(1). 概述
这一小篇,主要剖析,SI是如何解析service-activator标签的
(2). xml内容如下
<beans:bean id="helloService" class="org.springframework.integration.samples.helloworld.HelloService"/>
<service-activator input-channel="inputChannel"
output-channel="outputChannel"
ref="helloService"
method="sayHello"/>
(3). ServiceActivatorParser继承关系图
org.springframework.beans.factory.xml.AbstractBeanDefinitionParser
org.springframework.integration.config.xml.AbstractConsumerEndpointParser # 在SI的眼里<service-activator>是Consumer
org.springframework.integration.config.xml.AbstractDelegatingConsumerEndpointParser
org.springframework.integration.config.xml.ServiceActivatorParser
(4). AbstractConsumerEndpointParser
public abstract class AbstractConsumerEndpointParser extends AbstractBeanDefinitionParser {
protected static final String REF_ATTRIBUTE = "ref";
protected static final String METHOD_ATTRIBUTE = "method";
protected static final String EXPRESSION_ATTRIBUTE = "expression";
protected abstract BeanDefinitionBuilder parseHandler(Element element, ParserContext parserContext);
protected String getInputChannelAttributeName() {
return "input-channel";
}
@Override
protected final AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
// *****************************************************************************
// 1.委托给子类:AbstractDelegatingConsumerEndpointParser.parseHandler
// 最终返回的BeanDefinitionBuilder包裹着:ServiceActivatorFactoryBean
// 而,ServiceActivatorFactoryBean是一个工厂方法,每次都会创建一个新的:MessageHandler
// 也就是说:<service-activator>标签会解析出一个部信息,转化成:MessageHandler
// *****************************************************************************
BeanDefinitionBuilder handlerBuilder = this.parseHandler(element, parserContext);
// **********************************************************************
// 为ServiceActivatorFactoryBean配置outputChannel的引用
// **********************************************************************
IntegrationNamespaceUtils.setReferenceIfAttributeDefined(handlerBuilder, element, "output-channel");
// 为ServiceActivatorFactoryBean配置order
IntegrationNamespaceUtils.setValueIfAttributeDefined(handlerBuilder, element, "order");
// 配置:request-handler-advice-chain
Element adviceChainElement = DomUtils.getChildElementByTagName(element, IntegrationNamespaceUtils.REQUEST_HANDLER_ADVICE_CHAIN);
IntegrationNamespaceUtils.configureAndSetAdviceChainIfPresent(adviceChainElement, null, handlerBuilder.getRawBeanDefinition(), parserContext);
// handlerBeanDefinition = org.springframework.integration.config.ServiceActivatorFactoryBean
AbstractBeanDefinition handlerBeanDefinition = handlerBuilder.getBeanDefinition();
// input-channel
String inputChannelAttributeName = this.getInputChannelAttributeName();
//true
boolean hasInputChannelAttribute = element.hasAttribute(inputChannelAttributeName);
if (parserContext.isNested()) { // false
String elementDescription = IntegrationNamespaceUtils.createElementDescription(element);
if (hasInputChannelAttribute) {
parserContext.getReaderContext().error("The '" + inputChannelAttributeName
+ "' attribute isn't allowed for a nested (e.g. inside a <chain/>) endpoint element: "
+ elementDescription + ".", element);
}
if (!replyChannelInChainAllowed(element)) {
if (StringUtils.hasText(element.getAttribute("reply-channel"))) {
parserContext.getReaderContext().error("The 'reply-channel' attribute isn't"
+ " allowed for a nested (e.g. inside a <chain/>) outbound gateway element: "
+ elementDescription + ".", element);
}
}
return handlerBeanDefinition;
} else {
if (!hasInputChannelAttribute) { // false
String elementDescription = IntegrationNamespaceUtils.createElementDescription(element);
parserContext.getReaderContext().error("The '" + inputChannelAttributeName
+ "' attribute is required for the top-level endpoint element: "
+ elementDescription + ".", element);
}
}
// ********************************************************************************
// 2. 声明Bean:ConsumerEndpointFactoryBean这是核心类
// ********************************************************************************
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(ConsumerEndpointFactoryBean.class);
// handlerBeanName = org.springframework.integration.config.ServiceActivatorFactoryBean#0
String handlerBeanName = BeanDefinitionReaderUtils.generateBeanName(handlerBeanDefinition, parserContext.getRegistry());
// handlerAlias = null
String[] handlerAlias = IntegrationNamespaceUtils.generateAlias(element);
// ********************************************************************************
// 3. 向Spring容器中注册bean,
// id = org.springframework.integration.config.ServiceActivatorFactoryBean#0
// class = org.springframework.integration.config.ServiceActivatorFactoryBean)
// ********************************************************************************
parserContext.registerBeanComponent(new BeanComponentDefinition(handlerBeanDefinition, handlerBeanName, handlerAlias));
// 为ConsumerEndpointFactoryBean配置:handler = org.springframework.integration.config.ServiceActivatorFactoryBean#0
builder.addPropertyReference("handler", handlerBeanName);
// inputChannel
String inputChannelName = element.getAttribute(inputChannelAttributeName);
// 判断bean定义(inputChannel)在spring容器中是否存在.
