Explore the technical foundation of the scaldi framework in the Java library
The ScalDi framework is a lightweight dependencies injection (DI) framework used in the Java library.This article will explore the technical foundation of ScalDi in the Java class library and how to use the framework to achieve dependency injection.
1. Overview of SCALDI framework
ScalDi is an open source DI framework, which aims to simplify the dependency injection of the Java application.It provides a concise and flexible way to manage the dependency relationship between objects and can easily handle complex dependency diagrams.
The core principle of ScalDi is to facing interface programming and dependent reversal, which makes applications more scalable and testable.The framework provides a built -in DSL (Domain Specific Language) to support intuitive and type security dependency injection.
Second, dependence in injection foundation
Dependent injection is a design model for the creation and use of decoupled objects.By dependent injection, the object is no longer responsible for creating and maintaining its dependence relationship, but handed over these responsibilities to external containers to handle.
In ScalDi, dependency injection is implemented by binding.Binding is a definition that associated the interface and implementation to tell the container how to create and provide instances.The following is a simple example:
trait Database {
def query(sql: String): ResultSet
}
class MySQLDatabase extends Database {
def query(sql: String): ResultSet = {
// Implement mysql database query logic
}
}
class UserDAO(database: Database) {
// Use the DataBase interface to be injected with
}
// Create scaldi binding
val module = new Module {
bind [Database] to new MySQLDatabase
}
// Create a scaldi injectioner
val injector = new SimpleInjector(module)
// Use an injector to create objects
val userDao = injector.get[UserDAO]
In the above example, ScalDi tells the container how to create an instance of DataBase by binding the DataBase interface to the implementation of mysqldataBase.In the UserDao class, we use the injecting DataBase interface without having to care about how it is created.
3. SCALDI framework characteristics
1. Configurable dependencies: ScalDi supports a variety of different types of dependencies, such as single cases, prototypes, delay loading, etc., can be configured according to the needs of the application.
2. Life cycle management: ScalDi can automatically manage the life cycle of the object to ensure that the object is created and destroyed correctly when needed.
3. Modular design: ScalDi uses module (Module) as a basic construction block that depends on injection. The module can contain a set of related binding to facilitate code tissue and maintenance.
4. Height scalability: ScalDi provides a mechanism that dynamically binds and replace dependencies during runtime, which can dynamically change objects according to actual needs.
4. Application of SCALDI in the Java library for example
Here are a Java class library example using the SCALDI framework to show how to use ScalDi for dependent injection:
interface Logger {
void log(String message);
}
class ConsoleLogger implements Logger {
public void log(String message) {
System.out.println("[LOG] " + message);
}
}
class UserService {
@Inject
private Logger logger;
public void addUser(String username) {
// Execute the logic of users
logger.log("User added: " + username);
}
}
class LibraryModule extends Module {
public void configure() {
bind(Logger.class).to(ConsoleLogger.class);
bind(UserService.class).toSelf();
}
}
public class LibraryApp {
public static void main(String[] args) {
Injector injector = new SimpleInjector(new LibraryModule());
UserService userService = injector.get(UserService.class);
userService.addUser("John Doe");
}
}
In the above examples, we define the Logger interface and ConsoleLogger implementation, and the UserService class dependencies to inject the Logger interface.Then, the ScalDi binding is performed through the LibraryModule class, and the Logger interface is bound to the ConsoleLogger.
In LibraryApp's main method, we created a ScalDi injection and using an injectionter to obtain an instance of UserService.We can see that in the Adduser method, we can use the instance of the Logger interface directly without having to care about how it is created.
5. Summary
ScalDi is a lightweight DI framework that helps simplify the Java library.By using ScalDi, developers can easily manage the dependence between objects and improve the scalability and testability of code.This article explores the technical foundation of ScalDi in the Java library and provides a simple example to show how to use the framework to achieve dependency injection.
