java - Autowiring 的 bean 在 setter 之外为空

Question

我通过setter将一个bean注入(inject)到Spring Boot中的另一个bean中。在 setter 内部时，bean 不为 null，但是当我从另一个方法调用它时，它返回 null。

我已经尝试了所有组合(通过构造函数和 setter 注入(inject)、仅 Autowiring 字段、 Autowiring 字段和 setter ...)。

SpringConfiguration.java

@Bean
public BeanToInject beanToInject(){
    return new BeanToInject();
}
@Bean
public TargetClass targetClass(){
    return new TargetClass();
}

BeanToInject.java

@Component
public class BeanToInject{
    public BeanToInject(){}
    //More stuff
}

TargetClass.java

@Component
public class TargetClass {

    private BeanToInject beanToInject;

    public TargetClass(){}

    @Autowired
    public void setBeanToInject(BeanToInject beanToInject){
        this.beanToInject = beanToInject;
        System.out.print("1. " + this.beanToInject); //Here is instanced
    }

    public void anotherMethod(){
        System.out.print("2. " + beanToInject); //Here is null
        beanToInject.doSomeStuff(); //Here comes the exception
    }

}

输出:

//Spring stuff...
1. com.foo.bar.BeanToInject@blahblah
2. null

//------And then, the exception

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at acteso.standard.deskapp.gui.LoginController.btAceptar(LoginController.java:82)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8411)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:432)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:410)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$3(WinApplication.java:177)
    at java.lang.Thread.run(Unknown Source)

我猜这个异常根本没有用。我正在使用 JavaFX，但异常何时来自 Spring 并不重要。

我不知道是否缺少任何注释或者是否配置错误。

编辑:

实际上这是 Spring 和 JavaFX 创建自己的 TargetClass 实例的问题，因此 BeanToInject 是重复的。我按照本教程通过让 Spring 管理 JavaFX Controller 解决了这个问题:Add Spring to JavaFX 。感谢大家的帮助!

Answer 1

一个例子

BeanOne(BeanToInject)

public class BeanOne {

}

BeanTwo(目标类)

public class BeanTwo {

    BeanOne beanOne;


    @Autowired
    public void setBeanOne(BeanOne beanOne) {
        this.beanOne = beanOne;
        System.out.println("From setter "+beanOne);
    }

    public void testMethod() {
        System.out.println("From testMethod "+beanOne);
    }


}

配置。注意，这里只使用了@Bean

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class TestConfiguration {

    @Bean
    public BeanOne getBeanOne() {
        return new BeanOne();
    }

    @Bean
    public BeanTwo getBeanTwo() {
        return new BeanTwo();
    }
}

测试应用程序

public class TestApp {

    public static void main(String[] args) {

        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(TestConfiguration.class);

        ctx.registerShutdownHook();

        BeanTwo bean = ctx.getBean(BeanTwo.class);

        bean.testMethod();
    }

}

运行时的输出

From setter BeanOne@7f1302d6
From testMethod BeanOne@7f1302d6

Spring 容器在创建 BeanTwo 时注入(inject) BeanOne 的实例。在此期间，将打印“From setter”消息。

然后我们从 ApplicationContext 获取这个 BeanTwo 实例，并调用 testMethod()，这会给出“From testMethod”消息。

从外观上看，在您的情况下，您正在自己创建 BeanTwo (TargetClass) 实例 (new TargetClass())。这样的 bean 不受 Spring 容器管理，创建时 BeanOne 引用将为 null。