[Jaav SE/程序生命周期] 优雅的Java应用程序的启停钩子框架

序

• 了解 spring 生态及框架的 java er 都知道，spring 应用的生命周期管理及配套接口较为优雅、可扩展。

• 但脱离 spring 的 java 应用程序，如何优雅地启停、管理程序的生命周期呢？（以便应用程序在我们需要的运行阶段中进行相应的动作）

概述：Java普通应用程序的启停钩子框架

前置知识

java.lang.FunctionalInterface注解

• 推荐文献

• java.lang.FunctionalInterface : 函数式接口(JDK8+) - [Java SE/JDK] Java 注解机制 - 博客园/千千寰宇

Java普通应用程序的启停钩子框架

ApplicationStartupHook: 抽象的启动钩子接口

package org.example.app.hooks.startup;

@FunctionalInterface
public interface ApplicationStartupHook {
    /**
     * execute the task
     * @throws Exception
     */
    void execute() throws Exception;
}

ApplicationStartupHookManager : 统一管理启动钩子

package org.example.app.hooks.startup;

import java.util.ArrayList;
import java.util.List;

public class ApplicationStartupHookManager {
    private static final List<ApplicationStartupHook> hooks = new ArrayList<>();
    private static boolean executed = false;

    // 注册启动任务
    public static void registerHook(ApplicationStartupHook hook) {
        if (executed) {
            throw new IllegalStateException("Application startup hooks already executed");
        }
        hooks.add(hook);
    }

    // 执行所有启动任务
    public static void run() throws Exception {
        if (!executed) {
            for (ApplicationStartupHook hook : hooks) {
                hook.execute();
            }
            executed = true;
        }
    }
}

ApplicationShutdownHook : 关闭钩子

package org.example.app.hooks.shutdown;

@FunctionalInterface
public interface ApplicationShutdownHook {
    /**
     * execute the task
     * @throws Exception
     */
    void execute() throws Exception;
}

ApplicationShutdownHookManager : 统一管理关闭钩子

package org.example.app.hooks.shutdown;

import lombok.Getter;
import org.example.app.hooks.startup.ApplicationStartupHook;

import java.util.ArrayList;
import java.util.List;

public class ApplicationShutdownHookManager {
    private static final List<ApplicationShutdownHook> hooks = new ArrayList<>();
    @Getter
    private static boolean executed = false;

    // 注册启动任务
    public static void registerHook(ApplicationShutdownHook hook) {
        if (executed) {
            throw new IllegalStateException("Application shutdown hooks already executed");
        }
        hooks.add(hook);
    }

    // 执行所有启动任务
    public static void run() throws Exception {
        if (!executed) {
            for (ApplicationShutdownHook hook : hooks) {
                hook.execute();
            }
            executed = true;
        }
    }
}

Demo应用 : Slf4j + Log4j2 + Log4j2 KafkaAppender + Kafka

Maven 依赖

<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>

    <parent>
        <groupId>org.example</groupId>
        <artifactId>demos-application-parent</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../pom.xml</relativePath>
    </parent>

    <artifactId>log4j2-kafka-appender-demo-application</artifactId>
    <packaging>jar</packaging>

    <name>bdp-diagnosticbox-model</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <lombok.version>1.18.22</lombok.version>
        <slf4j.version>1.7.30</slf4j.version>
        <log4j.version>2.20.0</log4j.version>
        <kafka-clients.version>2.7.2</kafka-clients.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>${lombok.version}</version>
        </dependency>

        <!-- log -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>${log4j.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>${log4j.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-slf4j-impl</artifactId>
            <version>${log4j.version}</version>
            <exclusions>
                <exclusion>
                    <artifactId>slf4j-api</artifactId>
                    <groupId>org.slf4j</groupId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-jul</artifactId>
            <!--<version>2.13.3</version>-->
            <version>${log4j.version}</version>
            <scope>compile</scope>
        </dependency>
        <!-- log [end] -->

