Spring boot H2 console returns 404 - spring-boot

Question

I have a simple Springboot application and it's up running. I am able to call REST endpoints through Postman. However, when I try to access the console using http://localhost:8080/h2 it keeps returning 404.
2020-08-29 08:06:37.577 INFO 6507 --- [ main] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [
name: default
...]
2020-08-29 08:06:37.644 INFO 6507 --- [ main] org.hibernate.Version : HHH000412: Hibernate Core {5.2.17.Final}
2020-08-29 08:06:37.645 INFO 6507 --- [ main] org.hibernate.cfg.Environment : HHH000206: hibernate.properties not found
2020-08-29 08:06:37.677 INFO 6507 --- [ main] o.hibernate.annotations.common.Version : HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
2020-08-29 08:06:37.787 INFO 6507 --- [ main] org.hibernate.dialect.Dialect : HHH000400: Using dialect: org.hibernate.dialect.H2Dialect
2020-08-29 08:06:38.247 INFO 6507 --- [ main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
2020-08-29 08:06:38.737 INFO 6507 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2020-08-29 08:06:38.738 INFO 6507 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Bean with name 'dataSource' has been autodetected for JMX exposure
2020-08-29 08:06:38.741 INFO 6507 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Located MBean 'dataSource': registering with JMX server as MBean [com.zaxxer.hikari:name=dataSource,type=HikariDataSource]
2020-08-29 08:06:38.813 INFO 6507 --- [ctor-http-nio-1] r.ipc.netty.tcp.BlockingNettyContext : Started HttpServer on /0:0:0:0:0:0:0:0:8080
2020-08-29 08:06:38.813 INFO 6507 --- [ main] o.s.b.web.embedded.netty.NettyWebServer : Netty started on port(s): 8080
2020-08-29 08:06:38.816 INFO 6507 --- [ main] c.v.t.c.m.tenant.discovery.Application : Started Application in 3.4 seconds (JVM running for 3.661)
2020-08-29 08:06:48.527 WARN 6507 --- [ctor-http-nio-2] .a.w.r.e.DefaultErrorWebExceptionHandler : Failed to handle request [GET http://localhost:8080/h2]: Response status 404
2020-08-29 08:23:07.301 WARN 6507 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Retrograde clock change detected (housekeeper delta=29s626ms), soft-evicting connections from pool.
2020-08-29 08:57:06.586 WARN 6507 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Thread starvation or clock leap detected (housekeeper delta=33m59s284ms).
2020-08-29 09:35:49.699 WARN 6507 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Thread starvation or clock leap detected (housekeeper
My application.yml file looks like this.
spring:
datasource:
url: jdbc:h2:mem:test
platform: h2
username: sa
password:
driverClassName: org.h2.Driver
hikari:
maximum-pool-size: 50
h2:
console:
enabled: true
path: /h2
settings:
web-allow-others: true
jpa:
database-platform: org.hibernate.dialect.H2Dialect
hibernate:
ddl-auto: update
server:
port: 8080

Answer 1

As per your logs, I found that, you are using an embedded server, other than tomcat, i.e, spring-boot-starter-reactor-netty that comes along with spring webflux dependency.
H2ConsoleAutoConfiguration will not be executed for spring webflux & netty(reactor based), as H2 console will only be available to servlet based applications. So, you have to configure H2 server manually in this spring boot application, with spring webflux & netty.
Sample H2Server (working code):
package com.example.springbootnettyserver;
import org.h2.tools.Server;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;
import static org.h2.tools.Server.createWebServer;
#Component
public class H2ServerManual {
Logger log = LoggerFactory.getLogger(H2ServerManual.class);
private Server webServer;
#Value("${h2-server.port}")
Integer h2ConsolePort;
#EventListener(ContextRefreshedEvent.class)
public void start() throws java.sql.SQLException {
log.info("starting h2 console at port "+ h2ConsolePort);
this.webServer = createWebServer("-webPort", h2ConsolePort.toString(),
"-tcpAllowOthers").start();
System.out.println(webServer.getURL());
}
#EventListener(ContextClosedEvent.class)
public void stop() {
log.info("stopping h2 console at port "+h2ConsolePort);
this.webServer.stop();
}
}
Note: org.h2.tools.Server class will be resolved only when h2 dependency is added without scope of runtime. (remove scope element in dependency)
In application.properties, you will add port details for h2 server like
h2-server:
port: 8081
Here, now, the H2 console will be available at http://localhost:8081
Following properties can be removed
# h2:
# console:
# enabled: true
# path: /h2
# settings:
# web-allow-others: true
For Reference: https://github.com/donthadineshkumar/webflux-netty-server-h2-example.git