Eclipse插件开发6-OSGI简介

OSGi是Open Services Gateway initiative的缩写，叫做开放服务网关协议。容许你动态的启动，停止，安装，删除其中的模块而无需重启服务，至于OSGI的模块层、生命周期层、服务层等的概念网上有很多的文章大概看一下就可以有所了解了，下面我通过一个例子简单的介绍OSGI的应用
新建一个plugin in project项目,比如名字叫com.osgi.hellowordl，记得勾选an OSGI framwork,点击下一步，填入ID(helloworld),然后点击完成。新建一个借口Hello 写一个方法sayHello,然后写一个实现类HelloImpl实现sayHello方法。

package com.osgi.helloworld;

public interface Hello {
   void sayHello();
}

package com.org.helloworld.impl;

import com.osgi.helloworld.Hello;

public class HelloImpl implements Hello {
    
	private final String message;
	
	public HelloImpl(String message){
		this.message = message;
	}
	@Override
	public void sayHello() {
		// TODO Auto-generated method stub
         System.out.println(this.message);
	}

}

接着修改MANIFEST.MF文件把Hello接口暴露给外部模块

增加Export-Package: com.osgi.helloworld;version="1.0"这句

在Activator类start方法中增加注册服务代码，stop卸载服务代码

package com.osgi.helloworld;

import java.util.ArrayList;
import java.util.List;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceRegistration;

import com.org.helloworld.impl.HelloImpl;

public class Activator implements BundleActivator {

	private static BundleContext context;
	
	private List<ServiceRegistration> registrations = new ArrayList<ServiceRegistration>();

	static BundleContext getContext() {
		return context;
	}

	/*
	 * (non-Javadoc)
	 * @see org.osgi.framework.BundleActivator#start(org.osgi.framework.BundleContext)
	 */
	public void start(BundleContext bundleContext) throws Exception {
		Activator.context = bundleContext;
		registrations.add(context.registerService(Hello.class.getName(), new HelloImpl("欢迎您"), null));
	}

	/*
	 * (non-Javadoc)
	 * @see org.osgi.framework.BundleActivator#stop(org.osgi.framework.BundleContext)
	 */
	public void stop(BundleContext bundleContext) throws Exception {
		for(ServiceRegistration regist : registrations){
			System.out.println("unregister"+regist);
			regist.unregister();
		}
		Activator.context = null;
	}

}

3. 新建一个client模块，com.osgi.helloworldclient项目名，步骤与上个项目一样，ＩＤ为helloworldclient.

在MANIFEST.MF文件中导入Hello服务 import-package添加com.osgi.helloworld;version=“1.0”多个模块用逗号分开

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Helloworldclient
Bundle-SymbolicName: helloworldclient
Bundle-Version: 1.0.0.qualifier
Bundle-Activator: com.osgi.helloworldclient.Activator
Bundle-Vendor: OSGI
Bundle-RequiredExecutionEnvironment: JavaSE-1.8
Import-Package: com.osgi.helloworld;version="1.0",
 org.osgi.framework;version="1.3.0"
Bundle-ActivationPolicy: lazy

修改Activator类在启动时候获取Hello服务的引用，通过引用获取sayHello服务，并加入异常处理

package com.osgi.helloworldclient;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import com.osgi.helloworld.Hello;


public class Activator implements BundleActivator {

	private static BundleContext context;

	static BundleContext getContext() {
		return context;
	}

	/*
	 * (non-Javadoc)
	 * @see org.osgi.framework.BundleActivator#start(org.osgi.framework.BundleContext)
	 */
	public void start(BundleContext bundleContext) throws Exception {
		Activator.context = bundleContext;
		ServiceReference reference = context.getServiceReference(Hello.class.getName());
		if(null != reference){
			Hello hello = null;
			try{
				hello = (Hello) context.getService(reference);
			    if(null != hello){
			    	hello.sayHello();
			    }
			    else{
			    	System.out.println("Service:Hello is null");
			    }
			}
			catch (Exception e) {
				// TODO: handle exception
				e.printStackTrace();
			}
			finally {
				context.ungetService(reference);
			}
		}
		else{
			System.out.println("Service:Hello not exists");
		}
	}

	/*
	 * (non-Javadoc)
	 * @see org.osgi.framework.BundleActivator#stop(org.osgi.framework.BundleContext)
	 */
	public void stop(BundleContext bundleContext) throws Exception {
		Activator.context = null;
	}

}

4 .点击run configurations选择osgi Framwork新建一个，随便输入个名字，下面的workspace会出现我们建立的2个项目，选中他。旧版的eclipse只需要osgi一个JAR包就可以运行了，目前比较新的eclipse需要5个jar包截图如下选中它们，然后运行。

运行后输出

欢迎您

osgi>

服务调用成功，你可以使用osgi的一些命令比如ss来查看模块id等信息,stop 加id停止某个模块,start加id启动某个模块，比如我helloworld 的id 是11 运行 stop 11然后再输入ss这个模块的状态从ACTIVE变成了RESOLVED这个时候刷新客户端refresh 10就会提示Hello服务不存在了。

Eclipse插件开发6-OSGI简介

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