Javax inject framework introduction and usage method
Javax inject framework introduction and usage method
Javax Inject is a core framework used in Java to achieve dependency injection.Dependent injection is a design pattern that can achieve loosening, maintenance and scalable application development.This framework provides a set of annotations and interfaces for labeling and management dependencies, thereby achieving decoupling between objects.
The core concept in Javax Inject is annotations. Through annotations, they can mark the classes, attributes, and constructors to indicate their dependencies.Common annotations include:@inject,@named,@Singleton,@Qualifier, etc.Among them,@inject annotations indicate that they need to inject dependencies, which can be applied to constructors, fields, and ordinary methods.
The following is a simple example to demonstrate how to use Javax Inject to achieve dependency injection:
import javax.inject.Inject;
public class UserService {
private UserRepository userRepository;
@Inject
public UserService(UserRepository userRepository) {
this.userRepository = userRepository;
}
public void saveUser(User user) {
userRepository.save(user);
}
}
In the above example, the UserService class has a user -based dependencies and is injected through the constructor.Through @inject annotations, the framework can automatically processes the dependencies inject.
Javax Inject also supports the use of limited -limited to achieve a finer granular dependencies.Limited symbols are a type of custom annotation that is used to further mark dependencies.For example, a custom limited character can be defined to annotate a specific userRepository instance, and then use the limited symbol to distinguish different UserRepository instances when injected.
import javax.inject.Inject;
import javax.inject.Named;
public class UserService {
private UserRepository userRepository;
private UserRepository adminRepository;
@Inject
public UserService(@Named("User") UserRepository userRepository, @Named("Admin") UserRepository adminRepository) {
this.userRepository = userRepository;
this.adminRepository = adminRepository;
}
public void saveUser(User user) {
userRepository.save(user);
}
public void saveAdmin(User user) {
adminRepository.save(user);
}
}
In the above examples, two different limited characters are defined on the constructor parameter through the @Named annotation: @named ("user") and @named ("admin").In this way, Javax Inject will be able to distinguish different UserRePOSITORY instances and inject correctly.
In short, the Javax Inject framework provides a simple and powerful dependency injection mechanism for Java developers.By using annotations and interface marking dependencies, developers can realize loose, tested and maintained code.It is one of the important tools for building high -quality Java applications.
Please note that the Javax Inject framework is a specification, and the Java standard library does not provide it.Therefore, before using the Javax Inject framework, developers need to introduce related third -party libraries, such as Google Guice or Spring Framework to achieve the function of dependence.
