JBPM4配置文件解析

xml -> Binding -> Descriptor -> WireDefinition -> WireContext

xml     :JBPM配置文件，主配置文件jbpm.cfg.xml；
binding :解析JBPM配置文件中的标签，解析后生成Descritor对象；每个bind对象和xml中的标签一一对应；可以参看WireParser类中对bind的解析和初始化，bindings定义文件jbpm.wire.bindings.xml；
descritor:JBPM配置文件的描述对象，暂且没有实例化，但是有创建和初始化的方法；
wireDefinition:description对象的集合，用Map对象实现；
wireContext:解析上下文，包含wireDefine对象，封装了descrition的创建方法，相当于descritor的代理；


1、jbpm.tx.hibernate.cfg.xml中有如下定义：
    <command-service name="txRequiredCommandService">
      <skip-interceptor />
      <retry-interceptor />
      <environment-interceptor />
      <standard-transaction-interceptor />
    </command-service>

    <command-service name="newTxRequiredCommandService">
      <retry-interceptor />
      <environment-interceptor policy="requiresNew" />
      <standard-transaction-interceptor />
    </command-service>

2、Binding对象用于解析xml：

public class CommandServiceBinding extends WireDescriptorBinding {

  public CommandServiceBinding() {
    super("command-service");
  }
 
  protected CommandServiceBinding(String tagName) {
    super(tagName);
  }

  public Object parse(Element element, Parse parse, Parser parser) {
    CommandServiceDescriptor commandServiceDescriptor = new CommandServiceDescriptor();

    CommandService commandService = getCommandService(element, parse, parser);
    commandServiceDescriptor.setCommandService(commandService);
   
    List<Element> interceptorElements = XmlUtil.elements(element);
    for (Element interceptorElement : interceptorElements) {
      Descriptor interceptorDescriptor = (Descriptor) parser.parseElement(interceptorElement, parse, WireParser.CATEGORY_INTERCEPTOR);
      commandServiceDescriptor.addInterceptorDescriptor(interceptorDescriptor);
    }

    return commandServiceDescriptor;
  }

  protected CommandService getCommandService(Element element, Parse parse, Parser parser) {
    Boolean async = XmlUtil.attributeBoolean(element, "async", parse);
    if (Boolean.TRUE.equals(async)) {
      AsyncCommandService asyncCommandService = new AsyncCommandService();

      Boolean propagateUserId = XmlUtil.attributeBoolean(element, "propagate-auth", parse);
      if (propagateUserId!=null) {
        asyncCommandService.setPropagateUserId(propagateUserId);
      }
      return asyncCommandService;
    }
   
    return new DefaultCommandService();
  }
}

3、Descriptor的代码：
public class CommandServiceDescriptor extends AbstractDescriptor {

  private static final long serialVersionUID = 1L;
 
  CommandService commandService;
  List<Descriptor> interceptorDescriptors;

  public Object construct(WireContext wireContext) {
    CommandService interceptedCommandService = commandService;
    if (interceptorDescriptors!=null) {
      for (int i=interceptorDescriptors.size()-1 ; i>=0; i--) {
        Descriptor descriptor = interceptorDescriptors.get(i);
        Interceptor interceptor = (Interceptor) descriptor.construct(wireContext);
        interceptor.setNext(interceptedCommandService);
        interceptedCommandService = interceptor;
      }
    }
    return interceptedCommandService;
  }
 
  public Class< ? > getType(WireDefinition wireDefinition) {
    return (name==null ? CommandService.class : null);
  }
 
  public void addInterceptorDescriptor(Descriptor descriptor) {
    if (interceptorDescriptors==null) {
      interceptorDescriptors = new ArrayList<Descriptor>();
    }
    interceptorDescriptors.add(descriptor);
  }
 
  public void setCommandService(CommandService commandService) {
    this.commandService = commandService;
  }
}