Detailed Introduction to Dubbo SPI Plugin Definition and Usage on Apache Dubbo

Protocol Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

RPC protocol extension, encapsulating remote call details.

Contract:

When the user calls the invoke() method of the Invoker object returned by refer(), the protocol should execute the invoke() method of the Invoker object passed in by remote export() with the same URL.
The Invoker returned by refer() is implemented by the protocol, which usually sends a remote request within this Invoker. The Invoker passed in by export() is implemented and provided by the framework, which the protocol does not need to be concerned about.

Note

The protocol does not concern itself with the transparent proxying of business interfaces; it is Invoker centric, with the outer layer converting Invoker to the business interface.
The protocol does not necessarily have to be TCP network communication, such as through shared files, IPC inter-process communication, etc.

Extension Interface

org.apache.dubbo.rpc.Protocol
org.apache.dubbo.rpc.Exporter
org.apache.dubbo.rpc.Invoker

public interface Protocol {
 /**
 * Expose remote service:<br>
 * 1. The protocol, upon receiving requests, should record the request source address information: RpcContext.getContext().setRemoteAddress();<br>
 * 2. export() must be idempotent, meaning exposing the same URL's Invoker twice is the same as exposing it once.<br>
 * 3. The Invoker passed to export() is provided by the framework, and the protocol does not need to be concerned.<br>
 * 
 * @param <T> Service type
 * @param invoker Service execution body
 * @return exporter Reference to exposed service for cancellation
 * @throws RpcException Thrown when an error occurs in exposing the service, such as port occupied.
 */
 <T> Exporter<T> export(Invoker<T> invoker) throws RpcException;
 
 /**
 * Reference a remote service:<br>
 * 1. When the user calls invoke() on the Invoker object returned by refer(), the protocol should execute the invoke() method of the Invoker object passed in by remote export() with the same URL.<br>
 * 2. The Invoker returned by refer() is implemented by the protocol, typically sending the remote request within this Invoker.<br>
 * 3. When check=false is set in the URL, connection failures should not throw exceptions but should automatically recover internally.<br>
 * 
 * @param <T> Service type
 * @param type Service type
 * @param url Remote service's URL
 * @return invoker Local proxy of the service
 * @throws RpcException Thrown when connection to the service provider fails.
 */
 <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException;
 
}

Extension Configuration

<!-- Declare protocol, if no id is configured, name will be used as id -->
<dubbo:protocol id="xxx1" name="xxx" />
<!-- Reference protocol, if no protocol attribute is configured, it will automatically scan protocol configuration in ApplicationContext -->
<dubbo:service protocol="xxx1" />
<!-- Default value for referenced protocol, used when <dubbo:service> does not configure protocol attribute -->
<dubbo:provider protocol="xxx1" />

Known Extensions

org.apache.dubbo.rpc.protocol.injvm.InjvmProtocol
org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol
org.apache.dubbo.rpc.protocol.rmi.RmiProtocol
org.apache.dubbo.rpc.protocol.http.HttpProtocol
org.apache.dubbo.rpc.protocol.http.hessian.HessianProtocol
org.apache.dubbo.rpc.support.MockProtocol

Extension Example

Maven project structure:

Call Interceptor Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

The interception during the call process of service providers and consumers is mainly implemented based on this extension point. This interceptor is executed each time a remote method is invoked, so be mindful of its impact on performance.

Convention:

User-defined filters are executed after built-in filters by default.
The special value default indicates the position where the default extension point is inserted. For example: filter="xxx,default,yyy" means xxx is before the default filter, and yyy is after it.
The special symbol - indicates exclusion. For example: filter="-foo1" excludes the default extension point foo1. For instance: filter="-default" excludes all default extension points.
When filters are configured for both provider and service, all filters are accumulated rather than overridden. For example: <dubbo:provider filter="xxx,yyy"/> and <dubbo:service filter="aaa,bbb" /> means xxx, yyy, aaa, bbb will all be effective. To override, configure: <dubbo:service filter="-xxx,-yyy,aaa,bbb" />

Extension Interface

org.apache.dubbo.rpc.Filter

Invoker Listener Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

This event is triggered when there is a service reference.

