spring 自定义解析类

Posted 2021-01-30 R.Z

• 设计配置属性和JavaBean
• 编写XSD文件
• 编写NamespaceHandler和BeanDefinitionParser完成解析工作
• 编写spring.handlers和spring.schemas串联起所有部件
• 在Bean文件中应用

 

 

会用到NamespaceHandler和BeanDefinitionParser这两个概念。具体说来NamespaceHandler会根据schema和节点名找到某个BeanDefinitionParser，然后由BeanDefinitionParser完成具体的解析工作。因此需要分别完成NamespaceHandler和BeanDefinitionParser的实现类，Spring提供了默认实现类NamespaceHandlerSupport和AbstractSingleBeanDefinitionParser，简单的方式就是去继承这两个类。
先看个示例吧。spring  scheduling命名空间下的   scheduled-tasks 解析。

/**
 * Parser for the ‘scheduled-tasks‘ element of the scheduling namespace.
 *
 * @author Mark Fisher
 * @author Chris Beams
 * @since 3.0
 */

public class ScheduledTasksBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {

   private static final String ELEMENT_SCHEDULED = "scheduled";

   private static final long ZERO_INITIAL_DELAY = 0;

//解析方法
@Override
protected void doParse(Element element, ParserContext parserContext, BeanDefinitionBuilder builder) {
   builder.setLazyInit(false); // lazy scheduled tasks are a contradiction in terms -> force to false
   ManagedList<RuntimeBeanReference> cronTaskList = new ManagedList<>();
   ManagedList<RuntimeBeanReference> fixedDelayTaskList = new ManagedList<>();
   ManagedList<RuntimeBeanReference> fixedRateTaskList = new ManagedList<>();
   ManagedList<RuntimeBeanReference> triggerTaskList = new ManagedList<>();
   NodeList childNodes = element.getChildNodes();
   for (int i = 0; i < childNodes.getLength(); i++) {
      Node child = childNodes.item(i);
      if (!isScheduledElement(child, parserContext)) {
         continue;
      }
      Element taskElement = (Element) child;
      String ref = taskElement.getAttribute("ref");
      String method = taskElement.getAttribute("method");

      // Check that ‘ref‘ and ‘method‘ are specified
      if (!StringUtils.hasText(ref) || !StringUtils.hasText(method)) {
         parserContext.getReaderContext().error("Both ‘ref‘ and ‘method‘ are required", taskElement);
         // Continue with the possible next task element
         continue;
      }

      String cronAttribute = taskElement.getAttribute("cron");
      String fixedDelayAttribute = taskElement.getAttribute("fixed-delay");
      String fixedRateAttribute = taskElement.getAttribute("fixed-rate");
      String triggerAttribute = taskElement.getAttribute("trigger");
      String initialDelayAttribute = taskElement.getAttribute("initial-delay");

      boolean hasCronAttribute = StringUtils.hasText(cronAttribute);
      boolean hasFixedDelayAttribute = StringUtils.hasText(fixedDelayAttribute);
      boolean hasFixedRateAttribute = StringUtils.hasText(fixedRateAttribute);
      boolean hasTriggerAttribute = StringUtils.hasText(triggerAttribute);
      boolean hasInitialDelayAttribute = StringUtils.hasText(initialDelayAttribute);

      if (!(hasCronAttribute || hasFixedDelayAttribute || hasFixedRateAttribute || hasTriggerAttribute)) {
         parserContext.getReaderContext().error(
               "one of the ‘cron‘, ‘fixed-delay‘, ‘fixed-rate‘, or ‘trigger‘ attributes is required", taskElement);
         continue; // with the possible next task element
      }

      if (hasInitialDelayAttribute && (hasCronAttribute || hasTriggerAttribute)) {
         parserContext.getReaderContext().error(
               "the ‘initial-delay‘ attribute may not be used with cron and trigger tasks", taskElement);
         continue; // with the possible next task element
      }

