导入作为单例 bean（具有工厂方法）的 OSGi 服务

Question

如何导入作为单例 bean 的导出的 OSGi 服务？

我最终得到如下异常：

Unable to start blueprint container for bundle opaClient
org.osgi.service.blueprint.container.ComponentDefinitionException: Unable to find a matching constructor on class com.opa.gateway.OPAGateway for arguments [] when instantiating bean opaGateway
    at org.apache.aries.blueprint.container.BeanRecipe.getInstance(BeanRecipe.java:336)

My Blueprint xml导出服务的地方如下：

<bean id="opaGateway" class="com.opa.gateway.OPAGateway" factory-method="getInstance"/>
<service ref="opaGateway" interface="com.opa.gateway.IOPAGateway" />

并且该服务在另一个包中被引用如下：

<reference interface="com.opa.gateway.OPAGateway" component-name="opaGateway" availability="mandatory" />

有没有办法直接引用作为 OSGi 服务的单例 bean？

Answer 1

是的，您可以引用作为 OSGi 服务的单例。确保（如@Balazs 所建议的那样）你的 class 有一个没有参数的静态 function/method getInstance()。

看看下面的蓝图。希望它能给你一个线索......（如果你需要完整的示例，我可以尝试 post 它。

<bean   id="opaGateway"
        class="org.test.OPAGateway" factory-method="getInstance">
</bean>

<bean id="opaClient"
      class="org.test.client.OPAClient"
        init-method="startup"
        destroy-method="shutdown">
</bean>

<service ref="opaGateway" interface="org.test.IOPAGateway" />


<reference interface="org.test.IOPAGateway" availability="optional">
    <reference-listener bind-method="setOPAGateway"
                    unbind-method="unsetOPAGateway">
        <ref component-id="opaClient"/>
    </reference-listener>
</reference>

bean opaGateway (org.test.OPAGateway)。它是 class 实现 org.test.IOPAGateway。它通过静态方法实例化 getInstance():

public class OPAGateway implements IOPAGateway {
    private static OPAGateway instance = null;

    public static OPAGateway getInstance () {
        if(instance == null) {
            instance = new OPAGateway();
        }
        return instance;
    }

    // A very simple method...
    @Override
    public String printMessage() {
        return "I AM AN OPAGATEWAY";
    }
}

bean: opaClient: 它只是一个消费者或引用 opaGateway 的 class:

public class OPAClient {
    public void setOPAGateway(IOPAGateway c) {
        if(c != null) {
            System.out.println("Message: " + c.printMessage());
        }
    }
    public void unsetOPAGateway(IOPAGateway c) {

    }
}

参考侦听器：使用bind/unbind-method.

opaClient

opaGateway

您可以在此处找到更多信息：http://www.ibm.com/developerworks/library/os-osgiblueprint/

导入作为单例 bean（具有工厂方法）的 OSGi 服务

Importing a OSGi service that is a singleton bean (that has a factory method)

osgi

blueprint-osgi

osgi-bundle

jbossfuse