax highlighting for gEdit

Mon, 17 Jan 2011 00:00:00 +0000

This article offers the syntax highlighting definition file for gEdit 2.16.

Place the following content into the file ~/.gnome2/gtksourceview-1.0/language-specs/opl.lang. The definitions are not yet complete, I will update them eventually.

Due to gEdit limitations, the definitions allow highlighting according to lexical analysis, but they do not understand grammar. That means that the syntax will be highlighted according to the token used, but not according to their meaning within the model.

ILOG OPL cannot distinguish apples from oranges

Mon, 10 Jan 2011 00:00:00 +0000

I used to think about OPL that promotes obligatorily mathematical rigor as one would expect from a mathematical modeling language. I was misunderstood: it seems that OPL deludes itself when comparing apples and oranges. OPL still requires enhancements that address serious idiosyncrasies how the model is handled.

Objectives

The article presents some OPL examples for expressions that do not satisfy type safety. It additionally relates possible error messages.

The Apple and Orange model

Eclipse subversive plugins frustrate me every day…

Thu, 25 Nov 2010 00:00:00 +0000

Please apologize, but I really need to expose my anger to the subversive plugins. The statement on Subversive – SVN Team Provider that “At the same time project is stable and had a long history on the previous location at the the Polarion.com” is really a very bad joke.

I have been using svn projects on eclipse for about 6 years and always praised this combination. It was a pleasure to see polairon plugins providing a better integration over time. Unfortunately, since the subversion plugins have been available on eclipse repositories, I cannot anymore talk any good word about subversive.

How to prevent EOFException when socket is closed

Tue, 09 Nov 2010 00:00:00 +0000

When one needs some very simple java client that reads some data from socket, then it might be a bit annoying to effectively detect that there is no more data to read, aka “End of File”. Here I show an approach to solve some issues to avoid spurious IOExceptions.

Consider two Java applications that exchange data over a socket, lets call them Alice and Bob. On my example, Bob sends triples of integers, and when he does not have any more triples to send, he takes initiative to close the socket. Here I only show a simple code for Alice.

About the Transcend SDHC Class 10 8GB memory card

Wed, 20 Oct 2010 00:00:00 +0000

The “Class 10” label on Transcend card suggest that is should work 2½ as fast as the my plain 3 years old Kingston SDHC Class 4 8GB memory card. Indeed, I was disappointed to realize the opposite: Transcend class 10 was on average about twice as slow as Kingstone class 4.

The Transcend SDHC Class 10 8GB memory card was the best compromise among price, speed and capacity. “Class 10” means that the card is expected to read and write data at a rate of at least 10MB/s.

Java: Class.forName() to retrieve inner class

Thu, 19 Aug 2010 00:00:00 +0000

Sounds trivial, but was not obvious because Eclipse IDE mislead me: How do I get a reference to a inner class by calling Class.forName() ?

package a.b.c;
public class Outer {
 ...
 public static class Inner {
 ...
 }
 ...
}

I first tried to call Class.forName() passing as parameter the fully qualified name generated by Eclipse:

Class innerClass = Class.forName("a.b.c.Outer.Inner");

But that was wrong! After wondering for some time, I found the (obvious solution):

Class innerClass = Class.forName("a.b.c.Outer$Inner");

Looks like as Eclipse “fully qualified” name is not exactly the same fully qualified name that the Java compiler uses to identify inner classes.

On fixing CPLEX variable names generated by OPL

Thu, 19 Aug 2010 00:00:00 +0000

You wrote your OPL model for your important mathematical programming problem. But the result looks weird: the model just cannot produce such solution. The most desperate approach consists in diving though the mathematical programming model generated by OPL, checking each (in)equation one by one.

Here I describe some issues that happened while using the OPL Java interface to create the CPLEX model and to print out the mathematical programming model as a .lp file. And after days of frustration with this .lp printout, I found myself writing my own Java class that renames all CPLEX variables generated by OPL…

Serializing Hibernate objects as XML using XStream

Fri, 16 Jul 2010 00:00:00 +0000

People have been looking for serializing Hibernate as XML using XStream, a task that is not straightforward.

