标签解析
dubbo的jar包依赖里面，可以看到两个文件：
spring.schemas
http\://dubbo.apache.org/schema/dubbo/dubbo.xsd=META-INF/dubbo.xsd
http\://code.alibabatech.com/schema/dubbo/dubbo.xsd=META-INF/compat/dubbo.xsd
spring.handlers
http\://dubbo.apache.org/schema/dubbo=org.apache.dubbo.config.spring.schema.DubboNamespaceHandler <!--解析标签的类-->
http\://code.alibabatech.com/schema/dubbo=org.apache.dubbo.config.spring.schema.DubboNamespaceHandler
DubboNamespaceHandler.java
@Override
public void init() {
//这里是专门解析<dubbo:application />标签的, ApplicationConfig.class里面包含了标签里面所有的属性定义。下面的标签解析也是一样的意思
registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
registerBeanDefinitionParser("config-center", new DubboBeanDefinitionParser(ConfigCenterBean.class, true));
registerBeanDefinitionParser("metadata-report", new DubboBeanDefinitionParser(MetadataReportConfig.class, true));
registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
registerBeanDefinitionParser("metrics", new DubboBeanDefinitionParser(MetricsConfig.class, true));
registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
registerBeanDefinitionParser("annotation", new AnnotationBeanDefinitionParser());
}
DubboBeanDefinitionParser.java
/**
* Dubbo标签解析器构造器
* @param beanClass 标签属性读出值所封装的类型
* @param required 指定id属性在当前标签中是否是必须的
*/
public DubboBeanDefinitionParser(Class<?> beanClass, boolean required) {
this.beanClass = beanClass;
this.required = required;
}
/**
* 解析指定标签
* @param element 要解析的标签元素
* @param parserContext 解析上下文，其中包含了当前配置文件中所有其它标签的解析信息
* @param beanClass 标签属性读出值所封装的类型，是一种物理性封装
* @param required 指定id属性在当前标签中是否是必须的
* @return 解析对象。即当前标签最终解析出的“逻辑实例”的Bean定义器实例
*/
@SuppressWarnings("unchecked")
private static BeanDefinition parse(Element element, ParserContext parserContext, Class<?> beanClass, boolean required) {
// ========================== 1 创建并初始化解析对象 ================
RootBeanDefinition beanDefinition = new RootBeanDefinition();
beanDefinition.setBeanClass(beanClass);
beanDefinition.setLazyInit(false);//是否开启懒加载机制
// ========================== 2 解决id问题：为空的问题 与 重复的问题 ================
// 获取当前标签中的id属性
String id = element.getAttribute("id");
if (StringUtils.isEmpty(id) && required) {
// 获取当前标签的name属性
String generatedBeanName = element.getAttribute("name");
if (StringUtils.isEmpty(generatedBeanName)) {
// 若当前解析的标签为<dubbo:protocol/>，则name属性值设置为dubbo
// 否则，取interface属性值
if (ProtocolConfig.class.equals(beanClass)) {
generatedBeanName = "dubbo";
} else {
generatedBeanName = element.getAttribute("interface");
}
}
// 若到这里name属性仍为空，则name属性值取beanClass的类名
if (StringUtils.isEmpty(generatedBeanName)) {
generatedBeanName = beanClass.getName();
}
// 代码走到这里，name属性一定不空，即id属性一定不空
id = generatedBeanName;
int counter = 2;
// 遍历解析对象上下文，判断生成的id是否发生重复。
// 若重复，则在其名称后添加一个数字，走到不重复为止
while (parserContext.getRegistry().containsBeanDefinition(id)) {
id = generatedBeanName + (counter++);
}
} // end-if
// ========================== 3 将id属性写入到解析对象 ================
if (id != null && id.length() > 0) {
// 若用户在标签中自己指定的id属性在解析上下文中重复，则直接抛出异常
if (parserContext.getRegistry().containsBeanDefinition(id)) {
throw new IllegalStateException("Duplicate spring bean id " + id);
}
// 将 id-解析对象 写入到解析上下文
parserContext.getRegistry().registerBeanDefinition(id, beanDefinition);
// 将id属性写入到解析对象中
beanDefinition.getPropertyValues().addPropertyValue("id", id);
}
// ========================== 4 对特殊标签的特殊处理 ================
// 处理<dubbo:protocol/>标签
if (ProtocolConfig.class.equals(beanClass)) {
for (String name : parserContext.getRegistry().getBeanDefinitionNames()) {
BeanDefinition definition = parserContext.getRegistry().getBeanDefinition(name);
PropertyValue property = definition.getPropertyValues().getPropertyValue("protocol");
if (property != null) {
Object value = property.getValue();
if (value instanceof ProtocolConfig && id.equals(((ProtocolConfig) value).getName())) {
definition.getPropertyValues().addPropertyValue("protocol", new RuntimeBeanReference(id));
}
}
}
// 处理<dubbo:service/>标签
} else if (ServiceBean.class.equals(beanClass)) {
String className = element.getAttribute("class");
if (className != null && className.length() > 0) {
