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title: Code Analysis For Dubbo Plugin author: midnight2104 author_title: Apache ShenYu Committer author_url: https://github.com/midnight2104 tags: [plugin,dubbo,Apache ShenYu]

Apache ShenYu is an asynchronous, high-performance, cross-language, responsive API gateway.

The Apache ShenYu gateway uses the dubbo plugin to make calls to the dubbo service. You can see the official documentation Dubbo Quick Start to learn how to use the plugin.

This article is based on shenyu-2.4.3 version for source code analysis, please refer to Dubbo Service Access for the introduction of the official website.

1. Service Registration

Take the example provided on the official website shenyu-examples-dubbo. Suppose your dubbo service is defined as follows (spring-dubbo.xml).

<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
       https://code.alibabatech.com/schema/dubbo/dubbo.xsd">

    <dubbo:application name="test-dubbo-service"/>
    <dubbo:registry address="${dubbo.registry.address}"/>
    <dubbo:protocol name="dubbo" port="20888"/>

    <dubbo:service timeout="10000" interface="org.apache.shenyu.examples.dubbo.api.service.DubboTestService" ref="dubboTestService"/>

</beans>

Declare the application service name, register the center address, use the dubbo protocol, declare the service interface, and the corresponding interface implementation class.

/**
 * DubboTestServiceImpl.
 */
@Service("dubboTestService")
public class DubboTestServiceImpl implements DubboTestService {
    
    @Override
    @ShenyuDubboClient(path = "/findById", desc = "Query by Id")
    public DubboTest findById(final String id) {
        return new DubboTest(id, "hello world shenyu Apache, findById");
    }

    //......
}

In the interface implementation class, use the annotation @ShenyuDubboClient to register the service with shenyu-admin. The role of this annotation and its rationale will be analyzed later.

The configuration information in the configuration file application.yml.

server:
  port: 8011
  address: 0.0.0.0
  servlet:
    context-path: /
spring:
  main:
    allow-bean-definition-overriding: true
dubbo:
  registry:
    address: zookeeper://localhost:2181  # dubbo registry
    
shenyu:
  register:
    registerType: http 
    serverLists: http://localhost:9095 
    props:
      username: admin 
      password: 123456
  client:
    dubbo:
      props:
        contextPath: /dubbo  
        appName: dubbo

In the configuration file, declare the registry address used by dubbo. The dubbo service registers with shenyu-admin, using the method http, and the registration address is http://localhost:9095.

See Application Client Access for more information on the use of the registration method.

1.1 Declaration of registration interface

Use the annotation @ShenyuDubboClient to register the service to the gateway. The simple demo is as follows.

// dubbo sevice
@Service("dubboTestService")
public class DubboTestServiceImpl implements DubboTestService {
    
    @Override
    @ShenyuDubboClient(path = "/findById", desc = "Query by Id") // need to be registered method
    public DubboTest findById(final String id) {
        return new DubboTest(id, "hello world shenyu Apache, findById");
    }

    //......
}

annotation definition:

/**
 * Works on classes and methods
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
@Inherited
public @interface ShenyuDubboClient {
    
	//path
    String path();
    
    //rule name
    String ruleName() default "";
   
    //desc
    String desc() default "";

    //enabled
    boolean enabled() default true;
}

1.2 Scan annotation information

Annotation scanning is done through the ApacheDubboServiceBeanListener, which implements the ApplicationListener<ContextRefreshedEvent> interface and starts executing the event handler method when a context refresh event occurs during the Spring container startup onApplicationEvent().

During constructor instantiation.

• Read property configuration
• Start the thread pool
• Start the registry for registering with shenyu-admin

public class ApacheDubboServiceBeanListener implements ApplicationListener<ContextRefreshedEvent> {

	// ......

    //Constructor
    public ApacheDubboServiceBeanListener(final PropertiesConfig clientConfig, final ShenyuClientRegisterRepository shenyuClientRegisterRepository) {
        //1.Read property configuration
        Properties props = clientConfig.getProps();
        String contextPath = props.getProperty(ShenyuClientConstants.CONTEXT_PATH);
        String appName = props.getProperty(ShenyuClientConstants.APP_NAME);
        if (StringUtils.isBlank(contextPath)) {
            throw new ShenyuClientIllegalArgumentException("apache dubbo client must config the contextPath or appName");
        }
        this.contextPath = contextPath;
        this.appName = appName;
        this.host = props.getProperty(ShenyuClientConstants.HOST);
        this.port = props.getProperty(ShenyuClientConstants.PORT);
        //2.Start the thread pool
        executorService = Executors.newSingleThreadExecutor(new ThreadFactoryBuilder().setNameFormat("shenyu-apache-dubbo-client-thread-pool-%d").build());
        //3.Start the registry for registering with `shenyu-admin`
        publisher.start(shenyuClientRegisterRepository);
    }

    /**
     * Context refresh event, execute method logic
     */
    @Override
    public void onApplicationEvent(final ContextRefreshedEvent contextRefreshedEvent) {
        //......
    }

• ApacheDubboServiceBeanListener#onApplicationEvent()

Rewritten method logic: read Dubbo service ServiceBean, build metadata object and URI object, and register it with shenyu-admin.

    @Override
    public void onApplicationEvent(final ContextRefreshedEvent contextRefreshedEvent) {
        //read ServiceBean
        Map<String, ServiceBean> serviceBean = contextRefreshedEvent.getApplicationContext().getBeansOfType(ServiceBean.class);
        if (serviceBean.isEmpty()) {
            return;
        }
        //The method is guaranteed to be executed only once
        if (!registered.compareAndSet(false, true)) {
            return;
        }
        //handle metadata 
        for (Map.Entry<String, ServiceBean> entry : serviceBean.entrySet()) {
            handler(entry.getValue());
        }
        //handle URI
        serviceBean.values().stream().findFirst().ifPresent(bean -> {
            publisher.publishEvent(buildURIRegisterDTO(bean));
        });
    }

• handler()

  In the handler() method, read all methods from the serviceBean, determine if there is a ShenyuDubboClient annotation on the method, build a metadata object if it exists, and register the method with shenyu-admin through the registry.

    private void handler(final ServiceBean<?> serviceBean) {
        //get proxy
        Object refProxy = serviceBean.getRef();
        //get class
        Class<?> clazz = refProxy.getClass();
        if (AopUtils.isAopProxy(refProxy)) {
            clazz = AopUtils.getTargetClass(refProxy);
        }
        //all methods
        Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(clazz);
        for (Method method : methods) {
            //read ShenyuDubboClient annotation
            ShenyuDubboClient shenyuDubboClient = method.getAnnotation(ShenyuDubboClient.class);
            if (Objects.nonNull(shenyuDubboClient)) {
                //build meatdata and registry
                publisher.publishEvent(buildMetaDataDTO(serviceBean, shenyuDubboClient, method));
            }
        }
    }

