This project shows how to build "micro" applications with Spring and Spring Boot - the smallest, functional units, with the fewest dependencies and fastest start times

Building the Apps

Build the jar:

$ ./mvnw clean install -DskipTests

Run it

$ java -jar target/micro-0.0.1-SNAPSHOT.jar
...
2018-05-23 10:03:41.776 [main] INFO  com.example.demo.DemoApplication - Started DemoApplication in 1.885 seconds (JVM running for 3.769)
...

The default app is relatively full-bodied - it uses Spring Boot and auto-configuration.

You can run the smaller apps using command line flags:

$ java -jar target/micro-0.0.1-SNAPSHOT.jar --thin.main=com.example.mini.MiniApplication
...
May 23, 2018 10:05:41 AM reactor.util.Loggers$Slf4JLogger info
INFO: Started HttpServer on /127.0.0.1:8080

The main class could be one of

Main	Description
com.example.demo.DemoApplication	(The default). Spring Boot with Webflux and full autoconfiguration
com.example.manual.ManualApplication	Spring Boot with Webflux but manually importing autoconfiguration using @ImportAutoConfiguration
com.example.boot.BootApplication	Spring Boot with Webflux and RouterFunction but no autoconfiguration
com.example.func.FuncApplication	Spring (not Boot) with Webflux and RouterFunction using manual functional bean registration
com.example.func.BuncApplication	Spring Boot with Webflux and RouterFunction using manual functional bean registration
com.example.mini.MiniApplication	Raw Spring, no autoconfiguration, but using @Configuration and RouterFunction
com.example.micro.MicroApplication	Raw Spring with no @Configuration

The thin.profile could be empty (the default) for just spring-boot-starter-webflux dependencies, or you can try jack for a more "normal" set of dependencies, e.g. with hibernate-validator, jackson, and logback. Other choices add more dependencies (e.g. actr for spring-boot-starter-actuator). You will need the "jack" profile to use actuators, so --thin.profile=actr,jack.

The apps are already systematically benchmarked here with regular JVMs: https://github.com/dsyer/spring-boot-startup-bench/blob/master/flux/README.adoc. The point of this project is just to extract them out of the JMH benchmarks, and make them easily executable as standalone apps. In the benchmarks, the "jack" profile is the default, and "jlog" is the faster reduced set of dependencies.

Benchmarks

Spring Boot 3.0.0-SNAPSHOT (Java 17):

class          method  sample beans    classes   heap   memory  median mean  range
MicroBenchmark main    empt   43.000   4081.000  6.982  33.689  0.568  0.593 0.046
MicroBenchmark main    demo   122.000  5662.000  10.669 48.869  0.849  0.901 0.085
MicroBenchmark main    manl   57.000   5035.000  9.142  44.431  0.633  0.665 0.031
MicroBenchmark main    func   44.000   3921.000  7.310  36.758  0.435  0.464 0.023
CdsBenchmark   main    empt   43.000   4161.000  7.077  24.739  0.376  0.399 0.037
CdsBenchmark   main    demo   121.000  6081.000  11.122 30.677  0.497  0.521 0.047
CdsBenchmark   main    manl   57.000   5669.000  9.871  29.126  0.393  0.410 0.021

with AOT:

class          method  sample beans    classes   heap   memory  median mean  range
MicroBenchmark main    demo   118.000  5296.000  9.448  53.407  0.785  0.814 0.026
CdsBenchmark   main    demo   118.000  5917.000  10.576 30.216  0.418  0.440 0.032

Spring Boot 2.7.3 (Java 17):