RootBeanDefinition classDefinition = new RootBeanDefinition();
classDefinition.setBeanClass(ReflectUtils.forName(className));
classDefinition.setLazyInit(false);
parseProperties(element.getChildNodes(), classDefinition);
beanDefinition.getPropertyValues().addPropertyValue("ref", new BeanDefinitionHolder(classDefinition, id + "Impl"));
}
// 处理<dubbo:provider/>标签
} else if (ProviderConfig.class.equals(beanClass)) {
// 嵌套解析<dubbo:servie/>与<dubbo:provider/>标签
parseNested(element, parserContext, ServiceBean.class, true, "service", "provider", id, beanDefinition);
// 处理<dubbo:consumer/>标签
} else if (ConsumerConfig.class.equals(beanClass)) {
// 嵌套解析<dubbo:reference/>与<dubbo:consumer/>标签
parseNested(element, parserContext, ReferenceBean.class, false, "reference", "consumer", id, beanDefinition);
}
// ========================== 5 对所有标签的普适性处理 ================
Set<String> props = new HashSet<>();
ManagedMap parameters = null;
for (Method setter : beanClass.getMethods()) {
String name = setter.getName();
if (name.length() > 3 && name.startsWith("set")
&& Modifier.isPublic(setter.getModifiers())
&& setter.getParameterTypes().length == 1) {
Class<?> type = setter.getParameterTypes()[0];
String beanProperty = name.substring(3, 4).toLowerCase() + name.substring(4);
String property = StringUtils.camelToSplitName(beanProperty, "-");
props.add(property);
// check the setter/getter whether match
Method getter = null;
try {
getter = beanClass.getMethod("get" + name.substring(3), new Class<?>[0]);
} catch (NoSuchMethodException e) {
try {
getter = beanClass.getMethod("is" + name.substring(3), new Class<?>[0]);
} catch (NoSuchMethodException e2) {
// ignore, there is no need any log here since some class implement the interface: EnvironmentAware,
// ApplicationAware, etc. They only have setter method, otherwise will cause the error log during application start up.
}
}
if (getter == null
|| !Modifier.isPublic(getter.getModifiers())
|| !type.equals(getter.getReturnType())) {
continue;
}
if ("parameters".equals(property)) {
parameters = parseParameters(element.getChildNodes(), beanDefinition);
} else if ("methods".equals(property)) {
parseMethods(id, element.getChildNodes(), beanDefinition, parserContext);
} else if ("arguments".equals(property)) {
parseArguments(id, element.getChildNodes(), beanDefinition, parserContext);
} else {
String value = element.getAttribute(property);
if (value != null) {
value = value.trim();
if (value.length() > 0) {
if ("registry".equals(property) && RegistryConfig.NO_AVAILABLE.equalsIgnoreCase(value)) {
RegistryConfig registryConfig = new RegistryConfig();
registryConfig.setAddress(RegistryConfig.NO_AVAILABLE);
beanDefinition.getPropertyValues().addPropertyValue(beanProperty, registryConfig);
} else if ("provider".equals(property) || "registry".equals(property) || ("protocol".equals(property) && ServiceBean.class.equals(beanClass))) {
/**
* For 'provider' 'protocol' 'registry', keep literal value (should be id/name) and set the value to 'registryIds' 'providerIds' protocolIds'
* The following process should make sure each id refers to the corresponding instance, here's how to find the instance for different use cases:
* 1. Spring, check existing bean by id, see{@link ServiceBean#afterPropertiesSet()}; then try to use id to find configs defined in remote Config Center
* 2. API, directly use id to find configs defined in remote Config Center; if all config instances are defined locally, please use {@link org.apache.dubbo.config.ServiceConfig#setRegistries(List)}
*/
beanDefinition.getPropertyValues().addPropertyValue(beanProperty + "Ids", value);
} else {
Object reference;
if (isPrimitive(type)) {
if ("async".equals(property) && "false".equals(value)
|| "timeout".equals(property) && "0".equals(value)
|| "delay".equals(property) && "0".equals(value)
|| "version".equals(property) && "0.0.0".equals(value)
|| "stat".equals(property) && "-1".equals(value)
|| "reliable".equals(property) && "false".equals(value)) {
// backward compatibility for the default value in old version's xsd
