From: http://www.xeclipse.com/?p=1165
Bundle是OSGI中的基础元件,不同的bundle之间可以相互依赖、引用,这样许多bundle才会共同协作,实现一些比较复杂的功能。Bundle的依赖一直是一个比较棘手的问题,包括Lazy start等,下面我们具体Bundle依赖到底是怎么一回事。
测试场景:Eclipse 3.6, Equinox
先看看基础的依赖问题
准备环境
新建2个插件,注意选择“An OSGI Framework”
新建2个基础plugin project:org.salever.osgi.depends.clientbundle、org.salever.osgi.depends.hostbundle
然后启动一个OSGI Framework,在Eclipse里面Run configuration里面,新建一个OSGI Framework:
在新建的OSGI Framework里面,仅选择新建的2个插件,然后点击add Required Bundles:
为了测试顺利,建议添加-clean参数:
如果不出意外,将会出现OSGI的控制台:
输入ss,将列举当前的bundles:
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osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 1
0.0 .qualifier 2
0.0 .qualifier |
这时候仅仅有三个bundle启动,下面我们将尝试添加依赖关系,然后看看依赖关系不满足的时候,bundle的表现。
依赖
我们将尝试几种不同的场景:
- 【LAZY下】依赖不满足的时候,bundle的行为
- 正常运行的bundle,强行停止其依赖的bundles,该bundle的行为
- 无依赖的情况下,bundle的行为
在测试之前,必须先把OSGI Framework配置改下,将所有的bundle该为Lazy start,不然影响测试结果。
注意红线部分的设置。然后重启OSGI Framework。出现以下的内容,表明此时所有的bundle都是Lazy-start并且没有启动:
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osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 3
0.0 .qualifier 4
0.0 .qualifier |
注意先要把Bundle都设为Lazy-start。实现Lazy-start的bundle很简单,在MANIFEST.MF中,添加
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Bundle-ActivationPolicy: lazy |
就可以了。
测试场景1——简单依赖
这时候修改新建的2个bundle,在org.salever.osgi.depends.clientbundle中添加对org.salever.osgi.depends.hostbundle的依赖:
保存重启OSGI Framework,然后尝试启动org.salever.osgi.depends.clientbundle
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osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 3
0.0 .qualifier 5
0.0 .qualifier osgi> start 5 |
然后看看运行效果:
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osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 3
0.0 .qualifier 5
0.0 .qualifier osgi> |
这时候org.salever.osgi.depends.clientbundle已经启动,而依赖的bundle——org.salever.osgi.depends.hostbundle依然是
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3
0.0 .qualifier |
看看clientbundle的header信息:
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osgi> headers 5 Bundle headers: Bundle-ActivationPolicy = lazy Bundle-Activator = org.salever.osgi.depends.clientbundle.Activator Bundle-ManifestVersion = 2 Bundle-Name = Clientbundle Bundle-RequiredExecutionEnvironment = JavaSE- 1.6 Bundle-SymbolicName = org.salever.osgi.depends.clientbundle;singleton:= true Bundle-Version = 1.0 . 0 .qualifier Import-Package = org.osgi.framework;version= "1.3.0" Manifest-Version = 1.0 Require-Bundle = org.salever.osgi.depends.hostbundle;bundle-version= "1.0.0" |
这时候尝试停止hostbundle:
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osgi> stop 3 osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 3
0.0 .qualifier 5
0.0 .qualifier |
说明了即使被依赖的bundle不启动,clientbundle亦一样可以启动。
这里的依赖仅仅是简单的Add Required Bundle,没有使用里面的具体类,如果使用了依赖的bundle中的类了么?
测试场景2——添加具体Class调用
在hostbundle中新建类HostService:
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package
/** * @author LiXP * */ public HostService { public static void
System.out.println(HostService. class .toString() + ": Service" ); } } |
然后Export这个package,使其能被其他bundle使用:
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Export-Package: org.salever.osgi.depends.hostbundle |
最后在clientbundle中添加使用,修改ClientActivator.java,使其在启动的时候调用
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/* * (non-Javadoc) * * @see * org.osgi.framework.BundleActivator#start(org.osgi.framework.BundleContext * ) */ public start(BundleContext bundleContext) throws Exception { ClientActivator.context = bundleContext; HostService.service(); } |
重启OSGI Framework,
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osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 1
0.0 .qualifier 2
0.0 .qualifier osgi> start 2 class
osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 1
0.0 .qualifier 2
0.0 .qualifier osgi> |
这时候,hostbundle也启动了。这个与OSGI的lazy-start机制有关。bundle的lclass或者其它资源被Class loader装载的时候,该bundle才会启动。注意<<LAZY>>和RESOLVED 是2种状态。
测试场景3——强制停止依赖的插件
停止hostbundle:
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osgi> stop 1 osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 1
0.0 .qualifier 2
0.0 .qualifier osgi> |
clientbundle依然运行,说明在bundle已经启动以后,停止依赖的bundle,对其无影响。
依次停止2个bundle,然后启动clientbundle,看看结果:
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osgi> stop 2 osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 1
0.0 .qualifier 2
0.0 .qualifier osgi> start 2 class
osgi> |
2个bundle都启动。
修改一下代码,看看如果clientbundle一直调用hostbundle的时候,bundle的行为:
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/* * (non-Javadoc) * * @see * org.osgi.framework.BundleActivator#start(org.osgi.framework.BundleContext * ) */ public start(BundleContext bundleContext) throws Exception { ClientActivator.context = bundleContext; new Thread( new
@Override public void run() { while ( true ) { HostService.service(); try { Thread.sleep( 5000 ); } catch (InterruptedException e) { } System.out.println( this .toString() + ": Sleep 5000ms" ); } } }).start(); } |
