Detailed explanation of the autowire framework in the Java class library
The Autowire framework is an important feature in the Java class library, which can help developers automatically assemble (automatic association) objects and their dependence.This article will introduce the concept, working principle, and Java code example of the Autowire framework in detail.
What is the Autowire framework?
The Autowire framework is a core feature in the Spring framework. It allows developers to use Autowiring to achieve dependency injection between objects.In traditional Java applications, the dependency relationship between objects is usually manually injected by constructing functions or setter methods.With the Autowire framework, these dependencies can be automatically completed through configuration and annotation.
The working principle of the Autowire framework:
1. Class that requires automatic associations: In the definition of the Java class, the @Autowired annotation marker requires automatic association attributes or constructors.
2. Configuration automatic association method: In the Spring configuration file, set the autowire property to Byname, Bytype, Constructor, etc. to determine the automatic correlation method.
-Byname: Related through the attribute name, Spring will find the same bean in the container with the same bean.
-Bytype: Related through the type of attribute type, Spring will find the same bean in the container to associate with the same Bean.
-CONSTRUCTOR: With the constructive function, Spring will find the corresponding bean in the container based on the type of the constructor parameter.
3. Create a Spring container: In the application start -up phase, create a Spring container by reading the Spring configuration file.
4. Automatic association object: When the Spring container starts, it will automatically scan the class that needs to be associated automatically. According to the configuration method, find the relevant bean in the container for automatic association.
5. Use automatic association objects: In other categories, you can use @Autowired annotations to inject objects that need to be automatically associated and use their methods and attributes directly.
Example code:
Below is a simple example code that demonstrates how to use the Autowire framework to implement the automatic connection.
First, create an interface GreetingService:
public interface GreetingService {
void greet();
}
Then, create two implementation classes to achieve different ways of greeting:
public class EnglishGreetingService implements GreetingService {
@Override
public void greet() {
System.out.println("Hello!");
}
}
public class ChineseGreetingService implements GreetingService {
@Override
public void greet() {
System.out.println ("Hello!");
}
}
Then, create a class that requires greeting services:
public class GreetingController {
@Autowired
private GreetingService greetingService;
public void sayHello() {
greetingService.greet();
}
}
Finally, perform related configuration in the Spring configuration file:
<bean id="englishGreetingService" class="com.example.EnglishGreetingService" />
<bean id="chineseGreetingService" class="com.example.ChineseGreetingService" />
<bean id="greetingController" class="com.example.GreetingController" autowire="byType" />
In the above examples, we have created two classes that implement the GreetingService interface, which are EnglishgreetingService and ChinesegreetingService.Then, in the GreetingController class, it will automatically associate the class into the GreetingService properties through the @Autowired annotation.Finally, set the autowire property of the GreetingController class in the Spring configuration file to Bytype, so that the Spring will automatically associate with the same Bean of the GreetingService property type.
Through this configuration and code, when the application starts, the Spring container will automatically create the GreetingController object, and it will automatically associate into the GreetingService attribute (in this example is chinesegreetingService).In this way, the Greet () method can be called directly when using GreetingService to achieve an automatic connection of the object.
Summarize:
The Autowire framework is a core function in the Spring framework. It realizes the dependency injection between objects by automatic assembly.Developers only need to mark the attributes or constructor that need to be automatically associated to @AutowIred through annotations, and then configure the automatic association in the Spring configuration file to realize the automatic association of the object.Using the Autowire framework can greatly simplify the development process and improve the maintenance and flexibility of the code.
