The Inquisitive Programmer

Force Quit on Mac Apps

2009-10-30T14:18:00.000-04:00

Command + Option + Escape

Capturing Screenshots On Mac

2009-10-13T21:59:00.002-04:00

Great tips for capturing screen shots on the Mac. I got this from..

http://www.techiecorner.com/138/how-to-do-print-screen-in-mac-os-x/

There are few ways to do screen capture in Mac OS X.
Follow the steps below and you will be able to do a screen capture in Mac OS X.

Switch to the screen that you wan to to do screen capture
Hold down Apple key ⌘ + Shift + 3 and release all
then use your mouse to click on the screen
Done. You will see a picture file in at your desktop. That’s the screen capture picture.

You can also do a screen capture for a portion of your screen.

Switch to the screen that you wan to to do screen capture
Hold down Apple key ⌘ + Shift + 4 and release all key
Now, You will see the mouse cursor will change to +
You can start to drag your mouse to select the portion you wish to capture.
Once finish, you will see a picture file in at your desktop. That’s the screen capture picture!

If you want to do a screen capture for a particular application window, you can follow this:-

Switch to the screen that you wan to to do screen capture
Hold down Apple key ⌘ + Shift + 4 and release all key
Now, You will see the mouse cursor will change to +
Press the space bar once
You will see the mouse cursor change to a camera
Now you can use the camera to select which application window to screen capture
Once finish, you will see a picture file in at your desktop. That’s the screen capture picture!

Character-set Encoding Issues

2009-09-25T08:35:00.005-04:00

Great site for inspecting characters to troubleshoot character encoding issues.

http://www.ltg.ed.ac.uk/~richard/utf-8.cgi?input=%3F&mode=char

DBUnit and Foriegn Key Constraints

2009-09-24T09:07:00.004-04:00

DB Unit is great, except for the FK constraint hell you go through until you learn to do..

1. IDataSet dataset = new FlatXmlDataSet(
                     ClassLoader.getSystemResourceAsStream(
                     datasetFilename));

2. dataset = new FilteredDataSet(
            new DatabaseSequenceFilter(
            getConnection()), dataset);

Line 2 there looks at the constraints and the dataset and determines the correct ordering for the SQL statements for your database, so that when they're run in the setup/teardown of your DBUnit tests you don't get FK constraint violations.

There are many blog postings that give all kinds of ways to disable or defer FK checks by the database, but this works better I think, for me since I have the test setup in Java. This came from the comments in a Matt Raible post from 2006.

You're in Timeout

2009-09-10T13:21:00.007-04:00

I recently had an issue with some code I wrote to connect to a service with a "rest like" interface that returns XML data given a simple query over a HTTP GET request.

I used that java.net.URL class to send the query and retrieve the results as follows..


private InputStream executeQuery(String query) {

   InputStream rawResults = null;

   try {
      query = baseUrl + "?query=" + query;
      if(LOG.isDebugEnabled()) {
        LOG.debug("Full Query : " + query);
      }
      URL request = new URL(query);
      rawResults = request.openStream();
   }
   catch (IOException e) {
      LOG.warn(e.getMessage(), e);
   }

   return rawResults;
}

If the host on which this service runs is down (or doesn't exist) before URL.openStream() gets invoked, a java.net.UnknownHostException is quickly thrown (within about 4000 milliseconds), the catch block is executed, and the process goes on.

However, if the service goes down after the socket connection is made, but before the data is read back from the service, this method call to URL.openStream will block indefinitely by default.

Eric Burke has written a post defining this problem and a simple solution, which can be found here. The solution is to set the read timeout on the URLConnection so that you can break after so many milliseconds if you are't getting the data back.

