在Talend产品中,模块之间的依赖都是给予代码直接访问,每个插件项目没有自身的使用规则。造成插件间的混乱无序依赖。参见大型RCP项目,降低插件依赖度
例如:
上图中, org.talend.designer.core插件项目要依赖于如此多的其它项目。
从整个系统的体系结构看,org.talend.designer.core对于红线连接的插件的依赖是不符合逻辑的。
另外,其他插件之间也存在着相互依赖的情况,例如Runprocess就要依赖于Repository。
随着以后插件项目的增多,这么复杂的依赖型将导致软件的维护越来越困难。
解决的方案是提供一个服务的注册,提供机制,所有的服务在一个地方统一注册,其他插件到这里取用。
以Repository模块为例:可以体现为如下设计方案。
Repository作为服务的提供者,其他使用该功能的插件作为消费者。
实际实现
1 在基础项目org.talend.core中提供统一的服务注册接口程序如下:
package org.talend.core;
import java.util.HashMap;
import java.util.Map;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.talend.commons.exception.ExceptionHandler;
/** *//**
* DOC qian class global comment. A global service register provides the service registration and acquirement.
public class GlobalServiceRegister ...{
// The shared instance
private static GlobalServiceRegister instance = new GlobalServiceRegister();
private static IConfigurationElement[] configurationElements;
public static GlobalServiceRegister getDefault() ...{
return instance;
}
private MapClass, IService> services = new HashMapClass, IService>();
static ...{
IExtensionRegistry registry = Platform.getExtensionRegistry();
configurationElements = registry.getConfigurationElementsFor("org.talend.core.service");
}
/** *//**
* DOC qian Comment method "getService".Gets the specific IService.
*
* @param klass the Service type you want to get
* @return IService IService
*/
public IService getService(Class klass) ...{
IService service = services.get(klass);
if (service == null) ...{
service = findService(klass);
if (service == null) ...{
throw new RuntimeException("The service " + klass.getName() + " has not been registered.");
}
services.put(klass, service);
}
return service;
}
/** *//**
* DOC qian Comment method "findService".Finds the specific service from the list.
*
* @param klass the interface type want to find.
* @return IService
*/
private IService findService(Class klass) ...{
String key = klass.getName();
for (int i = 0; i configurationElements.length; i++) ...{
IConfigurationElement element = configurationElements[i];
String id = element.getAttribute("serviceId");
if (!key.endsWith(id)) ...{
continue;
}
try ...{
Object service = element.createExecutableExtension("class");
if (klass.isInstance(service)) ...{
return (IService) service;
}
} catch (CoreException e) ...{
ExceptionHandler.process(e);
}
}
return null;
}
}
import java.util.HashMap;
import java.util.Map;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.talend.commons.exception.ExceptionHandler;
/** *//**
* DOC qian class global comment. A global service register provides the service registration and acquirement.
*
* $Id: talend-code-templates.xml 1 2006-09-29 17:06:40 +0000 (星期五, 29 九月 2006) nrousseau $
*
public class GlobalServiceRegister ...{
// The shared instance
private static GlobalServiceRegister instance = new GlobalServiceRegister();
private static IConfigurationElement[] configurationElements;
public static GlobalServiceRegister getDefault() ...{
return instance;
}
private MapClass, IService> services = new HashMapClass, IService>();
static ...{
IExtensionRegistry registry = Platform.getExtensionRegistry();
configurationElements = registry.getConfigurationElementsFor("org.talend.core.service");
}
/** *//**
* DOC qian Comment method "getService".Gets the specific IService.
*
* @param klass the Service type you want to get
* @return IService IService
*/
public IService getService(Class klass) ...{
IService service = services.get(klass);
if (service == null) ...{
service = findService(klass);
if (service == null) ...{
throw new RuntimeException("The service " + klass.getName() + " has not been registered.");
}
services.put(klass, service);
}
return service;
}
/** *//**
* DOC qian Comment method "findService".Finds the specific service from the list.
*
* @param klass the interface type want to find.
