Question

创建新按钮我必须在新线程中运行代码。

通常我们使用new Thread(....).start();，但我想知道为什么我们不能使用@Async - 注释。

这是代码：

package net.vectorpublish.desktop.vp;

import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Set;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

import javax.annotation.PostConstruct;
import javax.inject.Inject;
import javax.inject.Named;
import javax.swing.ImageIcon;
import javax.swing.SwingUtilities;

import org.springframework.scheduling.annotation.Async;

import net.vectorpublish.desktop.vp.api.history.Redo;
import net.vectorpublish.desktop.vp.api.layer.Layer;
import net.vectorpublish.desktop.vp.api.ui.Dialog;
import net.vectorpublish.desktop.vp.api.ui.KeyframeSlider;
import net.vectorpublish.desktop.vp.api.ui.ToolBar;
import net.vectorpublish.desktop.vp.api.ui.VPAbstractAction;
import net.vectorpublish.desktop.vp.api.vpd.DocumentNode;
import net.vectorpublish.desktop.vp.api.vpd.VectorPublishNode;
import net.vectorpublish.desktop.vp.gantt.AddTaskData;
import net.vectorpublish.desktop.vp.gantt.AddTaskHistoryStep;
import net.vectorpublish.desktop.vp.gantt.Priority;
import net.vectorpublish.desktop.vp.utils.SetUtils;
import net.vectorpublish.destkop.vp.gantt.rule.VetoableTaskAdder;

@SuppressWarnings("restriction")
@Named
public class AddTask extends VPAbstractAction implements NodeSelectionChangeListener {

    public AddTask() {
        super(GanttText.ADD_TASK, GanttText.ADD_TASK_TT, false);
    }

    @Inject
    private final Dialog dlg = null;

    @Inject
    private final History hist = null;

    @Inject
    private final Redo redo = null;

    @Inject
    private final Layer layer = null;

    @Inject
    private final ToolBar toolbar = null;

    @Inject
    private final KeyframeSlider slider = null;

    @Inject
    private final Set<VetoableTaskAdder> council = null;

    private DocumentNode doc;

    @Async // <----------------------------------------------- This creates the Exception!
    public void actionPerformed(ActionEvent arg0) {
        try {
            VectorPublishNode selected = layer.getSelection().iterator().next();
            Future<String> taskId = dlg.ask(GanttText.NAMESPACE, "ID", "");
            Future<String> info = dlg.ask(GanttText.NAMESPACE, "Detail", "");
            Future<Priority> prio = dlg.ask(GanttText.NAMESPACE, "Name", Priority.values());
            Future<Float> points = dlg.ask(GanttText.NAMESPACE, "Storypoints", 3f);
            Future<String> username = dlg.ask(GanttText.NAMESPACE, "User", "");
            Future<String> avatar = dlg.ask(GanttText.NAMESPACE, "Avatar-Image", "www.test.com/User.png");
            AddTaskData addTaskData = new AddTaskData(taskId.get(), info.get(), prio.get(),
                    SetUtils.nodeToImmutableIndex(selected), slider.getTime(), points.get(), username.get(),
                    load(avatar.get()));
            AddTaskHistoryStep data = new AddTaskHistoryStep(hist, addTaskData);
            redo.actionPerformed(arg0);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
    }

    private BufferedImage load(String string) throws MalformedURLException {
        ImageIcon ii = new ImageIcon(new URL(string));
        return (BufferedImage) ii.getImage();
    }

    public void changedNodeSelection() {
        Set<VectorPublishNode> nodes = layer.getSelection();
        if (nodes.size() != 1) {
            setEnabled(false);
        } else {
            boolean veto = false;
            for (VetoableTaskAdder vetoableTaskAdder : council) {
                veto &= vetoableTaskAdder.hasVeto(nodes);
            }
            setEnabled(!veto);
        }
    }

