The principle of the Objenesis framework in the Java class library and its actual application in the project

Objeneis is an open source Java class library, which is mainly used to create object instances by bypass the constructor.Its goal is to solve part of the problems in Java, such as a class instance without a parameter constructor and the parameters of the constructor when creating objects. The principle of Objeneis is very simple. It creates an object instance by directly operating the Java bytecode instead of a constructing function.Under normal circumstances, creating a Java object instance requires the initialization object by calling the constructor of the class, and then executing the code logic in the constructor.However, some classes may not have a parameter constructor, or the parameters of the constructor are too complicated, making it difficult for us to call the constructor to create objects.OBJNESIS can bypass these restrictions and create objects directly through bytecode. In the project, ObjinSis is widely used.The following are some actual application scenarios: 1. MOCK test: In the unit test, sometimes we need to create an object instance with a private field or no parameter constructor.Using Objeneis can bypass these restrictions and quickly create instances required to facilitate simulation testing. 2. Serialization and deesessment: In some cases, we may need to create an object instance that does not implement the Serializable interface and serialize it into a disk or network.Using Objeneis can create such object instances and conduct serialized and dependentization operations on the object through other methods. Here are some examples of Java code using Objeneis: import org.objenesis.Objenesis; import org.objenesis.ObjenesisStd; public class ObjenesisExample { public static void main(String[] args) { // Use Objeneisis to create an object example Objenesis objenesis = new ObjenesisStd(); ExampleClass example = objenesis.newInstance(ExampleClass.class); System.out.println(example.getMessage()); // 输出: Hello, Objenesis! } static class ExampleClass { private String message; public ExampleClass() { this.message = "Hello, Objenesis!"; } public String getMessage() { return message; } } } In the above example, we use Objenesis to create an ExampleClass object instance, even if the ExampleClass class does not have a parameter constructor.Then we can call the getMessage () method through this object to obtain the message in the object. In summary, Objeneis is a powerful Java class library. By bypassing the constructor creation object instance, it can solve the instance of the object in some Java.Whether in MOCK testing or serialization and deefravation, Objeneis has good application potential.