创建 bean 时出错，无法将新的 LinkedBlockingQueue 作为构造函数注入到 ThreadPoolExecutor答案

【问题标题】：Error creating bean, can't inject a new LinkedBlockingQueue as a constructor to ThreadPoolExecutor创建 bean 时出错，无法将新的 LinkedBlockingQueue 作为构造函数注入到 ThreadPoolExecutor
【发布时间】：2011-06-18 10:35:47
【问题描述】：

我正在尝试创建一个 ThreadPoolExecutor bean，它需要作为属性传递给许多其他 bean。

我已经定义了以下内容，但是在创建 LinkedBlockingQueue 时遇到了一个奇怪的错误（如下所示）。

<bean name="moduleExecutorService" class="java.util.concurrent.ThreadPoolExecutor">
    <constructor-arg value="1" />   <!-- Minimun # of threads in pool -->
    <constructor-arg value="20" />  <!-- Maximum # of threads in pool (pool is a caching pool that will only keep open those necessary) -->
    <constructor-arg value="60" />  <!-- Shutdown unused threads after this TimeUnit -->
    <constructor-arg>
        <bean class="java.util.concurrent.TimeUnit" factory-method="valueOf">
            <constructor-arg value="SECONDS" />
        </bean>
    </constructor-arg>
    <constructor-arg type="java.util.concurrent.LinkedBlockingQueue"><bean class="java.util.concurrent.LinkedBlockingQueue" /></constructor-arg>
</bean>

错误：

446  [main] DEBUG org.springframework.beans.TypeConverterDelegate  - Cannot create copy of Collection type [java.util.concurrent.LinkedBlockingQueue] - injecting original Collection as-is
java.lang.InstantiationException: java.util.concurrent.BlockingQueue

【问题讨论】：

尝试在构造函数参数上不使用 type="..."，或尝试指定 type="java.util.concurrent.BlockingQueue"。

标签： java spring ioc-container javabeans

【解决方案1】：

我不太清楚为什么会出现此消息。最后它只是一个DEBUG 消息，它不应该阻止你启动你的应用程序。或者，您可以使用 FactoryBean 来代替实例化 ThreadPoolExecutor。

public class ThreadPoolExecutorFactory implements FactoryBean 
{
    private final ReentrantLock lock = new ReentrantLock();   
    private ThreadPoolExecutor executor;
    private int corePoolSize;
    private int maximumPoolSize;
    private long keepAliveTime;
    private TimeUnit unit;

    public Object getObject() 
    {
        lock.lock();
        if (executor == null)
            executor = new ThreadPoolExecutor(corePoolSize, maximumPoolSize,
                    keepAliveTime, unit, new LinkedBlockingQueue<Runnable>());
        lock.unlock();
        return executor;
    }

    public Class getObjectType() 
    {
        return ThreadPoolExecutor.class;
    }

    public boolean isSingleton()    
    {
        return true;
    }
}

在您的应用程序上下文中，您将像这样创建 bean：

<bean name="moduleExecutorService" class="ThreadPoolExecutorFactory">
    <constructor-arg value="1" /> 
    <constructor-arg value="20" /> 
    <constructor-arg value="60" />
    <constructor-arg>
        <bean class="java.util.concurrent.TimeUnit" factory-method="valueOf">
            <constructor-arg value="SECONDS" />
        </bean>
    </constructor-arg>
</bean>

【讨论】：