value = null;
}
reference = value;
} else if ("onreturn".equals(property)) {
int index = value.lastIndexOf(".");
String returnRef = value.substring(0, index);
String returnMethod = value.substring(index + 1);
reference = new RuntimeBeanReference(returnRef);
beanDefinition.getPropertyValues().addPropertyValue("onreturnMethod", returnMethod);
} else if ("onthrow".equals(property)) {
int index = value.lastIndexOf(".");
String throwRef = value.substring(0, index);
String throwMethod = value.substring(index + 1);
reference = new RuntimeBeanReference(throwRef);
beanDefinition.getPropertyValues().addPropertyValue("onthrowMethod", throwMethod);
} else if ("oninvoke".equals(property)) {
int index = value.lastIndexOf(".");
String invokeRef = value.substring(0, index);
String invokeRefMethod = value.substring(index + 1);
reference = new RuntimeBeanReference(invokeRef);
beanDefinition.getPropertyValues().addPropertyValue("oninvokeMethod", invokeRefMethod);
} else {
if ("ref".equals(property) && parserContext.getRegistry().containsBeanDefinition(value)) {
BeanDefinition refBean = parserContext.getRegistry().getBeanDefinition(value);
if (!refBean.isSingleton()) {
throw new IllegalStateException("The exported service ref " + value + " must be singleton! Please set the " + value + " bean scope to singleton, eg: <bean id=\"" + value + "\" scope=\"singleton\" ...>");
}
}
reference = new RuntimeBeanReference(value);
}
beanDefinition.getPropertyValues().addPropertyValue(beanProperty, reference);
}
}
}
}
}
}
NamedNodeMap attributes = element.getAttributes();
int len = attributes.getLength();
for (int i = 0; i < len; i++) {
Node node = attributes.item(i);
String name = node.getLocalName();
if (!props.contains(name)) {
if (parameters == null) {
parameters = new ManagedMap();
}
String value = node.getNodeValue();
parameters.put(name, new TypedStringValue(value, String.class));
}
}
if (parameters != null) {
beanDefinition.getPropertyValues().addPropertyValue("parameters", parameters);
}
return beanDefinition;
}
重要接口
Invocation.java
//封装RPC远程调用的信息
public interface Invocation {
/**调用方法名称
* get method name.
*
* @return method name.
* @serial
*/
String getMethodName();
/**参数类型(行参)
* get parameter types.
*
* @return parameter types.
* @serial
*/
Class<?>[] getParameterTypes();
/** 实参
* get arguments.
*
* @return arguments.
* @serial
*/
Object[] getArguments();
/**
* get attachments(附件).
*
* @return attachments.
* @serial
*/
Map<String, String> getAttachments();
void setAttachment(String key, String value);
void setAttachmentIfAbsent(String key, String value);
/**
* get attachment by key.
*
* @return attachment value.
* @serial
*/
String getAttachment(String key);
/**
* get attachment by key with default value.
*
* @return attachment value.
* @serial
*/
String getAttachment(String key, String defaultValue);
/** 封装了调用接口
* get the invoker in current context.
*
* @return invoker.
* @transient
*/
Invoker<?> getInvoker();
}
Invoker.java
/** 若继承自Node，故可以通过getUrl()方法获取到URL，即，Invoker可以作为Adaptive方法的参数
* 是提供者 provider 的代理对象，在代码中就代表提供者。特别是在消费者进行远程调
* 用时，其通过服务路由、负载均衡、集群容错等机制要查找的就是 Invoker。找到了其需要
* 的 Invoker 实例就可以进行远程调用了。
* */
public interface Invoker<T> extends Node {
/**
* get service interface.
* 调用的接口(服务名称)
* @return service interface.
*/
Class<T> getInterface();
/**
* invoke.
* 执行调用并返回结果
* @param invocation
* @return result
* @throws RpcException
*/
Result invoke(Invocation invocation) throws RpcException;
}
Exporter.java
/**
* 服务暴露对象。其包含一个很重要的方法 getInvoker()，用于获取当前服务暴露实例所
* 包含的远程调用实例 Invoker，即可以进行的远程调用。
*/
public interface Exporter<T> {
/**
* get invoker.
*
* @return invoker
*/
Invoker<T> getInvoker();
/**
* unexport. 取消暴露
* <p>
* <code>
* getInvoker().destroy();
* </code>
*/
void unexport();
}
Directory.java
// Directory 中包含一个很重要的方法 list()
// 其返回结果为一个 List<Invoker>。
// 可以将Directory理解为，提供某一具体服务的Invoker列表
public interface Directory<T> extends Node {
/**
* get service type.
*
* @return service type.
*/
Class<T> getInterface();
/**
* list invokers.
*
* @return invokers
*/
List<Invoker<T>> list(Invocation invocation) throws RpcException;
}