        <!-- kafka client -->
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-clients</artifactId>
            <version>${kafka-clients.version}</version>
        </dependency>
    </dependencies>
</project>

配置文件

• resource/log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--<Configuration status="debug" name="demo-application" packages="org.example.app">-->
<Configuration status="off">
    <!-- 自定义属性 -->
    <Properties>
        <!-- 应用程序名称 -->
        <Property name="application.name">bdp-xxx-app</Property>
        <!-- 应用程序实例的主机地址 -->
        <Property name="application.instance.host">${env:HOST_IP:-127.0.0.1}</Property>
        <!-- 应用程序实例的名称，默认值: localInstance -->
        <Property name="application.instance.name">${env:INSTANCE_NAME:-localInstance}</Property>

        <!-- 字符集 -->
        <Property name="log.encoding">UTF-8</Property>
        <!-- 日志等级，默认 INFO -->
        <Property name="log.level" value="${env:LOG_ACCESS:-INFO}" />
        <!--<Property name="log.access.level">${env:LOG_ACCESS:-INFO}</Property>-->
        <!--<Property name="log.operation.level">${env:LOG_OPERATE:-INFO}</Property>-->
        <Property name="log.threshold">${log.level}</Property>

        <!-- org.apache.log4j.PatternLayout -->
        <!--<Property name="log.layout" value="CustomPatternLayout"></Property>-->
        <Property name="log.layout" value="PatternLayout"></Property>

        <!-- property.log.layout.consolePattern=%d{yyyy/MM/dd HH:mm:ss.SSS} %-5p | %T | %t | (%C{1}.java:%L %M) | %m%n -->
        <!-- [%d{yyyy/MM/dd HH:mm:ss.SSS}] [%traceId] [%-5p] [%t] [%C{1}.java:%L %M] %m%n -->
        <!-- [%d{yyyy/MM/dd HH:mm:ss.SSS}] [%X{traceId}] [%-5p] [%t] [%C{1}.java:%L %M] %m%n -->
        <!-- [%traceId] [${application.name}] [system] [%d{yyyy/MM/dd HH:mm:ss.SSS}] [%-5p] [%t] [%C{1}] %M:%L__|%X{traceId}|__%m%n -->
        <!-- [${application.name}] [${instance.name}] [${env:HOST_IP}] [${env:CONTAINER_IP}] [%d{yyyy/MM/dd HH:mm:ss.SSS}] [%p] [%t] [%l] %m%n -->
        <!-- ↓ sample: 2023-02-02 14:35:38,664 WARN  main (MonitorController.java:141 lambda$null$0) name: cn.seres.bd.dataservice.common.query, configLevel(Level):DEBUG, effectiveLevel: DEBUG -->
        <!-- %d %-5p %t (%C{1}.java:%L %M) %m%n -->
        <!-- [%d %r] [%-5p] [%t] [%l] [%m]%n -->
        <!-- %d{yyyy-MM-dd HH\:mm\:ss} %-5p[%t] : %m%n -->
        <!-- ↓ sample: 2025-02-21 15:24:27 INFO  | [2aa06a7b-a81f-469b-a0a0-679005bc35a3] | Log4jKafkaAppenderDemoEntry:36 - 这是一条信息日志 -->
        <!--%d{HH:mm:ss.SSS} %-5p [%-7t] %F:%L - %m%n -->
        <!--[%-4level] | %d{YYYY-MM-dd HH:mm:ss} | [%X{REQ_ID}] | %m| ${sys:java.home}%n-->
        <!-- %d{yyyy-MM-dd HH:mm:ss} %-5p | [%X{REQ_ID}] | %c{1}:%L - %m%n -->
        <!-- ${log.appender.kafka.producer.bootstrap.servers} | ${bundle:application:org.example.confgKey} | ${main:\\-logLevel} |  ${main:\\-\-log\.appender\.kafka\.producer\.bootstrap\.servers} | %c{1}:%L - %m%n -->
        <Property name="log.layout.consolePattern">
            [%d{yyyy/MM/dd HH:mm:ss.SSS}] [%X{traceId}] [%-5p] [%t] [%C{1}.java:%L %M] %m%n
        </Property>
        <Property name="log.layout.mainPattern" value="${log.layout.consolePattern}" />

