Java, Helidon SE get URL query string parameters example

Hello everyone, Today, we will show you how to create a simple REST API with Helidon SE 2.5.0 and Java 17 and how to get URL query string parameters.

Quick Overview:

• Helidon SE is designed to be a microframework that fortifies the reactive programming model. Helidon SE features three core APIs to engender a microservice -- a web server, configuration, and security -- for building microservices-predicated applications. 

• Helidon's web server is an asynchronous and reactive API that runs on top of Netty. The WebServer interface includes support for configuration, routing, error handling, and building metrics and health endpoints.

• The Config loads and processes configuration properties(application.properties or application.yaml) in key/value format. 

• The Security class provides support for authentication, sanction, and audit.

• Query parameters are a defined set of parameters affixed to the end of a url. They are extensions of the URL that are used to avail define specific content or actions predicated on the data being passed.

Final Project Directory:

Maven [pom.xml]:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>io.helidon.applications</groupId>
        <artifactId>helidon-se</artifactId>
        <version>2.5.0</version>
        <relativePath>../../../applications/se/pom.xml
                      </relativePath>
    </parent>
    <groupId>com.knf.dev.demo</groupId>
    <artifactId>helidon-se-query-path-param-example</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>helidon-se-query-path-param-example</name>
    <description>Demo project for Helidon SE</description>
    <properties>
        <version.java>17</version.java>
        <mainClass>com.knf.dev.demo.helidonseresthelloworld.
            HelidonSeRestHelloWorldApplication</mainClass>
    </properties>
    <dependencies>
        <dependency>
            <groupId>io.helidon.webserver</groupId>
            <artifactId>helidon-webserver</artifactId>
        </dependency>
        <dependency>
            <groupId>io.helidon.media</groupId>
            <artifactId>helidon-media-jsonp</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>${version.java}</source>
                    <target>${version.java}</target>
                    <release>${version.java}</release>
                    <forceJavacCompilerUse>true
                              </forceJavacCompilerUse>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

MyService.java:

package com.knf.dev.demo.helidonseresthelloworld;
import java.util.Collections;
import javax.json.Json;
import javax.json.JsonBuilderFactory;
import io.helidon.config.Config;
import io.helidon.webserver.Routing.Rules;
import io.helidon.webserver.ServerRequest;
import io.helidon.webserver.ServerResponse;
import io.helidon.webserver.Service;
public class MyService implements Service {
    private static final JsonBuilderFactory JSON = Json.
                 createBuilderFactory(Collections.emptyMap());
    MyService(Config config) {
    }
    @Override
    public void update(Rules rules) {
        rules.get("/", this::getDefaultMessageHandler);
    }
    private void getDefaultMessageHandler
          (ServerRequest request, ServerResponse response) {
        var params = request.queryParams().toMap();
        System.out.println("name: " + params.get("name").get(0));
        System.out.println("email: " + params.get("email").get(0));
        sendResponse(response, params.get("name").get(0));
    }
    private void sendResponse
            (ServerResponse response, String name) {
        var returnObject = JSON.createObjectBuilder().
                    add("name", name).build();
        response.send(returnObject);
    }
}

application.properties:

server.port=8080

Main.java:

package com.knf.dev.demo.helidonseresthelloworld;
import java.util.logging.Logger;
import io.helidon.common.reactive.Single;
import io.helidon.config.Config;
import io.helidon.media.jsonp.JsonpSupport;
import io.helidon.webserver.Routing;
import io.helidon.webserver.WebServer;
public class HelidonSeRestApplication {
    private static final Logger LOGGER = Logger.
      getLogger(HelidonSeRestApplication.class.getName());
    public static void main(final String[] args) {
        startServer();
    }
    private static Single<WebServer> startServer() {
        // Load the default configuration using 
        // the create() method.
        var config = Config.create();

        var server = WebServer.builder(createRouting(config))
                     .config(config.get("server"))
                      .addMediaSupport(JsonpSupport.create())
                       .build();
        // Start web server
        var webserver = server.start();
        webserver.thenAccept(ws -> {
            LOGGER.info("Web server started! http://localhost:" 
               + ws.port() + "/hello");
            ws.whenShutdown().thenRun(() -> LOGGER.
                 info("Web server is down!"));
        }).exceptionallyAccept(t -> {
            LOGGER.severe("Web startup failed: " + t.getMessage());
        });
        return webserver;
    }
    private static Routing createRouting(Config config) {
        var helloService = new MyService(config);
        return Routing.builder()
                .register("/hello", helloService).build();
    }
}

Download the source code

Local Setup and Run the application:

Step1: Download or clone the source code to a local machine. - Click here

Step2: mvn clean install

Step3: Run the Main java application

http://localhost:8080/hello?name=knowledgefactory&email=knowledgefactory@knf.dev

Console output:

name: knowledgefactory 

email: knowledgefactory@knf.dev