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操作步骤如下：
1. k8s环境下，consumer端开启mesh模式
2. consumer端需要调用多个provider
3. provider有应用级注册和接口级注册，并且需要的provider不再同一个namespace下
4. 原有项目存在dubbo2.6与3.1多版本间的相互调用，在开启消费端mesh（dubbo3.1）后，无法调用到2.6的服务提供者

**问题：**

1. 如何实现在一个consumer下，调用多个namespace下的provider，并且provider有应用级注册和接口级注册
2. dubbo3.1消费端在开启mesh后，如何调用版本是2.6的服务提供者
/**
     * Service target URL for direct invocation, if this is specified, then registry center takes no effect.
     */
    String url() default "";
    /**
     * Client transport type, default value is "netty"
     */
    String client() default "";
    /**
     * Whether to enable generic invocation, default value is false
     *
     * @deprecated Do not need specify generic value, judge by injection type and interface class
     */
    @Deprecated
    boolean generic() default false;
    /**
     * When enable, prefer to call local service in the same JVM if it's present, default value is true
     *
     * @deprecated using scope="local" or scope="remote" instead
     */
    @Deprecated
    boolean injvm() default true;
    /**
     * Check if service provider is available during boot up, default value is true
     */
    boolean check() default true;
    /**
     * Whether eager initialize the reference bean when all properties are set, default value is true ( null as true)
     *
     * @see ReferenceConfigBase#shouldInit()