micronaut-first-app

Mark

Description

A Micronaut application written in Java.

Prerequisites

JDK 17+

Create a Micronaut app written in Java:

mn create-app zjc.example.micronaut.first.app.micronaut-first-app --build=maven --lang=java

Project Structure

Application.java

package zjc.example.micronaut.first.app;

import io.micronaut.runtime.Micronaut;

public class Application {
    public static void main(String[] args) {
        Micronaut.run(Application.class, args);
    }
}

Create a Controller

In order to create a microservice that responds with “Hello World” you need a controller:

package zjc.example.micronaut.first.app;

import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Produces;

@Controller("/hello")
public class HelloController {
    @Get
    @Produces(MediaType.TEXT_PLAIN)
    public String index() {
        return "Hello World";
    }
}

Testing the Example

./mvnw test

Running the Example

./mvnw mn:run
Output:
 __  __ _                                  _   
|  \/  (_) ___ _ __ ___  _ __   __ _ _   _| |_ 
| |\/| | |/ __| '__/ _ \| '_ \ / _` | | | | __|
| |  | | | (__| | | (_) | | | | (_| | |_| | |_ 
|_|  |_|_|\___|_|  \___/|_| |_|\__,_|\__,_|\__|
18:57:04.953 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 493ms. Server Running: http://localhost:8080

Browser:

http://localhost:8080/hello

Native Executable with GraalVM

Native executable – see: http://jreact.com/index.php/quarkus-2/native-executable/

./mvnw package -Dpackaging=native-image
GraalVM Native Image: Generating 'micronaut-first-app' (executable)...
========================================================================================================================
[1/8] Initializing...                                                                                    (6.0s @ 0.14GB)
 Java version: 21.0.1+12, vendor version: Oracle GraalVM 21.0.1+12.1
 Graal compiler: optimization level: 2, target machine: x86-64-v3, PGO: ML-inferred
 C compiler: gcc (linux, x86_64, 11.4.0)
 Garbage collector: Serial GC (max heap size: 80% of RAM)
 2 user-specific feature(s):
 - com.oracle.svm.thirdparty.gson.GsonFeature
 - io.micronaut.core.io.service.ServiceLoaderFeature
------------------------------------------------------------------------------------------------------------------------
Build resources:
 - 11.67GB of memory (75.6% of 15.45GB system memory, determined at start)
 - 8 thread(s) (100.0% of 8 available processor(s), determined at start)
Found pending operations, continuing analysis.
[2/8] Performing analysis...  [******]                                                                  (61.9s @ 1.03GB)
   13,728 reachable types   (88.8% of   15,455 total)
   20,297 reachable fields  (58.6% of   34,647 total)
   74,222 reachable methods (63.7% of  116,560 total)
    4,562 types,   494 fields, and 4,713 methods registered for reflection
       64 types,    61 fields, and    57 methods registered for JNI access
        4 native libraries: dl, pthread, rt, z
[3/8] Building universe...                                                                               (7.2s @ 1.62GB)
[4/8] Parsing methods...      [****]                                                                    (20.2s @ 1.16GB)
[5/8] Inlining methods...     [***]                                                                      (2.3s @ 1.37GB)
[6/8] Compiling methods...    [***********]                                                            (137.7s @ 1.37GB)
[7/8] Layouting methods...    [***]                                                                      (9.6s @ 1.52GB)
[8/8] Creating image...       [***]                                                                      (8.4s @ 1.38GB)
  38.10MB (54.52%) for code area:    44,407 compilation units
  27.51MB (39.36%) for image heap:  335,605 objects and 307 resources
   4.28MB ( 6.12%) for other data
  69.89MB in total
------------------------------------------------------------------------------------------------------------------------
Top 10 origins of code area:                                Top 10 object types in image heap:
  14.49MB java.base                                           10.62MB byte[] for code metadata
   4.12MB svm.jar (Native Image)                               4.57MB byte[] for java.lang.String
   3.15MB java.xml                                             2.96MB java.lang.Class
   1.33MB netty-buffer-4.1.107.Final.jar                       2.34MB java.lang.String
   1.11MB micronaut-inject-4.3.11.jar                        904.13kB byte[] for reflection metadata
   1.03MB micronaut-http-server-netty-4.3.11.jar             764.51kB byte[] for general heap data
 918.08kB micronaut-http-4.3.11.jar                          643.50kB com.oracle.svm.core.hub.DynamicHubCompanion
 899.93kB micronaut-serde-support-2.8.2.jar                  399.41kB c.o.svm.core.hub.DynamicHub$ReflectionMetadata
 850.10kB reactor-core-3.5.11.jar                            342.00kB java.util.HashMap$Node
 765.44kB micronaut-core-4.3.11.jar                          321.01kB java.lang.String[]
   9.22MB for 51 more packages                                 3.73MB for 2916 more object types
                              Use '-H:+BuildReport' to create a report with more details.
------------------------------------------------------------------------------------------------------------------------
Security report:
 - Binary includes Java deserialization.
 - Use '--enable-sbom' to embed a Software Bill of Materials (SBOM) in the binary.
------------------------------------------------------------------------------------------------------------------------
Recommendations:
 G1GC: Use the G1 GC ('--gc=G1') for improved latency and throughput.
 PGO:  Use Profile-Guided Optimizations ('--pgo') for improved throughput.
 INIT: Adopt '--strict-image-heap' to prepare for the next GraalVM release.
 HEAP: Set max heap for improved and more predictable memory usage.
 CPU:  Enable more CPU features with '-march=native' for improved performance.
------------------------------------------------------------------------------------------------------------------------
                       19.5s (7.6% of total time) in 589 GCs | Peak RSS: 3.12GB | CPU load: 6.52
------------------------------------------------------------------------------------------------------------------------
Produced artifacts:
 /home/zbyszek/IdeaProjects/reactive/github/zjc-examples/micronaut/micronaut-first-app/target/micronaut-first-app (executable)
========================================================================================================================
Finished generating 'micronaut-first-app' in 4m 14s.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  04:22 min
[INFO] Finished at: 2024-04-04T19:17:18+02:00
[INFO] ------------------------------------------------------------------------

Running executable

./target/micronaut-first-app
 __  __ _                                  _   
|  \/  (_) ___ _ __ ___  _ __   __ _ _   _| |_ 
| |\/| | |/ __| '__/ _ \| '_ \ / _` | | | | __|
| |  | | | (__| | | (_) | | | | (_| | |_| | |_ 
|_|  |_|_|\___|_|  \___/|_| |_|\__,_|\__,_|\__|
19:45:42.771 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 14ms. Server Running: http://localhost:8080

http://localhost:8080/hello

Source code: https://github.com/ZbCiok/zjc-examples/tree/main/micronaut/micronaut-first-app

–

Mark