java spring boot 依赖注入
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spring boot dependency injection
提问by 5er
Im new to Spring, last couple of days I've been learning about it. Now Im trying to do something with it. It seems to me that with spring boot everything has changed. There is no applicationContext file, I should use @Bean. Ok. In in tutorials the code is working, for me it fails. What did I miss?
我是 Spring 的新手，最近几天我一直在学习它。现在我想用它做点什么。在我看来，有了 Spring Boot，一切都变了。没有 applicationContext 文件，我应该使用@Bean。行。在教程中，代码正在运行，对我来说它失败了。我错过了什么？
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
the controller:
控制器：
@RestController
public class GreetingController {
private final Test test;
@Autowired
public GreetingController(Test test){
this.test = test;
}
@RequestMapping("/greeting")
public String greeting(@RequestParam(value = "name", defaultValue = "World") String name) {
return "greeting" + test.getTest();
}
}
class Test {
public String getTest() {
return "tetst";
}
}
error:
错误：
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [hello.Test] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}
at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1301)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1047)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:942)
at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:813)
at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:741)
... 18 more
I assume that bean has to be defined... But in tutorials there is no defenicion of bean.. Or I didnt see it.
我认为 bean 必须被定义......但在教程中没有 bean 的防御......或者我没有看到它。
回答by Branislav Lazic
Testclass is not recognized as a Spring component. Therefore, you cannot inject it in your GreetingController. In order to inject Testobject in that controller, annotate Testclass with like @Componentannotation (or with some other annotation that indicates that your class can be auto scanned).
Test类不被识别为 Spring 组件。因此，您不能将其注入您的GreetingController. 为了Test在该控制器中注入对象，请Test使用类似@Component注释（或使用其他一些表明您的类可以自动扫描的注释）来注释类。
回答by spencergibb
Missed the full error. You need @Componenton Test.
错过了完整的错误。你需要@Component在Test.
