My Observations

The BouncyCastle libraries provide a systematic and simple set of APIs and tools to work with encryption and encoding of data to be used in secure communication channels like HTTPS. The X.509 standard is the standard for creating certificates issued to Certificate Authorities (CA) and End Entities.

import org.bouncycastle.asn1.x509.Extension;
import org.bouncycastle.cert.X509V3CertificateBuilder;
....
...
String caName = ...
String subjectName =  ...
KeyPair pair = KeyGenerator.getInstance("RSA").generateKeyPair();
X509v3CertificateBuilder builder = new X509v3CertificateBuilder(
                createSimpleDN(caName), valueOf(System.currentTimeMillis()),
                notBefore, notAfter, createSimpleDN(subjectName),
                getInstance(pair.getPublic().getEncoded()));
builder.addExtension("1.3.6.1.5.5.7.48.1", false, new DERIA5String("http://crl.cacert.org/revoke.crl")   // Sample CRL 

But in the above code snippet, instead of passing the values to the addExtension method, if you have an instance of org.bouncycastle.asn1.x509.Extension object, how would you use it? Unfortunately the org.bouncycastle.cert.X509V3CertificateBuilder does not provide a 

builder.addExtension(<extension object>) // not available, oops!!

variant.

The solution is to pass the OID, isCritical and Value fields of the org.bouncycastle.asn1.x509.Extension object.

But oh wait, you see that org.bouncycastle.asn1.x509.Extension provides two methods that return value, namely:

• getExtValue  - this returns the ASN1OctetString corresponding to the value used when creating the instance of org.bouncycastle.asn1.x509.Extensio)  
• getParsedValue - this returns the corresponding ASN1Primitive of the value set during object construction

Invalid encoding exception

when the extension is stored in the java.security.cert.X509Certificate object (i.e. if you try to fetch the extension value from the object)

The getParsedValue() should be used instead to get the extension properly loaded into the java.security.cert.X509Certificate object as shown below:

builder.addExtension(extension.getExtOid(), extension.isCritical(),  extension.getParsedValue());

Hope that this article helps when you are stuck with a similar encoding exception as I faced.

Please leave your comments on this article. 

When using I18n rails API, you will most likely find examples of how to use parameter lists to the translation API.

For e.g.

If you have the following entry in your en.yml
          en:
               test_message_specific: "This is a specific test message for user %{user}"

Now if you have to use this key along with a parameter, you will most likely specify

I18n.t("test_message_specific", user: "Bob")

If you want to use a default key if the specified key is not available, again the API provides clear examples for this case:

E.g.

  en:
       test_message_specific: "This is a specific test message"
       test_message_default "This is a default test message"

We will then translate as follows:

I18n.t("test_message_specific", default: t("test_message_default"))

But what if we want to have both, i.e. parameter lists and default key as well, with both the specified key and default key needing same number of parameters? At least I could not find clear examples for this case from the API but it does support this. Now when will you need this? Let's say, you have a key whose value has to be overridden for say a few cases (say a few countries where the application is used), but for most other cases you want to use a default key, wouldn't it be easy if we are able to declare just as many custom keys instead of many repeated keys even for countries that don't need customisation?

E.g. if our application is used in US, UK, and Canada (this list is small but you will really feel the pinch if you have a long list and had to duplicate the same key for every case unless Rails I18n API provided this feature), and let's say we want to override only for Canada, then we can simply declare only two keys,

e.g.
      en: 
          test_message_default: "This is the default test message for %{user}"
          test_message_ca: "This is the canadian test message for %{user}"

Now let's see how to use the I18n API with these keys:

I18n.t("test_message_"+@country, default: I18n.t("test_message_default"), user: @user)

and ....

Voila! It works! When country is CA, it uses Canadian message and substitutes the "user" parameter, else it uses the default message, but still substitutes the parameter.


PS: Please leave your comment on this post (as long as it is not abusive ;)), as it will help me understand the usefulness.

Recently, I had been working on a UI project where we used Ember.js as the MVC framework to render screens for the single-page application we were building.

Programmers who have dabbled excessively with String manipulation in Java and have used the split method offered by Java's String class and the one offered by StringUtils class from Apache Commons library inter-changeably must have come across the subtle difference mentioned below some time.

The difference lies in how the two split methods consider an empty token before the first occurrence of the delimiter. The 'split' method in String class includes the empty token while the one offered by StringUtils does not.

E.g.

",1,2,3,".split(",") - returns the array [<>, <1>, <2>, <3>] (the '<>' used intentionally to illustrate the empty token). Trailing tokens are anyway discarded by even this split method (refer Javadoc)

StringUtils.split(",1,2,3,") - returns the array [<1>, <2>, <3>] (note the empty token is not returned here).

The difference lies in the way 'split' in String class works. It internally uses Matcher and Pattern and the one line comment below in Matcher explains the reason:

public String[] split(CharSequence input, int limit) {
        ...
        ...

        Matcher m = matcher(input);

        // Add segments before each match found
        while(m.find()) {
        ...
        ...
}

The StringUtils class also has a mechanism to preserve all tokens but the default split method passes false to this parameter and hence the difference.

P.S.: This class however has the 'splitPreserveAllTokens' method and its overloaded variants that retain even trailing tokens (which is the main difference between this set of methods and the 'split' in String class).

So for e.g.

StringUtils.splitPreserveAllTokens(",1,2,3,") - returns the array [<>,<1>, <2>, <3>,<>]

PS: Please leave your comment on this post (as long as it is not abusive ;)), as it will help me understand the usefulness.