Extension Interface

org.apache.dubbo.rpc.InvokerListener

Extension Configuration

<!-- Reference Service Listener -->
<dubbo:reference listener="xxx,yyy" /> 
<!-- Default Listener for Reference Services -->
<dubbo:consumer listener="xxx,yyy" />

Known Extensions

org.apache.dubbo.rpc.listener.DeprecatedInvokerListener

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxInvokerListener.java (implements InvokerListener interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.rpc.InvokerListener (text file containing: xxx=com.xxx.XxxInvokerListener)

XxxInvokerListener.java:

package com.xxx;
 
import org.apache.dubbo.rpc.InvokerListener;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.RpcException;
 
public class XxxInvokerListener implements InvokerListener {
 public void referred(Invoker<?> invoker) throws RpcException {
 // ...
 }
 public void destroyed(Invoker<?> invoker) throws RpcException {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.rpc.InvokerListener:

Export Listener Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

This event is triggered when services are exposed.

Extension Interface

org.apache.dubbo.rpc.ExporterListener

Extension Configuration

<!-- Service export listener -->
<dubbo:service listener="xxx,yyy" />
<!-- Default listener for service export -->
<dubbo:provider listener="xxx,yyy" />

Known Extension

org.apache.dubbo.registry.directory.RegistryExporterListener

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxExporterListener.java (implements ExporterListener interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.rpc.ExporterListener (plain text file, content: xxx=com.xxx.XxxExporterListener)

XxxExporterListener.java:

package com.xxx;
 
import org.apache.dubbo.rpc.ExporterListener;
import org.apache.dubbo.rpc.Exporter;
import org.apache.dubbo.rpc.RpcException;
 
 
public class XxxExporterListener implements ExporterListener {
 public void exported(Exporter<?> exporter) throws RpcException {
 // ...
 }
 public void unexported(Exporter<?> exporter) throws RpcException {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.rpc.ExporterListener:

Cluster extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

When there are multiple service providers, organize them into a cluster and masquerade as a single provider.

Extension Interface

org.apache.dubbo.rpc.cluster.Cluster

Extension Configuration

<dubbo:protocol cluster="xxx" />
<!-- Default configuration; if <dubbo:protocol> does not configure cluster, this configuration will be used -->
<dubbo:provider cluster="xxx" />

Known Extensions

org.apache.dubbo.rpc.cluster.support.wrapper.MockClusterWrapper
org.apache.dubbo.rpc.cluster.support.FailoverCluster
org.apache.dubbo.rpc.cluster.support.FailfastCluster
org.apache.dubbo.rpc.cluster.support.FailsafeCluster
org.apache.dubbo.rpc.cluster.support.FailbackCluster
org.apache.dubbo.rpc.cluster.support.ForkingCluster
org.apache.dubbo.rpc.cluster.support.AvailableCluster
org.apache.dubbo.rpc.cluster.support.MergeableCluster
org.apache.dubbo.rpc.cluster.support.BroadcastCluster
org.apache.dubbo.rpc.cluster.support.registry.ZoneAwareCluster

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxCluster.java (implements Cluster interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.rpc.cluster.Cluster (plain text file with content: xxx=com.xxx.XxxCluster)

XxxCluster.java:

Router Extensions

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Select one from multiple service providers to call.

Extension Interfaces

org.apache.dubbo.rpc.cluster.RouterFactory
org.apache.dubbo.rpc.cluster.Router

Known Extensions

org.apache.dubbo.rpc.cluster.router.ScriptRouterFactory
org.apache.dubbo.rpc.cluster.router.FileRouterFactory
org.apache.dubbo.rpc.cluster.router.condition.config.AppRouterFactory
org.apache.dubbo.rpc.cluster.CacheableRouterFactory
org.apache.dubbo.rpc.cluster.router.condition.ConditionRouterFactory
org.apache.dubbo.rpc.cluster.router.mock.MockRouterFactory
org.apache.dubbo.rpc.cluster.router.condition.config.ServiceRouterFactory
org.apache.dubbo.rpc.cluster.router.tag.TagRouterFactory

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxRouterFactory.java (implements RouterFactory interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.rpc.cluster.RouterFactory (plain text file, content: xxx=com.xxx.XxxRouterFactory)

XxxRouterFactory.java:

package com.xxx;
 
import org.apache.dubbo.rpc.cluster.RouterFactory;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.Invocation;
import org.apache.dubbo.rpc.RpcException;
 
public class XxxRouterFactory implements RouterFactory {
 public Router getRouter(URL url) {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.rpc.cluster.RouterFactory:

Load Balance Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Select one from multiple service providers for invocation.