• buildMetaDataDTO()

  Constructs a metadata object where the necessary information for method registration is constructed and subsequently used for selector or rule matching.

    private MetaDataRegisterDTO buildMetaDataDTO(final ServiceBean<?> serviceBean, final ShenyuDubboClient shenyuDubboClient, final Method method) {
        //app name
        String appName = buildAppName(serviceBean);
        //path
        String path = contextPath + shenyuDubboClient.path();
        //desc
        String desc = shenyuDubboClient.desc();
        //service name
        String serviceName = serviceBean.getInterface();
        //rule name
        String configRuleName = shenyuDubboClient.ruleName();
        String ruleName = ("".equals(configRuleName)) ? path : configRuleName;
        //method name 
        String methodName = method.getName();
        //parameter Types
        Class<?>[] parameterTypesClazz = method.getParameterTypes();
        String parameterTypes = Arrays.stream(parameterTypesClazz).map(Class::getName).collect(Collectors.joining(","));
        return MetaDataRegisterDTO.builder()
                .appName(appName)
                .serviceName(serviceName)
                .methodName(methodName)
                .contextPath(contextPath)
                .host(buildHost())
                .port(buildPort(serviceBean))
                .path(path)
                .ruleName(ruleName)
                .pathDesc(desc)
                .parameterTypes(parameterTypes)
                .rpcExt(buildRpcExt(serviceBean)) //dubbo ext
                .rpcType(RpcTypeEnum.DUBBO.getName())
                .enabled(shenyuDubboClient.enabled())
                .build();
    }

• buildRpcExt()

  dubbo ext information.

   private String buildRpcExt(final ServiceBean serviceBean) {
       DubboRpcExt build = DubboRpcExt.builder()
               .group(StringUtils.isNotEmpty(serviceBean.getGroup()) ? serviceBean.getGroup() : "")//group
               .version(StringUtils.isNotEmpty(serviceBean.getVersion()) ? serviceBean.getVersion() : "")//version
               .loadbalance(StringUtils.isNotEmpty(serviceBean.getLoadbalance()) ? serviceBean.getLoadbalance() : Constants.DEFAULT_LOADBALANCE)//load balance
               .retries(Objects.isNull(serviceBean.getRetries()) ? Constants.DEFAULT_RETRIES : serviceBean.getRetries())//retry
               .timeout(Objects.isNull(serviceBean.getTimeout()) ? Constants.DEFAULT_CONNECT_TIMEOUT : serviceBean.getTimeout())//time
               .sent(Objects.isNull(serviceBean.getSent()) ? Constants.DEFAULT_SENT : serviceBean.getSent())//sent
               .cluster(StringUtils.isNotEmpty(serviceBean.getCluster()) ? serviceBean.getCluster() : Constants.DEFAULT_CLUSTER)//cluster
               .url("")
               .build();
       return GsonUtils.getInstance().toJson(build);
   }

• buildURIRegisterDTO()

  Construct URI objects to register information about the service itself, which can be subsequently used for service probing live.

private URIRegisterDTO buildURIRegisterDTO(final ServiceBean serviceBean) {
        return URIRegisterDTO.builder()
                .contextPath(this.contextPath) //context path
                .appName(buildAppName(serviceBean))//app name
                .rpcType(RpcTypeEnum.DUBBO.getName())//dubbo
                .host(buildHost()) //host
                .port(buildPort(serviceBean))//port
                .build();
 }

The specific registration logic is implemented by the registration center, please refer to Client Access Principles .

//To the registration center, post registration events   
publisher.publishEvent();

1.3 Processing registration information

The metadata and URI data registered by the client through the registry are processed at the shenyu-admin end, which is responsible for storing to the database and synchronizing to the shenyu gateway. The client-side registration processing logic of the Dubbo plugin is in the ShenyuClientRegisterDubboServiceImpl. The inheritance relationship is as follows.

• ShenyuClientRegisterService: client registration service, top-level interface.
• FallbackShenyuClientRegisterService: registration failure, provides retry operation.
• AbstractShenyuClientRegisterServiceImpl: abstract class, implements part of the public registration logic.
• ShenyuClientRegisterDubboServiceImpl: implementation of the Dubbo plugin registration.

1.3.1 Registration Service

• org.apache.shenyu.admin.service.register.AbstractShenyuClientRegisterServiceImpl#register()

  The metadata MetaDataRegisterDTO object registered by the client through the registry is picked up and dropped in the register() method of shenyu-admin.

   @Override
    public String register(final MetaDataRegisterDTO dto) {
        //1. register selector
        String selectorHandler = selectorHandler(dto);
        String selectorId = selectorService.registerDefault(dto, PluginNameAdapter.rpcTypeAdapter(rpcType()), selectorHandler);
        //2. register rule
        String ruleHandler = ruleHandler();
        RuleDTO ruleDTO = buildRpcDefaultRuleDTO(selectorId, dto, ruleHandler);
        ruleService.registerDefault(ruleDTO);
        //3. register metadata
        registerMetadata(dto);
        //4. register contextPath
        String contextPath = dto.getContextPath();
        if (StringUtils.isNotEmpty(contextPath)) {
            registerContextPath(dto);
        }
        return ShenyuResultMessage.SUCCESS;
    }

1.3.1.1 Register Selector

• org.apache.shenyu.admin.service.impl.SelectorServiceImpl#registerDefault()

Construct contextPath, find if the selector information exists, if it does, return id; if it doesn't, create the default selector information.

    @Override
    public String registerDefault(final MetaDataRegisterDTO dto, final String pluginName, final String selectorHandler) {
        // build contextPath
        String contextPath = ContextPathUtils.buildContextPath(dto.getContextPath(), dto.getAppName());
        // Find if selector information exists by name
        SelectorDO selectorDO = findByNameAndPluginName(contextPath, pluginName);
        if (Objects.isNull(selectorDO)) {
            // Create a default selector message if it does not exist
            return registerSelector(contextPath, pluginName, selectorHandler);
        }
        return selectorDO.getId();
    }

• Default selector information

  Construct the default selector information and its conditional properties here.

