不能为生产者方法代理非JSR299 bean

Question

我知道，如果通过生产者方法实例化，不符合JSP-299的类可以用于注入。

我把这解释为，如果我想让一个带有带参数的构造函数的bean成为可注入的，我可以通过使用生产者方法来实现。

然而，当我这样做时，我在部署时得到了以下异常：

2015-11-11T21:35:12.099+0000|Grave: Exception during lifecycle processing
org.glassfish.deployment.common.DeploymentException: CDI deployment failure:Exception List with 2 exceptions:
Exception 0 :
org.jboss.weld.exceptions.DeploymentException: WELD-001435 Normal scoped bean class org.....MongoConfiguration is not proxyable because it has no no-args constructor - Producer Method [MongoConfiguration] with qualifiers [@Any @Default] declared as [[BackedAnnotatedMethod] @Produces @ApplicationScoped public org.....PropertiesProducer.produceMongoConfiguration()]. 

下面是制作人：

public class PropertiesProducer {

    private static final String PROPERTIES_FILE = "mongo.properties";

    private Properties properties = new Properties();

    public static final String DATABASE_NAME        = "database.name";
    public static final String PORT                 = "database.port";
    public static final String HOST                 = "database.host";
    public static final String USERNAME             = "database.username";
    public static final String PASSWORD             = "database.password";

    @Produces
    @ApplicationScoped
    public MongoConfiguration produceMongoConfiguration(){

        final InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(PROPERTIES_FILE);
        if (in == null) {
            return new MongoConfiguration(properties);
        }
        try {
            properties.load(in);
        } catch (IOException e) {
            throw new RuntimeException("Failed to load properties", e);
        }
        finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (IOException e) {
                // don't care
            }
        }

        return new MongoConfiguration(properties);
    }
}

其用法如下：

public class MongoDatastore {

    @Inject
    MongoConfiguration mongoConfiguration;

    @Inject
    MongoClient mongoClient;
    Datastore datastore;

    @PostConstruct
    private void setupDatastore() {
        Morphia morphia = new Morphia();
        datastore = morphia.createDatastore(mongoClient, mongoConfiguration.getDatabaseName());
    }

 }

我是不是漏掉了什么很明显的东西？

Answer 1

最简单的解决方案是将作用域从@ApplicationScoped更改为@Singleton

import javax.inject.Singleton;

@Produces
@Singleton
public MongoConfiguration produceMongoConfiguration(){
     // ...
     return new MongoConfiguration(properties);
}

有关说明，您可以查看this SO answer。

顺便说一句:与@Singleton伪作用域相比，通常首选普通作用域@ApplicationScoped。为什么？例如，因为这样的bean的串行化+反串行化将完美地工作。但在日常工作中，有时我们会遇到第三方类，是不可代理的，我们无法更改它。因此，我们有可能的解决方案：

• 使用@Singleton bean作为接口，而不是具体的bean(在生产者方法返回类型和普通代码内部)。