After springboot started, the following error occurred. The compiler told us that there was no matching bean.
The following is the code in the startup class:
package com.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
@SpringBootApplication
public class MainApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run= SpringApplication.run(MainApplication.class,args);
User user=new User("张三",21);
run.getBean(User.class);
System.out.println(user);
}
}
User class:
package com.springboot;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.stereotype.Controller;
@Data
@AllArgsConstructor
@NoArgsConstructor
@Controller
public class User {
private String name;
private Integer age;
}
The reason for the above error is that when springboot's startup class scans components, it will only scan the package and sub-packages where the startup class is located . Later, I checked and it was indeed the case, as shown below:
User is indeed not under the startup class package or sub-package, so it is not scanned.
The solution is as follows:
We only need to add the component User to the package or sub-package of the startup class!
The output looks like this:
