Use the Giulius Annotations framework to implement the dependency injection in the Java class library
Use the Giulius Annotations framework to implement the dependency injection in the Java class library
Introduction:
Dependency inject (DI) is a software design pattern to reduce the coupling between components.Giulius Annotions is an annotation -based dependent injection framework that can simplify the dependency injection process in the Java class library.This article will introduce how to use the Giulius Annotations framework in the Java library to achieve dependent injection and provide the corresponding Java code example.
Features of Giulius Annotations framework:
1. Support field, constructor and method dependency injection.
2. Use annotations to simplify the description and management of dependencies.
3. You can inject dependencies through the way of scanning paths or manual configuration.
4. You can flexibly handle different types of dependencies injected scenarios.
5. The frame itself is lightweight and easy to use.
Instructions:
1. Introduce Giulius Anotations dependencies
Add the dependencies of the Giulius Annotations framework to the construction file of the Java project (such as Pom.xml or Build.gradle).
Maven configuration example:
<dependency>
<groupId>org.apache.geronimo.specs</groupId>
<artifactId>geronimo-atinject_1.0_spec</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>com.google.inject</groupId>
<artifactId>guice</artifactId>
<version>2.0</version>
</dependency>
<dependency>
<groupId>org.mangosdk.spi</groupId>
<artifactId>guice-annotations</artifactId>
<version>1.0</version>
</dependency>
Gradle configuration example:
compile group: 'org.apache.geronimo.specs', name: 'geronimo-atinject_1.0_spec', version: '1.0'
compile group: 'com.google.inject', name: 'guice', version: '2.0'
compile group: 'org.mangosdk.spi', name: 'guice-annotations', version: '1.0'
2. Define the dependencies to be injected
In the Java library, the dependencies to be injected are used to define the annotation definition.You can use the following annotations for dependence injection:
-`@Singlet`: There is only one instance for marking a class, and the same instance is used when each injection.
-`@Inject`: The fields, constructors or methods for marking the need to be injected.
-`@Named`: The dependencies used to specify the injection are an instance of a specific name.
Example code:
@Singleton
public class DatabaseService {
public void connect() {
// Connect to the database
}
}
public class UserService {
@Inject
private DatabaseService databaseService;
public void getUserInfo() {
databaseService.connect();
// Get user information
}
}
3. Configuration dependency injection environment
Create a dependency relationship that depends on the injection container and configures to inject.You can automatically find the dependencies with annotations through the scanning path, or you can manually configure the dependencies.
Example code:
public class DependencyInjectionConfig {
public static void main(String[] args) {
Injector injector = Guice.createInjector(new AbstractModule() {
@Override
protected void configure() {
// Manual configuration dependencies
bind(DatabaseService.class).in(Scopes.SINGLETON);
}
});
// Get the instance of injecting dependencies
UserService userService = injector.getInstance(UserService.class);
}
}
4. Use injected dependencies
Obtain instances injects through dependence in injection containers and use them.
Example code:
public class Main {
public static void main(String[] args) {
DependencyInjectionConfig config = new DependencyInjectionConfig();
UserService userService = config.injector.getInstance(UserService.class);
userService.getUserInfo();
}
}
Summarize:
Through the Giulius Annotations framework, we can easily achieve dependent injection in the Java library, and simplify the description and management of dependencies through annotations.Using this framework can effectively reduce the coupling between components and improve the maintenance of code and testability.
