Spring extension schema of Dubbo source code

1. Demand

              1) Familiar with Spring custom tags

              2) Dubbo extends the schema in Spring

2. Analysis

         This part of the code is mainly in com.alibaba.dubbo.config.spring.schema

package com.alibaba.dubbo.config.spring.schema

         1 Through the NamespaceHandler, a BeanDefinitionParser will be found according to the schema and node name, and then the BeanDefinitionParser will complete the specific parsing work

        Dubbo source code

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 AnnotationBeanDefinitionParser());
    }

}

DubboNamespaceHandler method inherits NamespaceHandler

Then register the schema and specific BeanDefinitionParser to Spring through registerBeanDefinitionParser in the init method

2.BeanDefinitionParser completes the specific parsing work

Spring provides default implementation classes NamespaceHandlerSupport and AbstractSingleBeanDefinitionParser

Dubbo source code

public class DubboBeanDefinitionParser implements BeanDefinitionParser {

    private static final Logger logger = LoggerFactory.getLogger(DubboBeanDefinitionParser.class);
    private static final Pattern GROUP_AND_VERION = Pattern.compile("^[\\-.0-9_a-zA-Z]+(\\:[\\-.0-9_a-zA-Z]+)?$");
    private final Class<?> beanClass;
    private final boolean required;

    public DubboBeanDefinitionParser(Class<?> beanClass, boolean required) {
        this.beanClass = beanClass;
        this.required = required;
    }


  private static BeanDefinition parse(Element element, ParserContext parserContext, Class<?> beanClass, boolean required) {
        RootBeanDefinition beanDefinition = new RootBeanDefinition();
        beanDefinition.setBeanClass(beanClass);
        beanDefinition.setLazyInit(false);
        String id = element.getAttribute("id");
        if ((id == null || id.length() == 0) && required) {
            String generatedBeanName = element.getAttribute("name");
            if (generatedBeanName == null || generatedBeanName.length() == 0) {
                if (ProtocolConfig.class.equals(beanClass)) {
                    generatedBeanName = "dubbo";
                } else {
                    generatedBeanName = element.getAttribute("interface");
                }
            }
            if (generatedBeanName == null || generatedBeanName.length() == 0) {
                generatedBeanName = beanClass.getName();
            }
            id = generatedBeanName;
            int counter = 2;
            while (parserContext.getRegistry().containsBeanDefinition(id)) {
                id = generatedBeanName + (counter++);
            }
        }
        if (id != null && id.length() > 0) {
            if (parserContext.getRegistry().containsBeanDefinition(id)) {
                throw new IllegalStateException("Duplicate spring bean id " + id);
            }
            parserContext.getRegistry().registerBeanDefinition(id, beanDefinition);
            beanDefinition.getPropertyValues().addPropertyValue("id", id);
        }
        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));
                    }
                }
            }
        } 

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    public BeanDefinition parse(Element element, ParserContext parserContext) {
        return parse(element, parserContext, beanClass, required);
    }

}

 

Dubbo parses the corresponding tags by implementing the BeanDefinitionParse interface

 

2. Write Dubbo's xsd file

Spring provides two configuration files, spring.handlers and spring.schemas, to do this work. These two files need to be written by ourselves and placed in the META-INF folder. The addresses of these two files must be META-INF. /spring.handlers and META-INF/spring.schemas, spring will load them by default,

spring.handlers in dubbo looks like this:

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

 

spring.schemas in dubbo looks like this:

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