![](/img/trans.png)
[英]NoSuchBeanDefinitionException : No bean available in Spring
[英]Spring Framework 5 Simple bean example - Why the NoSuchBeanDefinitionException
我是注釋風格的Spring框架的新手,並且配置了一個簡單的bean,無法使@ComponentScan正常工作。 bean和應用程序都在同一包中。
package springdemo;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class Pet {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Bean
public Pet fido() {
Pet p = new Pet();
p.setName("fido");
return p;
}
}
以及應用:
package springdemo;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan
public class BeanApplication {
public static void main(String[] args) {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
ctx.refresh();
ctx.start();
Pet dog = (Pet) ctx.getBean("fido");
System.out.println(dog.getName());
ctx.stop();
}
}
當我運行此程序時,應用程序找不到bean(我假設組件掃描也可以拾取bean ...):
Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'fido' available
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:772)
at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1212)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:294)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1083)
at springmvc.bean.BeanApplication.main(BeanApplication.java:15)
我可以通過scan()方法而不是通過注釋使組件掃描在代碼中起作用。
您需要傳遞一個配置類,在其中提供將由Spring容器管理的bean。
沒有Spring Boot的經典Spring應用程序示例
public class SpringApplication {
public static void main(String[] args){
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
Pet dog = (Pet)ctx.getBean("fido");
System.out.println(dog.getName());
}
}
@Configuration
class AppConfig {
@Bean
public Pet fido() {
Pet p = new Pet();
p.setName("fido");
return p;
}
}
class Pet {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Spring啟動示例:
@SpringBootApplication
public class SpringApplication {
public static void main(String[] args) {
ApplicationContext ctx = SpringApplication.run(SpringApplication.class, args);
Pet dog = (Pet) ctx.getBean("fido");
System.out.println(dog.getName());
}
}
@Configuration
class AppConfig {
@Bean
public Pet fido() {
Pet p = new Pet();
p.setName("fido");
return p;
}
}
class Pet {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.