        <!-- KafkaAppender 的属性值 -->
        <!-- 方式1: 从环境变量获取 -->
        <!--<Property name="log.appender.kafka.producer.bootstrap.servers" value="${env:KAFKA_PRODUCER_BOOTSTRAP_SERVERS:-127.0.0.1:9092}"/>-->
        <!-- 方式2: 从 日志框架 MDC 中获取 -->
        <!--<Property name="log.appender.kafka.producer.bootstrap.servers" value="%X{log.appender.kafka.producer.bootstrap.servers}"/>-->
        <!-- 方式3: 从 应用程序的 main 方法启动入参中获取 -->
        <Property name="log.appender.kafka.producer.bootstrap.servers" value="${main:\\-\-log\.appender\.kafka\.producer\.bootstrap\.servers}"/>

        <!-- 目标 Appenders | 注: 属性值(如: ConsoleAppender)，对应的是 <Appender> 标签的 `name` 属性值 -->
        <!-- 1. 标准输出/控制台的 Appender -->
        <Property name="log.consoleAppender" value="MyConsoleAppender"/>
        <!-- 2. 文件输出 系统类日志的 Appender -->
        <Property name="log.systemFileAppender" value="MySystemFileAppender"/>
        <!-- 3. 文件输出 访问类日志的 Appender -->
        <!--<Property name="log.accessFileAppender">MyAccessFileAppender</Property>-->
        <!-- 4. 文件输出 操作类日志的 Appender -->
        <!--<Property name="log.operationFileAppender">MyOperationFileAppender</Property>-->
        <!-- 5. 文件输出 协议类日志的 Appender -->
        <!--<Property name="log.protocolFileAppender">MyProtocolFileAppender</Property>-->
        <!-- 6. 远程 链路追踪系统的 Appender -->
        <!--<Property name="log.linkTraceClientTargetAppender">MySkyWalkingClientAppender</Property>-->
        <!-- 7. 远程 KAFKA/ELK 的 Appender -->
        <Property name="log.loggingSystemMessageQueueAppender" value="MyKafkaAppender"/>
    </Properties>

    <!-- 输出器 -->
    <Appenders>
        <Console name="MyConsoleAppender" target="SYSTEM_OUT">
            <PatternLayout pattern="${log.layout.consolePattern}" />
            <!-- com.platform.sp.framework.log.layout.CustomPatternLayout -->
            <!--<CustomPatternLayout pattern="${log.layout.consolePattern}" />-->
        </Console>

        <!--
            @warn
                1. 此 KafkaAppender 不建议在 生产环境 的 log4j2.xml/properties 中启用，因 无法从外部动态注入 kafka broker servers
                2. 针对第1点，需通过 自定义的 {@link org.example.app.hooks.startup.impl.Log4j2KafkaAppenderInitializer } ，实现程序启动时动态注册 KafkaAppender
            @Appender : KafkaAppender | org.apache.logging.log4j.core.appender.mom.kafka.KafkaAppender | log4j-core:2.20.0
            @note
                1. 计划在下一个主要版本中删除此附加程序！如果您正在使用此库，请使用官方支持渠道 与 Log4j 维护人员联系。
                    from https://logging.apache.org/log4j/2.x/manual/appenders/message-queue.html#KafkaAppender
                2. 使用 Kafka Appender 需要额外的运行时依赖项 : org.apache.kafka:kafka-clients:{version}
                    from https://logging.apache.org/log4j/2.x/manual/appenders/message-queue.html#KafkaAppender
                3. Kafka appender ignoreExceptions 必须设置为false，否则无法触发 FailOver Appender
                4. 确保不要让 `org.apache.kafka`Logger 日志记录的日志级别为 DEBUG，因为这将导致`KafkaAppender`递归日志记录
                    from https://logging.apache.org/log4j/2.x/manual/appenders/message-queue.html#KafkaAppender
            @property
                //配置属性
                * name: Log Framework's Appender 's Name
                * topic : Kafka Topic Name