   //register selector
   private String registerSelector(final String contextPath, final String pluginName, final String selectorHandler) {
        //build selector
        SelectorDTO selectorDTO = buildSelectorDTO(contextPath, pluginMapper.selectByName(pluginName).getId());
        selectorDTO.setHandle(selectorHandler);
        //register default selector
        return registerDefault(selectorDTO);
    }
     //build selector
    private SelectorDTO buildSelectorDTO(final String contextPath, final String pluginId) {
        //build default
        SelectorDTO selectorDTO = buildDefaultSelectorDTO(contextPath);
        selectorDTO.setPluginId(pluginId);
         //build the conditional properties of the default selector
        selectorDTO.setSelectorConditions(buildDefaultSelectorConditionDTO(contextPath));
        return selectorDTO;
    }

• Build default selector

private SelectorDTO buildDefaultSelectorDTO(final String name) {
    return SelectorDTO.builder()
            .name(name) // name
            .type(SelectorTypeEnum.CUSTOM_FLOW.getCode()) // default type cutom
            .matchMode(MatchModeEnum.AND.getCode()) //default match mode
            .enabled(Boolean.TRUE)  //enable
            .loged(Boolean.TRUE)  //log
            .continued(Boolean.TRUE) 
            .sort(1) 
            .build();
}

• Build default selector conditional properties

private List<SelectorConditionDTO> buildDefaultSelectorConditionDTO(final String contextPath) {
    SelectorConditionDTO selectorConditionDTO = new SelectorConditionDTO();
    selectorConditionDTO.setParamType(ParamTypeEnum.URI.getName()); // default URI
    selectorConditionDTO.setParamName("/");
    selectorConditionDTO.setOperator(OperatorEnum.MATCH.getAlias()); // default  match
    selectorConditionDTO.setParamValue(contextPath + AdminConstants.URI_SUFFIX); 
    return Collections.singletonList(selectorConditionDTO);
}

• Register default selector

@Override
public String registerDefault(final SelectorDTO selectorDTO) {
    //selector information
    SelectorDO selectorDO = SelectorDO.buildSelectorDO(selectorDTO);
    //selector conditional properties
    List<SelectorConditionDTO> selectorConditionDTOs = selectorDTO.getSelectorConditions();
    if (StringUtils.isEmpty(selectorDTO.getId())) {
        // insert selector information into the database
        selectorMapper.insertSelective(selectorDO);
          // inserting selector conditional properties to the database
        selectorConditionDTOs.forEach(selectorConditionDTO -> {
            selectorConditionDTO.setSelectorId(selectorDO.getId());            
            selectorConditionMapper.insertSelective(SelectorConditionDO.buildSelectorConditionDO(selectorConditionDTO));
        });
    }
    // Publish synchronization events to synchronize selection information and its conditional attributes to the gateway
    publishEvent(selectorDO, selectorConditionDTOs);
    return selectorDO.getId();
}

1.3.1.2 Registration Rules

In the second step of registering the service, start building the default rules and then register the rules.

@Override
    public String register(final MetaDataRegisterDTO dto) {
        //1. handle selector
        //......
        
        //2. handle rule
        
        String ruleHandler = ruleHandler();
        // build default rule
        RuleDTO ruleDTO = buildRpcDefaultRuleDTO(selectorId, dto, ruleHandler);
        // register rule
        ruleService.registerDefault(ruleDTO);
        
        //3. reigster metadata
        //......
        
        //4. register ContextPath
        //......
        
        return ShenyuResultMessage.SUCCESS;
    }

• 默认规则处理属性

    @Override
    protected String ruleHandler() {
        // default rule
        return new DubboRuleHandle().toJson();
    }

Dubbo plugin default rule handling properties.

public class DubboRuleHandle implements RuleHandle {

    /**
     * dubbo version.
     */
    private String version;

    /**
     * group.
     */
    private String group;

    /**
     * retry.
     */
    private Integer retries = 0;

    /**
     * loadbalance:RANDOM
     */
    private String loadbalance = LoadBalanceEnum.RANDOM.getName();

    /**
     * timeout default 3000
     */
    private long timeout = Constants.TIME_OUT;
}

• build default rule

  // build default rule
    private RuleDTO buildRpcDefaultRuleDTO(final String selectorId, final MetaDataRegisterDTO metaDataDTO, final String ruleHandler) {
        return buildRuleDTO(selectorId, ruleHandler, metaDataDTO.getRuleName(), metaDataDTO.getPath());
    }
   //  build default rule
    private RuleDTO buildRuleDTO(final String selectorId, final String ruleHandler, final String ruleName, final String path) {
        RuleDTO ruleDTO = RuleDTO.builder()
                .selectorId(selectorId)
                .name(ruleName) 
                .matchMode(MatchModeEnum.AND.getCode()) 
                .enabled(Boolean.TRUE) 
                .loged(Boolean.TRUE) 
                .sort(1)
                .handle(ruleHandler)
                .build();
        RuleConditionDTO ruleConditionDTO = RuleConditionDTO.builder()
                .paramType(ParamTypeEnum.URI.getName()) 
                .paramName("/")
                .paramValue(path) 
                .build();
        if (path.indexOf("*") > 1) {
            ruleConditionDTO.setOperator(OperatorEnum.MATCH.getAlias()); 
        } else {
            ruleConditionDTO.setOperator(OperatorEnum.EQ.getAlias()); 
        }
        ruleDTO.setRuleConditions(Collections.singletonList(ruleConditionDTO));
        return ruleDTO;
    }

• org.apache.shenyu.admin.service.impl.RuleServiceImpl#registerDefault()

Registration rules: insert records to the database and publish events to the gateway for data synchronization.

    @Override
    public String registerDefault(final RuleDTO ruleDTO) {
        RuleDO exist = ruleMapper.findBySelectorIdAndName(ruleDTO.getSelectorId(), ruleDTO.getName());
        if (Objects.nonNull(exist)) {
            return "";
        }

        RuleDO ruleDO = RuleDO.buildRuleDO(ruleDTO);
        List<RuleConditionDTO> ruleConditions = ruleDTO.getRuleConditions();
        if (StringUtils.isEmpty(ruleDTO.getId())) {
            // insert rule information into the database
            ruleMapper.insertSelective(ruleDO);
            //insert  rule body conditional attributes into the database
            ruleConditions.forEach(ruleConditionDTO -> {
                ruleConditionDTO.setRuleId(ruleDO.getId());     
                ruleConditionMapper.insertSelective(RuleConditionDO.buildRuleConditionDO(ruleConditionDTO));
            });
        }
        // Publish events to the gateway for data synchronization
        publishEvent(ruleDO, ruleConditions);
        return ruleDO.getId();
    }

1.3.1.3 Register Metadata

Metadata is mainly used for RPC service calls.