      String runnableName =
            runnableReference(ref, method, taskElement, parserContext).getBeanName();

      if (hasFixedDelayAttribute) {
         fixedDelayTaskList.add(intervalTaskReference(runnableName,
               initialDelayAttribute, fixedDelayAttribute, taskElement, parserContext));
      }
      if (hasFixedRateAttribute) {
         fixedRateTaskList.add(intervalTaskReference(runnableName,
               initialDelayAttribute, fixedRateAttribute, taskElement, parserContext));
      }
      if (hasCronAttribute) {
         cronTaskList.add(cronTaskReference(runnableName, cronAttribute,
               taskElement, parserContext));
      }
      if (hasTriggerAttribute) {
         String triggerName = new RuntimeBeanReference(triggerAttribute).getBeanName();
         triggerTaskList.add(triggerTaskReference(runnableName, triggerName,
               taskElement, parserContext));
      }
   }
   String schedulerRef = element.getAttribute("scheduler");
   if (StringUtils.hasText(schedulerRef)) {
      builder.addPropertyReference("taskScheduler", schedulerRef);
   }
   builder.addPropertyValue("cronTasksList", cronTaskList);
   builder.addPropertyValue("fixedDelayTasksList", fixedDelayTaskList);
   builder.addPropertyValue("fixedRateTasksList", fixedRateTaskList);
   builder.addPropertyValue("triggerTasksList", triggerTaskList);
}

以上就是默认的xml解析

注解解析的类是  AnnotationDrivenBeanDefinitionParser

/**
 * Parser for the ‘annotation-driven‘ element of the ‘task‘ namespace.
 *
 * @author Mark Fisher
 * @author Juergen Hoeller
 * @author Ramnivas Laddad
 * @author Chris Beams
 * @author Stephane Nicoll
 * @since 3.0
 */
public class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {

   private static final String ASYNC_EXECUTION_ASPECT_CLASS_NAME =
         "org.springframework.scheduling.aspectj.AnnotationAsyncExecutionAspect";



//解析方法

@Override
@Nullable
public BeanDefinition parse(Element element, ParserContext parserContext) {
   Object source = parserContext.extractSource(element);

   // Register component for the surrounding <task:annotation-driven> element.
   CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);
   parserContext.pushContainingComponent(compDefinition);

   // Nest the concrete post-processor bean in the surrounding component.
   BeanDefinitionRegistry registry = parserContext.getRegistry();

   String mode = element.getAttribute("mode");
   if ("aspectj".equals(mode)) {
      // mode="aspectj"
      registerAsyncExecutionAspect(element, parserContext);
   }
   else {
      // mode="proxy"
      if (registry.containsBeanDefinition(TaskManagementConfigUtils.ASYNC_ANNOTATION_PROCESSOR_BEAN_NAME)) {
         parserContext.getReaderContext().error(
               "Only one AsyncAnnotationBeanPostProcessor may exist within the context.", source);
      }
      else {
         BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(
               "org.springframework.scheduling.annotation.AsyncAnnotationBeanPostProcessor");
         builder.getRawBeanDefinition().setSource(source);
         String executor = element.getAttribute("executor");
         if (StringUtils.hasText(executor)) {
            builder.addPropertyReference("executor", executor);
         }
         String exceptionHandler = element.getAttribute("exception-handler");
         if (StringUtils.hasText(exceptionHandler)) {
            builder.addPropertyReference("exceptionHandler", exceptionHandler);
         }
         if (Boolean.valueOf(element.getAttribute(AopNamespaceUtils.PROXY_TARGET_CLASS_ATTRIBUTE))) {
            builder.addPropertyValue("proxyTargetClass", true);
         }
         registerPostProcessor(parserContext, builder, TaskManagementConfigUtils.ASYNC_ANNOTATION_PROCESSOR_BEAN_NAME);
      }
   }

   if (registry.containsBeanDefinition(TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
      parserContext.getReaderContext().error(
            "Only one ScheduledAnnotationBeanPostProcessor may exist within the context.", source);
   }
   else {
      BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(
            "org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor");
      builder.getRawBeanDefinition().setSource(source);
      String scheduler = element.getAttribute("scheduler");
      if (StringUtils.hasText(scheduler)) {
         builder.addPropertyReference("scheduler", scheduler);
      }
      registerPostProcessor(parserContext, builder, TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME);
   }

   // Finally register the composite component.
   parserContext.popAndRegisterContainingComponent();

   return null;
}