For example:


private InputStream executeQuery(String query) {

   InputStream rawResults = null;

   try {
      query = baseUrl + "?query=" + query;
      if(LOG.isDebugEnabled()) {
        LOG.debug("Full Query : " + query);
      }
       URL url = new URL(query);
       URLConnection conn = url.openConnection();
       
       // Seems set to 4000ms by default already.
       conn.setConnectTimeout( 4000 ); 
       
       // Set to 0 by default, T/O never occurs!
       conn.setReadTimeout( 10000 ); 

       rawResults = conn.getInputStream();
     
   } catch (java.net.UnknownHostException e) {
      LOG.warn("Could not make connection to 
                host within the allotted connectTimeout", e);
   } catch (java.net.SocketTimeoutException e) {
      LOG.warn("Could finish reading data from the 
                socket within the allotted readTimeout", e);
   }

   return rawResults;
}


Now as the catch blocks indicate, the host can go down, or the service can be unresponsive before or during the read, and we'll cut out after our chosen timeout.

JAX-WS / Maven / WSIMPORT

2009-08-28T10:28:00.008-04:00

To use JAXB during your maven build use something similar to..


<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>StaticDetailLogAccessServiceClient</groupId>
    <artifactId>StaticDetailLogAccessServiceClient</artifactId>
    <version>1.0</version>
    <dependencies>
        <dependency>
            <groupId>com.sun.xml.bind</groupId>
            <artifactId>jaxb-impl</artifactId>
            <version>2.1.6</version>
        </dependency>
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.3.1</version>
          <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <defaultGoal>install</defaultGoal>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>2.1</version>
                <executions>
                    <execution>
                        <id>copy</id>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>copy</goal>
                        </goals>
                        <configuration>
                            <artifactItems>
                                <artifactItem>
                                    <groupId>com.yourco.schemas</groupId>
                                   <artifactId>DetailLogAccess</artifactId>
                                    <version>1.0.1</version>
                                    <type>xsd</type>
                                    <overWrite>true</overWrite>
                                    <outputDirectory>${project.build.directory}/classes</outputDirectory>
                                </artifactItem>
                            </artifactItems>
                            <!-- other configurations here -->
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.jvnet.jaxb2.maven2</groupId>
                <artifactId>maven-jaxb2-plugin</artifactId>
                <version>0.6.1</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <schemaDirectory>${project.build.directory}/classes</schemaDirectory>
                    <includeSchemas>
                        <includeSchema>**/*.xsd</includeSchema>
                        <includeSchema>**/*.dtd</includeSchema>
                    </includeSchemas>
                    <excludeSchemas>
                        <excludeSchema>test*.xsd</excludeSchema>
                    </excludeSchemas>
                    <includeBindings>
                        <includeBinding>*.xjb</includeBinding>
                    </includeBindings>
                    <strict>false</strict>
                    <verbose>true</verbose>
                    <extension>true</extension>
                </configuration>
            </plugin>
            <plugin>
                <inherited>true</inherited>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.5</source>
                    <target>1.5</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Found at https://jax-ws-commons.dev.java.net/jaxws-maven-plugin/usage.html

When downloading torrents...

2009-08-27T13:03:00.003-04:00

Block any uploads/downloads from the URLs found here..

http://www.bluetack.co.uk/config/level1.gz

Good Torrent Sites :

isohunt
demonoid (requires you to sign up)
pirate bay

Good Torrent Clients :

Vuze (not sure if it works on Mac, saw it on linux)

Some Commonly Used Hacked Mac OSX Systems:

Kalyway
iAtkos

WGET Flags for Entire Website

2009-08-25T09:37:00.002-04:00

From Prystash's blog, args to wget to grab an entire site cleanly.

$ wget --recursive \
     --no-clobber \
     --page-requisites \
     --html-extension \
     --convert-links \
     --restrict-file-names=windows \
     --domains somesite.org \
     --no-parent \
         www.somesite.org

Switching Bloggers

2008-05-02T10:25:00.003-04:00

I've decided to switch to Wordpress.com. I hated to do so after just starting to get the ball rolling on my posts here, but Wordpress has some really nice features and I thought it was better to do it now than wait until later.

Most notably for me I like the tagging and the feedback you get, when someone comes to your site from the result of a search, you can see what they were searching on, when they came to your blog. Also, they seems to have a wider variety of layouts, and they're editor is a little nicer.