   @Override
    public String register(final MetaDataRegisterDTO dto) {
        //1. register selector
        //......
        
        //2. register rule
        //......
        
        //3. register metadata
        registerMetadata(dto);
        
        //4. register ContextPath
        //......
        
        return ShenyuResultMessage.SUCCESS;
    }

• org.apache.shenyu.admin.service.register.ShenyuClientRegisterDubboServiceImpl#registerMetadata()

  Insert or update metadata and then publish sync events to the gateway.

    @Override
    protected void registerMetadata(final MetaDataRegisterDTO dto) {
            // get metaDataService
            MetaDataService metaDataService = getMetaDataService();
            MetaDataDO exist = metaDataService.findByPath(dto.getPath());
            //insert or update metadata
            metaDataService.saveOrUpdateMetaData(exist, dto);
    }

    @Override
    public void saveOrUpdateMetaData(final MetaDataDO exist, final MetaDataRegisterDTO metaDataDTO) {
        DataEventTypeEnum eventType;
        // DTO->DO
        MetaDataDO metaDataDO = MetaDataTransfer.INSTANCE.mapRegisterDTOToEntity(metaDataDTO);
        // insert data
        if (Objects.isNull(exist)) {
            Timestamp currentTime = new Timestamp(System.currentTimeMillis());
            metaDataDO.setId(UUIDUtils.getInstance().generateShortUuid());
            metaDataDO.setDateCreated(currentTime);
            metaDataDO.setDateUpdated(currentTime);
            metaDataMapper.insert(metaDataDO);
            eventType = DataEventTypeEnum.CREATE;
        } else {
            // update
            metaDataDO.setId(exist.getId());
            metaDataMapper.update(metaDataDO);
            eventType = DataEventTypeEnum.UPDATE;
        }
        // Publish sync events to gateway
        eventPublisher.publishEvent(new DataChangedEvent(ConfigGroupEnum.META_DATA, eventType,
                Collections.singletonList(MetaDataTransfer.INSTANCE.mapToData(metaDataDO))));
    }

1.3.2 Register URI

• org.apache.shenyu.admin.service.register.FallbackShenyuClientRegisterService#registerURI()

The server side receives the URI information registered by the client and processes it.

    @Override
    public String registerURI(final String selectorName, final List<URIRegisterDTO> uriList) {
        String result;
        String key = key(selectorName);
        try {
            this.removeFallBack(key);
            // register URI
            result = this.doRegisterURI(selectorName, uriList);
            logger.info("Register success: {},{}", selectorName, uriList);
        } catch (Exception ex) {
            logger.warn("Register exception: cause:{}", ex.getMessage());
            result = "";
            // Retry after registration failure
            this.addFallback(key, new FallbackHolder(selectorName, uriList));
        }
        return result;
    }

• org.apache.shenyu.admin.service.register.AbstractShenyuClientRegisterServiceImpl#doRegisterURI()

Get a valid URI from the URI registered by the client, update the corresponding selector handle property, and send a selector update event to the gateway.

@Override
    public String doRegisterURI(final String selectorName, final List<URIRegisterDTO> uriList) {
        //check
        if (CollectionUtils.isEmpty(uriList)) {
            return "";
        }
        
        SelectorDO selectorDO = selectorService.findByNameAndPluginName(selectorName, PluginNameAdapter.rpcTypeAdapter(rpcType()));
        if (Objects.isNull(selectorDO)) {
            throw new ShenyuException("doRegister Failed to execute,wait to retry.");
        }
        // gte valid URI
        List<URIRegisterDTO> validUriList = uriList.stream().filter(dto -> Objects.nonNull(dto.getPort()) && StringUtils.isNotBlank(dto.getHost())).collect(Collectors.toList());
        // build handle
        String handler = buildHandle(validUriList, selectorDO);
        if (handler != null) {
            selectorDO.setHandle(handler);
            SelectorData selectorData = selectorService.buildByName(selectorName, PluginNameAdapter.rpcTypeAdapter(rpcType()));
            selectorData.setHandle(handler);
            // Update the handle property of the selector to the database
            selectorService.updateSelective(selectorDO);
            // Send selector update events to the gateway
            eventPublisher.publishEvent(new DataChangedEvent(ConfigGroupEnum.SELECTOR, DataEventTypeEnum.UPDATE, Collections.singletonList(selectorData)));
        }
        return ShenyuResultMessage.SUCCESS;
    }

The source code analysis on service registration is completed as well as the analysis flow chart is as follows.

The next step is to analyze how the dubbo plugin initiates calls to the http service based on this information.

2. Service Invocation

The dubbo plugin is the core processing plugin used by the ShenYu gateway to convert http requests into the dubbo protocol and invoke the dubbo service.

Take the case provided by the official website Quick Start with Dubbo as an example, a dubbo service is registered with shenyu-admin through the registry, and then requested through the ShenYu gateway proxy, the request is as follows.

GET http://localhost:9195/dubbo/findById?id=100
Accept: application/json

The class inheritance relationship in the Dubbo plugin is as follows.

• ShenyuPlugin: top-level interface, defining interface methods.
• AbstractShenyuPlugin: abstract class that implements plugin common logic.
• AbstractDubboPlugin: dubbo plugin abstract class, implementing dubbo common logic.
• ApacheDubboPlugin: ApacheDubbo plugin.

ShenYu Gateway supports ApacheDubbo and AlibabaDubbo\

2.1 Receive requests

After passing the ShenYu gateway proxy, the request entry is ShenyuWebHandler, which implements the org.springframework.web.server.WebHandler interface.

public final class ShenyuWebHandler implements WebHandler, ApplicationListener<SortPluginEvent> {
    //......
    
    /**
     * hanlde request
     */
    @Override
    public Mono<Void> handle(@NonNull final ServerWebExchange exchange) {
       // execute default plugin chain
        Mono<Void> execute = new DefaultShenyuPluginChain(plugins).execute(exchange);
        if (scheduled) {
            return execute.subscribeOn(scheduler);
        }
        return execute;
    }
    
    private static class DefaultShenyuPluginChain implements ShenyuPluginChain {

        private int index;

        private final List<ShenyuPlugin> plugins;

  
        DefaultShenyuPluginChain(final List<ShenyuPlugin> plugins) {
            this.plugins = plugins;
        }

        /**
         * execute.
         */
        @Override
        public Mono<Void> execute(final ServerWebExchange exchange) {
            return Mono.defer(() -> {
                if (this.index < plugins.size()) {
                    // get plugin 
                    ShenyuPlugin plugin = plugins.get(this.index++);
                    boolean skip = plugin.skip(exchange);
                    if (skip) {
                        // next
                        return this.execute(exchange);
                    }
                    // execute
                    return plugin.execute(exchange, this);
                }
                return Mono.empty();
            });
        }
    }
}

2.2 Match Rule

• org.apache.shenyu.plugin.base.AbstractShenyuPlugin#execute()

Execute the matching logic for selectors and rules in the execute() method.

