Photostream App – Part 2

In the the second part of the “Photostream” trilogy, we will look at how the server notifies all the clients who are observing its stream. There are 2 ways we can do this; either by using server sent events or with websocket.

Since JavaEE 7 supports websocket I’ll be using websocket. Websocket is a 2 way communication channel. In photostream app, the notification/data only flows on way viz. from the server to the client (those observing our photostream) so server sent event (SSE) is actually more appropriate. But to use SSE in JavaEE (in Glassfish/Payara in particular), you have to use add additional libraries.

In you’re using Glassfish/Payara and you would like to try SSE, see this document.

The source code for part 2 is available here.

Till next time.

Photostream App Trilogy

I’ve started a new screencast. In the screencast, I’ll show you how to develop a photostream application. The photostream application has 2 parts

1. Allow users to upload images

2. Push the newly uploaded images (a photostream) to connected clients.

The following is a list of open source projects and technologies that I’m using to write this application

    Rather than creating one long screencast, I’ve split it into 3 parts.

The first part – upload service and and Angular client.

The second part – server notification using websocket

The third part – hybrid mobile app to take pictures and uploading them.

Here is the first part

 

Some points to note about

  • I’m using asynchronous Servlet to handle the file upload. This is to improve performance and to better utilize server resources by releasing the request thread when the image file is being persisted. We can resume the request once the file have been saved
  • Since this is a simple application, I’ve saved the images directly in the document root. You should use a CMS or something like a GridFS to save your images
    Till next time.

MongoDB Realm for Glassfish

Saving user’s login and password into RDBMS is an extremely popular way for JavaEE applications to authenticate against. Most, if not all JEE application servers support JDBC realm out of the box.  Setting up a JDBC realm is quite easy. Here is one for Glassfish.

I’ve always wanted to use NoSQL database, and MongoDB in particular as a security realm. One big advantage, for me at least, Mongo have over its JDBC counterpart is that I don’t have to setup the group table with composite key. I found 2 implementation of MongoDB realm for Glassfish in github; see this and this. I’ll be adding my implementation to this lists.

How Glassfish Security Realm Works?

Before we use my MongoDB realm, lets take a look at how Glassfish handles security.

pic4 (Click to enlarge)

Glassfish uses 2 components (or classes) to collect user’s credentials and authenticate users. To collect your username and password, Glassfish delegates that to Java Authentication and Authorization Service or JAAS. The Mongo JAAS (pronounce as Jazz) module is configured in $DOMAIN_DIR/config/login.conf file. You can see this on the top right corner in the above diagram. A JAAS entry consist of the name (mongodbRealm), also know as the JAAS context, and a FQCN of the login module (at.oneminutedistraction.mongodbrealm.MongoDBRealmLoginModule). See this document for an explanation of the required keyword.

The second step is to configure Glassfish so that it recognizes our MongoDB realm and to associated that with the login module. This is typically done in the admin console which we’ll look at later in this blog. For the time being, lets look at the actual configuration file. The domain.xml holds all information about a Glassfish domain. Again, you can find this file under $DOMAIN_DIR/config directory. A auth-realm defines a security realm. It defines 3 pieces of critical information; see the middle portion of the above figure

  • classname attribute – a FQCN of the the class that implements this security realm. In our case this will be at.oneminutedistraction.mongodbrealm.MongoDBRealm.
  • name attribute – a unique name for this realm (mongodb-realm here). This name will be referenced by our web application that uses this realm
  • jaas-context property – the value of this property is the name of the MongoDB login module ( in login.conf file). This property associates the realm with the login module defined in . 

Now to use this realm in your web application, simply specify the realm name (mongodb-realm) in your web.xml.

Configuring MongoDB Realm

Step 1 – Copy JARs to Domain Directory

To use MongoDB realm, download the following 2 files

  • MongoDBRealm – the compiled JAR (JavaSE 8) is available here. If you prefer to build it yourself, the source is available here.
  • MongoDB Java driver – available here

Copy the 2 JARs into $DOMAIN_DIR/lib directory.

Step 2 – Add JAAS Entry to login.conf File

Edit $DOMAIN_DIR/config/login.conf file and add the following lines to the end of the file

mongodbRealm {
   at.oneminutedistraction.mongodbrealm.MongoDBRealmLoginModule required;
}

I’ve called the JAAS context as mongodbRealm. You can use any name you like just as long as its unique within the login.conf. Make a note of this name as we’ll need it when for creating the realm.