Sorry Blogspot :( .. and finally, when I put :( on my Wordpress entry, it automatically changed it to an emoticon. How cool is that!.. How nerdy am I :)

My new blog is at ericmaxwell.wordpress.com.

Groovy Ignores Scope

2008-04-28T10:51:00.007-04:00

Let me start out with.. I like Groovy. I haven't used it extensively yet on any of my projects, but I have done odd jobs with it.

With that said, there seems to be an important issue with Groovy in my opinion and I don't understand why there aren't many posts about it, or why it's not mentioned in the documentation, or why it still exists... Groovy does not currently enforce scoping constraints.

Take the following for example:
class PrivateMethodClass {

private static String privateMessage = 'foo'
private static String getPrivateMessage() { 'boo' }

private String privateInstanceMessage = 'instanceFoo'
private String getPrivateInstanceMessage() { 'instanceBoo' }

private static void sayHelloStatic() { println('hello static') }
private void sayHelloInstance() { println('hello instance') }
}

If you were to attempt to call any of these private variables/methods in Java, outside of the PrivateMethodClass, you would get an error when attempting to compile. In groovy on the other hand, this is totally acceptable to do.

So in Groovy this:
class PrivateMethodClassTest {

public static void main(String[] args) {
println 'attempt to call static.'

PrivateMethodClass.sayHelloStatic()

new PrivateMethodClass().sayHelloInstance()

println PrivateMethodClass.privateMessage

println PrivateMethodClass.getPrivateMessage()

println new PrivateMethodClass().privateInstanceMessage

println new PrivateMethodClass().getPrivateInstanceMessage()
}
}

Yields:
C:\projects\grovvyScopingFlaw>groovy PrivateMethodClassTest.groovy
attempt to call static.
hello static
hello instance
foo
boo
instanceBoo
instanceBoo

There is a Jira issue for this at http://jira.codehaus.org/browse/GROOVY-1875 and it is supposed to be fixed in 2.0 if I'm reading the issue ticket correctly.

I debated about whether I should post about this or not as I thought this might be old news, but as I mentioned this to people around me who are very interested in Groovy, I got a lot of surprised responses. So there it is.

Annotation @Override: Making the compiler work for you

2008-02-01T12:39:00.001-05:00

I was writing/running JUnit tests for a project at work today when I came accross some odd behavior with the assertEquals method. Before I go into the problem, let me over simplify the model I was working with.

I created a class Foo that extended a class Boo, written by another project team. Boo overrode the Object.equals method (or so I thought), as shown in the diagram below.

Now from the simple diagram, coupled with the fact that you know somethings up, you may have guessed that they didn't really override the equals method in Boo. They overloaded it by changing the signature from

boolean equals(Object boo)

boolean equals(Boo boo)

This was a mistake on their part, an oversight on mine, and the result was the following statement in my JUnit test failed

assertEquals( fooA, fooB );

Whereas the following statements passed without a problem.

assertTrue( fooA.equals( fooB ) );

assertTrue( fooB.equals( fooA ) );

It took me a while to take notice of the signature mismatch on Boo.equals. (no jokes or insults please :) ).

It passed on assertTrue because assertTrue invoked fooA.equals( fooB ), and when the JVM didn't find an exact signature match on the method in Foo, or a method of equal name but more general types, it went to the next closest match, which was the equals method of Boo taking a Boo for comparison.

It failed on assertEquals because assertEquals treated both objects passed in as java.lang.Objects. This meant that the equals method of Object, unless overridden, was going to be called. Since it wasn't overridden, the result was the equivelant of fooA == fooB.

My Point

My point is that, if they had put an annotation tag @Override on their equals method, Boo wouldn't have compiled in the first place and I wouldn't have gone through this. And I thought it was worth brining attention to on my blog as I haven't seen many people use it yet since made available in Java 1.5.

My First Post

2008-01-30T22:00:00.000-05:00

So I have a blog. What does one say on their first post? I do not know.

Weebles wobble, but they don't fall down!

How's that. Future entries will hopefully be more technical in nature than this.

That's all for now. Thanks for reading.