I designed a solution that I would like to share with the open source community, called xstream-for-pojo.

It seams a quite simple approach at the beginning. Until you discover that Hibernate injected a lot of additional fields into your original objects and that sometimes Hibernate exchanges your original objects with proxies. Even worse, data may not yet be loaded on fields declared as lazy. Hibernate collections are even more complicated.

OPL and Java: loading dynamic Linux libraries

Mon, 12 Jul 2010 00:00:00 +0000

When calling IBM ILOG OPL (Optimization Programming Language) from a Java application running on Linux, one will face some issues regarding loading dynamic OPL libraries. Typical error messages look like:

Native code library failed to load: ensure the appropriate library (oplXXX.dll/.so) is in your path.

java.lang.UnsatisfiedLinkError: no opl63 in java.library.path
java.lang.UnsatisfiedLinkError: no opl_lang_wrap_cpp in java.library.path
java.lang.UnsatisfiedLinkError: no cp_wrap_cpp_java63 in java.library.path
java.lang.UnsatisfiedLinkError: no concert_wrap_cpp_java63 in java.library.path

This article explains my considerations and some approaches how to fix it.

Running Eclipse on a machine without Java

Sat, 03 Jul 2010 00:00:00 +0000

As “portable applications” are getting more and more popular, it is important to say that Eclipse has always been portable: just unzip it anywhere and run it. The real issue is not having Java Runtime Environment installed on the machine where you want to run Eclipse. Unfortunately, installing Java on Windows requires full administrator rights.

I decided to create my portable Eclipse distribution on an USB hard drive (a Western Digital Passport) instead of an USB pen drive. The latter would be impractically too slow to support applications that require handling thousands of files.

OPL language: the battle of array declarations

Thu, 24 Jun 2010 00:00:00 +0000

The OPL Development Studio, created by ILOG (and recently acquired by IBM), provides tools based on the Optimization Programming Language. This tool intends to simplify the process of feeding data and model formulae to other ILOG optimization tools for mathematical programming and constraint programming.

Experience has been proven OPL to be extremely helpful as a compact and high level language for both data and model. Nevertheless, this language still reveals some constructs that are not well understood nor well documented.

Criticism on SWT

Tue, 20 Apr 2010 00:00:00 +0000

The Standard Widget Toolkit (SWT) is a graphical widget toolkit for the Java platform. It conceived as an alternative to the AWT or Swing toolkits provided by Sun Microsystems. It has the intent for better performance (to run faster and and to consume less memory), native look and feel and deep platform integration.

As there is already a lot of discussion about Swing and SWT on the web and I will not compare them again. I personally prefer SWT because I felt more productive with this toolkit. Nevertheless, I still did not yet feel productive enough to consider SWT valuable. Let me explain why.

Java and incorrect timezone on Windows XP

Thu, 15 Apr 2010 00:00:00 +0000

How reliable is Java date, time and timezone API? In this article I discuss a relevant issue that may compromise application correctness when relying not only on date/time calculations, but also on reporting date/time according to local timezone and locale.

Recently I was debugging an activity scheduling application that was reporting events to weird time. Even worse, the weird time varied according to the desktop PC the application was running on. First, we assured that all date/time calculations were done correctly. Then, we double checked if Java reads the correct date/time from the system. Also, date, time and timezone configurations were set properly on the underlying platform. The odd behavior appeared on Java Virtual Machines from Sun, both JRE 1.5 and JRE. What was happening? We compared Java API results to Joda Time API.

Create a front page for WordPress that does not show up twice

Mon, 11 Jan 2010 00:00:00 +0000

Note: I think this is not an issue anymore, since WordPress finally created the “menu” design feature. There is no need anymore to create front pages to show content as tabs at the top of the page. The “menu” feature works better than front pages.