                key:String : Kafka Message(`ProducerRecord`) 的 key。 支持 运行时属性替换，并在全局上下文 中进行评估。
                    参考: https://logging.apache.org/log4j/2.x/manual/appenders/message-queue.html#KafkaAppender
                    参考 : https://logging.apache.org/log4j/2.x/manual/lookups.html#global-context
                    推荐值: key="$${web:contextName}" | contextName 是 log4j2 内置的变量
                ignoreExceptions:boolean[DefaultValue:true] : 如果false，日志记录异常将被转发给日志记录语句的调用者。否则，它们将被忽略。
                syncSend:boolean[DefaultValue:true] : 如果true，附加器将阻塞，直到 Kafka 服务器确认该记录为止。否则，附加器将立即返回，从而实现更低的延迟和更高的吞吐量。

                //嵌套属性
                Filter
                Layout
                Property[0..n] : 这些属性会直接转发给 Kafka 生产者。 有关更多详细信息，请参阅 Kafka 生产者属性。
                    参考: https://kafka.apache.org/documentation.html#producerconfigs
                    bootstrap.servers : 此属性是必需的
                    key.serializer : 不应使用这些属性
                    value.serializer : 不应使用这些属性
        -->
        <Kafka name="MyKafkaAppender" topic="flink_monitor_log" key="$${web:contextName}" syncSend="true" ignoreExceptions="false">
            <!--<JsonTemplateLayout/>-->
            <PatternLayout pattern="${log.layout.mainPattern}"/>
            <Property name="bootstrap.servers" value="${log.appender.kafka.producer.bootstrap.servers}"/>
            <Property name="max.block.ms">2000</Property>
        </Kafka>

        <RollingFile name="MyFailoverKafkaLogAppender" fileName="../log/failover/request.log"
                     filePattern="../log/failover/request.%d{yyyy-MM-dd}.log">
            <ThresholdFilter level="INFO" onMatch="ACCEPT" onMismatch="DENY"/>
            <PatternLayout>
                <Pattern>${log.layout.mainPattern}</Pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy />
            </Policies>
        </RollingFile>

<!--
        <Failover name="Failover" primary="kafkaLog" retryIntervalSeconds="600">
            <Failovers>
                <AppenderRef ref="MyFailoverKafkaLogAppender"/>
            </Failovers>
        </Failover>
-->

        <!--
            异步输出 | org.apache.logging.log4j.core.async.AsyncLoggerConfig
            1. AsyncAppender接受对其他Appender的引用，并使LogEvents在单独的Thread上写入它们。
            2. 默认情况下，AsyncAppender使用 java.util.concurrent.ArrayBlockingQueue ，它不需要任何外部库。
                请注意，多线程应用程序在使用此appender时应小心：阻塞队列容易受到锁争用的影响，并且我们的 测试 表明，当更多线程同时记录时性能可能会变差。
                考虑使用无锁异步记录器以获得最佳性能。
 -->
<!--        <AsyncLogger name="kafkaAyncLogger" level="INFO" additivity="false">
            <appender-ref ref="Failover"/>
        </AsyncLogger>-->
    </Appenders>

