Instructions for use
This annotation is mainly used in methods, stating that the current method body contains the logic that eventually generates a bean instance, and the return value of the method is a bean . This bean will be added to the container for management by Spring. By default, the bean name is the method name using the bean annotation. @Bean is generally used with @Component or @Configuration.
@Bean Explicitly declare the correspondence between classes and beans, and allow users to create and configure bean instances according to actual needs.
This annotation is equivalent to:
<bean id="useService" class="com.test.service.UserServiceImpl"/>
Common components
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MyConfigration {
@Bean
public User user() {
return new User;
}
}
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class UserController {
@Autowired
User user;
@GetMapping("/test")
public User test() {
return user.test();
}
}
Named component
The bean is named: user, the alias is: myUser, both can be used
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MyConfigration {
@Bean(name = "myUser")
public User user() {
return new User;
}
}
The bean is named: user, the alias is: myUser / yourUser, all three can be used
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MyConfigration {
@Bean(name = {"myUser", "yourUser"})
public User user() {
return new User;
}
}
Bean initialization and destruction
public class MyBean {
public void init() {
System.out.println("MyBean初始化...");
}
public void destroy() {
System.out.println("MyBean销毁...");
}
public String get() {
return "MyBean使用...";
}
}
@Bean(initMethod="init", destroyMethod="destroy")
public MyBean myBean() {
return new MyBean();
}
Only @Bean can not be used @Component
@Bean
public OneService getService(status) {
case (status) {
when 1:
return new serviceImpl1();
when 2:
return new serviceImpl2();
when 3:
return new serviceImpl3();
}
}
Reference: https://www.hangge.com/blog/cache/detail_2506.html
https://www.jianshu.com/p/2f904bebb9d0