Extension Interface

org.apache.dubbo.rpc.cluster.LoadBalance

Extension Configuration

<dubbo:protocol loadbalance="xxx" />
<!-- Default value settings, when <dubbo:protocol> does not configure loadbalance, this configuration is used -->
<dubbo:provider loadbalance="xxx" />

Known Extensions

org.apache.dubbo.rpc.cluster.loadbalance.RandomLoadBalance
org.apache.dubbo.rpc.cluster.loadbalance.RoundRobinLoadBalance
org.apache.dubbo.rpc.cluster.loadbalance.LeastActiveLoadBalance
org.apache.dubbo.rpc.cluster.loadbalance.ConsistentHashLoadBalance
org.apache.dubbo.rpc.cluster.loadbalance.ShortestResponseLoadBalance

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxLoadBalance.java (implements LoadBalance interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.rpc.cluster.LoadBalance (plain text file, content: xxx=com.xxx.XxxLoadBalance)

XxxLoadBalance.java：

Merger Result Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Merging return results, used for grouping aggregation.

Extension Interface

org.apache.dubbo.rpc.cluster.Merger

Extension Configuration

<dubbo:method merger="xxx" />

Known Extensions

org.apache.dubbo.rpc.cluster.merger.ArrayMerger
org.apache.dubbo.rpc.cluster.merger.ListMerger
org.apache.dubbo.rpc.cluster.merger.SetMerger
org.apache.dubbo.rpc.cluster.merger.MapMerger
org.apache.dubbo.rpc.cluster.merger.ByteArrayMerger
org.apache.dubbo.rpc.cluster.merger.CharArrayMerger
org.apache.dubbo.rpc.cluster.merger.ShortArrayMerger
org.apache.dubbo.rpc.cluster.merger.IntArrayMerger
org.apache.dubbo.rpc.cluster.merger.LongArrayMerger
org.apache.dubbo.rpc.cluster.merger.FloatArrayMerger
org.apache.dubbo.rpc.cluster.merger.DoubleArrayMerger
org.apache.dubbo.rpc.cluster.merger.BooleanArrayMerger

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxMerger.java (implements Merger interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.rpc.cluster.Merger (plain text file, content: xxx=com.xxx.XxxMerger)

XxxMerger.java：

package com.xxx;
 
import org.apache.dubbo.rpc.cluster.Merger;
 
public class XxxMerger<T> implements Merger<T> {
 public T merge(T... results) {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.rpc.cluster.Merger：

Registry Center Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Responsible for the registration and discovery of services.

Extension Interfaces

org.apache.dubbo.registry.RegistryFactory
org.apache.dubbo.registry.Registry

Extension Configuration

<!-- Define the registry -->
<dubbo:registry id="xxx1" address="xxx://ip:port" />
<!-- Reference the registry, if the registry attribute is not configured, it will automatically scan the registry configuration in the ApplicationContext -->
<dubbo:service registry="xxx1" />
<!-- Reference the default value of the registry, when <dubbo:service> does not configure the registry attribute, use this configuration -->
<dubbo:provider registry="xxx1" />

Extension Contracts

RegistryFactory.java：

Monitoring Center Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Responsible for monitoring service call counts and call times.

Extension Interfaces

org.apache.dubbo.monitor.MonitorFactory
org.apache.dubbo.monitor.Monitor

Extension Configuration

<!-- Define the monitoring center -->
<dubbo:monitor address="xxx://ip:port" />

Known Extensions

org.apache.dubbo.monitor.support.dubbo.DubboMonitorFactory

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxMonitorFactory.java (implements the MonitorFactory interface)
 |-XxxMonitor.java (implements the Monitor interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.monitor.MonitorFactory (text file, content: xxx=com.xxx.XxxMonitorFactory)

XxxMonitorFactory.java：

package com.xxx;
 
import org.apache.dubbo.monitor.MonitorFactory;
import org.apache.dubbo.monitor.Monitor;
import org.apache.dubbo.common.URL;
 
public class XxxMonitorFactory implements MonitorFactory {
 public Monitor getMonitor(URL url) {
 return new XxxMonitor(url);
 }
}

XxxMonitor.java：

Extension Point Loading Extensions

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

The loading container for extension points, capable of loading extension points from different containers.