    <!-- 日志器-->
    <Loggers>
        <!-- 定义 RootLogger 等 全局性配置(不可随意修改) -->
        <!-- rootLogger, 根记录器，所有记录器的父辈 | 指定根日志的级别 | All < Trace < Debug < Info < Warn < Error < Fatal < OFF -->
        <Root level="${log.level}"> <!-- ${log.level} -->
            <!-- 2.17.2 版本以下通过这种方式将 root 和 Appender关联起来 / 2.17.2 版本以上有更简便的写法 -->

            <!-- rootLogger.appenderRef.stdout.ref=${log.consoleAppender} -->
            <AppenderRef ref="${log.consoleAppender}" level="INFO" />

            <!-- rootLogger.appenderRef.kafka.ref=${log.loggingSystemMessageQueueAppender} -->
<!--            <AppenderRef ref="${log.loggingSystemMessageQueueAppender}"/> --><!-- MyKafkaAppender -->
        </Root>

        <!-- 指定个别 Class 的 Logger (可随意修改，建议在 nacos 上修改) -->

        <!-- KafkaAppender | org.apache.logging.log4j.core.appender.mom.kafka.KafkaAppender
            1. 确保不要让 org.apache.kafka Logger 的日志级别为 DEBUG，因为这将导致递归日志记录
            2. 请记住将配置 additivity 属性设置为false
         -->
        <Logger name="org.apache.kafka" level="WARN" additivity="false">
            <AppenderRef ref="${log.consoleAppender}"/>
        </Logger>

    </Loggers>
</Configuration>

Log4j2KafkaAppenderInitializer implements ApplicationStartupHook : 负责实现具体的启动钩子

package org.example.app.hooks.startup.impl;

import lombok.Getter;
import lombok.extern.slf4j.Slf4j;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.appender.mom.kafka.KafkaAppender;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.Property;
import org.apache.logging.log4j.core.layout.PatternLayout;
import org.example.app.constant.Constants;
import org.example.app.hooks.startup.ApplicationStartupHook;
import org.slf4j.MDC;

import java.nio.charset.Charset;
import java.util.Collections;
import java.util.Map;
import java.util.Optional;
import java.util.Properties;

/**
 * @description 基于 log4j2 日志框架，在程序启动时，根据程序的启动参数（kafka brokers地址）动态追加 KafkaAppender
 * @refrence-doc
 *  [1] Log4j2 配置日志记录发送到 kafka 中 - CSDN | https://blog.csdn.net/u010454030/article/details/132589450 【推荐】
 *  [2] 使用代码动态进行 Log4j2 的日志配置 - CSDN | https://blog.csdn.net/scruffybear/article/details/130230414 【推荐】
 *  [3] Apache Log4j2.x - Kafka Appender 【推荐】
 *      https://logging.apache.org/log4j/2.x/manual/appenders.html#KafkaAppender
 *      https://logging.apache.org/log4j/2.x/manual/appenders/message-queue.html#KafkaAppender
 *      {@link org.apache.logging.log4j.core.appender.mom.kafka.KafkaAppender }
 *  -----
 *  [4] Log4j2 - 动态生成Appender - 博客园 | https://www.cnblogs.com/yulinlewis/p/10217385.html
 *  [5] springboot动态添加log4j2的Appender - CSDN | https://blog.csdn.net/qq_25379811/article/details/127620062
 *  [6] log4j2.xml中动态读取配置 - CSDN | https://blog.csdn.net/xiaokanfuchen86/article/details/126695010 【推荐】
 *      https://logging.apache.org/log4j/2.x/manual/lookups.html#global-context 【推荐】
 * @gpt-promt
 */
@Slf4j
public class Log4j2KafkaAppenderInitializer implements ApplicationStartupHook {

    @Getter
    private Properties applicationProperties;

    public Log4j2KafkaAppenderInitializer(Properties applicationProperties) {
        this.applicationProperties = applicationProperties;
    }

    @Override
    public void execute() throws Exception {
        log.debug("Initializing {} ...", this.getClass().getCanonicalName());

        LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
        Configuration config = ctx.getConfiguration();
        Appender kafkaAppender = createKafkaAppender(ctx, config, applicationProperties);
        kafkaAppender.start();//防止错误: Attempted to append to non-started appender testName

        Level level = getLevel(applicationProperties);
        config.getRootLogger().addAppender(kafkaAppender, level, null);// 添加 Appender 到配置中
        ctx.updateLoggers();

        log.debug("Initialized {} ...", this.getClass().getCanonicalName());
    }

    /**
     * @note
     *  1. required properties:
     *      1. {@link Constants.Log4j2KafkaAppender#LEVEL_PARAM}
     * @param applicationProperties
     * @return
     */
    private static Level getLevel(Properties applicationProperties) {
        Level level = null;
        String levelStr = applicationProperties == null ? Constants.Log4j2KafkaAppender.LEVEL_DEFAULT : applicationProperties.getProperty( Constants.Log4j2KafkaAppender.LEVEL_PARAM );
        levelStr = (levelStr == null || levelStr.equals("") ) ? Constants.Log4j2KafkaAppender.LEVEL_DEFAULT : levelStr.toUpperCase();
        level = Level.getLevel(levelStr);
        log.info("user config's `{}`'s log level: {}", KafkaAppender.class.getCanonicalName(), levelStr);
        return level;
    }

    /**
     * create a kafka appender base on log4j2 framework
     * @reference-doc
     *  1. https://logging.apache.org/log4j/2.x/manual/appenders/message-queue.html#KafkaAppender
     * @note
     *  1. required properties:
     *      1. {@link Constants.Log4j2KafkaAppender#KAFKA_PRODUCER_TOPIC_PARAM}
     *      2. {@link ProducerConfig#BOOTSTRAP_SERVERS_CONFIG }
     *  2. optional properties:
     *      {@link ProducerConfig } 's Config Properties
     * @return
     */
    private static Appender createKafkaAppender(LoggerContext loggerContext,Configuration configuration, Properties applicationProperties) {
        KafkaAppender kafkaAppender = null;
        if(loggerContext == null){
            loggerContext = (LoggerContext) LogManager.getContext(false);
        }
        if(configuration == null){
            configuration = loggerContext.getConfiguration();
        }

        final PatternLayout layout = PatternLayout.newBuilder()
                .withCharset(Charset.forName("UTF-8"))
                .withConfiguration(configuration)
                .withPattern("%d %p %c{1.} [%t] %m%n").build();

        Filter filter = null;

        String topic = applicationProperties.getProperty(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_TOPIC_PARAM);
        String appenderName = applicationProperties.getProperty(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_TOPIC_PARAM) + "Log4J2KafkaAppender";

        Property [] propertyArray = propertiesToPropertyArray(applicationProperties);

        String messageKey = applicationProperties.getProperty( Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_KEY_PARAM );
        Boolean isIgnoreExceptions = Boolean.getBoolean(applicationProperties.getProperty(Constants.Log4j2KafkaAppender.KAFKA_APPENDER_IGNORE_EXCEPTIONS_PARAM, Constants.Log4j2KafkaAppender.KAFKA_APPENDER_IGNORE_EXCEPTIONS_DEFAULT));
        Boolean syncSend = Boolean.getBoolean(applicationProperties.getProperty(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_SYNC_SEND_PARAM, Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_SYNC_SEND_DEFAULT));
        Boolean sendEventTimestamp = Boolean.getBoolean(applicationProperties.getProperty(Constants.Log4j2KafkaAppender.KAFKA_APPENDER_SEND_EVENT_TIMESTAMP_PARAM, Constants.Log4j2KafkaAppender.KAFKA_APPENDER_SEND_EVENT_TIMESTAMP_DEFAULT));

