![]() This test is critically important because, if we miss copying a field, the new data object won’t carry the value forward from the original-creating a potentially serious bug. We want to test the copy behavior of this object and its builder. In this post well see how to use Reflection in Java to get information about any class at run time. When we want to change one of these data objects in our code, we use a builder that reads all the fields from the original, accepts changed values via its own methods, then builds a new data object with the original values as defaults and the specified values changed. In Java, reflection allows us to inspect and manipulate classes, interfaces, constructors, methods, and fields at run time. Reflection lets Java code look at an object. It’s got a lot of private fields, with a getter for each field. As its name suggests, reflection is the ability for a class or object to examine itself. ![]() (or self-reflection) a Java class can look at itself, or any other class. As it turns out, using reflection is also a useful way to inspect the structure of a complex object with a lot of properties that share a common behavior, so we can test that behavior efficiently for each property in turn.Īs an example, let’s take a large immutable data object implemented in Java. Class class represents data types in Java and, along with the classes in the. It’s often used in library code to work with objects whose structures are unknown. Reflection, or introspection, is a technique available in many languages by which you inspect an object’s structure at runtime. Thankfully, there’s a way to reclaim that efficiency and maximize our test coverage. We don’t always completely think through the impact of those changes, sometimes accidentally leaving pieces of functionality untested and creating bugs. But some code can challenge that efficiency-when code is simple in function yet complex in structure, making minor structure changes can be problematic. Having code with automated tests keeps our quality high and makes us more efficient. Lets say I know theres a method fooMethod on this object (I can even check this with Class.forName(Foobar).
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