Several people wonder how to configure WordPress to show ones own page when opening the blog (also called front page). There are instructions on wordpress support.

JFace table sorting

Mon, 04 Jan 2010 00:00:00 +0000

Nowadays, when the application displays as a table, the modern user expects to click on the the column header to change the ordering criteria. Unfortunately, SWT/JFace API have not yet implemented this feature transparently. The programmer is required to write a bunch of code to implement this feature on each table.
For this purpose, I have written a single class that listens to table columns and applies ordering to the table viewer.

When Java code becomes funny

Mon, 04 Jan 2010 00:00:00 +0000

Eventually, some fun happens while writing Java code.

Apache Commons: Error or Success?

An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch. (see Java API docs). Does it make sense to call such subclass “Error“?

Found at org.apache.commons.configuration.plist.PropertyListParser

Two way names

Particularly, the Eclipse naming convention resulted this interesting symmetric method declaration.

protected void initialize(ColumnViewer viewer, ViewerColumn column)

Printing java logger configuration

Thu, 10 Dec 2009 00:00:00 +0000

I have been wondering for some time how to print out a list with details how loggers were configured.
In order to work, one requires to create at least one logger instance of each logger that shall be listed.
I will provide further details in future.


public void print(PrintStream out) {
	out.println("Configuração de log: ");
	LogManager logManager = LogManager.getLogManager();
	Enumeration<String> loggerNames = logManager.getLoggerNames();
	Set<String> names = new TreeSet<String>();
	Set<Handler> handlerSet = new HashSet<Handler>();
	while (loggerNames.hasMoreElements()) {
		String name = loggerNames.nextElement();
		names.add(name);
	}
	for (String name : names) {
		Logger logger = logManager.getLogger(name);
		String nome = logger.getName();
		if (nome.length() == 0) nome = "<root>";
//		boolean inheritedLevel = false;
		Level level = logger.getLevel();
//		boolean inheritedHandler = false;
		Handler[] handlers = logger.getHandlers();

		Logger parentLevelLogger = null;
		if (level == null) {
			parentLevelLogger = logger.getParent();
			while (parentLevelLogger != null && level == null) {
				Level parentLevel = parentLevelLogger.getLevel();
				if (parentLevel != null) {
					level = parentLevel;
				} else {
					parentLevelLogger = parentLevelLogger.getParent();
				}
			}
		}
		Logger parentHandlerLogger = null;
		if (handlers == null) {
			parentHandlerLogger = logger.getParent();
			while (parentHandlerLogger != null && handlers == null) {
				Handler[] parentHandlers = parentHandlerLogger.getHandlers();
				if (parentHandlers != null) {
					handlers = parentHandlers;
				} else {
					parentHandlerLogger = parentHandlerLogger.getParent();
				}
			}
		}
		String nivel = "?";
		if (level != null) nivel = level.getName();
		if (parentLevelLogger != null) {
			if (parentLevelLogger.getName().length() == 0)
				nivel = "<root>:"+nivel;
			else
				nivel = parentLevelLogger.getName()+":"+nivel;
		}
		String lista = "?";
		if (handlers != null) {
			List<Handler> list = Arrays.asList(handlers);
			if (list.size() == 0) {
				lista = "";
			} else {
				lista = null;
				for (Handler handler : list) {
					if (lista == null) lista = handler.getClass().getName();
					else lista += ", " + handler.getClass().getSimpleName();
				}
			}
		}
		if (parentHandlerLogger != null) {
			if (parentHandlerLogger.getName().length() == 0)
				nivel = "<root>:"+lista;
			else
				nivel = parentHandlerLogger.getName()+":"+lista;
		}
		out.format(" - %s (%s): %s\n", nome, nivel, lista);
	}
	for (Handler handler : handlerSet) {
		String nome = handler.getClass().getSimpleName();
		String nivel = handler.getLevel().getName();
		out.format(" - %s (%s)\n", nome, nivel);
	}
}

Ubuntu 9.04: External and internal speaker issues

Sat, 08 Aug 2009 00:00:00 +0000

If you run Ubuntu 9.04 and your desktop or laptop is featured with both internal speaker and TRS jacks for external speakers, then you might face some issues that sound is played on both. I have written some articles where I propose some very simple solutions and you may try them and choose the one you like most.

