Call Interceptor Extension

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

Extension Configuration

<!-- Consumer call process interception -->
<dubbo:reference filter="xxx,yyy" />
<!-- Default interceptor for consumer call process, which intercepts all references -->
<dubbo:consumer filter="xxx,yyy"/>
<!-- Provider call process interception -->
<dubbo:service filter="xxx,yyy" />
<!-- Default interceptor for provider call process, which intercepts all services -->
<dubbo:provider filter="xxx,yyy"/>

Known Extensions

• org.apache.dubbo.rpc.filter.EchoFilter
• org.apache.dubbo.rpc.filter.GenericFilter
• org.apache.dubbo.rpc.filter.GenericImplFilter
• org.apache.dubbo.rpc.filter.TokenFilter
• org.apache.dubbo.rpc.filter.AccessLogFilter
• org.apache.dubbo.rpc.filter.CountFilter
• org.apache.dubbo.rpc.filter.ActiveLimitFilter
• org.apache.dubbo.rpc.filter.ClassLoaderFilter
• org.apache.dubbo.rpc.filter.ContextFilter
• org.apache.dubbo.rpc.filter.ConsumerContextFilter
• org.apache.dubbo.rpc.filter.ExceptionFilter
• org.apache.dubbo.rpc.filter.ExecuteLimitFilter
• org.apache.dubbo.rpc.filter.DeprecatedFilter

Extension Example

Maven project structure:

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

XxxFilter.java:

package com.xxx;

import org.apache.dubbo.rpc.Filter;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.Invocation;
import org.apache.dubbo.rpc.Result;
import org.apache.dubbo.rpc.RpcException;

public class XxxFilter implements Filter {
    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        // before filter ...
        Result result = invoker.invoke(invocation);
        // after filter ...
        return result;
    }
}

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

xxx=com.xxx.XxxFilter