* @return IService
*/
private IService findService(Class klass) ...{
String key = klass.getName();
for (int i = 0; i configurationElements.length; i++) ...{
IConfigurationElement element = configurationElements[i];
String id = element.getAttribute("serviceId");
if (!key.endsWith(id)) ...{
continue;
}
try ...{
Object service = element.createExecutableExtension("class");
if (klass.isInstance(service)) ...{
return (IService) service;
}
} catch (CoreException e) ...{
ExceptionHandler.process(e);
}
}
return null;
}
}
2 服务接口为:
public interface IService ...{
}
}
3 插件扩展点定义为;
org.talend.core/plugin.xml
extension-point id="service" name="Service Registration" schema="schema/service.exsd"/>
4对于希望提供服务插件需要声明自己的服务类型。
例如org.talend.repository插件希望提供服务。
定义IRepositoryService.java 此类放入org.talend.core中。
在org.talend.repository实现IrepositoryService
public interface IRepositoryService extends IService ...{
public IComponentsFactory getComponentsFactory();
public IPath getPathFileName(String folderName, String fileName);
public IProxyRepositoryFactory getProxyRepositoryFactory();
public IPath getRepositoryPath(RepositoryNode node);
}
public IComponentsFactory getComponentsFactory();
public IPath getPathFileName(String folderName, String fileName);
public IProxyRepositoryFactory getProxyRepositoryFactory();
public IPath getRepositoryPath(RepositoryNode node);
}
public class RepositoryService implements IRepositoryService ...{
public IComponentsFactory getComponentsFactory() ...{
return ComponentsFactoryProvider.getInstance();
}
public IPath getPathFileName(String folderName, String fileName) ...{
return RepositoryPathProvider.getPathFileName(folderName, fileName);
}
public IProxyRepositoryFactory getProxyRepositoryFactory() ...{
return ProxyRepositoryFactory.getInstance();
}
public IPath getRepositoryPath(RepositoryNode node)...{
return RepositoryNodeUtilities.getPath(node);
}
}
public IComponentsFactory getComponentsFactory() ...{
return ComponentsFactoryProvider.getInstance();
}
public IPath getPathFileName(String folderName, String fileName) ...{
return RepositoryPathProvider.getPathFileName(folderName, fileName);
}
public IProxyRepositoryFactory getProxyRepositoryFactory() ...{
return ProxyRepositoryFactory.getInstance();
}
public IPath getRepositoryPath(RepositoryNode node)...{
return RepositoryNodeUtilities.getPath(node);
}
}
5 org.talend.repository使用扩展点,使自己注册到org.talend.core中.
org.talend.repository/plugin.xml
extension
point="org.talend.core.service">
Service
serviceId="IRepositoryService"
class="org.talend.repository.RepositoryService"/>
extension>
point="org.talend.core.service">
Service
serviceId="IRepositoryService"
class="org.talend.repository.RepositoryService"/>
extension>
6 消费者使用org.talend.repository提供的服务时,只需要调用
/** *//**
* DOC get a implement of IRepositoryService.
*
* @return a implement of IRepositoryService
*/
public IRepositoryService getRepositoryService() ...{
IService service = GlobalServiceRegister.getDefault().getService(IRepositoryService.class);
return (IRepositoryService) service;
}
* DOC get a implement of IRepositoryService.
*
* @return a implement of IRepositoryService
*/
public IRepositoryService getRepositoryService() ...{
IService service = GlobalServiceRegister.getDefault().getService(IRepositoryService.class);
return (IRepositoryService) service;
}
经过这样的改造,所有的插件都只要依赖org.talend.core即可,解决了插件间依赖结构混乱的问题。而且系统具有很好的开放性,很容易的加入其他服务的注册,有利于今后的扩展。
P.S. 一开始想利用Eclipse 的getAdaptable(Class) 机制来实现此功能,虽然也能实现,但是使用者还要自己写Facotry类,增加了扩展的难度,而且getAdaptable(Class)机制也不是用来解决这种问题的。而且自己控制服务的加载可以避免很多额外的麻烦。