Of course, I discarded any inappropriate solutions that were proposed in several forums: editing mysterious configuration files,recompiling the kernel and unplugging the internal speaker from the motherboard.

Ubuntu 9.04: External and internal speaker issues – part 2

Sat, 08 Aug 2009 00:00:00 +0000

Issue 2: Connecting the headset does not turn off internal speaker.

Try to connect/remove a headset from the external jack and observe if your internal speaker becomes automatically muted. If not, then some more configuration is required.

Ubuntu 9.04: Microphone issues

Sat, 08 Aug 2009 00:00:00 +0000

Continuing the discussion of audio configuration issues on Ubuntu 9.04…

If you are using Skype, please also read my next article that discusses Skype on Ubuntu 9.04.

I suggest testing the microphone with the “Sound Recorder” that is found in the “Applications”->”Sound and Video” menu of the top bar on the Ubuntu desktop. Ensure that “voice, lossless (.wav)” (may vary according to your language) is selected. Click on “Record” and talk to the microphone. The “Level” bar should increase as you talk louder. Click on “Stop” and “Play” to hear if your voice was recorded sucessfully.

Ubuntu 9.04: Skype issues

Sat, 08 Aug 2009 00:00:00 +0000

This article addresses an issue similar to another that I have already adressed for Ubuntu 8.04: How to correctly configure Skype on Ubuntu 9.04.

First, I assume that Skype was installed from midibuntu.org repositories.

Issue 1: Speakers do not work.

The first required configuration change is setting Skype to use Pulse Audio Support instead of default (ALSA) sound drivers. Go to Skype->Options->Audio Devices. Select “pulse” for all audio devices.

I also recommend to disable an option like “Allow Skype to automatically adjust mixer levels” for this first moment. While this option was enabled, I have experienced Skype undoing the correct configuration and turning off my microphone volume before each call . After you manage to have Skype working fine, then you may enable this option again to see if Skype continues working fine 🙂

How to correclty calculate days between two days

Mon, 13 Apr 2009 00:00:00 +0000

The standard Java API has no solution to calculate the period between two days, although this is a common request for someone who is doing calendar arithmetic.

Googling around, the are many people who expose their own solutions (see some of them 1, 2, 3, 4). All them suggest getting difference between the two dates, measured in number of milliseconds, and divide by 1000 * 60 * 60 * 24 (that means, the number of milliseconds in a day typical day).

Regex that matches path, filename and extension

Mon, 06 Apr 2009 00:00:00 +0000

I was looking for a regular expression for Python capable to match a string containing a valid path, file name and extension. Finally, I discovered following solution:
^(.*/)?(?:$|(.+?)(?:(\.[^.]*$)|$))
Let me explain how I got this regular expression. Fortunately, Scott Carpenter has written an excellent article about a regular expression to match a file name with extension. Matching the file name extension is not trivial for all possible situations.

Skype on Ubuntu 8.10: microphone and internal speaker issues

Wed, 18 Mar 2009 00:00:00 +0000

It has been a long time since my last post… Also, it has been some time I managed live without a PC and Internet. Now I have a PC and Internet again and I took the chance to immediately install Linux!

Updated: I also solved the issue of skype consuming 100% cpu during a call.

Although the Ubuntu Guide has a good description how to install Skype on Ubuntu Intrepid, it can be quite challenging to place a call successfully. Shame on Gnome, Pulse Audio and Skype! I had to overcome following issues:

Resume scp/rsync file transfer

Wed, 19 Nov 2008 00:00:00 +0000

This is very basic Linux knowledge, but the question has arisen too often and I decided to document it.

