初次建立dubbo專案，並啟動服務提供方時會看到如下的警告。

log4j:WARN No appenders could be found for logger (com.alibaba.dubbo.common.logger.LoggerFactory).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

現在希望使用logback來輸出日誌，因此需要新增相關依賴。
根據

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.7</version>
        </dependency>
        <dependency
 
>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.3</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId
 
>log4j-over-slf4j</artifactId>
            <version>1.7.7</version>
        </dependency>

根據官網提示

log4j-over-slf4j
SLF4J ship with a module called log4j-over-slf4j. It allows log4j users to migrate existing applications to SLF4J without changing a single line of code but simply by replacing the log4j.jar file with log4j-over-slf4j.jar, as described below.

因此在dubbo的依賴中要排除對log4j的依賴。

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>dubbo</artifactId>
            <version>2.8.4</version>
            <exclusions>
                <exclusion>
                    <groupId>log4j</groupId>
                    <artifactId>log4j</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

隨後新增logback配置檔案logback.xml在專案的資源目錄中，並啟動服務提供者可以看到日誌輸出。