Extension Interface

org.apache.dubbo.common.extension.ExtensionFactory

Extension Configuration

<dubbo:application compiler="jdk" />

Known Extensions

org.apache.dubbo.common.extension.factory.SpiExtensionFactory
org.apache.dubbo.config.spring.extension.SpringExtensionFactory

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxExtensionFactory.java (implements ExtensionFactory interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.common.extension.ExtensionFactory (plain text file, content: xxx=com.xxx.XxxExtensionFactory)

XxxExtensionFactory.java:

package com.xxx;
 
import org.apache.dubbo.common.extension.ExtensionFactory;
 
public class XxxExtensionFactory implements ExtensionFactory {
 public Object getExtension(Class<?> type, String name) {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.common.extension.ExtensionFactory:

Dynamic Proxy Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Converts the Invoker interface into a business interface.

Extension Interface

org.apache.dubbo.rpc.ProxyFactory

Extension Configuration

<dubbo:protocol proxy="xxx" />
<!-- Default configuration, used when the <dubbo:protocol> does not configure the proxy attribute -->
<dubbo:provider proxy="xxx" />

Known Extensions

org.apache.dubbo.rpc.proxy.JdkProxyFactory
org.apache.dubbo.rpc.proxy.JavassistProxyFactory

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxProxyFactory.java (implements ProxyFactory interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.rpc.ProxyFactory (plain text file, content: xxx=com.xxx.XxxProxyFactory)

XxxProxyFactory.java:

Liveness Probe

Mon, 01 Jan 0001 00:00:00 +0000

Extended Description

Expands the detection points for application liveness.

Extended Interface

org.apache.dubbo.qos.probe.LivenessProbe

Extended Configuration

Dubbo QOS live command auto-discovery

Known Extensions

No default implementation available

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxLivenessProbe.java (Implements LivenessProbe interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.qos.probe.LivenessProbe (Plain text file, content: xxx=com.xxx.XxxLivenessProbe)

XxxLivenessProbe.java:

package com.xxx;
 
public class XxxLivenessProbe implements LivenessProbe {
 
 public boolean check() {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.qos.probe.LivenessProbe:

Readiness Probe

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Extend application readiness detection points.

Extension Interface

org.apache.dubbo.qos.probe.ReadinessProbe

Extension Configuration

Dubbo QOS ready command auto-discovery

Known Extensions

org.apache.dubbo.qos.probe.impl.BootstrapReadinessProbe
org.apache.dubbo.qos.probe.impl.ProviderReadinessProbe

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxReadinessProbe.java (implements ReadinessProbe interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.qos.probe.ReadinessProbe (plain text file, content: xxx=com.xxx.XxxReadinessProbe)

XxxReadinessProbe.java:

package com.xxx;
 
public class XxxReadinessProbe implements ReadinessProbe {
 
 public boolean check() {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.qos.probe.ReadinessProbe:

xxx=com.xxx.XxxReadinessProbe

Startup Probe

Mon, 01 Jan 0001 00:00:00 +0000

Expansion Description

Detection points for extended application startup.

Extension Interface

org.apache.dubbo.qos.probe.StartupProbe

Extension Configuration

Dubbo QOS startup command auto-discovery

Known Extensions

org.apache.dubbo.qos.probe.impl.BootstrapLivenessProbe

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxStartupProbe.java (implements StartupProbe interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.qos.probe.StartupProbe (plain text file, content: xxx=com.xxx.XxxStartupProbe)

XxxStartupProbe.java:

package com.xxx;
 
public class XxxStartupProbe implements StartupProbe {
 
 public boolean check() {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.qos.probe.StartupProbe:

xxx=com.xxx.XxxStartupProbe

Compiler Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Java code compiler for dynamically generating bytecode to accelerate calls.

Extension Interface

org.apache.dubbo.common.compiler.Compiler

Extension Configuration

Automatically loaded

Known Extensions

org.apache.dubbo.common.compiler.support.JdkCompiler
org.apache.dubbo.common.compiler.support.JavassistCompiler

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxCompiler.java (implements Compiler interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.common.compiler.Compiler (text file containing: xxx=com.xxx.XxxCompiler)

XxxCompiler.java：

package com.xxx;
 
import org.apache.dubbo.common.compiler.Compiler;
 
public class XxxCompiler implements Compiler {
 public Object getExtension(Class<?> type, String name) {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.common.compiler.Compiler：

Configuration Center Extension

Mon, 01 Jan 0001 00:00:00 +0000

Design Purpose

The core function of the configuration center is to serve as a Key-Value storage. The Dubbo framework informs the configuration center of the keys it is concerned about, and the configuration center returns the corresponding value for those keys.

