How do synchronized static methods work in Java and can I use it for loading Hibernate entities?

java

synchronized-methods

hibernate-entities

thread-safety

byNikita Barsukov·Jan 8, 2025

When you see synchronized static methods in Java, imagine a traffic cop stationed at the Class level intersection, allowing only one thread at a time to proceed through any static synchronized method of that class.

public class EntityLoader {
    public static synchronized void load(int entityId) {
        // "No entry without permission", says the traffic cop (sync)
    }
}

This mimics the Los Angeles traffic system, ensuring atomicity and warding off concurrent hassles. But, you might end up causing bottlenecks. To sidestep, think about using Hibernate's concurrency strategies or ReentrantReadWriteLock for tailored locks.

In-detail understanding of static synchronized methods

Here comes the interesting part. A static synchronized method in Java locks on the Class itself. This means that only one thread can execute a static synchronized method within the same class. However, this lock doesn't prevent threads from entering non-synchronized methods or even synchronized instance methods of the same class.

Coming to Hibernate...

In the context of Hibernate, remember a primary principle: let Hibernate and the underlying RDBMS handle the thread safety rather than adding a synchronization layer on top.

Thread safety and Hibernate Session Factory

A crucial aspect to remember while working with Hibernate is creating a single instance of the Session Factory. Manipulating synchronized methods over an inherently thread-safe Session Factory would be unnecessary.

Database and Hibernate concurrency features

When managing SQL operations, thread safety is provided by the database driver through database-level locks. With Hibernate transactions and the right isolation levels, you can deal with concurrency issues without the need for synchronized.

Check synchronization traps and escape them

While it may seem that synchronized static methods are the "be-all and end-all" solution, be mindful of the traps such as performance bottlenecks and deadlocks. These methods can create congestion and unnecessary waits leading to lower throughput.

An optimal approach to avoid synchronization traps

Understanding how InnoDB (or your DB engine) works can be a game-changer. Keeping a vigilant eye on DB isolation levels and adjusting them can prevent most of the traps.

Tailored locking for better control

Java provides concurrency utilities like ReentrantLock and StampedLock that offer sophisticated locking mechanisms to balance read/write operations.

Reality check: Synchronized methods and Hibernate

Synchronized methods work great for Singleton initializations or system-wide configurations, but within the realm of Hibernate operations, thread safety is largely an RDBMS affair.

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