[java] [maven] [dropwizard] DropWizard HelloWorld API from scratch

[0] Preparation.

• java jdk 11(set JAVA_HOME path e.g. C:\Program Files\Java\jdk-11)
• maven
• curl
• IntelliJ IDE(optional)

[1] Make project directory

mkdir mydrophello cd mydrophello

[2] Create pom file

notepad pom.xml <project> <modelVersion>4.0.0</modelVersion> <groupId>com.mycompany.helloworld</groupId> <artifactId>helloworld</artifactId> <version>0.0.0</version> </project>

[3] Create source directory

mkdir -p src\main\java\com\mycompany\helloworld mkdir -p src\test\java\com\mycompany\helloworld

[4] Complete the pom file

The full pom file would be as follows:

<?xml version="1.0" encoding="UTF-8"?> <project> <modelVersion>4.0.0</modelVersion> <groupId>com.mycompany.helloworld</groupId> <artifactId>helloworld</artifactId> <version>0.0.0</version> <name>HelloWorld DropWizard</name> <properties> <dropwizard.version>2.0.0</dropwizard.version> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> <mainClass>com.mycompany.helloworld.HelloWorldApplication</mainClass> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>io.dropwizard</groupId> <artifactId>dropwizard-core</artifactId> <version>${dropwizard.version}</version> </dependency> <dependency> <groupId>io.dropwizard</groupId> <artifactId>dropwizard-testing</artifactId> <version>${dropwizard.version}</version> </dependency> <dependency> <groupId>org.assertj</groupId> <artifactId>assertj-core</artifactId> <version>3.6.2</version> <scope>test</scope> </dependency> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter-api</artifactId> <version>5.4.2</version> <scope>test</scope> </dependency> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter-engine</artifactId> <version>5.4.2</version> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-shade-plugin</artifactId> <version>3.1.1</version> <executions> <execution> <phase>package</phase> <goals> <goal>shade</goal> </goals> <configuration> <createDependencyReducedPom>true</createDependencyReducedPom> <transformers> <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer"> <mainClass>com.mycompany.helloworld.HelloWorldApplication</mainClass> </transformer> </transformers> </configuration> </execution> </executions> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-surefire-plugin</artifactId> <version>3.0.0-M5</version> </plugin> </plugins> </build> </project>

[5] Add Dropwizard files

• Configuration Class File
• Application Class File
• Representation Class File
• Resource Class File
• Health Check Class File (optional)
• Config File

[5.1] Configuration

Location:src\main\java\com\mycompany\helloworld\HelloWorldConfiguration.java

notepad src\main\java\com\mycompany\helloworld\HelloWorldConfiguration.java package com.mycompany.helloworld; import io.dropwizard.Configuration; import com.fasterxml.jackson.annotation.JsonProperty; import javax.validation.constraints.NotEmpty; public class HelloWorldConfiguration extends Configuration { @NotEmpty private String defaultMessage = "Hello World!"; @JsonProperty public String getDefaultMessage() { return defaultMessage; } @JsonProperty public void setDefaultMessage(String message) { this.defaultMessage = message; } }

[5.2] Application

Location:src\main\java\com\mycompany\helloworld\HelloWorldApplication.java

notepad src\main\java\com\mycompany\helloworld\HelloWorldApplication.java package com.mycompany.helloworld; import com.mycompany.helloworld.health.ConfigHealthCheck; import com.mycompany.helloworld.resources.HelloWorldResource; import io.dropwizard.Application; import io.dropwizard.setup.Environment; public class HelloWorldApplication extends Application<HelloWorldConfiguration> { public static void main(String[] args) throws Exception { new HelloWorldApplication().run(args); } @Override public String getName() { return "helloworld"; } @Override public void run(HelloWorldConfiguration configuration, Environment environment) { final HelloWorldResource resource = new HelloWorldResource( configuration.getDefaultMessage() ); final ConfigHealthCheck healthCheck; healthCheck = new ConfigHealthCheck(configuration.getDefaultMessage()); environment.healthChecks().register("defaultMessage", healthCheck); environment.jersey().register(resource); } }

[5.3] Representation

Location:src\main\java\com\mycompany\helloworld\api\HelloWorld.java

mkdir src\main\java\com\mycompany\helloworld\api notepad src\main\java\com\mycompany\helloworld\api\HelloWorld.java package com.mycompany.helloworld.api; import com.fasterxml.jackson.annotation.JsonProperty; public class HelloWorld { private long id; private String content; public HelloWorld(long id, String content) { this.id = id; this.content = content; } @JsonProperty public long getId() { return id; } @JsonProperty public String getContent() { return content; } }

[5.4] Resource

Location:src\main\java\com\mycompany\helloworld\resources\HelloWorldResource.java

mkdir src\main\java\com\mycompany\helloworld\resources notepad src\main\java\com\mycompany\helloworld\resources\HelloWorldResource.java package com.mycompany.helloworld.resources; import com.mycompany.helloworld.api.HelloWorld; import javax.ws.rs.GET; import javax.ws.rs.Path; import javax.ws.rs.Produces; import javax.ws.rs.core.MediaType; import java.util.concurrent.atomic.AtomicLong; @Path("/") @Produces(MediaType.APPLICATION_JSON) public class HelloWorldResource { private final String defaultMessage; private final AtomicLong counter; public HelloWorldResource(String defaultMessage) { this.counter = new AtomicLong(); this.defaultMessage = defaultMessage; } @GET public HelloWorld sayHello() { return new HelloWorld(counter.incrementAndGet(), defaultMessage); } }

[5.5] HealthCheck

Location:src\main\java\com\mycompany\helloworld\health\HelloWorldResource.java

mkdir src\main\java\com\mycompany\helloworld\health notepad src\main\java\com\mycompany\helloworld\health\ConfigHealthCheck.java package com.mycompany.helloworld.health; import com.codahale.metrics.health.HealthCheck; public class ConfigHealthCheck extends HealthCheck { private final String defaultMessage; public ConfigHealthCheck(String defaultMessage) { this.defaultMessage = defaultMessage; } @Override protected Result check() throws Exception { if (this.defaultMessage == null) { return Result.unhealthy("Config file doesn't contain key - defaultMessage"); } return Result.healthy(); } }

[5.6] Config

Location:config.yml

notepad config.yml defaultMessage: "Hello World!"

[6] Compile and run

mvn package java -jar target/helloworld-0.0.0.jar server config.yml

REF:https://geekyshacklebolt.wordpress.com/2021/01/06/dropwizard-helloworld-api-from-scratch/
https://github.com/GeekyShacklebolt/dropwizard-helloworld