Divided by application scenario, the configuration center primarily undertakes the following responsibilities in the Dubbo framework:

As an externalized configuration center, storing the dubbo.properties configuration file, where the key is usually the filename, such as dubbo.properties, and the value is the content of the configuration file.
Storing individual configuration items, such as various switches and constant values.
Storing service governance rules, where the key is usually organized in the format of “service name + rule type,” and the value is the specific governance rule.

To further implement grouped management of key-values, Dubbo’s configuration center has also integrated the concepts of namespace and group, which are reflected in many professional third-party configuration centers. Generally, the namespace is used to isolate different tenants, while the group is used to group the collection of keys for the same tenant.

Metadata Center Extension

Mon, 01 Jan 0001 00:00:00 +0000

Design Purpose

Please refer to the Metadata Center Manual

Extension Interfaces

org.apache.dubbo.metadata.store.MetadataReportFactory
org.apache.dubbo.metadata.store.MetadataReport

Known Extensions

Implementation Principles

SPI Definition

Reference: org.apache.dubbo.metadata.store.MetadataReportFactory, org.apache.dubbo.metadata.store.MetadataReport

@SPI("redis")
public interface MetadataReportFactory {
 @Adaptive({"protocol"})
 MetadataReport getMetadataReport(URL url);
}

Custom Metadata Storage

The following example describes the Redis storage.

Create a new project that needs to support the following modifications:

Extend AbstractMetadataReport

public class RedisMetadataReport extends AbstractMetadataReport {
 private final static Logger logger = LoggerFactory.getLogger(RedisMetadataReport.class);
 final JedisPool pool;

 public RedisMetadataReport(URL url) {
 super(url);
 pool = new JedisPool(new JedisPoolConfig(), url.getHost(), url.getPort());
 }
 @Override
 protected void doStoreProviderMetadata(ProviderMetadataIdentifier providerMetadataIdentifier, String serviceDefinitions) {
 this.storeMetadata(providerMetadataIdentifier, serviceDefinitions);
 }
 @Override
 protected void doStoreConsumerMetadata(ConsumerMetadataIdentifier consumerMetadataIdentifier, String value) {
 this.storeMetadata(consumerMetadataIdentifier, value);
 }
 private void storeMetadata(MetadataIdentifier metadataIdentifier, String v) {
 try (Jedis jedis = pool.getResource()) {
 jedis.set(metadataIdentifier.getIdentifierKey() + META_DATA_SOTRE_TAG, v);
 } catch (Throwable e) {
 logger.error("Failed to put " + metadataIdentifier + " to redis " + v + ", cause: " + e.getMessage(), e);
 throw new RpcException("Failed to put " + metadataIdentifier + " to redis " + v + ", cause: " + e.getMessage(), e);
 }
 }
}

Extend AbstractMetadataReportFactory

public class RedisMetadataReportFactory extends AbstractMetadataReportFactory {
 @Override
 public MetadataReport createMetadataReport(URL url) {
 return new RedisMetadataReport(url);
 }
}

Add MetadataReportFactory

META-INF/dubbo/internal/org.apache.dubbo.metadata.store.MetadataReportFactory

Message Dispatch Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Channel information dispatcher, used to specify thread pool model.

Extension Interface

org.apache.dubbo.remoting.Dispatcher

Extension Configuration

<dubbo:protocol dispatcher="xxx" />
<!-- Default value setting. When <dubbo:protocol> does not configure the dispatcher attribute, this configuration is used -->
<dubbo:provider dispatcher="xxx" />

Known Extensions

org.apache.dubbo.remoting.transport.dispatcher.all.AllDispatcher
org.apache.dubbo.remoting.transport.dispatcher.direct.DirectDispatcher
org.apache.dubbo.remoting.transport.dispatcher.message.MessageOnlyDispatcher
org.apache.dubbo.remoting.transport.dispatcher.execution.ExecutionDispatcher
org.apache.dubbo.remoting.transport.dispatcher.connection.ConnectionOrderedDispatcher

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxDispatcher.java (implements Dispatcher interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.remoting.Dispatcher (plain text file, content: xxx=com.xxx.XxxDispatcher)

XxxDispatcher.java：

Thread Pool Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

The thread pool implementation strategy for service providers requires creating a thread in the thread pool to execute the service provider’s business logic when the server receives a request.