• Matching selectors.
• Matching rules.
• Execute the plugin.

@Override
    public Mono<Void> execute(final ServerWebExchange exchange, final ShenyuPluginChain chain) {
        // plugin name
        String pluginName = named();
        // plugin data
        PluginData pluginData = BaseDataCache.getInstance().obtainPluginData(pluginName);
        if (pluginData != null && pluginData.getEnabled()) {
            // selector data
            final Collection<SelectorData> selectors = BaseDataCache.getInstance().obtainSelectorData(pluginName);
            if (CollectionUtils.isEmpty(selectors)) {
                return handleSelectorIfNull(pluginName, exchange, chain);
            }
            // match selector
            SelectorData selectorData = matchSelector(exchange, selectors);
            if (Objects.isNull(selectorData)) {
                return handleSelectorIfNull(pluginName, exchange, chain);
            }
            selectorLog(selectorData, pluginName);
            // rule data
            List<RuleData> rules = BaseDataCache.getInstance().obtainRuleData(selectorData.getId());
            if (CollectionUtils.isEmpty(rules)) {
                return handleRuleIfNull(pluginName, exchange, chain);
            }
            // match rule
            RuleData rule;
            if (selectorData.getType() == SelectorTypeEnum.FULL_FLOW.getCode()) {
                //get last
                rule = rules.get(rules.size() - 1);
            } else {
                rule = matchRule(exchange, rules);
            }
            if (Objects.isNull(rule)) {
                return handleRuleIfNull(pluginName, exchange, chain);
            }
            ruleLog(rule, pluginName);
            // execute
            return doExecute(exchange, chain, selectorData, rule);
        }
        return chain.execute(exchange);
    }

2.3 Execute GlobalPlugin

• org.apache.shenyu.plugin.global.GlobalPlugin#execute()

GlobalPlugin is a global plugin that constructs contextual information in the execute() method.

public class GlobalPlugin implements ShenyuPlugin {
    // shenyu context
    private final ShenyuContextBuilder builder;
    
    //......
    
    @Override
    public Mono<Void> execute(final ServerWebExchange exchange, final ShenyuPluginChain chain) {
       // build context information to be passed into the exchange
        ShenyuContext shenyuContext = builder.build(exchange);
        exchange.getAttributes().put(Constants.CONTEXT, shenyuContext);
        return chain.execute(exchange);
    }
    
    //......
}

• org.apache.shenyu.plugin.global.DefaultShenyuContextBuilder#build()

Build the default context information.

public class DefaultShenyuContextBuilder implements ShenyuContextBuilder {
    //......
    
    @Override
    public ShenyuContext build(final ServerWebExchange exchange) {
        //build data
        Pair<String, MetaData> buildData = buildData(exchange);
        //wrap ShenyuContext
        return decoratorMap.get(buildData.getLeft()).decorator(buildDefaultContext(exchange.getRequest()), buildData.getRight());
    }
    
    private Pair<String, MetaData> buildData(final ServerWebExchange exchange) {
        //......
        //get the metadata according to the requested uri
        MetaData metaData = MetaDataCache.getInstance().obtain(request.getURI().getPath());
        if (Objects.nonNull(metaData) && Boolean.TRUE.equals(metaData.getEnabled())) {
            exchange.getAttributes().put(Constants.META_DATA, metaData);
            return Pair.of(metaData.getRpcType(), metaData);
        } else {
            return Pair.of(RpcTypeEnum.HTTP.getName(), new MetaData());
        }
    }
    //set the default context information
    private ShenyuContext buildDefaultContext(final ServerHttpRequest request) {
        String appKey = request.getHeaders().getFirst(Constants.APP_KEY);
        String sign = request.getHeaders().getFirst(Constants.SIGN);
        String timestamp = request.getHeaders().getFirst(Constants.TIMESTAMP);
        ShenyuContext shenyuContext = new ShenyuContext();
        String path = request.getURI().getPath();
        shenyuContext.setPath(path); 
        shenyuContext.setAppKey(appKey);
        shenyuContext.setSign(sign);
        shenyuContext.setTimestamp(timestamp);
        shenyuContext.setStartDateTime(LocalDateTime.now());
        Optional.ofNullable(request.getMethod()).ifPresent(httpMethod -> shenyuContext.setHttpMethod(httpMethod.name()));
        return shenyuContext;
    }
 }

• org.apache.shenyu.plugin.dubbo.common.context.DubboShenyuContextDecorator#decorator()

wrap ShenyuContext:

public class DubboShenyuContextDecorator implements ShenyuContextDecorator {
    
    @Override
    public ShenyuContext decorator(final ShenyuContext shenyuContext, final MetaData metaData) {
        shenyuContext.setModule(metaData.getAppName());
        shenyuContext.setMethod(metaData.getServiceName()); 
        shenyuContext.setContextPath(metaData.getContextPath()); 
        shenyuContext.setRpcType(RpcTypeEnum.DUBBO.getName()); 
        return shenyuContext;
    }
    
    @Override
    public String rpcType() {
        return RpcTypeEnum.DUBBO.getName();
    }
}

2.4 Execute RpcParamTransformPlugin

The RpcParamTransformPlugin is responsible for reading the parameters from the http request, saving them in the exchange and passing them to the rpc service.

