[JAVA] Output embedded Tomcat access log to standard output with Spring Boot


The built-in Tomcat of Spring Boot can automatically output the access log to a file. This article will show you how to output this to standard output.


First, output the access log

Write a RestController that receives a nice GET and POST.

public class HelloController {

    public String hello() {
        return "Hello, world!";

    public String message(@RequestBody String message) {
        return "Hello, " + message + "!";

You can output the access log by describing the following settings in application.properties.


When I actually hit it locally, the access log was output to /path/to/dir/logs/access_log.yyyy-MM-dd.log.

$ curl localhost:8080/hello
Hello, world!
curl -H "Content-Type: text/plain" localhost:8080/hello -d "mito"
Hello, mito!
$ ls /path/to/dir/logs
$ cat /path/to/dir/logs/access_log.2019-11-08.log
0:0:0:0:0:0:0:1 - - [08/Nov/2019:17:59:56 +0900] "GET /hello HTTP/1.1" 200 13
0:0:0:0:0:0:0:1 - - [08/Nov/2019:18:00:01 +0900] "POST /hello HTTP/1.1" 200 16

Output access log to standard output

As also mentioned in the Twelve-Factor App, it is more common for modern applications to output logs to standard output.

There are several ways to output to standard output.

Output to / dev / stdout

You can output to standard output by devising the settings and setting the output destination file to / dev / stdout.


Use logback-access

In some cases, you may want to avoid touching / dev / stdout directly. You can set the output destination to standard output by using logback-access.

First, place logback-access.xml in src / main / resources / conf /. Describe logback-access.xml as follows so that it is output to stdout.

<?xml version="1.0" encoding="UTF-8"?>
  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
      <!--  combined log format-->

  <appender-ref ref="STDOUT" />


Add more logback-access dependency (below for gradle)

dependencies {
+	implementation group: 'ch.qos.logback', name: 'logback-access', version: '1.2.3'

By creating a Bean of TomcatServletWebSErverFactory, the settings are reflected in the embedded tomcat.

public class TomcatLoggingConfig {
    public TomcatServletWebServerFactory servletContainer() {
        TomcatServletWebServerFactory tomcatServletWebServerFactory = new TomcatServletWebServerFactory();
        //LogbackValve refers to resources and below, so this is logback-access.The contents of xml are reflected
        tomcatServletWebServerFactory.addContextValves(new LogbackValve());
        return tomcatServletWebServerFactory;

When you start it and actually make a request, you can see that the following log is output.

0:0:0:0:0:0:0:1 - - [08/11/2019:18:38:29 +0900] "GET /hello HTTP/1.1" 200 13 "-" "curl/7.54.0"
0:0:0:0:0:0:0:1 - - [08/11/2019:18:38:20 +0900] "POST /hello HTTP/1.1" 200 16 "-" "curl/7.54.0"

There is no need to set application.properties.

Use logback-access-spring-boot-starter

By using logback-access-spring-boot-starter, the above logback-access settings are automatically reflected. Will do it.

Add a dependency,

dependencies {
+ implementation group: 'net.rakugakibox.spring.boot', name: 'logback-access-spring-boot-starter', version: '2.7.1'

If you place logback-access.xml directly under src / main / resources, the access log will be output to the standard output. Convenient...!


https://www.baeldung.com/spring-boot-embedded-tomcat-logs http://logback.qos.ch/access.html https://stackoverflow.com/questions/36780680/how-do-you-tell-spring-boot-to-send-the-embedded-tomcats-access-logs-to-stdout?answertab=votes#tab-top https://github.com/akihyro/logback-access-spring-boot-starter

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