Extension Interface

org.apache.dubbo.common.threadpool.ThreadPool

Extension Configuration

<dubbo:protocol threadpool="xxx" />
<!-- Default value configuration, used when <dubbo:protocol> does not configure threadpool -->
<dubbo:provider threadpool="xxx" />

Known Extensions

org.apache.dubbo.common.threadpool.FixedThreadPool
org.apache.dubbo.common.threadpool.CachedThreadPool

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxThreadPool.java (implements ThreadPool interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.common.threadpool.ThreadPool (plain text file, content: xxx=com.xxx.XxxThreadPool)

XxxThreadPool.java:

Serialization Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Convert objects into byte streams for network transmission, and convert byte streams into objects for restoring the received byte stream data back into objects.

Extension Interfaces

org.apache.dubbo.common.serialize.Serialization
org.apache.dubbo.common.serialize.ObjectInput
org.apache.dubbo.common.serialize.ObjectOutput

Extension Configuration

<!-- Serialization method for the protocol -->
<dubbo:protocol serialization="xxx" />
<!-- Default value setting, when <dubbo:protocol> does not configure serialization, use this configuration -->
<dubbo:provider serialization="xxx" />

Known Extensions

org.apache.dubbo.common.serialize.dubbo.DubboSerialization
org.apache.dubbo.common.serialize.hessian.Hessian2Serialization
org.apache.dubbo.common.serialize.java.JavaSerialization
org.apache.dubbo.common.serialize.java.CompactedJavaSerialization

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxSerialization.java (implements Serialization interface)
 |-XxxObjectInput.java (implements ObjectInput interface)
 |-XxxObjectOutput.java (implements ObjectOutput interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.common.serialize.Serialization (plain text file, content: xxx=com.xxx.XxxSerialization)

XxxSerialization.java：

Network Transport Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Implementations for remote communication servers and client transports.

Extension Interfaces

org.apache.dubbo.remoting.Transporter
org.apache.dubbo.remoting.Server
org.apache.dubbo.remoting.Client

Extension Configuration

<!-- Server and client use the same transport implementation -->
<dubbo:protocol transporter="xxx" /> 
<!-- Server and client use different transport implementations -->
<dubbo:protocol server="xxx" client="xxx" /> 
<!-- Default settings, used when <dubbo:protocol> does not configure transporter/server/client attributes -->
<dubbo:provider transporter="xxx" server="xxx" client="xxx" />

Known Extensions

org.apache.dubbo.remoting.transport.transporter.netty.NettyTransporter
org.apache.dubbo.remoting.transport.transporter.mina.MinaTransporter
org.apache.dubbo.remoting.transport.transporter.grizzly.GrizzlyTransporter

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxTransporter.java (implements Transporter interface)
 |-XxxServer.java (implements Server interface)
 |-XxxClient.java (implements Client interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.remoting.Transporter (plain text file, contents: xxx=com.xxx.XxxTransporter)

XxxTransporter.java：

Information Exchange Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Implement the Request-Response information exchange semantics based on the transport layer.

Extension Interfaces

org.apache.dubbo.remoting.exchange.Exchanger
org.apache.dubbo.remoting.exchange.ExchangeServer
org.apache.dubbo.remoting.exchange.ExchangeClient

Extension Configuration

<dubbo:protocol exchanger="xxx" />
<!-- Default value setting, when <dubbo:protocol> does not configure the exchanger attribute, this configuration is used -->
<dubbo:provider exchanger="xxx" />

Known Extension

org.apache.dubbo.remoting.exchange.exchanger.HeaderExchanger

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxExchanger.java (implements Exchanger interface)
 |-XxxExchangeServer.java (implements ExchangeServer interface)
 |-XxxExchangeClient.java (implements ExchangeClient interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.remoting.exchange.Exchanger (plain text file, content: xxx=com.xxx.XxxExchanger)

XxxExchanger.java：

Networking Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Peer network node networker.

