How did I publish Android Library to JCenter from Android Studio

JCenter is a Maven Repository or file server hosted by Bintray for Android libraries. It’s a default repository for Android Studio. I wrote this post to log my experience with open sourcing an Android Library on JCenter.

Checkout my detailed post on Medium or at my techLog.

Dealing with Java Hell using JarJar life boat

Okay, so I wanted to use Hex.encodeHexString method from org.apache.commons.codec.binary.Hex (commons-codec-1.6.jar)library to generate encoded singnature. I was able to do this in plain Java, but not in Android. I googled for a while and found out this ticket about Android not supporting the latest versions of commons-codec-1.6.jar.The solutions was to use magical "jarjar" ! But How ??? Again, I googled and come across this and this, and I came up with solution to solve mystery of using  Hex.encodeHexString method in code running on Android (Dalvik VM). Android uses old version of commons-codec jar which doesn't define org.apache.commons.codec.binary.Hex.encodeHexString method signature. Even if you add new commons-codec-1.6.jar to build path of project, code will try to refer to built-in commons-codec not the new one that you added in build path. But, if you change the package name/namespaces for commons-codec-1.6.jar, then you can easily reference from your code and finally can use Hex.encodeHexString. So, you have to create a custom jar with modified package name structure.

Here is how you can spin a new custom jar, say : commons-codec-1.6-jarjar.jar:

Step-1: Create a build.xml like follows:

<project name="generate-jarjar">

    <property name="jarjarfile" value="commons-codec-1.6-jarjar.jar"/>

    <path id="classpath">

      <pathelement location="jarjar-1.4.jar"/>

      <pathelement location="asm-2.2.3.jar"/>

    </path>

    <taskdef name="jarjar" classname="com.tonicsystems.jarjar.JarJarTask"   classpathref="classpath"/>

    <delete file="${jarjarfile}"/>

    <jarjar destfile="${jarjarfile}">

    <zipfileset src="commons-codec-1.6.jar"/>

    <rule pattern="org.apache.**" result="org.jarjar.apache.@1"/>

    </jarjar>

</project>

Step-2: Run command "ant" from command line. This build script will generate a new jar  commons-codec-1.6-jarjar.jar, which you can add in your build path and use this new jar to import from.

You can download all the files mentioned in above script and build.xml from here.

How did I setup SSL with HTTPClient-4.1.2

I've been struggling to get this working for about 2 days now. I was able to POST a request directly from sockets, but it took me a while to see it working with HTTPClient-4.1.2. There are different variants out there in google for legacy HTTPClient and less than 4.1.x.
The key was to specify TrustManager and KeyManager while initializing SSLContext.

Step-1: First, you have to initialize SSLContext like this:

SSLContext ctx = SSLContext.getInstance("TLS");

Step-2: Getting TrustManager. Java look into its trust managers to check against authorized Certification Authorities(CA). Default trust store in Java is "jks". This is how you can get trust manager:
TrustManager[] getTrustManagers(String trustStoreType, InputStream trustStoreFile, String trustStorePassword) throws Exception {
KeyStore trustStore = KeyStore.getInstance(trustStoreType);
trustStore.load(trustStoreFile, trustStorePassword.toCharArray());
TrustManagerFactory tmfactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
tmfactory.init(trustStore);
return tmfactory.getTrustManagers();
}

It should be called as:
TrustManager[] trustManagers = getTrustManagers("jks", new FileInputStream(new File("/Library/Java/Home/lib/security/cacerts")), "changeit");

/Library/Java/Home/lib/security/cacerts is the default path to trust managers in Mac OSX

Step-3: Getting KeyManager: This is where your client certificates are stored. KeyManager in the code can be retrieved as :
KeyManager[] keyManagers = getKeyManagers("pkcs12", new FileInputStream(new File("clientCertificate.p12")), "password");

You have to get KeyManagers using KeyManagerFactory like this:

KeyManager[] getKeyManagers(String keyStoreType, InputStream keyStoreFile, String keyStorePassword) throws Exception {
KeyStore keyStore = KeyStore.getInstance(keyStoreType);
keyStore.load(keyStoreFile, keyStorePassword.toCharArray());
KeyManagerFactory kmfactory = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
kmfactory init(keyStore, keyStorePassword.toCharArray());
return kmfactory.getKeyManagers();
}

Step-4: Once you have TrustManager and KeyManager ready, pass them in SSLContext:
ctx.init(keyManagers, trustManagers, new SecureRandom());

Step-5: Now create a SSLSocketFactory object using SSLContext object:
SSLSocketFactory sf = new SSLSocketFactory(ctx, new StrictHostnameVerifier());

Step-6: Assign Scheme to the HttpClient:
DefaultHttpClient httpclient = new DefaultHttpClient();
ClientConnectionManager manager = httpclient.getConnectionManager();
manager.getSchemeRegistry().register(new Scheme("https", 443, sf));

Done !
Now use this httpclient in HttpPost, HttpGet ….