Springboot with log4j2，结构化JSON日志

Question

关于如何在SpringBoot应用程序中实现结构化日志记录的小问题，但使用log4j2(与logback一起工作，而不是log4j)。

我有一个超级简单的SpringBoot应用程序:

@RestController
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@RequestMapping("/")
public String index(@RequestHeader("accept") String acceptHeader) {
MDC.put("acceptHeader", acceptHeader);
LoggerFactory.getLogger(getClass()).info("Hello");
return "Greetings from Spring Boot!";
}
@Bean
public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
return args -> function(ctx);
}
private void function(ApplicationContext ctx) {
System.out.println("Let's inspect the beans provided by Spring Boot:");
String[] beanNames = ctx.getBeanDefinitionNames();
Arrays.sort(beanNames);
for (String beanName : beanNames) {
System.out.println(beanName);
}
}
}

用一个简单的pom:

<properties>
<java.version>11</java.version>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>2.5.5</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
<version>2.5.5</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-log4j2</artifactId>
<version>2.5.5</version>
</dependency>
<dependency>
<groupId>net.logstash.logback</groupId>
<artifactId>logstash-logback-encoder</artifactId>
<version>6.6</version>
</dependency>
</dependencies>

使用logback.xml(不是log4j2.xml)

<configuration>
<appender name="jsonConsoleAppender" class="ch.qos.logback.core.ConsoleAppender">
<encoder class="net.logstash.logback.encoder.LogstashEncoder"/>
</appender>
<root level="INFO">
<appender-ref ref="jsonConsoleAppender"/>
</root>
</configuration>

这个工作得很好，很高兴，我看到JSON格式的日志，结构化，很高兴。

我试图得到相同的结果，使用log4j2。我想它会"开箱即用"。但是当切换到log4j2.xml时，日志又回到了非JSON。

请注意，在pom.xml中我有:

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-log4j2</artifactId>
<version>2.5.5</version>
</dependency>

和log4j2.xml with I am trying:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="info">
<Appenders>
<Console name="Console" target="SYSTEM_OUT" follow="true">
<JsonTemplateLayout>
<EventTemplateAdditionalField key="HOME_DIR" value="${env:HOME}"/>
</JsonTemplateLayout>
</Console>
</Appenders>
<Loggers>
<Root level="info">
<AppenderRef ref="Console" />
</Root>
</Loggers>
</Configuration>

我很困惑为什么这不会产生一个结构化的JSON日志，而是丢失了结构化的JSON。

请问出了什么问题?

Answer 1

要在spring引导中使用log4j2进行日志记录，需要排除spring-boot-starter-logging依赖项。一旦我这样做了，我得到了错误Console contains an invalid element or attribute "JsonTemplateLayout"，这是由于奥利维尔提到的缺少log4j-layout-template-json依赖。在添加该依赖项之后，我从log4j2获得了预期的JSON日志，如下所示:

{"@timestamp":"2021-10-16T19:39:28.199Z","log.level":"INFO","message":"No active profile set, falling back to default profiles: default","process.thread.name":"main","log.logger":"com.example.demo.Application","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:28.791Z","log.level":"INFO","message":"Tomcat initialized with port(s): 8080 (http)","process.thread.name":"main","log.logger":"org.springframework.boot.web.embedded.tomcat.TomcatWebServer","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:28.801Z","log.level":"INFO","message":"Initializing ProtocolHandler ["http-nio-8080"]","process.thread.name":"main","log.logger":"org.apache.coyote.http11.Http11NioProtocol","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:28.802Z","log.level":"INFO","message":"Starting service [Tomcat]","process.thread.name":"main","log.logger":"org.apache.catalina.core.StandardService","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:28.802Z","log.level":"INFO","message":"Starting Servlet engine: [Apache Tomcat/9.0.53]","process.thread.name":"main","log.logger":"org.apache.catalina.core.StandardEngine","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:28.842Z","log.level":"INFO","message":"Initializing Spring embedded WebApplicationContext","process.thread.name":"main","log.logger":"org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/]","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:28.842Z","log.level":"INFO","message":"Root WebApplicationContext: initialization completed in 616 ms","process.thread.name":"main","log.logger":"org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:29.149Z","log.level":"INFO","message":"Exposing 1 endpoint(s) beneath base path '/actuator'","process.thread.name":"main","log.logger":"org.springframework.boot.actuate.endpoint.web.EndpointLinksResolver","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:29.165Z","log.level":"INFO","message":"Starting ProtocolHandler ["http-nio-8080"]","process.thread.name":"main","log.logger":"org.apache.coyote.http11.Http11NioProtocol","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:29.175Z","log.level":"INFO","message":"Tomcat started on port(s): 8080 (http) with context path ''","process.thread.name":"main","log.logger":"org.springframework.boot.web.embedded.tomcat.TomcatWebServer","HOME_DIR":"/some/path"}
{"@timestamp":"2021-10-16T19:39:29.188Z","log.level":"INFO","message":"Started Application in 1.193 seconds (JVM running for 1.723)","process.thread.name":"main","log.logger":"com.example.demo.Application","HOME_DIR":"/some/path"}

下面是我最终使用的pom.xml，尽管logstash-logback-encoder依赖现在未使用:

<properties>
<java.version>11</java.version>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>2.5.5</version>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
<version>2.5.5</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-log4j2</artifactId>
<version>2.5.5</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-layout-template-json</artifactId>
<version>2.14.1</version>
</dependency>
<dependency>
<groupId>net.logstash.logback</groupId>
<artifactId>logstash-logback-encoder</artifactId>
<version>6.6</version>
</dependency>
</dependencies>