        //kafkaAppender = KafkaAppender.createAppender(layout, filter, appenderName, isIgnoreExceptions, topic, propertyArray, configuration, key );//此方式不支持传入 syncSend 参数
        //kafkaAppender = new KafkaAppender(name, layout, filter, isIgnoreExceptions, kafkaManager, getPropertyArray(), getRetryCount());//此方式，因构造器是 private，不支持

        kafkaAppender = KafkaAppender.newBuilder()//此方式 √
                .setName(appenderName)
                .setConfiguration(configuration)
                .setPropertyArray(propertyArray)
                .setFilter(filter)
                .setLayout(layout)
                .setIgnoreExceptions(isIgnoreExceptions)
                .setTopic(topic)
                .setKey(messageKey)
                .setSendEventTimestamp(sendEventTimestamp)
                .setSyncSend(syncSend)
                .setRetryCount(3)
                .build();

        return kafkaAppender; // 需要替换为实际的 Appender 创建代码
    }

    /**
     * Java Properties 转 Log4j2 的 Property []
     * @return
     */
    public static Property [] propertiesToPropertyArray(Properties properties){
        if(properties == null){
            return new Property[] {};
        }
        Property [] propertyArray = new Property[ properties.size() + 1];
        int i = 0;
        for(Map.Entry<Object, Object> entry : properties.entrySet() ) {
            Property property = Property.createProperty((String) entry.getKey(), (String) entry.getValue());
            propertyArray[i] = property;
            i++;
        }

        /**
         * 注入 org.apache.logging.log4j.core.appender.mom.kafka.KafkaAppender 所需的必填参数 {@link ProducerConfig.BOOTSTRAP_SERVERS_CONFIG}
         */
        String kafkaBrokerServers = properties.getProperty(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM);
        if(kafkaBrokerServers != null && (!kafkaBrokerServers.trim().equals("")) ){
            propertyArray[i] = Property.createProperty( ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, kafkaBrokerServers);
        } else {
            throw new RuntimeException(
                String.format("The Property `%s` must be not empty for `%s`!"
                    , Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM
                    , KafkaAppender.class.getCanonicalName()
                )
            );
        }
        return propertyArray;
    }
}

Slf4Initializer implements ApplicationStartupHook : 负责具体实现的启动钩子

package org.example.app.hooks.startup.impl;

import lombok.Getter;
import lombok.extern.slf4j.Slf4j;
import org.example.app.constant.Constants;
import org.example.app.hooks.startup.ApplicationStartupHook;
import org.slf4j.MDC;

import java.util.Optional;
import java.util.Properties;

@Slf4j
public class Slf4Initializer implements ApplicationStartupHook {
    @Getter
    private Properties applicationProperties;

    public Slf4Initializer(Properties applicationProperties) {
        this.applicationProperties = applicationProperties;
    }

    @Override
    public void execute() throws Exception {
        log.debug("Initializing {} ...", this.getClass().getCanonicalName());

        //设置 kafka 主机地址
        String kafkaProducerBootstrapServers = applicationProperties.getProperty(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM);
        kafkaProducerBootstrapServers = Optional.ofNullable(kafkaProducerBootstrapServers).<RuntimeException>orElseThrow(() -> {
            throw new RuntimeException(String.format("`{}` must be not empty!", Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM));
        });
        MDC.put(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM, kafkaProducerBootstrapServers);
        log.info("MDC | {} : {}", Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM, MDC.get(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM) );

        log.debug("Initialized {} ...", this.getClass().getCanonicalName());
    }
}

Slf4Finalizer implements ApplicationShutdownHook : 负责具体实现的钩子

package org.example.app.hooks.shutdown.impl;

import lombok.Getter;
import lombok.extern.slf4j.Slf4j;
import org.example.app.constant.Constants;
import org.example.app.hooks.shutdown.ApplicationShutdownHook;
import org.slf4j.MDC;

import java.util.Properties;

@Slf4j
public class Slf4Finalizer implements ApplicationShutdownHook {
    @Getter
    private Properties applicationProperties;

    public Slf4Finalizer(Properties applicationProperties) {
        this.applicationProperties = applicationProperties;
    }

