How do I improve the performance of a Java web application?

The belief remains that Java applications are slower than applications written in other languages. So, if performance is important to your application, then you shouldn’t consider Java as the programming language to use. This view was true about 20 years ago, when Java was originally used to develop applications. In early Java implementations, the Java Virtual Machine (JVM) took a long time to start. The first Java-based user interfaces were based on Swing technology and were slow.

Several references suggest that today’s Java programs are not much slower than other modern application programming technologies, such as Microsoft .NET.

New builds have been introduced in newer versions of Java to address some of the challenges associated with older versions of Java. Using these new designs can result in significant performance gains. The concurrent HashMap introduced in JDK 1.5, for example, is a more powerful data structure than the conventional Hashtable.

Although the JVM processes memory dynamically, you must configure it with enough memory to do its job. Here are some common symptoms that can indicate that you may not have configured memory correctly:

The app works fine when you start it, but it slows down over time. A restart often fixes the problem.

Java.lang.OutOfMemoryError detects errors while running the application. This error usually occurs when the JVM cannot allocate an object because it is low on memory and the garbage collector cannot reclaim more memory.

Garbage collection occurs frequently and the GC process takes many CPU cycles.

The JVM Xms argument determines the initial heap size. This means that the JVM starts with Xms memory and can use a maximum of Xmx memory.

Modern JVMs provide a variety of options for using the garbage collection algorithm. Here are some garbage collection options for JDK 12 and higher:

• Soros GC
• Parallel GIC
• GC simultaneous marking and scanning
• G1 GC
• Shenandoah GC
• Z GC
• Epsilon GC

The goal of optimizing the garbage collection performance of the JVM is to reduce the time required to complete the entire garbage collection cycle.

Web repositories such as Tomcat, JBoss, WebLogic, and WebSphere limit the number of threads that can be created while processing requests. The default settings for these containers are very low for most workloads. Make sure to check the web store thread set configuration and make sure that incoming requests are not waiting for threads to be available to add them to processing.

Most web applications today use connection sets to access the database. A database connection set is created in advance, and applications receive connections from that set, use those connections and return them to the set. By reusing connections for multiple queries, applications save additional database costs and thus improve responses to end users.