Extension Interface

org.apache.dubbo.remoting.p2p.Networker

Extension Configuration

<dubbo:protocol networker="xxx" />
<!-- Default setting. When <dubbo:protocol> does not configure the networker attribute, use this configuration -->
<dubbo:provider networker="xxx" />

Known Extensions

org.apache.dubbo.remoting.p2p.support.MulticastNetworker
org.apache.dubbo.remoting.p2p.support.FileNetworker

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxNetworker.java (implements Networker interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.remoting.p2p.Networker (plain text file, content: xxx=com.xxx.XxxNetworker)

XxxNetworker.java:

package com.xxx;
 
import org.apache.dubbo.remoting.p2p.Networker;
 
public class XxxNetworker implements Networker {
 public Group lookup(URL url) {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.remoting.p2p.Networker:

Peer-to-peer network node aggregator extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Peer-to-peer network node aggregator.

Extension Interfaces

org.apache.dubbo.container.page.PageHandler

Extension Configuration

<dubbo:protocol page="xxx,yyy" />
<!-- Default value settings, when <dubbo:protocol> does not configure the page attribute, use this configuration -->
<dubbo:provider page="xxx,yyy" />

Known Extensions

org.apache.dubbo.container.page.pages.HomePageHandler
org.apache.dubbo.container.page.pages.StatusPageHandler
org.apache.dubbo.container.page.pages.LogPageHandler
org.apache.dubbo.container.page.pages.SystemPageHandler

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxPageHandler.java (implements PageHandler interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.container.page.PageHandler (plain text file with content: xxx=com.xxx.XxxPageHandler)

XxxPageHandler.java：

Telnet Command Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

All servers support telnet access for manual intervention.

Extension Interface

org.apache.dubbo.remoting.telnet.TelnetHandler

Extension Configuration

<dubbo:protocol telnet="xxx,yyy" />
<!-- Default value setting, when <dubbo:protocol> does not configure the telnet attribute, use this configuration -->
<dubbo:provider telnet="xxx,yyy" />

Known Extensions

org.apache.dubbo.remoting.telnet.support.ClearTelnetHandler
org.apache.dubbo.remoting.telnet.support.ExitTelnetHandler
org.apache.dubbo.remoting.telnet.support.HelpTelnetHandler
org.apache.dubbo.remoting.telnet.support.StatusTelnetHandler
org.apache.dubbo.rpc.dubbo.telnet.ListTelnetHandler
org.apache.dubbo.rpc.dubbo.telnet.ChangeTelnetHandler
org.apache.dubbo.rpc.dubbo.telnet.CurrentTelnetHandler
org.apache.dubbo.rpc.dubbo.telnet.InvokeTelnetHandler
org.apache.dubbo.rpc.dubbo.telnet.TraceTelnetHandler
org.apache.dubbo.rpc.dubbo.telnet.CountTelnetHandler
org.apache.dubbo.rpc.dubbo.telnet.PortTelnetHandler

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxTelnetHandler.java (implements TelnetHandler interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.remoting.telnet.TelnetHandler (plain text file, content: xxx=com.xxx.XxxTelnetHandler)

XxxTelnetHandler.java:

Status Check Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Checks the status of various resources that the service depends on. This status check can be used for both telnet’s status command and hosting’s status page.

Extension Interface

org.apache.dubbo.common.status.StatusChecker

Extension Configuration

<dubbo:protocol status="xxx,yyy" />
<!-- Default value setting. When the <dubbo:protocol> does not have a status attribute configured, this configuration is used -->
<dubbo:provider status="xxx,yyy" />

Known Extensions

org.apache.dubbo.common.status.support.MemoryStatusChecker
org.apache.dubbo.common.status.support.LoadStatusChecker
org.apache.dubbo.rpc.dubbo.status.ServerStatusChecker
org.apache.dubbo.rpc.dubbo.status.ThreadPoolStatusChecker
org.apache.dubbo.registry.directory.RegistryStatusChecker
org.apache.dubbo.rpc.config.spring.status.SpringStatusChecker
org.apache.dubbo.rpc.config.spring.status.DataSourceStatusChecker

Extension Example

Maven project structure:

Container Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Service container extension for customizing loading content.

Extension Interface

org.apache.dubbo.container.Container

Extension Configuration

java org.apache.dubbo.container.Main spring jetty log4j

Known Extensions

org.apache.dubbo.container.spring.SpringContainer
org.apache.dubbo.container.spring.JettyContainer
org.apache.dubbo.container.spring.Log4jContainer

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxContainer.java (implements Container interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.container.Container (plain text file, content: xxx=com.xxx.XxxContainer)

XxxContainer.java：

package com.xxx;
 
org.apache.dubbo.container.Container;
 
 
public class XxxContainer implements Container {
 public Status start() {
 // ...
 }
 public Status stop() {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.container.Container：

Cache Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Use request parameters as keys to cache return results.

