If you are stepping into enterprise software development, you quickly realize one undeniable truth: Mainframes still run the world. While we love building flashy web apps using the latest JavaScript frameworks, the heavy lifting for global finance, healthcare, and retail is still done by legacy systems running COBOL, JCL, and VSAM datasets. The biggest challenge in enterprise architecture today isn't replacing these systems—it’s getting modern applications to talk to them. Today, let’s look at how we can bridge that gap using Java and Spring Boot . Why Spring Boot? Mainframes (like the IBM zSeries) are incredible at batch processing millions of records securely. However, they aren't exactly designed to serve JSON data directly to a mobile app. Spring Boot acts as the perfect middleman. It is robust, secure, and incredibly fast at standing up RESTful APIs that can securely query a legacy database and translate that data into a modern format.…