Foreword

Java has been the world’s most popular programming language for well over a decade. You can find it running everywhere: on super computers, servers, set top boxes, PCs, phones, tablets, routers, and robots. There are millions of expert engineers fluent in it, libraries for every conceivable purpose, and unparalleled tooling and management capabilities.

Despite Java’s success, few people consider it highly productive for quickly developing enterprise applications. Indeed, if we step back to the year 2000, the mainstream model revolved around a standard called EJB 2. It promoted patterns that are unthinkable in the modern era, including vast deployment descriptors, code that was virtually impossible to unit test, confusing lifecycle methods, meaningless layers, excessive redeployment delays, and so on.

These problems would not remain unchallenged. In the early 2000s, Spring introduced a vastly more productive approach that quickly replaced EJB 2 for new applications. It also significantly popularized the use of open source within traditionally conservative organizations that had previously only allowed vendor-endorsed products. Today, most developers enjoy considerable latitude in their ability to use liberally licensed open source software.