Dubbo-基于Spring开发（自定义标签及解析）

╰半橙微兮° 2022-01-29 01:25 215阅读 0赞

**首先dubbo实现Spring注入bean的方式思路如下：**

**Spring的自定义标签解析是通过，写一个继承自NamespaceHandlerSupport的类，并实现init()方法，在init()方法中，去注册解析器。然后在解析xml时，通过约定的key去Map中拿到相应的解析器进行解析。大致思路就是这样。对应的设计模式为：接口-适配器模式、抽象工厂模式、策略模式及模板方法模式**

## 一、Dubbo配置 ##

一般在项目中如果存在XML配置的我们会看到类似于这样：

<dubbo:application name="dubbo_source" id="aaa-bbb" logger="slf4j"/>
    
    <dubbo:registry id="dubbo_source-registry" address="${dubbo.registries.server.address}" protocol="${dubbo.registries.protocol}" group="${dubbo.registries.group}"/>
    
    <dubbo:protocol id="protocol" name="dubbo" port="${dubbo.protocol.port}" threadpool="cached" threads="512" />
    <dubbo:provider timeout="50000" retries="5" loadbalance="roundrobin" cluster="failover" registry="dubbo_source-registry" />
    
    
    <dubbo:service interface="com.aaa.bbb.ccc.ddd.api.QueryXXXInfoApi" ref="queryXXXInfoApi"/>

上面是Dubbo中的配置文件。

1.  我们看一下 Dubbo的META-INF下的dubbo.xsd文件。

比如说：dubbo:application，所以我们在xsd文件中应该有如下的代码

<xsd:element name="application" type="applicationType">
                  <xsd:annotation>
                <xsd:documentation><![CDATA[ The application config ]]></xsd:documentation>
            </xsd:annotation>
        </xsd:element>

这是声明一个**application**标签 类型为**applicationType**

<xsd:complexType name="applicationType">
            <xsd:sequence minOccurs="0" maxOccurs="unbounded">
                <xsd:element ref="parameter" minOccurs="0" maxOccurs="unbounded"/>
            </xsd:sequence>
            <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>

上面就是applicationType类型的定义 里面有相应的属性。如：id、name、logger。

我们在完成相应标签的编写后需要做下面的事情：

## 二.配置文件： ##

完成了xsd文件编写后，还需要让该文件生效，就需要在项目的resource/META-INF包里面配置2个文件spring.handlers和spring.schemas

![20190520171547757.png][]

### 2.1 spring.schemas ###

改配置文件主要是用一个url来映射我们第一步配置好的文件，形式如下：

http\://code.alibabatech.com/schema/dubbo/dubbo.xsd=META-INF/dubbo.xsd

这样，就可以在Spring的xml配置文件中加入spring.schemas的url，省略掉其他的，在<beans>标签中增加如下信息

完成这步以后，就可以在xml中写自定义标签了，例如自定义标签的namespace为dubbo,

<?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"
           default-autowire="byName">
    
        
        <dubbo:application name="dubbo-service" id="dubbo-service" logger="slf4j"/>
        
        <dubbo:registry id="dubbo-service-registry" address="${dubbo.registries.server.address}" protocol="${dubbo.registries.protocol}" group="${dubbo.registries.group}"/>
        
        <dubbo:protocol id="protocol" name="dubbo" port="${dubbo.protocol.port}" threadpool="cached" threads="512" />
        <dubbo:provider timeout="50000" retries="5" loadbalance="roundrobin" cluster="failover" registry="dubbo-service-registry" />
    	<dubbo:service interface="com.aaa.bbb.ccc.ddd.api.QueryXXXInfoApi" ref="queryXXXInfoApi"/>
         
    </beans>

### 2.2 spring.handlers ###

这个配置文件用来配置解析我们dubbo标签,然后生成一些BeanDefinition进行注册。例如：

http\://code.alibabatech.com/schema/dubbo=com.alibaba.dubbo.config.spring.schema.DubboNamespaceHandler

DubboNamespaceHandler就是我们自己定义的标签解析类。

## 三. 自定义标签解析 ##

在上一步中，我们配置了**com.alibaba.dubbo.config.spring.schema.DubboNamespaceHandler**类作为解析自定义标签的类，所以namespace为**dubbo**的标签，都会用这里注册的标签解析器来解析。

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    package com.alibaba.dubbo.config.spring.schema;
    
    import com.alibaba.dubbo.common.Version;
    import com.alibaba.dubbo.config.ApplicationConfig;
    import com.alibaba.dubbo.config.ConsumerConfig;
    import com.alibaba.dubbo.config.ModuleConfig;
    import com.alibaba.dubbo.config.MonitorConfig;
    import com.alibaba.dubbo.config.ProtocolConfig;
    import com.alibaba.dubbo.config.ProviderConfig;
    import com.alibaba.dubbo.config.RegistryConfig;
    import com.alibaba.dubbo.config.spring.AnnotationBean;
    import com.alibaba.dubbo.config.spring.ReferenceBean;
    import com.alibaba.dubbo.config.spring.ServiceBean;
    import org.springframework.beans.factory.xml.NamespaceHandlerSupport;
    
    public class DubboNamespaceHandler extends NamespaceHandlerSupport {
        public DubboNamespaceHandler() {
        }
    
        public void init() {
            this.registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
            this.registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
            this.registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
            this.registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
            this.registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
            this.registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
            this.registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
            this.registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
            this.registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
            this.registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true));
        }
    
        static {
            Version.checkDuplicate(DubboNamespaceHandler.class);
        }
    }

我们自己定义的标签解析器要实现BeanDefinitionParser 接口

一般来说，注册bean的基本流程为:

1.  解析标签
2.  根据解析的值生成BeanDefinition,
3.  注册标签

解析标签就不用说，重点说说怎么生成BeanDefinition

### 3.1 生成BeanDefinition ###

生成BeanDefine 需要我们实现 BeanDefinitionParser 的parse()方法

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1lhbmd6YWlMZUhlSGU_size_16_color_FFFFFF_t_70][]

### 3.2 注册bean ###

注册BeanDefinitionParser 接口的函数中有个参数ParserContext,有个方法为getRegistry()，因此，注冊bean的時候就很简单了

parserContext.getRegistry().registerBeanDefinition("beanName",nodeWrapDefinition);

## 四、综上所述 ##

Dubbo通过以上三步，就实现了自己定义标签，并且在Spring容器中注入相关Dubbo的bean。

[20190520171547757.png]: /images/20220129/b3f8939c09ab47ac9111fb9bf8059bac.png
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