Extension Interface

org.apache.dubbo.cache.CacheFactory

Extension Configuration

<dubbo:service cache="lru" />
<!-- Method-level caching -->
<dubbo:service><dubbo:method cache="lru" /></dubbo:service> 
<!-- Default value setting, used when <dubbo:service> does not configure the cache property -->
<dubbo:provider cache="xxx,yyy" />

Known Extensions

org.apache.dubbo.cache.support.lru.LruCacheFactory
org.apache.dubbo.cache.support.threadlocal.ThreadLocalCacheFactory
org.apache.dubbo.cache.support.jcache.JCacheFactory

Extension Examples

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxCacheFactory.java (implements CacheFactory interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.cache.CacheFactory (plain text file, content: xxx=com.xxx.XxxCacheFactory)

XxxCacheFactory.java:

Validation Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Parameter validation extension point.

Extension Interface

org.apache.dubbo.validation.Validation

Extension Configuration

<dubbo:service validation="xxx,yyy" />
<!-- Default value setting, when <dubbo:service> does not configure the validation attribute, use this configuration -->
<dubbo:provider validation="xxx,yyy" />

Known Extensions

org.apache.dubbo.validation.support.jvalidation.JValidation

Extension Examples

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxValidation.java (implements Validation interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.validation.Validation (plain text file, content: xxx=com.xxx.XxxValidation)

XxxValidation.java：

package com.xxx;
 
import org.apache.dubbo.validation.Validation;
 
public class XxxValidation implements Validation {
 public Object getValidator(URL url) {
 // ...
 }
}

XxxValidator.java：

Logger Adapter Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

Log output adaptation extension point.

Extension Interface

org.apache.dubbo.common.logger.LoggerAdapter

Extension Configuration

<dubbo:application logger="xxx" />

or:

-Ddubbo:application.logger=xxx

Known Extensions

org.apache.dubbo.common.logger.slf4j.Slf4jLoggerAdapter
org.apache.dubbo.common.logger.jcl.JclLoggerAdapter
org.apache.dubbo.common.logger.log4j.Log4jLoggerAdapter
org.apache.dubbo.common.logger.log4j2.Log4j2LoggerAdapter
org.apache.dubbo.common.logger.jdk.JdkLoggerAdapter

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxLoggerAdapter.java (implements LoggerAdapter interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.common.logger.LoggerAdapter (plain text file, content: xxx=com.xxx.XxxLoggerAdapter)

XxxLoggerAdapter.java:

package com.xxx;
 
import org.apache.dubbo.common.logger.LoggerAdapter;
 
public class XxxLoggerAdapter implements LoggerAdapter {
 public Logger getLogger(URL url) {
 // ...
 }
}

XxxLogger.java:

QoS Anonymous Access Permission Verification Extension

Mon, 01 Jan 0001 00:00:00 +0000

Extension Description

QoS anonymous access permission verification extension point.

Extension Interface

org.apache.dubbo.qos.permission.PermissionChecker

Extension Configuration

Dubbo QoS dubbo.application.qos-anonymous-access-permission-level anonymous access permission verification.

Default Implementation

org.apache.dubbo.qos.permission.DefaultAnonymousAccessPermissionChecker

Extension Example

Maven project structure:

src
 |-main
 |-java
 |-com
 |-xxx
 |-XxxPermissionChecker.java (Implementing the PermissionChecker interface)
 |-resources
 |-META-INF
 |-dubbo
 |-org.apache.dubbo.qos.permission.PermissionChecker` (Plain text file, content: qosPermissionChecker=com.xxx.XxxPermissionChecker)

XxxPermissionChecker.java:

package com.xxx.qos.permission;

import org.apache.dubbo.qos.permission.PermissionChecker;

public class XxxAnonymousAccessPermissionChecker implements PermissionChecker {

 @Override
 public boolean access(CommandContext commandContext, PermissionLevel defaultCmdRequiredPermissionLevel) {
 // ...
 }
}

META-INF/dubbo/org.apache.dubbo.qos.permission.PermissionChecker: