The technical principles of the Dagger framework in the Java library analysis

1. Explicit modularity: One of the most important concepts in Dagger is the module.The module is a class marked in the form of annotations to provide the creation logic of dependent objects.By clarifying the source of dependence, Dagger implements the principle of explicit modularity.The following is a simple module definition example: @Module public class MyModule { @Provides public MyDependency provideMyDependency() { return new MyDependency(); } } @Component(modules = MyModule.class) public interface MyComponent { void inject(MyClass myClass); } 3. Dependency Injection: One of the core goals of Dagger is to achieve dependency injection, and to improve the maintenance and testability of the code through automatic analysis and providing objects between objects.The following is a simple dependency injection example: public class MyClass { @Inject MyDependency myDependency; public void doSomething() { // Use myDependency object } } 4. Single Responsibility: Dagger encourages developers to follow the principle of single responsibilities, that is, each class should only pay attention to one specific function.By defining a clear dependence relationship, Dagger enables each class to focus on its own responsibilities, thereby improving the understanding of the code and maintainability. 5. Reusability and testability: Use Dagger for dependencies to injects to improve the reuse and testability of the code.By decoupled dependence and use interface definition dependencies, we can reuse components and modules in different contexts, and easier to write unit testing.This is a test example using Dagger for dependencies: public class MyClassTest { @Mock MyDependency myDependency; @InjectMocks MyClass myClass; @Before public void setup() { MockitoAnnotations.initMocks(this); DaggerMyComponent.builder().myModule(new MyModuleMock()).build().inject(this); } @Test public void testDoSomething() { } } By following the above technical principles, the Dagger framework is widely used in the Java class library, providing developers with a flexible and efficient dependent injection solution.Whether in developing large applications or writing testable unit tests, Dagger can help us improve the quality and maintenance of code.