    @PostConstruct
    public void setup() {
        toolbar.add(this);
    }
}

这是例外：

DefaultI8nImageFactory Found: Image for key net.vectorpublish:io/new/large in cache!     (DefaultI8nImageFactory > NewFile)
DefaultI8nImageFactory Found: Image for key net.vectorpublish:io/open/small in cache!    (DefaultI8nImageFactory > OpenImpl)
DefaultI8nImageFactory Found: Image for key net.vectorpublish:io/open/large in cache!    (DefaultI8nImageFactory > OpenImpl)
Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'addTask': Bean with name 'addTask' has been injected into other beans [nodeSelectionChangeImpl,translation] in its raw version as part of a circular reference, but has eventually been wrapped. This means that said other beans do not use the final version of the bean. This is often the result of over-eager type matching - consider using 'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.
org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'addTask': Bean with name 'addTask' has been injected into other beans [nodeSelectionChangeImpl,translation] in its raw version as part of a circular reference, but has eventually been wrapped. This means that said other beans do not use the final version of the bean. This is often the result of over-eager type matching - consider using 'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:583)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:754)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:866)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:84)
    at net.vectorpublish.desktop.vp.VectorPublishApplicationContext.<init>(VectorPublishApplicationContext.java:18)
    at net.vectorpublish.desktop.vp.Startup.main(Startup.java:30)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:282)
    at java.lang.Thread.run(Thread.java:745)

修改

由于一些更高的决定，我必须尊重：

我必须拥有字段final和
无法使用构造函数进行自动装配。

Answer 1

在这种情况下，BeanCurrentlyInCreationException的根本原因是@Inject上使用了@Autowired（或其Spring的等效final ）字段。

要了解应该考虑bean生命周期的行为。

Spring首先构造对象，其字段具有默认值，即null。
构建对象后，Spring使用反射来注入，即初始化字段的实际值

因此，第二步与字段上的final声明相矛盾，该声明规定该字段可以具有一个且仅有一个值，该值应在构造时分配。

因此要解决此问题要么从字段中删除final声明，要么使用构造函数注入（在给定依赖项数的情况下，以前在这种特殊情况下是可取的）

如果需要更多信息，请在评论中告知。

希望这有帮助！

PS ：虽然我无法在任何官方文档中找到明确提及此行为的内容，但here在示例中巧妙地解释了该字段已标记为final在构造函数注入的情况下仅。

编辑： -
引入@Async强制Spring来创建和使用bean proxies，如果有循环引用则会导致BeanCurrentlyInCreationException。

这是因为Spring最初注入bean的原始版本并尝试将方面应用于它并失败，因为Nicolas Labrot指出默认情况下会禁用RawInjectionDespiteWrapping。

要克服这个问题

打破循环引用（虽然推荐，但需要重新设计，因此需要付出很多努力）

使用延迟初始化（，如下所述）

懒豆初始化
如果使用 xml 配置，请在根元素
中提供default-lazy-init="true"，如下所示
<beans default-lazy-init="true" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns="http://www.springframework.org/schema/beans" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">  </beans>

对于 Java 配置，请使用下面的

@Configuration @Lazy // For all Beans to load lazily (equivalent to default-lazy-init="true") public class SomeConfig { @Bean // @Lazy - Only if particular bean should load lazily public SomeBean someBean() { return new SomeBean(); } }

如果使用组件扫描（通过Java或xml配置），请确保标记为@Inject的字段应附带@Lazy，例如请参阅下文

@Inject @Lazy private Dialog dlg;

Answer 2

如果查看抛出异常（org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean）的代码，则抛出异常，因为您有循环引用和代理，并且您的配置不允许RawInjectionDespiteWrapping。

根据您的例外，似乎有一个循环引用。我将在圆形引用Foo＆lt; =＆gt;的另一侧调用AddTask bean。 Foo。

Spring初始化Foo。 Foo需要AddTask的实例
- Spring首先实例化AddTask并注入Foo。
然后初始化AddTask，它已由Foo实例化（并注入）。由于@Async注释，它必须被代理。因此，注入Foo实例的实例将与代理实例不同。

这导致异常。修复循环引用，它应该修复异常。 作为一种良好做法，我建议不允许循环引用。

注意：在我看来，final字段不是必需的，容易出错并且它阻碍了单元测试/模拟。如果你删除它或保留它但使用构造函数注入可能会更好。

Answer 3

VPAbstractAction始终是循环播放的。你不能同步一个渴望的豆。

actionCerformed（AWT）的BeanCurrentlyInCreationException

修改

3 个答案: