The implementation of the AUTOWIRE framework in the Java class library
The Autowire framework is an important feature in the Java class library. It has realized the dependency injection between objects by automatic assembly.This article will introduce the implementation principle of the Autowire framework and provide some Java code examples.
1. What is the AUTOWIRE framework?
The AUTOWIRE framework is one of the core features of the Spring framework. It automatically injects the dependency relationship between objects through automatic scanning and matching corresponding dependencies without manually writing a tedious dependent injection code.
2. The implementation of the AUTOWIRE framework
The implementation of the AUTOWIRE framework can be divided into the following steps:
1. Scan all class files under the class path, and give these classes to Bean to define parsers for analysis.BEAN defines the analyzer to analyze the relevant information of each category according to the annotation or configuration file, such as category, attributes, dependency relationships, etc.
2. Each class of information that is parsed will be encapsulated into the Beandefinition object, which contains all the information of the class.The Beandefinition object is stored in a container for subsequent dependencies injection operations.
3. When an instance of a certain class needs to be created, the AutoWire framework will obtain the Beandefinition object in this class and create an object instance through the reflection mechanism.
4. After creating an object instance, the Autowire framework traverses all the attributes of the object. According to the annotation or type information of the attribute, it will automatically find the corresponding dependent object in the container.If the corresponding dependencies are found, the Autowire framework will inject it into the attribute.
5. Repeat the above steps until the attributes of all objects are completed.
Third, code example of the Autowire framework
The following is a simple example that demonstrates the use of the Autowire framework:
public class UserService {
@Autowired
private UserDao userDao;
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
public void saveUser(User user) {
userDao.save(user);
}
}
public class UserDao {
public void save(User user) {
// Save the logic of user information
}
}
@Configuration
@ComponentScan("com.example")
public class AppConfig {
@Bean
public UserDao userDao() {
return new UserDao();
}
@Bean
public UserService userService() {
return new UserService();
}
}
public class Main {
public static void main(String[] args) {
ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
UserService userService = context.getBean(UserService.class);
User user = new User();
userService.saveUser(user);
}
}
In the above examples, the UserService class needs to rely on the UserDao class to save the user information.After marking the userdao attribute with @AutowIRED annotation, the AutoWire framework will automatically inject the UserDao object into the UserService class.Through @Configuration annotation and @ComponentScan annotation, the Autowire framework can automatically scan and create the Bean object defined in the configuration class to generate the corresponding Beandefinition.
Summarize:
The AUTOWIRE framework is one of the core features of the Spring framework. The dependency injection between objects is realized by automatic assembly.Its implementation principle is to define information through scanning and analytical class, create object instances, and automatically inject dependencies.By simplifying the process of dependence injection, the Autowire framework improves the efficiency of Java development and the maintenance of code.
