Duygu's Weblog

Sunday morning iphone users couldn’t woken-up by their setted alarms.End of daylight saving time caused a bug on the iphone: Alarm rings an hour later! If you set alarm for 7:00 o’clock, alarm rings at 8:00 o’clock.

Users reported the issue.We are still waiting for the Apple to release an update to fix this problem… It is an embarrassed problem for a smartphone like iPhone.

Setting the alarm an hour early can be a temporary solution until Apple updates the iOS( Apple’s mobile operating system)… Or you can delete and re-set all your alarms.

As you know during development it is an efficient functionality to use content-assist. Content(or code) assist helps you to write your code faster.

If you have a custom JSF component (JSF version :1.2) you must follow some steps to enable the content assist functionality. Otherwise you will get the “Content assist is not available error” message when you try to auto-complete the component’s properties. In order to activate content assist functionality for the custom component a jsp tag class, renderer class, jsp tld config, faces-config.xml config files are needed.

These files are needed for JSF 1.2. If you use JSF 2.0 (I haven’t tried yet) it is reported that one .xhtml is enough for a custom component.

Custom component class called MyOutputText.

Steps to enable content assist:

1. Create a tag class MyOutputTextTag extending from UIComponentELTag for your custom component. You need to create a separate tag class for each component. This tag class is consist of the custom component’s properties, and the getter-setter methods of the properties.

public class MyOutputTextTag  extends UIComponentELTag{
    private String text;
    private String encryptedText;
    private String styleClass;
    private String id;

    Getter-setter methods
}

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Java Service Wrapper is an open source useful tool to convert a java application into windows service.
[myApp] = refer to the path of the new created folder for the java application
[javaServiceWrapper] = refer to the path of the Java Service Wrapper software extracted folder

INSTALLING THE SERVICE

1. Download Java Service Wrapper software(in this article 3.5.3) and extract to [javaServiceWrapper].

2. Create a path [myApp] for the java application that is going to be converted to windows service.

3. Create bin, conf, lib, logs folders under [myApp] directory.

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Using the Predicate interface of commons collections api and the FilterIterator is an alternative to filter a collection that is based on a predicate.

1. First download and include apache commons-collections api.
2. Create a new class, implementing the Predicate interface, then override evaluate method and perform your filtering criteria.

import org.apache.commons.collections.Predicate;

public class MyPredicate implements Predicate {

	public boolean evaluate(Object object) {
		 //Perform your filtering criteria in this method.
		boolean result = false;
		if (object != null &&  object instanceof MyObject) {
			result = true;
		}
		return result;
	}

}

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In my application there are too many processes that poll bulk data into database asynchronously. Therefore the size of the tables and the response time of the queries were too big. I need to reduce the amount of data for particular SQL operations to reduce overall response times.

Firstly, I have changed the storage engine from MyISAM to InnoDB.

Reasons to change the storage engine:

1. MyISAM has a good performance if the size of data is small. But InnoDB must be preferred if asynchron processes are running on large amount of data. MyISAM locks the whole table, InnoDB has row locking.
2. On the other side InnoDB is transaction-safe. MyISAM in most cases will be faster.But I have many asynchron processes in my application therefore row locking increased my performance.

Then I used the partitioning feature of MySQL coming with 5.1 . Queries access only necessary partitions during execution. It decreases the response time so the performance of the queries increase.

Let’s start partitioning:

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I executed “mvn compile” command for compiling my application’s source codes via Maven 2.(software project management and comprehension tool). But JVM hasn’t got enough memory available for compiling source codes and I’m getting an OutOfMemoryError as seen on the screenshot.
In order to solve this problem I created an environment variable with a name “MAVEN_OPTS” :

MAVEN_OPTS = -Xmx1024m -Xms512m -XX:PermSize=128m -XX:MaxPermSize=256m

If still it is not enough you can increase the size of “XX:MaxPermSize” parameter.

Used parameter explanations:
Xmx: is the maximum Java memory (heap) size –default 512MB
Xms: is the initial / minimum Java memory (heap) size –default 256MB
XX:PermSize: is the heap size reserved for the permanent generation.(heap space that is not garbage collected)
XX:MaxPermSize: is the max heap size reserved for the permanent generation