Problem:

Transfer (or upload/download) a large tree of files and directories from one machine to another using a ssh connection, and being able to resume/continue if the operation is interrupted.

Solution:

Until now, I believe that the best solution is using rsync over ssh, since rsync has a feature to resume interrupted file transfer, even when an entire tree of directories is involved.

About Trilead SSH open source project

Thu, 13 Nov 2008 00:00:00 +0000

Some time ago I have written an article about the JSch open source project. However, I soon lost all my motivation when I faced, again, the code complexity required for JSch just to start a execution session, a file copy or a port forwarding with JSch. Nevertheless the completely misunderstood authentication API for JSch let me to a mood even worse. I started looking for alternatives and fortunately I found Trilead SSH, a pure Java implementation of SSH, available with the BSD license.

PCMan: the real and true Gnome file manager

Fri, 24 Oct 2008 00:00:00 +0000

I have modified this post after several people complained that I was misunderstood: Nautilus can, sure, display a tree view of the file system. Sure, but only for “who-knows-how”.

I do not like Gnome desktop environment because of its excessively simplified GUI that leverages all users as if they lack minimal skill to interact with a computer. And what I dislike most on Gnome is even more oversimplified vision of the file system provided by Nautilus on its default configuration.

Fortified compiling prevents building older RPM

Mon, 13 Oct 2008 00:00:00 +0000

Today I had to build and test some older Open MPI RPM packages. However, I was prevented to build them, although the code apparently was correct.

The command:

rpmbuild -ba openmpi-1.2.1.spec

The error message was:

In function 'open',
 inlined from 'orte_abort' at runtime/orte_abort.c:91:
/usr/include/bits/fcntl2.h:51: error: call to '__open_missing_mode' declared with attribute error: open with O_CREAT in second argument needs 3 arguments

The line of source code that causes the error is:

A poem about Subversion

Tue, 07 Oct 2008 00:00:00 +0000

I found an interesting poem from Peter Kriens about SVN (subversion) that was posted to the Eclipse committer mailing list. Really interesting how frustration can encourage your imagination in others arts besides computer programming.

(I do not want to start a new discussion about pros vs. cons of SVN. Neither discuss who is right or who is wrong. I am sharing the poem just because it is curious.)

Hear! Hear! And I started drinking way too much coffee due to SVN because it gives me ample time … Last year I wrote my first poem ever (and likely last) during a checkout:

Oh, how I long for the days of CVS
When checkouts were a bless
Updates found to be a breeze
And a build went in a wheeze
Now we are old and wise
It is SVN that I despise
A simple checkout takes forever
And often it ends never
It is hungry for files and directories
About disk usage it has no worries
And with its split personality
Using it from the shell has a penalty
But alas, progress should not be blamed
Directories can now be renamed!- A sad SVN user

Ok, I won’t pursue a career in this area, but it illustrates my frustration …

Kind regards,

Peter Kriens

About JSch open source project

Tue, 30 Sep 2008 00:00:00 +0000

There are many, many open source, pure java implementation for the SSH/SFTP protocol. However, in my opinion, there are two of them that can be taken seriously. One of them is JSch, the other one is Trilead SSH. I will talk about my experience on the former one while implementing the RemoteTools framework for the Parallel Tools Platform for Eclipse.

JSch is one of the few (if not the only one) open source, pure Java implementation with the a complete implementation of the SSH specification, covering both SSH versions. It also covers less common ssh use cases, like High Performance Enabled SSH/SCP (although I have not yet seen a SSH server willing to easily support this). The JSch maintainers are very careful to adhere strictly to the ssh specification. They even refuse to implement workarounds for known issues for common ssh servers. They reply: “Ask your ssh server provider for a fix”. And I tend to agree with them.

Smaller font sizes for Eclipse on Linux

Wed, 24 Sep 2008 00:00:00 +0000

This article describes some approaches to launch Eclipse on Linux with smaller font sizes and customized graphical user interface (GUI).