    @Override
    public void execute() throws Exception {
        log.debug("Finalizing {} ...", Slf4Finalizer.class.getCanonicalName());

        // 清理MDC
        log.info("clear MDC before | {} : {}", Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM, MDC.get(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM) );
        //MDC.clear();
        MDC.remove( Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM );//或仅清理需要的属性
        log.info("clear MDC after | {} : {}", Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM, MDC.get(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM) );

        log.debug("Finalized {} ...", Slf4Finalizer.class.getCanonicalName());
    }
}

Log4jKafkaAppenderDemoEntry

package org.example.app;

import org.apache.logging.log4j.core.layout.PatternLayout;
import org.example.app.constant.Constants;
import org.example.app.hooks.shutdown.ApplicationShutdownHookManager;
import org.example.app.hooks.shutdown.impl.Slf4Finalizer;
import org.example.app.hooks.startup.ApplicationStartupHookManager;
import org.example.app.hooks.startup.impl.Log4j2KafkaAppenderInitializer;
import org.example.app.hooks.startup.impl.Slf4Initializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Properties;

public class Log4jKafkaAppenderDemoEntry {
    private static final Logger logger = LoggerFactory.getLogger(Log4jKafkaAppenderDemoEntry.class);

    private static final String APPLICATION_NAME = "Log4jKafkaAppenderDemoApplication";

    public static void main(String[] args) throws Exception {
        //从 nacos 等处动态获取配置 (此处可视为在模拟)
        Properties applicationProperties = new Properties();
        applicationProperties.put(Constants.Log4j2KafkaAppender.LEVEL_PARAM, "WARN");
        applicationProperties.put(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_BOOTSTRAP_SERVERS_PARAM, "127.0.0.1:9092");
        applicationProperties.put(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_TOPIC_PARAM, "flink_monitor_log");
        applicationProperties.put(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_KEY_PARAM, APPLICATION_NAME);
        applicationProperties.put(Constants.Log4j2KafkaAppender.KAFKA_PRODUCER_SYNC_SEND_PARAM, "true");
        applicationProperties.put(Constants.Log4j2KafkaAppender.KAFKA_APPENDER_IGNORE_EXCEPTIONS_PARAM, "false");

        enableLog4j2MainLookup(args);//可选步骤（非必须）

        runStartupHooks(applicationProperties);//运行启动钩子
        // 测试不同级别的日志
        logger.info("这是一条信息日志");
        logger.warn("这是一条警告日志");
        try {
            throw new RuntimeException("测试异常");
        } catch (Exception e) {
            logger.error("发生错误", e);
        }

        //关停钩子
        runShutdownHooks(applicationProperties);
    }

    public static void enableLog4j2MainLookup(String [] args){
        /**
         * 若 log4j2.[xml/properties/yaml] 中 Appender 的 pattern 欲以 `${main:\\-logLevel}` ，则需启用如下代码
         */
        try {
            Class.forName("org.apache.logging.log4j.core.lookup.MainMapLookup")
                    .getDeclaredMethod("setMainArguments", String[].class)
                    .invoke(null, (Object) args);
        } catch (final ReflectiveOperationException e) {
            // Log4j Core is not used.
        }
    }

    public static void runStartupHooks(Properties applicationProperties) throws Exception {
        ApplicationStartupHookManager.registerHook( new Slf4Initializer(applicationProperties) );
        ApplicationStartupHookManager.registerHook( new Log4j2KafkaAppenderInitializer(applicationProperties) );
        ApplicationStartupHookManager.run();
    }

    public static void runShutdownHooks(Properties applicationProperties) throws Exception {
        ApplicationShutdownHookManager.registerHook( new Slf4Finalizer(applicationProperties) );
        ApplicationShutdownHookManager.run();
    }
}

X 参考文献

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