英文:
OSGI: Activate and Bind methods changes starting order after restarting the bundle
问题
在我的项目中，我有一个OSGI bundle。在这个bundle中，我有一个Activated方法和一个bind(to ConfigurationAdmin)方法。
当我第一次运行项目时，Activated方法首先被调用，因此我可以初始化所有我需要的东西，但是如果我停止bundle，然后再次启动它，bind方法会首先被调用，然后我会遇到一个空指针异常（因为在Activated中的初始化尚未被调用）。
bind方法中的引用为"cardinality = ReferenceCardinality.OPTIONAL, policy = ReferencePolicy.DYNAMIC"
为什么第二次启动时顺序会改变？
@Component(configurationPid = "ConsulService", immediate = true, service = ConsulService.class)
public class ConsulServiceImpl implements ConsulService {
private ConfigurationAdmin configurationAdmin;
private BundleContext context;
private Consul consul;
@Override
public AgentClient agentClient() {
return consul.agentClient();
}
@Override
public KeyValueClient keyValueAgent() {
return consul.keyValueClient();
}
@Activate
public void activate(BundleContext bundleContext) {
//这会在停止和重新启动bundle后导致空指针异常
//因为此方法未被调用，"consul"为null
this.consul = Consul.builder().build();
this.context = bundleContext;
}
...
@Reference(cardinality = ReferenceCardinality.OPTIONAL, policy = ReferencePolicy.DYNAMIC, unbind = "unbindConfigurationAdmin")
public void bindConfigurationAdmin(final ConfigurationAdmin configurationAdmin) {
this.configurationAdmin = configurationAdmin;
//在这里我遇到空指针异常，因为consul未初始化
KeyValueClient keyValueAgent = keyValueAgent();
...
}
}
英文:
in my project I have an OSGI bundle. In this bundle I have an Activated method and a bind(to ConfigurationAdmin) method.
When I run the project for the first time the Activated method is called first, so i can initialize all the things I need, but if I stop the bundle and then start it again the bind method is called first and I have a nullpointer(because the initializations in Activate are not called yet).
The reference at the bind method is "cardinality = ReferenceCardinality.OPTIONAL, policy = ReferencePolicy.DYNAMIC"
Why when started for the second time the order changes?
@Component(configurationPid = "ConsulService", immediate = true, service = ConsulService.class)
public class ConsulServiceImpl implements ConsulService {
private ConfigurationAdmin configurationAdmin;
private BundleContext context;
private Consul consul;
@Override
public AgentClient agentClient() {
return consul.agentClient();
}
@Override
public KeyValueClient keyValueAgent() {
return consul.keyValueClient();
}
@Activate
public void activate(BundleContext bundleContext) {
//this cause the nullpointer after the stop and the restarting of this bundle
//since this method is not called "consul" is null
this.consul = Consul.builder().build();
this.context = bundleContext;
}
...
@Reference(cardinality = ReferenceCardinality.OPTIONAL, policy = ReferencePolicy.DYNAMIC, unbind = "unbindConfigurationAdmin")
public void bindConfigurationAdmin(final ConfigurationAdmin configurationAdmin) {
this.configurationAdmin = configurationAdmin;
// Here I have nullpointer because consul is not initializated
KeyValueClient keyValueAgent = keyValueAgent();
...
}
答案1
得分: 1
绑定方法可以在激活方法之前调用。实际上，绑定方法必须在激活方法之前调用，以供静态引用使用。将激活方法视为后构造方法。如果您希望将激活方法作为构造函数使用，则可以使用在DS 1.4中支持的构造函数注入。
英文:
Bind methods can be called before the activate method. In fact, bind methods must be called before the activate method for static references. Think of an activate method as a post-construct method. If you require your activate method to be your constructor, then use constructor injection which is supported in DS 1.4.
答案2
得分: 0
似乎在服务可用时调用了绑定方法。
在第一次启动时，当调用Activated方法时，configurationAdmin尚不可用，但是当我停止捆绑包，然后再次重新启动时，configurationAdmin就可用了，并且在激活之前调用了绑定。
英文:
It seems that the binding method is called when the service is available.
At the first start when the Activated method is called the configurationAdmin is not available yet, but when I stop the bundle and then restart it again the configurationAdmin is available and the bind is called before activated.
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