Step 3 – Configure MongoDB Realm in Glassfish

Start up Glassfish version 4.1 and must be running on JavaSE 8. Please make sure that Glassfish is using the same domain as in step 1 and 2 above. If you’re not sure, you can start Glassfish like so

asadmin start-domain -–domaindir /path/to/domain/dir domainname

Open up the admin console. This is usually localhost:4848

pic0(Click to enlarge)

and expand server-config, security as shown in the above figure. Next click on the Realm node.

pic5 (Click to enlarge)

You should see a table with all the preconfigured realms. Click on the New to create a new realm.

pic1 (Click to enlarge)

Define the MongoDB realm using the following values

  • Name – mongodb-realm
  • Class Name – at.oneminutedistraction.mongodbrealm.MongoDBRealm
  • Add the following properties: name = jaas-context, value = mongodbReam. The value must correspond to the entry name in login.conf.

This will create the auth-realm entry in domain.xml. Click OK should instantiate the realm. Besides setting the jaas-context property, the following is an exhaustive list of parameters that you can set to configure MongoDB realm

  • mongodbRealm.db – the name of MongoDB database name. The default name is mongodbRealm
  • mongodbRealm.collection – the collection name. The default name is users
  • jaas-context – the JAAS context. The default value is mongodbRealm
  • mongodbRealm.clientFactory – this is the FQCN of the class that creates MongoClient instance of the realm. The default factory is at.oneminutedistraction.mongodbrealm.DefaultMongoClientFactory. There will be an explanation later that describes how you can implement your own client factory
  • mongodbRealm.server – if you are using the default client factory, then this parameter specifies the list of servers that the MongoClient connects to. This is a list of space separated server:port numbers; for example localhost<space>myserver:1234<space>myotherserver connects to localhost, myotherserver and myserver at port 1234. The default value of this is localhost
  • mongodbRealm.passwordManager – this is the FQCN that performs the password encryption. The default password manager class is at.oneminutedistraction.mongodbrealm.SHA256PasswordManager. We will explain how you can create your own password manager class to perform your password encryption
  • mongodbRealm.algorithm – If you are using SHA256PasswordManager, you can set the value of this to either SHA-256 or SHA-512 which uses the respective hash algorithm for hashing user passwords. The default is SHA-256

Username, password and group information are stored in a JSON structure shown below

{ username: "fred",
password: "999f36dd648c74f52972745be2ee94c4b53c48639debbf310bfd5d5fc84ee4f6",
groups: [ "bedrock", "flintstones", "cartoon" ] }

There are 3 properties for each JSON document that describes a user; the username is the login name, the password is the SHA-256 hashed password (assuming I’m using the default password manager) and groups which holds an array of group names. All values are String. Property names viz. username, password and groups are not configurable.

The following code snippet shows how the above JSON is created using MongoDB’s Java API

BasicDBList groups = new BasicDBList();
groups.addAll(Arrays.asList(new String[]{"bedrock", "flintstones", "cartoon"}));
BasicDBObject fred = new BasicDBObject("user", "fred")
      .append("password", "999f3…d5d5fc84ee4f6")
      .append("groups", groups);

We can finally configure our web application to use the realm.

pic3 (Click to enlarge)

When you are configuring container security for your web application, set the name of Realm Name to mongodb-realm.

Customizing MongoDB Realm

To accommodate the various MongoDB and password requirements, there are 2 interfaces you can implement. The first of these is MongoClientFactory.  The purpose of this interface is to allow you to have control over the creation of the MongoClient instance.The interface has the following methods

  • void init(Properties prop) – This method is called when the factory in initialized. A Properties object is passed into the implementation. The property values comes from the values that you enter when you are creating the realm (see image above with New Realm header).
  • MongoClient create() – This method creates the MongoClient instance using the properties from init(). Put your code to create MongoClient in here.

The second interface, PasswordManager, deals with password encryption and validation. It has the following methods

  • void init(Properities prop) – Similar to MongoClientFactory
  • String encrypt(String password) – Returns an encrypted version of the parameter
  • boolean isValid(String encrypted, String password) – This method validates a password by testing the encrypted parameter against the password parameter

Once you’ve implemented either one or both of the above interfaces, bundle them in a JAR and drop them into $DOMAIN_DIR/lib directory. Now set the following two properties to the FQCN of you implementation  when you are configuring MongoDB;

mongodbRealm.clientFactory
mongodbRealm.passwordManager

 

On a separate note, its heartening to see that Glassfish application server now has commercial conterpart in the form of Payara. Its a drop in replacement for Glassfish and it’s build off Glassfish sources. Disclaimer: I’m not associated with Payara in any form save for the fact that I downloaded their application server this morning. There is even a cute Mario like Youtube video introducing it.

Till next time.

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