• org.apache.shenyu.plugin.base.RpcParamTransformPlugin#execute()

In the execute() method, the core logic of the plugin is executed: get the request information from exchange and process the parameters according to the form of content passed in by the request.

public class RpcParamTransformPlugin implements ShenyuPlugin {

    @Override
    public Mono<Void> execute(final ServerWebExchange exchange, final ShenyuPluginChain chain) {
        //get request information from exchange
        ServerHttpRequest request = exchange.getRequest();
        ShenyuContext shenyuContext = exchange.getAttribute(Constants.CONTEXT);
        if (Objects.nonNull(shenyuContext)) {
           // APPLICATION_JSON
            MediaType mediaType = request.getHeaders().getContentType();
            if (MediaType.APPLICATION_JSON.isCompatibleWith(mediaType)) {
                return body(exchange, request, chain);
            }
            // APPLICATION_FORM_URLENCODED
            if (MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(mediaType)) {
                return formData(exchange, request, chain);
            }
            //query
            return query(exchange, request, chain);
        }
        return chain.execute(exchange);
    }
    
    //APPLICATION_JSON
    private Mono<Void> body(final ServerWebExchange exchange, final ServerHttpRequest serverHttpRequest, final ShenyuPluginChain chain) {
        return Mono.from(DataBufferUtils.join(serverHttpRequest.getBody())
                .flatMap(body -> {
                    exchange.getAttributes().put(Constants.PARAM_TRANSFORM, resolveBodyFromRequest(body));//解析body，保存到exchange中
                    return chain.execute(exchange);
                }));
    }
   // APPLICATION_FORM_URLENCODED
    private Mono<Void> formData(final ServerWebExchange exchange, final ServerHttpRequest serverHttpRequest, final ShenyuPluginChain chain) {
        return Mono.from(DataBufferUtils.join(serverHttpRequest.getBody())
                .flatMap(map -> {
                    String param = resolveBodyFromRequest(map);
                    LinkedMultiValueMap<String, String> linkedMultiValueMap;
                    try {
                        linkedMultiValueMap = BodyParamUtils.buildBodyParams(URLDecoder.decode(param, StandardCharsets.UTF_8.name())); //格式化数据
                    } catch (UnsupportedEncodingException e) {
                        return Mono.error(e);
                    }
                    exchange.getAttributes().put(Constants.PARAM_TRANSFORM, HttpParamConverter.toMap(() -> linkedMultiValueMap));// 保存到exchange中
                    return chain.execute(exchange);
                }));
    }
    //query
    private Mono<Void> query(final ServerWebExchange exchange, final ServerHttpRequest serverHttpRequest, final ShenyuPluginChain chain) {
        exchange.getAttributes().put(Constants.PARAM_TRANSFORM, HttpParamConverter.ofString(() -> serverHttpRequest.getURI().getQuery()));//保存到exchange中
        return chain.execute(exchange);
    }
    //......
 }

2.5 Execute DubboPlugin

• org.apache.shenyu.plugin.dubbo.common.AbstractDubboPlugin#doExecute()

In the doExecute() method, the main purpose is to check the metadata and parameters.

public abstract class AbstractDubboPlugin extends AbstractShenyuPlugin {
    
    @Override
    public Mono<Void> doExecute(final ServerWebExchange exchange,
                                   final ShenyuPluginChain chain,
                                   final SelectorData selector,
                                   final RuleData rule) {
        //param
        String param = exchange.getAttribute(Constants.PARAM_TRANSFORM);
        //context
        ShenyuContext shenyuContext = exchange.getAttribute(Constants.CONTEXT);
        assert shenyuContext != null;
        //metaData
        MetaData metaData = exchange.getAttribute(Constants.META_DATA);
        //check metaData
        if (!checkMetaData(metaData)) {
            LOG.error(" path is : {}, meta data have error : {}", shenyuContext.getPath(), metaData);
            exchange.getResponse().setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
            Object error = ShenyuResultWrap.error(exchange, ShenyuResultEnum.META_DATA_ERROR, null);
            return WebFluxResultUtils.result(exchange, error);
        }
        //check
        if (Objects.nonNull(metaData) && StringUtils.isNoneBlank(metaData.getParameterTypes()) && StringUtils.isBlank(param)) {
            exchange.getResponse().setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
            Object error = ShenyuResultWrap.error(exchange, ShenyuResultEnum.DUBBO_HAVE_BODY_PARAM, null);
            return WebFluxResultUtils.result(exchange, error);
        }
        //set rpcContext
        this.rpcContext(exchange);
        //dubbo invoke
        return this.doDubboInvoker(exchange, chain, selector, rule, metaData, param);
    }
}

• org.apache.shenyu.plugin.apache.dubbo.ApacheDubboPlugin#doDubboInvoker()

Set special context information in the doDubboInvoker() method, and then start the dubbo generalization call.

public class ApacheDubboPlugin extends AbstractDubboPlugin {
    
    @Override
    protected Mono<Void> doDubboInvoker(final ServerWebExchange exchange,
                                        final ShenyuPluginChain chain,
                                        final SelectorData selector,
                                        final RuleData rule,
                                        final MetaData metaData,
                                        final String param) {
        //set the current selector and rule information, and request address for dubbo graying support
        RpcContext.getContext().setAttachment(Constants.DUBBO_SELECTOR_ID, selector.getId());
        RpcContext.getContext().setAttachment(Constants.DUBBO_RULE_ID, rule.getId());
        RpcContext.getContext().setAttachment(Constants.DUBBO_REMOTE_ADDRESS, Objects.requireNonNull(exchange.getRequest().getRemoteAddress()).getAddress().getHostAddress());
        //dubbo generic invoker
        final Mono<Object> result = dubboProxyService.genericInvoker(param, metaData, exchange);
        //execute next plugin in chain
        return result.then(chain.execute(exchange));
    }
}

• org.apache.shenyu.plugin.apache.dubbo.proxy.ApacheDubboProxyService#genericInvoker()

genericInvoker() method.

• Gets the ReferenceConfig object.
• Gets the generalization service GenericService object.
• Constructs the request parameter pair object.
• Initiates an asynchronous generalization invocation.

public class ApacheDubboProxyService {
    //...... 

    /**
     * Generic invoker object.
     */
    public Mono<Object> genericInvoker(final String body, final MetaData metaData, final ServerWebExchange exchange) throws ShenyuException {
        //1.Get the ReferenceConfig object
        ReferenceConfig<GenericService> reference = ApacheDubboConfigCache.getInstance().get(metaData.getPath());

        if (Objects.isNull(reference) || StringUtils.isEmpty(reference.getInterface())) {
            //Failure of the current cache information
            ApacheDubboConfigCache.getInstance().invalidate(metaData.getPath());
            //Reinitialization with metadata
            reference = ApacheDubboConfigCache.getInstance().initRef(metaData);
        }
        //2.Get the GenericService object of the generalization service
        GenericService genericService = reference.get();
        //3.Constructing the request parameter pair object
        Pair<String[], Object[]> pair;
        if (StringUtils.isBlank(metaData.getParameterTypes()) || ParamCheckUtils.dubboBodyIsEmpty(body)) {
            pair = new ImmutablePair<>(new String[]{}, new Object[]{});
        } else {
            pair = dubboParamResolveService.buildParameter(body, metaData.getParameterTypes());
        }
        //4.Initiating asynchronous generalization calls
        return Mono.fromFuture(invokeAsync(genericService, metaData.getMethodName(), pair.getLeft(), pair.getRight()).thenApply(ret -> {
            //handle result
            if (Objects.isNull(ret)) {
                ret = Constants.DUBBO_RPC_RESULT_EMPTY;
            }
            exchange.getAttributes().put(Constants.RPC_RESULT, ret);
            exchange.getAttributes().put(Constants.CLIENT_RESPONSE_RESULT_TYPE, ResultEnum.SUCCESS.getName());
            return ret;
        })).onErrorMap(exception -> exception instanceof GenericException ? new ShenyuException(((GenericException) exception).getExceptionMessage()) : new ShenyuException(exception));//处理异常
    }
    