if (!parserContext.getRegistry().containsBeanDefinition(inputChannelName)) { // false
// ntegrationContextUtils.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME = $autoCreateChannelCandidates
if (parserContext.getRegistry().containsBeanDefinition(IntegrationContextUtils.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME)) {
BeanDefinition channelRegistry = parserContext.getRegistry().getBeanDefinition(IntegrationContextUtils.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
ConstructorArgumentValues caValues = channelRegistry.getConstructorArgumentValues();
ValueHolder vh = caValues.getArgumentValue(0, Collection.class);
if (vh == null) { //although it should never happen if it does we can fix it
caValues.addIndexedArgumentValue(0, new ManagedSet<String>());
}
@SuppressWarnings("unchecked")
Collection<String> channelCandidateNames = (Collection<String>) caValues.getArgumentValue(0, Collection.class).getValue();
channelCandidateNames.add(inputChannelName);
} else {
parserContext.getReaderContext().error("Failed to locate '" +
IntegrationContextUtils.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME + "'", parserContext.getRegistry());
}
}
IntegrationNamespaceUtils.checkAndConfigureFixedSubscriberChannel(element, parserContext, inputChannelName,handlerBeanName);
// 为ConsumerEndpointFactoryBean配置:inputChannelName=inputChannel
builder.addPropertyValue("inputChannelName", inputChannelName);
// 针对子节点<poller/>处理
List<Element> pollerElementList = DomUtils.getChildElementsByTagName(element, "poller");
if (!CollectionUtils.isEmpty(pollerElementList)) {
if (pollerElementList.size() != 1) {
parserContext.getReaderContext().error(
"at most one poller element may be configured for an endpoint", element);
}
IntegrationNamespaceUtils.configurePollerMetadata(pollerElementList.get(0), builder, parserContext);
}
// 为ConsumerEndpointFactoryBean配置:autoStartup
IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, IntegrationNamespaceUtils.AUTO_STARTUP);
// 为ConsumerEndpointFactoryBean配置:phase
IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, IntegrationNamespaceUtils.PHASE);
String role = element.getAttribute(IntegrationNamespaceUtils.ROLE);
if (StringUtils.hasText(role)) {
if (!StringUtils.hasText(element.getAttribute(ID_ATTRIBUTE))) {
parserContext.getReaderContext().error("When using 'role', 'id' is required", element);
}
IntegrationNamespaceUtils.putLifecycleInRole(role, element.getAttribute(ID_ATTRIBUTE), parserContext);
}
// 获得ConsumerEndpointFactoryBean定义信息
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
// 解析出bean名称(org.springframework.integration.config.ConsumerEndpointFactoryBean#0)
String beanName = this.resolveId(element, beanDefinition, parserContext);
// ********************************************************************************
// 向Spring容器中,注册Bean
// id = org.springframework.integration.config.ConsumerEndpointFactoryBean#0
// class = org.springframework.integration.config.ConsumerEndpointFactoryBean
// ********************************************************************************
parserContext.registerBeanComponent(new BeanComponentDefinition(beanDefinition, beanName));
return null;
} // end parseInternal
}
(5). AbstractDelegatingConsumerEndpointParser
// <service-activator input-channel="inputChannel" output-channel="outputChannel" ref="helloService" method="sayHello"/>
protected final BeanDefinitionBuilder parseHandler(Element element, ParserContext parserContext) {
Object source = parserContext.extractSource(element);
// 定义Bean:ServiceActivatorFactoryBean
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(this.getFactoryBeanClassName());
// 解析子节点 <service-activator> <bean> ... </bean> </service-activator>
BeanComponentDefinition innerDefinition = IntegrationNamespaceUtils.parseInnerHandlerDefinition(element, parserContext);
// ref
String ref = element.getAttribute(REF_ATTRIBUTE);
// expression
String expression = element.getAttribute(EXPRESSION_ATTRIBUTE);
boolean hasRef = StringUtils.hasText(ref);
boolean hasExpression = StringUtils.hasText(expression);
// 解析子节点 <service-activator> <script> ... </script> </service-activator>
Element scriptElement = DomUtils.getChildElementByTagName(element, "script");
