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配置文件中的標籤，解析後生成Descritor對象；每個bind對象和xml中的標籤一一對應；可以參看WireParser類中對bind的解析和初始化，bindings定義文件jbpm.wire.bindings.xml；
descritor:JBPM配置文件的描述對象，暫且沒有實例化，但是有創建和初始化的方法；
wireDefinition:description對象的集合，用Map對象實現；
wireContext:解析上下文，包含wireDefine對象，封裝了descrition的創建方法，相當於descritor的代理；


1、jbpm.tx.hibernate.cfg.xml中有如下定義：
<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對象用於解析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的代碼：
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;
}
}