SSL and Java (ciak 2)

credits: Vagamundos (from flickr)

Last time we spoke about accessing a site via HTTPS using the pure Sun way.

Today, we see the same problem, solved with the apache HttpClient libraries. This library require a keystore specified in the code. In order to generate a keystore, you will have to download a certification file as described in the previous post and then create a keystore using the keytool program. I don’t remember well how to create a new keystore with the required certificate via keytool (I did’t write it down), but reading the help of the program it should be something like:

keytool -importcert -alias <my_alias_certificate> -file <path_to_the_cer_file> -keystore myKeystore.ks

where myKeystore.ks is the name of the file containing the keystore. The pros of using this approach is that you can provide a .ks file among with the program, in a location desired and the program will use it, avoiding post-installation procedures to register the certificate on each jvm.

So, assuming to have our keystore into a sub-directory certs the code for using the site is in the pdf as usual.

SSL and java

credits: ph0t0 (from flickr)

Sooner or later it happens that you have to access an https via Java. Accessing a generic http (non ssl) site is quite easy using the URL and URLConnection objects.

When you try to access a site through SSL the main problem is that most sites does not have a registration in the java’s Certificate Autorithy (CA), causing the framework to refuse connection to that site. So the main solution is to register the certificate of that site in the java’s CA.

So, the things to do are:

1. download the site certificate
2. register it in the java’s CA
3. accessing the site

Downloading the certificate

In order to download the certificate we are gonna use Firefox. With firefox navigate to the site and if required accept the certificate. Double click on the icon of the certificate (1), in the screen that appear choose view certificate (2), on details tab (3) use the export button (4) and save it wherever you want (5).

Register the certificate

Once downloaded the .cer file (X 509 Certificate DER), you can import it into the CA using the a command line program deployed with the j2se installation: keytool.

Java’s CA and keytool are available in the $JAVA_HOME/lib/security/ and an example of using the keytool (under windows) is the following

C:\Program Files\Java\jre6\lib\security>keytool -import -trustcacerts -alias fonsai -keystore cacerts -file fonsai.cer

where fonsai.cer the file name of the certificate just downloaded.

Maybe if you are using eclipse, you will have to restart the workbench in order to make the registration visible to the jvm.

The main counterpart of using this approach is that you have to register the certificate for each jvm running the program and since certificate can expire you should have to do this operation more than one time. I advise to automate the registration operation with a shell script to be distributed among with the program.

Accessing the site

Once registered the site’s certificate, you can access it as usual using the URL and URLConnection objects. It should be enough to tell (via System.properties) an SSL provider. Here is a PDF with the code.

rounding double in java

Credits: Gabri Le Cabri (from flickr)

Rounding a double in java is very simple. If you have to round it to the nearest integer you could use the Math.round(double) method, but what about if you have to round it with a desired number of decimals?

Quite easy too. Using the BigDecimal.setScale(int,int) method you can choose how to round it. Following a quick example:

BigDecimal bd = new BigDecimal(123.45);
bd = bd.setScale(1,BigDecimal.ROUND_HALF_UP);
System.out.println(bd.doubleValue()); //should output 123.5

Debian, eclipse and exit code 127

Just after installing eclipse from lenny repository, it crashed me up with the error JVM terminated. Exit code=127. After a bit of searching and watching at what a console execution told me, I tried execute eclipse from command line with a simple java -jar /usr/lib/eclipse/startup.jar. Well, in this way it starts up successfully without any problem. Then I tried again a startup from gnome menu and everything worked fine.

Now there is still the failing about integrated browser and the fact that eclipse shipped with lenny is the very obsolete 3.2.

execute shell command via java

It happened to me that working via an extranet on a citrix environment in a WSAD workspace, that I needed to remove the attribute to at least 200 files in different directories.

Since do it one by one via WSAD is unthinkable, and I didn’t have time to going to the client, loggin into the net in order to have a shell and I dind’t have a shell by my hands, I did it via java.

The environment is Windows machine and here is the source

package tests.runners;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;

public class ShellCommandRunner {
	public static void main(String[] args) throws IOException{
		OutputStream stdin = null;
		BufferedReader br = null;
		String line = null;
		String command = null;

		command = "cmd.exe /C attrib -r /S /D X:\\workspaces\\tuc-workspace\\*.*";

		System.out.println(command);
		Process p = Runtime.getRuntime().exec(command);
		stdin = p.getOutputStream(); //use this to push commands

		//processing stdout
		br = new BufferedReader(new InputStreamReader(p.getInputStream()));
		while((line=br.readLine())!=null) System.out.println(line);

		//processing stderr
		br = new BufferedReader(new InputStreamReader(p.getErrorStream()));
		while((line=br.readLine())!=null) System.err.println(line);

		System.out.println("done!");
	}
}

JUnit4: TestSuite of TestSuite

Again talking about JUnit 4. I’m used to use TestSuite to group tests. And add them to the AllTests class. In JUnit 4 it’s quite similar to the 3.x method, just using Java Annotation instead of the old TestSuite class.

Here is the pdf with the example code for having a TestSuite of TestSuite in JUnit 4.

JUnit 4 migration

Finally even me landed in the JUnit 4 planet.

The main difficulty in migration from 3.8.* is the class AllTests : a class with all the tests in it from where you can run all application tests in one shot.

The 4.x way is to use JDK (>=5) annotation, but if you for some reason have to use the JDK 1.4 you have two solutions. The one I prefer is to use junit 3.8.x but if you cannot tolerate the missing of JUnit 4.x in the attached PDF you’ll find the standard 4.x way (with annotation) and a workaround for using the old JUnit TestSuite syntax.

Here is the PDF

Hibernate and Websphere

Here is an hibernate configuration file that works under WSAD/Websphere with an Oracle9i. Just remember to fix datasource and default_schema.

Increase java heap size

It could happen sometimes (more often when working with images) that a java program hang up with a java.lang.OutOfMemoryError. This generally happen because there’s not enough space in the heap memory for storing objects.

You can change the heap size or by the Java Control Panel or by the command line. I prefer this last one and here is the syntax

java -Xms<startHeapSize> -Xmx<maximumMeapSize> …

By default values should be -Xms32m -Xmx128m but I often solved with this values

java -Xms32m -Xmx512m …