// 解析子节点 <service-activator> <expression> ... </expression> </service-activator>
Element expressionElement = DomUtils.getChildElementByTagName(element, "expression");
// <bean>与ref/expression是排它的,否则,会抛出异常
if (innerDefinition != null) {
if (hasRef || hasExpression || expressionElement != null) {
parserContext.getReaderContext().error("Neither 'ref' nor 'expression' are permitted when an inner bean (<bean/>) is configured on element " + IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
return null;
}
builder.addPropertyValue("targetObject", innerDefinition);
} else if (scriptElement != null) {
// <script>与ref/expression是排它的,否则,会抛出异常
if (hasRef || hasExpression || expressionElement != null) {
parserContext.getReaderContext().error("Neither 'ref' nor 'expression' are permitted when an inner script element is configured on element " + IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
return null;
}
BeanDefinition scriptBeanDefinition = parserContext.getDelegate().parseCustomElement(scriptElement, builder.getBeanDefinition());
builder.addPropertyValue("targetObject", scriptBeanDefinition);
} else if (expressionElement != null) {
// <expression>与ref/expression是排它的,否则,会抛出异常
if (hasRef || hasExpression) {
parserContext.getReaderContext().error(
"Neither 'ref' nor 'expression' are permitted when an inner 'expression' element is configured on element " + IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
return null;
}
BeanDefinitionBuilder dynamicExpressionBuilder = BeanDefinitionBuilder.genericBeanDefinition(
DynamicExpression.class);
String key = expressionElement.getAttribute("key");
String expressionSourceReference = expressionElement.getAttribute("source");
dynamicExpressionBuilder.addConstructorArgValue(key);
dynamicExpressionBuilder.addConstructorArgReference(expressionSourceReference);
builder.addPropertyValue("expression", dynamicExpressionBuilder.getBeanDefinition());
} else if (hasRef && hasExpression) {
parserContext.getReaderContext().error("Only one of 'ref' or 'expression' is permitted, not both, on element " + IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
return null;
} else if (hasRef) {
builder.addPropertyReference("targetObject", ref);
} else if (hasExpression) {
builder.addPropertyValue("expressionString", expression);
} else if (!this.hasDefaultOption()) {
parserContext.getReaderContext().error("Exactly one of the 'ref' attribute, 'expression' attribute, " +
"or inner bean (<bean/>) definition is required for element " +
IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
return null;
}
// 解析属性:method
String method = element.getAttribute(METHOD_ATTRIBUTE);
if (StringUtils.hasText(method)) {
if (hasExpression || expressionElement != null) {
parserContext.getReaderContext().error("A 'method' attribute is not permitted when configuring an 'expression' on element " + IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
}
if (hasRef || innerDefinition != null) {
builder.addPropertyValue("targetMethodName", method);
} else {
parserContext.getReaderContext().error("A 'method' attribute is only permitted when either " + "a 'ref' or inner-bean definition is provided on element " + IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
}
}
IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, "requires-reply");
IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, "send-timeout");
this.postProcess(builder, element, parserContext);
return builder;
}
(6). ServiceActivatorParser
public class ServiceActivatorParser extends AbstractDelegatingConsumerEndpointParser {
@Override
String getFactoryBeanClassName() {
return ServiceActivatorFactoryBean.class.getName();
}
@Override
boolean hasDefaultOption() {
return false;
}
@Override
void postProcess(BeanDefinitionBuilder builder, Element element, ParserContext parserContext) {
IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, "async");
}
}
(7). 总结
ServiceActivatorParser的主要目的是把XML解析成业务模型,需要注意的是,它会向Spring容器中,注册两个Bean(ServiceActivatorFactoryBean和ConsumerEndpointFactoryBean).
- ConsumerEndpointFactoryBean负责从input-channel里读取数据来着的,然后,向output-channel输出数据.
- ServiceActivatorFactoryBean工厂,会创建出ServiceActivatingHandler(output-channel)类,它实际是上:MessageHandler的实现类(主要负责接收消息,并处理消息).
