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前言
尽管使用了Dubbo许久,但其实对于其了解还是九牛一毛,上个月通读了Netty实战(粗略的了解),突然有了解读Dubbo源码的欲望,时不待我,那就赶紧开始吧。
熟悉Dubbo的朋友,可能都知道其采用全Spring配置方式,透明化接入应用,对应用没有任何API侵入,只需用Spring加载Dubbo的配置即可,Dubbo基于Spring的Schema扩展进行加载。
当然,如果你不想使用Spring配置,而希望通过API的方式进行调用,Dubbo也是支持的,但是官方是不推荐的(原因你猜)。
今天,就跟大家聊一聊Dubbo是如何基于Schema实现的。
准备
具体实现,需要使用到一下几个配置或者是类:
spring.handlers:解析所使用的类
spring.schemas:自定义标签的路径
DubboNamespaceHandler.java:处理器
DubboBeanDefinitionParser.java:解析器
xxxxConfig.java:JavaBean建模
实现
这里我们以dubbo:application做案例介绍
实体类ApplicationConfig.java
位于com.alibaba.dubbo.config包下,截取部分代码:
public class ApplicationConfig extends AbstractConfig { private static final long serialVersionUID = 5508512956753757169L; private String name; private String version; private String owner; private String organization; private String architecture; private String environment; private String compiler; private String logger; private List<RegistryConfig> registries; private MonitorConfig monitor; private Boolean isDefault; public ApplicationConfig() { } public ApplicationConfig(String name) { setName(name); }
编写dubbo.xsd文件
位于META-INF下,截取部分代码:
<?xml version="1.0" encoding="UTF-8" standalone="no"?> <xsd:schema xmlns="http://code.alibabatech.com/schema/dubbo" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:beans="http://www.springframework.org/schema/beans" xmlns:tool="http://www.springframework.org/schema/tool" targetNamespace="http://code.alibabatech.com/schema/dubbo"> <xsd:import namespace="http://www.w3.org/XML/1998/namespace"/> <xsd:import namespace="http://www.springframework.org/schema/beans"/> <xsd:import namespace="http://www.springframework.org/schema/tool"/> <xsd:annotation> <xsd:documentation><![CDATA[ Namespace support for the dubbo services provided by dubbo framework. ]]></xsd:documentation> </xsd:annotation> <xsd:complexType name="applicationType"> <xsd:attribute name="id" type="xsd:ID"> <xsd:annotation> <xsd:documentation><![CDATA[ The unique identifier for a bean. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="name" type="xsd:string" use="required"> <xsd:annotation> <xsd:documentation><![CDATA[ The application name. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="version" type="xsd:string"> <xsd:annotation> <xsd:documentation><![CDATA[ The application version. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="owner" type="xsd:string"> <xsd:annotation> <xsd:documentation><![CDATA[ The application owner name (email prefix). ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="organization" type="xsd:string"> <xsd:annotation> <xsd:documentation><![CDATA[ The organization name. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="architecture" type="xsd:string"> <xsd:annotation> <xsd:documentation><![CDATA[ The architecture. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="environment" type="xsd:string"> <xsd:annotation> <xsd:documentation><![CDATA[ The application environment, eg: dev/test/run ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="compiler" type="xsd:string"> <xsd:annotation> <xsd:documentation><![CDATA[ The java code compiler. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="logger" type="xsd:string"> <xsd:annotation> <xsd:documentation><![CDATA[ The application logger. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="registry" type="xsd:string" use="optional"> <xsd:annotation> <xsd:documentation><![CDATA[ The application registry. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="monitor" type="xsd:string" use="optional"> <xsd:annotation> <xsd:documentation><![CDATA[ The application monitor. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> <xsd:attribute name="default" type="xsd:string" use="optional"> <xsd:annotation> <xsd:documentation><![CDATA[ Is default. ]]></xsd:documentation> </xsd:annotation> </xsd:attribute> </xsd:complexType> <xsd:element name="annotation" type="annotationType"> <xsd:annotation> <xsd:documentation><![CDATA[ The annotation config ]]></xsd:documentation> </xsd:annotation> </xsd:element> </xsd:schema>
关于xsd:schema的各个属性具体含义就不作过多陈述,大家可以参见
http://www.w3school.com.cn/schema/schema_elements_ref.asp
DubboBeanDefinitionParser和DubboNamespaceHandler实现解析
DubboNamespaceHandler会根据schema和节点名找到某个DubboBeanDefinitionParser,然后由DubboBeanDefinitionParser完成具体的解析工作。因此需要分别继承NamespaceHandlerSupport和实现BeanDefinitionParser类。
两个类都位于com.alibaba.dubbo.config.spring.schema包下,以下是DubboNamespaceHandler部分代码:
public class DubboNamespaceHandler extends NamespaceHandlerSupport { static { Version.checkDuplicate(DubboNamespaceHandler.class); } public void init() { registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true)); registerBeanDefinitionParser("module", new DubboBeanDefinitionParser( ModuleConfig.class, true)); registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser( RegistryConfig.class, true)); registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser( MonitorConfig.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 DubboBeanDefinitionParser(AnnotationBean.class, true)); } }
DubboBeanDefinitionParser由于太长了,大家自行查阅源码。
定制spring.handlers和spring.schemas
编码完毕之后,还需要做一些配置工作。我们必须告诉Spring我们准备使用自定义的标签元素,告诉Spring如何解析元素,否则Spring没那么聪明。这里需要2个配置文件,spring.handlers和spring.schemas(位于META-INF下即可),用于告诉Spring自定义标签的文档结构以及解析它的类。两个文件内容分别如下:
spring.handlers:
http\://code.alibabatech.com/schema/dubbo/dubbo.xsd=META-INF/dubbo.xsd
spring.schemas:
http\://code.alibabatech.com/schema/dubbo=com.alibaba.dubbo.config.spring.schema.DubboNamespaceHandler
spring-context-dubbo.xml
好了,最终呈现给大家的就是这个样子:
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:dubbo="http://code.alibabatech.com/schema/dubbo" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd "> <!-- 提供方应用信息,用于计算依赖关系 部分代码--> <dubbo:application name="itstyle" /> </beans>
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