dubbo filter实现参数透传

1. RpcContext
   利用RpcContext实现consumer和provicer参数传递例如：

消费端：
RpcContext.getContext().setAttachment("bizId", "小程序"); 
//调用dubbo
activityAdminFacade.queryExchangeActivitiesByOption(option);

服务端：
@Override
    public PageResult<ExchangeActivityDTO> queryExchangeActivitiesByOption(ActivityQueryOption option) {
    String userInfo = RpcContext.getContext().getAttachment("bizId");
}

实际上rpcContext也是用到了dubbo filter 特性。ConsumerContextFilter attachment中参数会直接带到invocation对象，传递至provider端。finaly中RpcContext.getContext().clearAttachments(); 每次调用会直接清除。所以需要我们每次调用dubbo服务接口前都要设置setAttachment。

@Activate(group = Constants.CONSUMER, order = -10000)
public class ConsumerContextFilter implements Filter {

    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        RpcContext.getContext()
                .setInvoker(invoker)
                .setInvocation(invocation)
                .setLocalAddress(NetUtils.getLocalHost(), 0)
                .setRemoteAddress(invoker.getUrl().getHost(), 
                                  invoker.getUrl().getPort());
        if (invocation instanceof RpcInvocation) {
            ((RpcInvocation)invocation).setInvoker(invoker);
        }
        try {
            return invoker.invoke(invocation);
        } finally {
            RpcContext.getContext().clearAttachments();
        }
    }

}

2. 有的时候我们不想每次调用dubbo接口都要去设置RpcContext。所以需要我们自己去实现定义一个dubbo filter。当然我们也可以直接修改源码哈哈（不推荐）

2.1 范围：一个线程上下文内

public class BizIdUtils {
 
    private static final ThreadLocal<String> Cache
            = new ThreadLocal<String>();
 
    public static String getBizId() {
        return Cache.get();
    }
 
    public static void setBizId(String bizId) {
        Cache.set(bizId);
    }
 
    public static void clear() {
       Cache.remove();
    }
 
}

package com.test.dubbo;
 
public class TraceIdFilter implements Filter {
 
    @Override
    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        String traceId = RpcContext.getContext().getAttachment("BizId");
        if ( !StringUtils.isEmpty(BizId) ) {
            // *) 从RpcContext里获取bizId并保存
            BizIdUtils.setBizId(bizId);
        } else {
            // *) 交互前重新设置traceId, 避免信息丢失
            RpcContext.getContext().setAttachment("bizId", BizIdUtils.getBizId());
        }
        // *) 实际的rpc调用
        return invoker.invoke(invocation);
    }
}

BizIdUtils ThreadLocal就是用来保存当前线程的变量值。所以在一个线程上下文中，只需要在第一次设置RpcContext.setAttachment即可。比如web的一次请求。

2.2 范围：设置整个consumer端

public class MyFilter implements Filter {
    @Override
    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
 
        RpcContext.getContext().setAttachment("bizId", "电商");
        Result result = invoker.invoke(invocation);
       
        return result;
    }
}

这样我们consumer端就不需再调用RpcContext了。

3. 如何使filter生效
   我们自定义filter话，需要在resource下创建 /META-INFO/dubbo/com.alibaba.dubbo.rpc.Filter
   文件内容为

helloFilter=com.fcbox.mall.item.MyFilter

image.png

helloFilter为自定义的名称
然后再application.properties中配置
springboot：spring.dubbo.consumer.filter=helloFilter

spring dubbo需要我们自己去实现java配置，这个filter就存放在DubboProperties中consumerConfig中filter中：

@Configuration
@EnableConfigurationProperties(DubboProperties.class)
public class DubboAutoConfiguration {

    @Autowired
    private DubboProperties dubboProperties;

    @Autowired
    private Environment environment;

    @Bean
    public ApplicationConfig requestApplicationConfig() {
        ApplicationConfig applicationConfig = dubboProperties.getApplication();
        if(applicationConfig == null){
            applicationConfig = new ApplicationConfig();
        }
        return applicationConfig;
    }

    @Bean
    @Primary
    public RegistryConfig requestRegistryConfig() {
        RegistryConfig registryConfig = dubboProperties.getRegistry();
        if(registryConfig == null){
            registryConfig = new RegistryConfig();
        }
        return registryConfig;
    }

    @Bean
    public ProtocolConfig requestProtocolConfig() {
        ProtocolConfig protocolConfig = dubboProperties.getProtocol();

        if(protocolConfig == null){
            protocolConfig = new ProtocolConfig();
        }

        //获取启动参数,优先级最高
        String host=environment.getProperty("server.address");
        if(StringUtils.isNotEmpty(host)){
            protocolConfig.setHost(host);
        }


        return protocolConfig;
    }

    @Bean
    public MonitorConfig requestMonitorConfig() {
        MonitorConfig monitorConfig = dubboProperties.getMonitor();
        if(monitorConfig == null){
            monitorConfig = new MonitorConfig();
        }
        return monitorConfig;
    }
    
    @Bean
    public ProviderConfig requestProviderConfig(){
        ProviderConfig providerConfig = dubboProperties.getProvider();
        if(providerConfig == null){
            providerConfig = new ProviderConfig();
        }
        return providerConfig;
    }
    
    @Bean
    public ModuleConfig requestModuleConfig(){
        ModuleConfig moduleConfig = dubboProperties.getModule();
        if(moduleConfig == null){
            moduleConfig = new ModuleConfig();
        }
        return moduleConfig;
    }
    
    @Bean
    public MethodConfig requestMethodConfig(){
        MethodConfig  methodConfig = dubboProperties.getMethod();
        if(methodConfig == null){
            methodConfig = new MethodConfig();
        }
        return methodConfig;
    }
    
    @Bean
    public ConsumerConfig requestConsumerConfig(){
        ConsumerConfig consumerConfig = dubboProperties.getConsumer();
        if(consumerConfig == null){
            consumerConfig = new ConsumerConfig();
        }
        return consumerConfig;
    }

}

public class DubboProperties {

    private String scan;

    private ApplicationConfig application;

    private RegistryConfig registry;

    private ProtocolConfig protocol;

    private MonitorConfig monitor;
    
    private ProviderConfig provider;
    
    private ModuleConfig module;
    
    private MethodConfig method;
    
    private ConsumerConfig consumer;

consumer配置类：com.alibaba.dubbo.config.ConsumerConfig