The modern desktop environments like KDE or Gnome use larger font sizes to enhance readability of screen contents. However, Eclipse, looks better with a clean design and small fonts.

Views like Package Explorer or Outline may contain very large listings of important information. Eclipse uses are not willing to waste precious space neither with large fonts nor with fancy window decorations.

Fixing Copy-Paste issues on Eclipse and KDE

Sun, 10 Aug 2008 00:00:00 +0000

This article describes a solution to fix a long term issue (bug?) involving copy & paste when running Eclipse on KDE.

The problem

When launching Eclipse from KDE, one might experience several types failures with cut, copy and paste actions in Eclipse. The reported misbehavior is non-deterministic, but frequent enough to degrade user experience.

Inside the editor, specially the Java or C/C++ editor, selecting text and issuing the copy action (ctrl+c or equivalent menu entry) may not copy the select text to the clipboard (no text is copied).

Polling files on NFS shared directories

Wed, 06 Aug 2008 00:00:00 +0000

These days we were implementing a distributed application where processes read startup information from a shared file stored in an NFS directory. Unfortunately, the approach did not work as expected, and we faced strange situations. After all, we learned that polling NFS shared directories can be quite tricky.

The original approach

Let me explain shortly the algorithm that was initially intended for the application. There is one master process and other N slave processes running on different machines. All of them are started nearly at the same time. But the slave processes must first wait for a file with instructions created and written by the master process.

Running eclipse based apps on Fedora 9 x86_64

Wed, 30 Jul 2008 00:00:00 +0000

Many IBM applications are based on eclipse for i386 architectures. Just some examples: Lotus Notes, Sametime, Symphony, IES (IBM eclipse SDK). However, the Fedora 9 for x86_64 architectures does not install any 32 bits libraries anymore. How shall these applications now run on Fedora 9?

One one side, these applications were designed for Linux on 32 bit architectures. Therefore, they were build on the 32 bits eclipse framework that relies on several JNI (Java Native Interface) calls to 32 bit libraries. The most important library is the low level access to gtk API.

xfs forgetful?

Wed, 30 Jul 2008 00:00:00 +0000

I have been using xfs for some months now. Somewhere I had read about advantages of xfs and got convinced that I should store my files on that file system (sorry, I don’t remember the references anymore).

Today it happened that, suddenly, eclipse complained that all the files I was editing did not exist anymore on the workspace and that the file view was out of sync with the file system. Probably, a bug of new Ganymede version, I thought. But in sequence, everything crashed: KDE, firefox, Sametime, Notes, …

Backing up DVD movies on Linux now useful

Sun, 20 Jul 2008 00:00:00 +0000

For a long time I have been struggling on Linux to easily create backup copies of my favorite movies, until I finally found k9copy.

Before k9copy, backing up dvds was darkness

On one hand, there are many fancy video tools available for Windows. However, nearly all of them have some kind of embedded spyware or virus. On the other hand, Linux tools are all written for command line, and require a lot of expertise just to understand what they do.

Whats this? IOException: Write end dead

Wed, 16 Jul 2008 00:00:00 +0000

I like Java very much. Nevertheless, there are things I cannot stand in Java. Sure, and one of them are undocumented exceptions from the Java API, that nobody can explain.

I will talk about “Write end dead” IOExceptions. What does this mean? Why did this happen? Even if googling around, it is difficult to find a clear answer.

This article is a full explanation to understand this exception and shows how to fix your code. Just continue reading…

About

Mon, 01 Jan 0001 00:00:00 +0000

I’ve spent my career building shared understanding: between users and complex systems, among the people who build software, and between specifications and code. Now I’m studying how AI can do this for software development itself.

For 17 years at Petrobras I’ve worked in nearly every role of software development: requirements and business analysis, mathematical modeling, architecture, programming, databases, infrastructure, DevOps and technical leadership. Having been on both sides of almost every handover taught me a great deal about shared understanding, and about how processes, governance and regulatory requirements challenge it.