使用CDI注入命名的字符串

Question

我想以这种方式注入配置参数：

public class MyManagedBean {
    @Inject
    public MyManagedBean(@Named("user") String user){
        ....

    }
}

因此，我尝试通过这种方式实现生产者方法：

@ApplicationScoped
public class MyConfiguration {
    private Properties loadProperties() {
        Properties properties = new Properties();
        try {
            properties.load(getClass().getResourceAsStream(
                    "user.properties"));
        } catch (IOException e) {
            throw new RuntimeException();
        }
        return properties;
    }

    @Produces
    @Named("user")
    String getUser() {
        return loadProperties().getProperty("user");
    }
}

我用这种方式定义了其他bean：

public class OtherManagedBean {
    @Inject
    public OtherManagedBean(MyManagedBean myManagedBean){
        ....

    }
}

但是，在尝试部署它时遇到了这个异常：

INFO: WEB0671: Loading application [example-ear#example-war.war] at [example]
SEVERE: Exception while loading the app
SEVERE: Exception while loading the app : WELD-001410 The injection point [parameter 1] of [constructor] @Inject public com.example.OtherManagedBean(MyManagedBean) has non-proxyable dependencies
org.jboss.weld.exceptions.UnproxyableResolutionException: WELD-001410 The injection point [parameter 1] of [constructor] @Inject public com.example.OtherManagedBean(MyManagedBean) has non-proxyable dependencies
    at org.jboss.weld.bootstrap.Validator.validateInjectionPoint(Validator.java:317)
    at org.jboss.weld.bootstrap.Validator.validateBean(Validator.java:139)
    at org.jboss.weld.bootstrap.Validator.validateRIBean(Validator.java:162)
    at org.jboss.weld.bootstrap.Validator.validateBeans(Validator.java:385)
    at org.jboss.weld.bootstrap.Validator.validateDeployment(Validator.java:371)
    at org.jboss.weld.bootstrap.WeldBootstrap.validateBeans(WeldBootstrap.java:390)
    at org.glassfish.weld.WeldDeployer.event(WeldDeployer.java:190)
    at org.glassfish.kernel.event.EventsImpl.send(EventsImpl.java:128)
    at org.glassfish.internal.data.ApplicationInfo.start(ApplicationInfo.java:298)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:461)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:240)
    at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:370)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$1.execute(CommandRunnerImpl.java:355)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:370)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1067)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1200(CommandRunnerImpl.java:96)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1247)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1235)
    at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:465)
    at com.sun.enterprise.v3.admin.AdminAdapter.service(AdminAdapter.java:222)
    at com.sun.grizzly.tcp.http11.GrizzlyAdapter.service(GrizzlyAdapter.java:168)
    at com.sun.enterprise.v3.server.HK2Dispatcher.dispath(HK2Dispatcher.java:117)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:234)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:822)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:719)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1013)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:662)

任何想法？

谢谢。

Answer 1

它看起来像你需要一个默认的（无参数）构造函数您MyManagedBean使它proxyable。我真的不知道为什么它是需要的，因为MyManagedBean是一个@Dependentbean并因此不代理AFAIK;
老实说，我什至不知道为什么可代理bean需要一个默认的构造函数
这似乎是实现细节或CDI规范中被忽略的一点。无论如何，我敢打赌它可以提出一个很好的新问题:)

编辑
：我发现了为什么可代理bean需要默认构造。实际上，这并不是什么难事：由于bean的代理是同一bean的子类，因此代理需要super()在其自己的构造中调用构造函数。如果没有非私有默认构造函数，则不知道要调用哪个构造函数。甚至可以想象这样一种情况：调用注入的构造函数来创建代理，但是我不知道它会给CDI实现增加哪种复杂度；可能不是那么容易…