这里每隔5s,会发生一次调用:
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osgi> org.salever.osgi.depends.clientbundle.ClientActivator$ 1 @1808199 : Sleep 5000ms class
org.salever.osgi.depends.clientbundle.ClientActivator$ 1 @1808199 : Sleep 5000ms class
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然后停止hostbundle:
ss Framework is launched. id State Bundle 0 ACTIVE org.eclipse.osgi_3.6.2.R36x_v20110210 1 RESOLVED org.salever.osgi.depends.hostbundle_1.0.0.qualifier 2 ACTIVE org.salever.osgi.depends.clientbundle_1.0.0.qualifier osgi> org.salever.osgi.depends.clientbundle.ClientActivator$1@1808199: Sleep 5000ms class org.salever.osgi.depends.hostbundle.HostService: Service
试试卸载hostbundle:
osgi> uninstall 1 osgi> ss Framework is launched. id State Bundle 0 ACTIVE org.eclipse.osgi_3.6.2.R36x_v20110210 2 ACTIVE org.salever.osgi.depends.clientbundle_1.0.0.qualifier osgi> org.salever.osgi.depends.clientbundle.ClientActivator$1@763f5d: Sleep 5000ms class org.salever.osgi.depends.hostbundle.HostService: Service org.salever.osgi.depends.clientbundle.ClientActivator$1@763f5d: Sleep 5000ms class org.salever.osgi.depends.hostbundle.HostService: Service org.salever.osgi.depends.clientbundle.ClientActivator$1@763f5d: Sleep 5000ms class org.salever.osgi.depends.hostbundle.HostService: Service
说明,只要bundle启动了,就算依赖的bundle没有了,它也不会受其影响。一个可能的解释为,OSGI Framework缓存了这些bundle资源。
测试场景3——依赖的插件不存在
最后我们看看,依赖的bundle不存在的时候,bundle的行为。
回到New OSGI Framework的页面,去掉org.salever.osgi.depends.hostbundle。
启动环境:
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osgi> !SESSION 2012 - 04 - 05 17 : 22 : 06.432 ----------------------------------------------- eclipse.buildId=unknown java.version= 1.6 .0_17 java.vendor=Sun Microsystems Inc. BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=en_US Command-line arguments: -dev file:E:/workspace/common_ws/.metadata/.plugins/org.eclipse.pde.core/New OSGI/dev.properties -os win32 -ws win32 -arch x86 -consoleLog -console -clean !ENTRY org.eclipse.osgi 2 0
- 04 - 05 17 : 22 : 07.308 !MESSAGE One or more bundles are not resolved because the following root constraints are not resolved: !SUBENTRY 1 org.eclipse.osgi 2 0
- 04 - 05 17 : 22 : 07.309 !MESSAGE Bundle initial @reference :file:E:/workspace/common_ws/org.salever.osgi.depends.clientbundle/ was not resolved. !SUBENTRY 2 org.salever.osgi.depends.clientbundle 2 0
- 04 - 05 17 : 22 : 07.309 !MESSAGE Missing required bundle org.salever.osgi.depends.hostbundle_1. 0.0 . !ENTRY org.eclipse.osgi 2 0
- 04 - 05 17 : 22 : 07.311 !MESSAGE The following is a complete list of bundles which are not resolved, see the prior log entry for the root cause if it exists: !SUBENTRY 1 org.eclipse.osgi 2 0
- 04 - 05 17 : 22 : 07.311 !MESSAGE Bundle org.salever.osgi.depends.clientbundle_1. 0.0 .qualifier [ 1 ] !SUBENTRY 2 org.salever.osgi.depends.clientbundle 2 0
- 04 - 05 17 : 22 : 07.312 !MESSAGE Missing required bundle org.salever.osgi.depends.hostbundle_1. 0.0 . |
出现错误信息,尝试列举已有的bundle:
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osgi> ss Framework is launched. id State Bundle 0
6.2 .R36x_v20110210 1
0.0 .qualifier |
bundle状态为已安装,而没有启动,尝试启动:
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osgi> start 1 org.osgi.framework.BundleException: The bundle "org.salever.osgi.depends.clientbundle_1.0.0.qualifier [1]" could not be resolved. Reason: Missing Constraint: Require-Bundle: org.salever.osgi.depends.hostbundle; bundle-version= "1.0.0" at org.eclipse.osgi.framework.internal.core.AbstractBundle.getResolverError(AbstractBundle.java: 1317 ) at org.eclipse.osgi.framework.internal.core.AbstractBundle.getResolutionFailureException(AbstractBundle.java: 1301 ) at org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java: 319 ) at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java: 284 ) at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java: 276 ) at org.eclipse.osgi.framework.internal.core.FrameworkCommandProvider._start(FrameworkCommandProvider.java: 252 ) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java: 39 ) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java: 25 ) at java.lang.reflect.Method.invoke(Method.java: 597 ) at org.eclipse.osgi.framework.internal.core.FrameworkCommandInterpreter.execute(FrameworkCommandInterpreter.java: 155 ) at org.eclipse.osgi.framework.internal.core.FrameworkConsole.docommand(FrameworkConsole.java: 156 ) at org.eclipse.osgi.framework.internal.core.FrameworkConsole.runConsole(FrameworkConsole.java: 141 ) at org.eclipse.osgi.framework.internal.core.FrameworkConsole.run(FrameworkConsole.java: 105 ) at java.lang.Thread.run(Thread.java: 619 ) |
这里就很好的解释了,为什么我们再运行Eclipse RCP插件时候,出现的一些类似错误的原因了。
总结
- 一般情况下,最好把bundle设为Lazy-start,这样可以节约资源,在必要的情况下,bundle会自动启用
- 如果依赖的bundle停止了,正在运行的bundle不会马上停止,仍然会继续运行