JDK 12 switch statement... No expression

In Java language, there are lots of improvement and new paradigm changes like lambda expression, streams, etc.
In JDK 12 you can use switch statement as an expression instead of a statement. Okay, what is the difference?

Let's write code a code to understand the difference.

In the above code, you can clearly see these switch statement with fall through structure and irritating 😠 break statement. Expressing switch as a statement is error-prone, repetitive and roundabout.
In JDK 12 switch expression will come in non-fall through it means no break statement anymore.

So what does switch expression means?

static void howMany(int k) {
    System.out.println(
        switch (k) {
            case  1 -> "one"
            case  2 -> "two"
            default -> "many"
        }
    );
}

Let's rewrite the above come in JDK 12 using the latest switch expression and see how many lines of code we could reduce it and how readable our code it will be.

Keep it simple.

Oh ! please do remember that as this language enhancement not present in JDK 12 while compiling and running the JDK 12 code you need to add few arguments.

javac --enable-preview -source 12 -Xlint:preview Jdk12Switch.java 

java --enable-preview -source 12 Jdk12Switch 

 Please do share this with others and ask/discuss questions if you have.
Happy learning!

How to support multiple types of multi-tenancy database?

In this proposed solution, we are going to support multiple tenants with different types of multi-tenancy database models in one application.

To achieve this we need to have tenant identifier columns in all tables, and all query should have the association of tenant identifier as criteria.

We will be adding another column to have database identifier along with tenant identifier.

In this example, we have five tenants but T1 & T2 tenants have their own database implementation named D1 & D2 respectively, and T3, T4 & T5 tenant has the common database named ‘CD’/Common Database.


 

We going to have three databases named D1, D2 and CD, three data sources for these three databases. In application, we going to have the map of tenant identifier and the database identifier.  In the persistent layer of the application, we are going to retrieve the tenant identifier from the tenant context and get the data source with respect to it. We will be populating the tenant identifier in each persistence call and all the update, delete and retrieve call will have tenant identifier as criteria along with other criteria.

By this way, we can support multiple multiple types of multitenancy database implementation models.

Business Impact 

We can efficiently able to manage different categories of clients like we can group up small clients into a common database. As a result, these small clients will be benefited from shared storage cost and low database maintenance cost. On the other side, big clients could have their own database and it will make sure they can scale well in the future. 

Looking forward to your questions & suggestions.