In the last chapter, we started developing an e-commerce application and we created the functionality to look up products based on their ID and, also, by some parameters. In this chapter, we will extend the functionality so that we can also order the products we selected. While doing so, we will learn new technologies, focusing on functional programming in Java and on some other language features, such as reflection and annotation handling during runtime, and scripting interface.

As we did in the previous chapters, we will develop the application step by step. As we discover the newly learnt technologies, we will refactor the code to enroll the new tools and methods to produce more readable and effective code. We will also mimic the development of real-life projects in the sense that at the start, we will have simple requirements, and later, new requirements will be set as our imagined business develops and sells more and more products. We will become imagined millionaires.

We will use the code base of the previous chapter, and we will develop it further, though, in a new project. We will use Spring, Gradle, Tomcat, and soapUI, which are not new after we got acquainted with these in the previous chapter. In this chapter, you will learn the following topics:

• Annotation processing
• Using reflection
• Functional programming in Java using:
  • Lambda expressions
  • Streams
  • Invoking scripts from Java