class          method sample  beans  classes   heap   memory  median mean  range
MicroBenchmark main   empt  43.000   4025.000  6.862  33.436  0.562  0.586 0.030
MicroBenchmark main   demo  122.000  5548.000  10.442 48.377  0.848  0.902 0.056
MicroBenchmark main   manl  57.000   4998.000  9.005  44.235  0.634  0.659 0.024
CdsBenchmark   main   empt  43.000   4109.000  6.917  24.652  0.365  0.391 0.033
CdsBenchmark   main   demo  121.000  6023.000  10.882 30.494  0.492  0.514 0.020
CdsBenchmark   main   manl  57.000   5626.000  9.683  29.026  0.382  0.402 0.021
````

Spring Boot 2.5.4 (Java 17):

class method sample beans classes heap memory median mean range MicroBenchmark main empt 43.000 4003.000 6.796 33.240 0.544 0.564 0.022 MicroBenchmark main demo 117.000 5462.000 10.169 46.527 0.817 0.870 0.095 MicroBenchmark main manl 58.000 4935.000 8.848 42.608 0.616 0.650 0.053 CdsBenchmark main empt 43.000 4094.000 6.857 24.568 0.351 0.380 0.032 CdsBenchmark main demo 116.000 5938.000 10.663 29.255 0.471 0.496 0.033 CdsBenchmark main manl 58.000 5565.000 9.513 27.864 0.385 0.396 0.012

Spring Boot 2.4.3:

class method sample beans classes heap memory median mean range MicroBenchmark main empt 37.000 3492.000 5.047 36.515 0.528 0.543 0.012 MicroBenchmark main react ≈ 0 2191.000 6.269 31.371 0.235 0.240 0.009 MicroBenchmark main micro 6.000 3240.000 7.416 40.326 0.330 0.341 0.010 MicroBenchmark main mini 28.000 3827.000 7.370 43.582 0.473 0.480 0.009 MicroBenchmark main func 45.000 3419.000 7.707 40.650 0.466 0.481 0.017 MicroBenchmark main bunc 46.000 4129.000 6.200 43.422 0.554 0.581 0.047 MicroBenchmark main cunc 52.000 4320.000 6.661 44.926 0.588 0.618 0.045 MicroBenchmark main boot 29.000 3435.000 6.571 41.350 0.413 0.421 0.011 MicroBenchmark main manl 57.000 4478.000 6.753 45.894 0.655 0.675 0.021 MicroBenchmark main demo 108.000 4891.000 8.656 50.341 0.818 0.830 0.019 ProfileBenchmark main jack 106.000 5270.000 10.205 54.235 0.851 0.874 0.029 ProfileBenchmark main actr 186.000 5137.000 9.889 53.202 0.928 0.965 0.049 ProfileBenchmark main jdbc 143.000 5119.000 9.801 52.861 0.884 0.914 0.028 ProfileBenchmark main actj 227.000 5375.000 11.170 55.669 1.003 1.023 0.022

JDK 18 (EA):

class method sample beans classes heap memory median mean range MicroBenchmark main empt 43.000 3991.000 6.397 32.698 0.550 0.561 0.016 MicroBenchmark main demo 117.000 5451.000 9.655 45.752 0.818 0.843 0.027 MicroBenchmark main manl 58.000 4925.000 9.328 42.846 0.624 0.643 0.019 CdsBenchmark main empt 43.000 4084.000 6.469 24.158 0.342 0.352 0.013 CdsBenchmark main demo 116.000 5932.000 10.228 28.771 0.471 0.491 0.033 CdsBenchmark main manl 58.000 5556.000 9.106 27.410 0.356 0.371 0.020

JDK 17:

class method sample beans classes heap memory median mean range MicroBenchmark main empt 37.000 3854.000 6.133 31.948 0.490 0.511 0.020 MicroBenchmark main demo 108.000 5262.000 9.216 44.461 0.751 0.772 0.029 MicroBenchmark main manl 57.000 4864.000 8.269 41.515 0.625 0.656 0.037 CdsBenchmark main empt 37.000 3942.000 6.184 23.773 0.302 0.325 0.017 CdsBenchmark main demo 107.000 5709.000 9.715 27.987 0.434 0.444 0.016 CdsBenchmark main manl 57.000 5470.000 8.897 26.995 0.346 0.365 0.021

Spring Boot 2.3.0:

