問題描述

在使用Azure Event Hub的SDK時候，常規情況下，發現範例程式碼中並沒有SDK內部的紀錄檔輸出。因為在Java專案中，沒有新增 SLF4J 依賴，已致於在啟動時候有如下提示：

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.

那麼，有什麼方便的辦法，能把SDK中，內部處理Event Hub的紀錄檔列印出來，並且儲存在紀錄檔檔案中呢？

問題解答

是的，如提示所說，使用 SLF4J 就可以了。因為Azure Event Hub SDK中使用 (com.azure.core.util.logging.ClientLogger) 對紀錄檔進行輸出，所以在最外層(應用程式碼級)就需要有一個接收紀錄檔的Provider，那就是SLF4J。

下面的步驟，就是展示如何新增SLF4J依賴，如何新增輸出到檔案，輸出到Console的設定，最後檢視輸出結果。

前提要求：根據官方範例程式碼，已經成功執行消費端應用：https://docs.azure.cn/zh-cn/event-hubs/event-hubs-java-get-started-send (文末附帶本文的範例程式碼)

第一步：在 pom.xml 中新增 SLF4J 的3個依賴項

    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.25</version>
  </dependency>
  <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.25</version>
  </dependency>
  <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.17</version>
  </dependency>

第二步：在 .\src\main\resources 目錄中新增 log4j.properties 檔案，並設定最關鍵的紀錄檔輸出級別，路徑和格式

# Root logger option
log4j.rootLogger=INFO, stdout, FILE
# Direct log messages to stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1} - %m%n

# Direct log messages to file

# Define the file appender
log4j.appender.FILE=org.apache.log4j.FileAppender
# Set the name of the file
log4j.appender.FILE.File=Logs/log.out
# Set the immediate flush to true (default)
log4j.appender.FILE.ImmediateFlush=true
# Set the threshold to debug mode
log4j.appender.FILE.Threshold=debug
# Set the append to false, overwrite
log4j.appender.FILE.Append=false
# Define the layout for file appender
log4j.appender.FILE.layout=org.apache.log4j.PatternLayout
log4j.appender.FILE.layout.conversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1} - %m%n

第三步: 檢查輸出結果

1）實驗專案的檔案結構

2）pom.xml 中新增的 slf4j 依賴

3）為紀錄檔輸出到檔案和控制檯設定屬性

4）檢視檔案紀錄檔輸出

5）檢視控制檯紀錄檔輸出

附錄一：本文實驗中的全部程式碼

1：POM.XML 檔案內容

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>ConsumeMessageAbort</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>ConsumeMessageAbort</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>com.azure</groupId>
      <artifactId>azure-messaging-eventhubs</artifactId>
      <version>5.12.2</version>
    </dependency>
    <dependency>
      <groupId>com.azure</groupId>
      <artifactId>azure-messaging-eventhubs-checkpointstore-blob</artifactId>
      <version>1.14.0</version>
    </dependency>
    <dependency>
      <groupId>com.azure</groupId>
      <artifactId>azure-identity</artifactId>
      <version>1.5.3</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.25</version>
  </dependency>
  <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.25</version>
  </dependency>
  <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.17</version>
  </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>2.5.5</version>
        <configuration>
          <archive>
            <manifest>
              <mainClass>com.example.App</mainClass>
            </manifest>
          </archive>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

2：src\main\resources\log4j.properties 檔案內容

# Root logger option
log4j.rootLogger=INFO, stdout, FILE
# Direct log messages to stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1} - %m%n

# Direct log messages to file
# Define the file appender
log4j.appender.FILE=org.apache.log4j.FileAppender
# Set the name of the file
log4j.appender.FILE.File=Logs/log.out
# Set the immediate flush to true (default)
log4j.appender.FILE.ImmediateFlush=true
# Set the threshold to debug mode
log4j.appender.FILE.Threshold=debug
# Set the append to false, overwrite
log4j.appender.FILE.Append=false
# Define the layout for file appender
log4j.appender.FILE.layout=org.apache.log4j.PatternLayout
log4j.appender.FILE.layout.conversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1} - %m%n

3：src\main\java\com\example\App.java 檔案內容

package com.example;

import com.azure.messaging.eventhubs.EventData;
import com.azure.messaging.eventhubs.EventHubClientBuilder;
import com.azure.messaging.eventhubs.EventHubConsumerAsyncClient;
import com.azure.messaging.eventhubs.EventProcessorClientBuilder;

import java.io.IOException;
import java.sql.Date;
import java.time.Instant;
import java.time.temporal.TemporalUnit;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Consumer;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Hello world!
 *
 */
public class App {

    final static Logger logger = LoggerFactory.getLogger(App.class);
    private static final String azureEventHubConnectionString = "event hub namespace connection string";
    private static final String azureEventHubHostName = "event hub name";

    public static void main(String[] args) throws IOException {
        System.out.println("Hello World!");

        EventHubConsumerAsyncClient consumer = new EventHubClientBuilder()
                .connectionString(azureEventHubConnectionString, azureEventHubHostName)
                .consumerGroup(EventHubClientBuilder.DEFAULT_CONSUMER_GROUP_NAME)
                .buildAsyncConsumerClient();

        try {
            consumer.receive(true).subscribe(
                    event -> {
                        EventData data = event.getData();
                        String message = "SequenceNumber is" + data.getSequenceNumber().toString()
                                + " The eventData is "
                                + data.getBodyAsString();
                        System.out.println(message);
                        logger.info(message);
                    },
                    error -> logger.error("The iot hub failed to listen for messages， error is {}" + error.toString()));

        } catch (Exception e) {
            consumer = new EventHubClientBuilder()
                    .connectionString(azureEventHubConnectionString, azureEventHubHostName)
                    .consumerGroup(EventHubClientBuilder.DEFAULT_CONSUMER_GROUP_NAME)
                    .buildAsyncConsumerClient();
            System.out.println("recollect consumer");
            logger.warn("recollect consumer");
        }

        System.out.println("Press enter to stop.");
        logger.info("Press enter to stop.");
        System.in.read();

        System.out.println("...End...");
    }

}

4：檔案結構

參考資料

開啟 Apache Flink 製造者 Producer 範例程式碼中的紀錄檔輸出 : https://www.cnblogs.com/lulight/p/15789878.html

使用 Java 向/從 Azure 事件中心 (azure-messaging-eventhubs) 傳送/接收事件： https://docs.azure.cn/zh-cn/event-hubs/event-hubs-java-get-started-send

【Azure 事件中心】 org.slf4j.Logger 收集 Event Hub SDK(Java) 輸出紀錄檔並以檔案形式儲存