    //Generalized calls, asynchronous operations
    private CompletableFuture<Object> invokeAsync(final GenericService genericService, final String method, final String[] parameterTypes, final Object[] args) throws GenericException {
        genericService.$invoke(method, parameterTypes, args);
        Object resultFromFuture = RpcContext.getContext().getFuture();
        return resultFromFuture instanceof CompletableFuture ? (CompletableFuture<Object>) resultFromFuture : CompletableFuture.completedFuture(resultFromFuture);
    }
}

Calling the dubbo service at the gateway can be achieved by generalizing the call.

The ReferenceConfig object is the key object to support generalization calls , and its initialization operation is done during data synchronization. There are two parts of data involved here, one is the synchronized plugin handler information and the other is the synchronized plugin metadata information.

• org.apache.shenyu.plugin.dubbo.common.handler.AbstractDubboPluginDataHandler#handlerPlugin()

When the plugin data is updated, the data synchronization module synchronizes the data from shenyu-admin to the gateway. The initialization operation is performed in handlerPlugin().

public abstract class AbstractDubboPluginDataHandler implements PluginDataHandler {
    //......
    
    //Initializing the configuration cache
   protected abstract void initConfigCache(DubboRegisterConfig dubboRegisterConfig);

    @Override
    public void handlerPlugin(final PluginData pluginData) {
        if (Objects.nonNull(pluginData) && Boolean.TRUE.equals(pluginData.getEnabled())) {
            //Data deserialization
            DubboRegisterConfig dubboRegisterConfig = GsonUtils.getInstance().fromJson(pluginData.getConfig(), DubboRegisterConfig.class);
            DubboRegisterConfig exist = Singleton.INST.get(DubboRegisterConfig.class);
            if (Objects.isNull(dubboRegisterConfig)) {
                return;
            }
            if (Objects.isNull(exist) || !dubboRegisterConfig.equals(exist)) {
                // Perform initialization operations
                this.initConfigCache(dubboRegisterConfig);
            }
            Singleton.INST.single(DubboRegisterConfig.class, dubboRegisterConfig);
        }
    }
    //......
}

• org.apache.shenyu.plugin.apache.dubbo.handler.ApacheDubboPluginDataHandler#initConfigCache()

Perform initialization operations.

public class ApacheDubboPluginDataHandler extends AbstractDubboPluginDataHandler {

    @Override
    protected void initConfigCache(final DubboRegisterConfig dubboRegisterConfig) {
        //perform initialization operations
        ApacheDubboConfigCache.getInstance().init(dubboRegisterConfig);
        //cached results before failure
        ApacheDubboConfigCache.getInstance().invalidateAll();
    }
}

• org.apache.shenyu.plugin.apache.dubbo.cache.ApacheDubboConfigCache#init()

In the initialization, set registryConfig and consumerConfig.

public final class ApacheDubboConfigCache extends DubboConfigCache {
    //......  
   /**
     * init
     */
    public void init(final DubboRegisterConfig dubboRegisterConfig) {
        //ApplicationConfig
        if (Objects.isNull(applicationConfig)) {
            applicationConfig = new ApplicationConfig("shenyu_proxy");
        }
        //When the protocol or address changes, you need to update the registryConfig
        if (needUpdateRegistryConfig(dubboRegisterConfig)) {
            RegistryConfig registryConfigTemp = new RegistryConfig();
            registryConfigTemp.setProtocol(dubboRegisterConfig.getProtocol());
            registryConfigTemp.setId("shenyu_proxy");
            registryConfigTemp.setRegister(false);
            registryConfigTemp.setAddress(dubboRegisterConfig.getRegister());            Optional.ofNullable(dubboRegisterConfig.getGroup()).ifPresent(registryConfigTemp::setGroup);
            registryConfig = registryConfigTemp;
        }
        //ConsumerConfig
        if (Objects.isNull(consumerConfig)) {
            consumerConfig = ApplicationModel.getConfigManager().getDefaultConsumer().orElseGet(() -> {
                ConsumerConfig consumerConfig = new ConsumerConfig();
                consumerConfig.refresh();
                return consumerConfig;
            });
           
            //ConsumerConfig
            Optional.ofNullable(dubboRegisterConfig.getThreadpool()).ifPresent(consumerConfig::setThreadpool); 
            Optional.ofNullable(dubboRegisterConfig.getCorethreads()).ifPresent(consumerConfig::setCorethreads);
            Optional.ofNullable(dubboRegisterConfig.getThreads()).ifPresent(consumerConfig::setThreads);
            Optional.ofNullable(dubboRegisterConfig.getQueues()).ifPresent(consumerConfig::setQueues);
        }
    }
    
    //Does the registration configuration need to be updated
    private boolean needUpdateRegistryConfig(final DubboRegisterConfig dubboRegisterConfig) {
        if (Objects.isNull(registryConfig)) {
            return true;
        }
        return !Objects.equals(dubboRegisterConfig.getProtocol(), registryConfig.getProtocol())
                || !Objects.equals(dubboRegisterConfig.getRegister(), registryConfig.getAddress())
                || !Objects.equals(dubboRegisterConfig.getProtocol(), registryConfig.getProtocol());
    }

    //......
}

• org.apache.shenyu.plugin.apache.dubbo.subscriber.ApacheDubboMetaDataSubscriber#onSubscribe()

When the metadata is updated, the data synchronization module synchronizes the data from shenyu-admin to the gateway. The metadata update operation is performed in the onSubscribe() method.

public class ApacheDubboMetaDataSubscriber implements MetaDataSubscriber {
    //local memory cache
    private static final ConcurrentMap<String, MetaData> META_DATA = Maps.newConcurrentMap();