class method sample beans classes heap memory median mean range MicroBenchmark main empt 38.000 3344.000 5.556 36.461 0.515 0.523 0.010 MicroBenchmark main react ≈0 2163.000 5.995 30.828 0.223 0.228 0.007 MicroBenchmark main micro 6.000 3168.000 6.750 38.088 0.311 0.317 0.009 MicroBenchmark main mini 27.000 3731.000 6.625 41.262 0.450 0.455 0.008 MicroBenchmark main func 44.000 3325.000 7.117 39.532 0.447 0.455 0.008 MicroBenchmark main bunc 45.000 3955.000 6.859 43.211 0.505 0.521 0.023 MicroBenchmark main cunc 51.000 4145.000 6.057 43.402 0.545 0.571 0.046 MicroBenchmark main boot 28.000 3397.000 6.204 40.375 0.399 0.404 0.005 MicroBenchmark main manl 54.000 4301.000 6.323 44.583 0.612 0.619 0.012 MicroBenchmark main demo 105.000 4729.000 7.878 48.748 0.788 0.802 0.020 ProfileBenchmark main jack 103.000 5095.000 9.230 52.456 0.835 0.848 0.011 ProfileBenchmark main actr 190.000 5196.000 9.701 53.370 1.009 1.020 0.014 ProfileBenchmark main jdbc 140.000 5135.000 9.240 52.510 0.928 0.941 0.012 ProfileBenchmark main actj 230.000 5401.000 8.676 53.516 1.090 1.114 0.036

Spring Boot 2.2.1:

class method sample beans classes heap memory median mean range MicroBenchmark main react ≈ 0 2166.000 5.897 30.746 0.219 0.224 0.007 MicroBenchmark main empt 32.000 3269.000 6.366 36.951 0.469 0.481 0.015 MicroBenchmark main micro 6.000 3156.000 6.638 37.913 0.305 0.312 0.008 MicroBenchmark main mini 27.000 3734.000 6.660 41.262 0.444 0.450 0.008 MicroBenchmark main func 45.000 3298.000 6.870 39.068 0.435 0.444 0.012 MicroBenchmark main bunc 46.000 3915.000 6.806 42.849 0.503 0.537 0.040 MicroBenchmark main cunc 52.000 4101.000 5.868 42.908 0.529 0.577 0.054 MicroBenchmark main boot 28.000 4043.000 6.012 42.109 0.387 0.395 0.011 MicroBenchmark main manl 53.000 4231.000 6.105 43.980 0.574 0.583 0.011 MicroBenchmark main demo 100.000 4671.000 7.352 47.825 0.731 0.756 0.031 ProfileBenchmark main jack 98.000 5431.000 9.899 54.039 0.778 0.795 0.015 ProfileBenchmark main actr 188.000 5704.000 9.418 55.329 0.945 0.957 0.014 ProfileBenchmark main jdbc 138.000 5625.000 8.262 53.747 0.880 0.980 0.137 ProfileBenchmark main actj 228.000 5884.000 10.758 57.704 1.030 1.142 0.116

Snapshots after 2.2.0.M4:

class method sample beans classes heap memory median mean range MicroBenchmark main empt 29.000 3272.000 6.388 36.948 0.461 0.491 0.051 MicroBenchmark main micro 6.000 3135.000 6.554 37.536 0.296 0.301 0.007 MicroBenchmark main mini 27.000 3697.000 6.546 40.860 0.426 0.438 0.011 MicroBenchmark main func 45.000 3317.000 6.955 39.155 0.427 0.438 0.022 MicroBenchmark main bunc 46.000 3922.000 6.745 42.758 0.471 0.482 0.011 MicroBenchmark main cunc 52.000 4082.000 5.819 42.736 0.510 0.524 0.029 MicroBenchmark main demo 96.000 4632.000 7.120 47.307 0.712 0.738 0.060

Earlier results:

class method sample beans classes heap memory median mean range MainBenchmark main empt 24.000 3230.000 5.103 38.769 0.546 0.555 0.018 MainBenchmark main jlog 80.000 3598.000 6.141 43.006 0.667 0.679 0.019 MainBenchmark main demo 93.000 4365.000 8.024 49.564 0.766 0.773 0.011 MainBenchmark main actr 174.000 5172.000 8.538 54.216 0.902 0.911 0.020 MainBenchmark main jdbc 131.000 5261.000 9.174 55.252 0.883 0.902 0.031 MainBenchmark main actj 214.000 5510.000 9.007 56.571 0.995 1.021 0.065

class method sample beans classes heap memory median mean range MiniBenchmark boot jlog 28.000 3336.000 7.082 41.949 0.588 0.597 0.014 MiniBenchmark boot demo 28.000 4012.000 6.508 45.566 0.703 0.710 0.011 MiniBenchmark first jlog 2.000 2176.000 6.556 38.574 0.416 0.418 0.004 MiniBenchmark first demo 2.000 2913.000 5.647 42.091 0.515 0.523 0.008 MiniBenchmark micro jlog 2.000 2176.000 4.608 32.886 0.336 0.345 0.013 MiniBenchmark micro demo 2.000 2913.000 7.318 40.454 0.438 0.451 0.016 MiniBenchmark mini jlog 27.000 3059.000 5.487 38.953 0.534 0.545 0.018 MiniBenchmark mini demo 27.000 3732.000 5.969 43.726 0.631 0.636 0.007

== Building a Native Image

Checkout the "native" branch for details of how to build a native image using a buildpack and Spring Boot tooling. You can probably do it by hand with GraalVM as well if you need to, and use the thin jar to calculate its classpath for the build.