    //update metaData
    public void onSubscribe(final MetaData metaData) {
        // dubbo
        if (RpcTypeEnum.DUBBO.getName().equals(metaData.getRpcType())) {
            //Whether the corresponding metadata exists
            MetaData exist = META_DATA.get(metaData.getPath());
            if (Objects.isNull(exist) || Objects.isNull(ApacheDubboConfigCache.getInstance().get(metaData.getPath()))) {
                // initRef
                ApacheDubboConfigCache.getInstance().initRef(metaData);
            } else {
                // The corresponding metadata has undergone an update operation
                if (!Objects.equals(metaData.getServiceName(), exist.getServiceName())
                        || !Objects.equals(metaData.getRpcExt(), exist.getRpcExt())
                        || !Objects.equals(metaData.getParameterTypes(), exist.getParameterTypes())
                        || !Objects.equals(metaData.getMethodName(), exist.getMethodName())) {
                    //Build ReferenceConfig again based on the latest metadata
                    ApacheDubboConfigCache.getInstance().build(metaData);
                }
            }
            //local memory cache
            META_DATA.put(metaData.getPath(), metaData);
        }
    }

    //dalete
    public void unSubscribe(final MetaData metaData) {
        if (RpcTypeEnum.DUBBO.getName().equals(metaData.getRpcType())) {
            //使ReferenceConfig失效
            ApacheDubboConfigCache.getInstance().invalidate(metaData.getPath());
            META_DATA.remove(metaData.getPath());
        }
    }
}

• org.apache.shenyu.plugin.apache.dubbo.cache.ApacheDubboConfigCache#initRef()

Build ReferenceConfig objects from metaData.

public final class ApacheDubboConfigCache extends DubboConfigCache {
    //......
    
    public ReferenceConfig<GenericService> initRef(final MetaData metaData) {
            try {
                //First try to get it from the cache, and return it directly if it exists
                ReferenceConfig<GenericService> referenceConfig = cache.get(metaData.getPath());
                if (StringUtils.isNoneBlank(referenceConfig.getInterface())) {
                    return referenceConfig;
                }
            } catch (ExecutionException e) {
                LOG.error("init dubbo ref exception", e);
            }
          
            //build if not exist
            return build(metaData);
        }

        /**
         * Build reference config.
         */
        @SuppressWarnings("deprecation")
        public ReferenceConfig<GenericService> build(final MetaData metaData) {
            if (Objects.isNull(applicationConfig) || Objects.isNull(registryConfig)) {
                return new ReferenceConfig<>();
            }
            ReferenceConfig<GenericService> reference = new ReferenceConfig<>(); //ReferenceConfig
            reference.setGeneric("true"); //generic invoke
            reference.setAsync(true);//async

            reference.setApplication(applicationConfig);//applicationConfig
            reference.setRegistry(registryConfig);//registryConfig
            reference.setConsumer(consumerConfig);//consumerConfig
            reference.setInterface(metaData.getServiceName());//serviceName
            reference.setProtocol("dubbo");//dubbo
            reference.setCheck(false); 
            reference.setLoadbalance("gray");//gray

            Map<String, String> parameters = new HashMap<>(2);
            parameters.put("dispatcher", "direct");
            reference.setParameters(parameters);

            String rpcExt = metaData.getRpcExt();//rpc ext param
            DubboParam dubboParam = parserToDubboParam(rpcExt);
            if (Objects.nonNull(dubboParam)) {
                if (StringUtils.isNoneBlank(dubboParam.getVersion())) {
                    reference.setVersion(dubboParam.getVersion());//version
                }
                if (StringUtils.isNoneBlank(dubboParam.getGroup())) {
                    reference.setGroup(dubboParam.getGroup());//group
                }
                if (StringUtils.isNoneBlank(dubboParam.getUrl())) {
                    reference.setUrl(dubboParam.getUrl());//url
                }
                if (StringUtils.isNoneBlank(dubboParam.getCluster())) {
                    reference.setCluster(dubboParam.getCluster());
                }
                Optional.ofNullable(dubboParam.getTimeout()).ifPresent(reference::setTimeout);//timeout
                Optional.ofNullable(dubboParam.getRetries()).ifPresent(reference::setRetries);//retires
                Optional.ofNullable(dubboParam.getSent()).ifPresent(reference::setSent);//Whether to ack async-sent
            }
            try {
                //get GenericService
                Object obj = reference.get();
                if (Objects.nonNull(obj)) {
                    LOG.info("init apache dubbo reference success there meteData is :{}", metaData);
                    //cache reference
                    cache.put(metaData.getPath(), reference);
                }
            } catch (Exception e) {
                LOG.error("init apache dubbo reference exception", e);
            }
            return reference;
        }
    //......
    }

2.6 Execute ResponsePlugin

• org.apache.shenyu.plugin.response.ResponsePlugin#execute()

The response results are handled by the ResponsePlugin plugin.

    @Override
    public Mono<Void> execute(final ServerWebExchange exchange, final ShenyuPluginChain chain) {
        ShenyuContext shenyuContext = exchange.getAttribute(Constants.CONTEXT);
        assert shenyuContext != null;
        // handle results according to rpc type
        return writerMap.get(shenyuContext.getRpcType()).writeWith(exchange, chain);
    }

The processing type is determined by MessageWriter and the class inheritance relationship is as follows.

• MessageWriter: interface, defining message processing methods.
• NettyClientMessageWriter: processing of Netty call results.
• RPCMessageWriter: processing the results of RPC calls.
• WebClientMessageWriter: processing the results of WebClient calls.

Dubbo service call, the processing result is RPCMessageWriter of course.

• org.apache.shenyu.plugin.response.strategy.RPCMessageWriter#writeWith()

Process the response results in the writeWith() method.

public class RPCMessageWriter implements MessageWriter {

    @Override
    public Mono<Void> writeWith(final ServerWebExchange exchange, final ShenyuPluginChain chain) {
        return chain.execute(exchange).then(Mono.defer(() -> {
            Object result = exchange.getAttribute(Constants.RPC_RESULT); //result
            if (Objects.isNull(result)) { 
                Object error = ShenyuResultWrap.error(exchange, ShenyuResultEnum.SERVICE_RESULT_ERROR, null);
                return WebFluxResultUtils.result(exchange, error);
            }
            return WebFluxResultUtils.result(exchange, result);
        }));
    }
}

At this point in the analysis, the source code analysis of the Dubbo plugin is complete, and the analysis flow chart is as follows.

3. Summary

The source code analysis in this article starts from Dubbo service registration to Dubbo plug-in service calls. The Dubbo plugin is mainly used to handle the conversion of http requests to the dubbo protocol, and the main logic is implemented through generalized calls.