BAEL 3320 JCommander (#7971)

* init jcommander

* add model layer jcommander app

* service scaffolding

* init jcommander cli layer

* wire up services and commands

* splitter impl; validator impl; tests and cleanup

* cleanup pom

* integration tests

* fix uuid validator example

* optimise uuid regex; if-else to switch

* review comments

* fix builder formatting

* change list assertion in fetch charges tests

* missing minor edit

* move to new module libraries-3

* rm unwanted files

libraries-3/README.md

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+## Libraries-3
+
+This module contains articles about various Java libraries. 
+These are small libraries that are relatively easy to use and do not require any separate module of their own.
+
+The code examples related to different libraries are each in their own module.
+
+Remember, for advanced libraries like [Jackson](/jackson) and [JUnit](/testing-modules) we already have separate modules. Please make sure to have a look at the existing modules in such cases.
+

libraries-3/pom.xml

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+<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>libraries-3</artifactId>
+    <name>libraries-3</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <repositories>
+        <repository>
+            <id>jboss-public-repository-group</id>
+            <name>JBoss Public Repository Group</name>
+            <url>http://repository.jboss.org/nexus/content/groups/public/</url>
+            <releases>
+                <enabled>true</enabled>
+                <updatePolicy>never</updatePolicy>
+            </releases>
+            <snapshots>
+                <enabled>true</enabled>
+                <updatePolicy>daily</updatePolicy>
+            </snapshots>
+        </repository>
+    </repositories>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.beust</groupId>
+            <artifactId>jcommander</artifactId>
+            <version>${jcommander.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <jcommander.version>1.78</jcommander.version>
+        <lombok.version>1.18.6</lombok.version>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.target>1.8</maven.compiler.target>
+        <maven.compiler.source>1.8</maven.compiler.source>
+    </properties>
+</project>

libraries-3/src/main/java/com/baeldung/jcommander/helloworld/HelloWorldApp.java

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+package com.baeldung.jcommander.helloworld;
+
+import com.beust.jcommander.JCommander;
+import com.beust.jcommander.Parameter;
+
+public class HelloWorldApp {
+
+    /*
+     * Execute:
+     * mvn exec:java -Dexec.mainClass=com.baeldung.jcommander.helloworld.HelloWorldApp -q \
+     *   -Dexec.args="--name JavaWorld"
+     */
+    public static void main(String[] args) {
+        HelloWorldArgs jArgs = new HelloWorldArgs();
+        JCommander helloCmd = JCommander
+          .newBuilder()
+          .addObject(jArgs)
+          .build();
+
+        helloCmd.parse(args);
+        System.out.println("Hello " + jArgs.getName());
+    }
+}
+
+class HelloWorldArgs {
+
+    @Parameter(
+      names = "--name",
+      description = "User name",
+      required = true
+    )
+    private String name;
+
+    public String getName() {
+        return name;
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/UsageBasedBillingApp.java

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+package com.baeldung.jcommander.usagebilling;
+
+import com.baeldung.jcommander.usagebilling.cli.UsageBasedBilling;
+
+public class UsageBasedBillingApp {
+
+  /*
+   *  Entry-point: invokes the cli passing the command-line args
+   *  
+   *  Invoking "Submit" sub-command:
+   *  mvn exec:java \
+        -Dexec.mainClass=com.baeldung.jcommander.usagebilling.UsageBasedBillingApp -q \
+        -Dexec.args="submit --customer cb898e7a-f2a0-46d2-9a09-531f1cee1839 --subscription subscriptionPQRMN001 --pricing-type PRE_RATED --timestamp 2019-10-03T10:58:00 --quantity 7 --price 24.56"
+   *     
+   *  Invoking "Fetch" sub-command:
+   *  mvn exec:java \
+        -Dexec.mainClass=com.baeldung.jcommander.usagebilling.UsageBasedBillingApp -q \
+        -Dexec.args="fetch --customer cb898e7a-f2a0-46d2-9a09-531f1cee1839 --subscription subscriptionPQRMN001 subscriptionPQRMN002 subscriptionPQRMN003 --itemized"
+   */
+  public static void main(String[] args) {
+    new UsageBasedBilling().run(args);
+  }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/cli/FetchCurrentChargesCommand.java

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+package com.baeldung.jcommander.usagebilling.cli;
+
+import com.baeldung.jcommander.usagebilling.cli.splitter.ColonParameterSplitter;
+import com.baeldung.jcommander.usagebilling.cli.validator.UUIDValidator;
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesRequest;
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesResponse;
+import com.baeldung.jcommander.usagebilling.service.FetchCurrentChargesService;
+import com.beust.jcommander.Parameter;
+import com.beust.jcommander.Parameters;
+import lombok.Getter;
+
+import java.util.List;
+
+import static com.baeldung.jcommander.usagebilling.cli.UsageBasedBilling.*;
+import static com.baeldung.jcommander.usagebilling.service.FetchCurrentChargesService.getDefault;
+
+@Parameters(
+  commandNames = { FETCH_CMD },
+  commandDescription = "Fetch charges for a customer in the current month, can be itemized or aggregated"
+)
+@Getter
+class FetchCurrentChargesCommand {
+
+    FetchCurrentChargesCommand() {
+    }
+
+    private FetchCurrentChargesService service = getDefault();
+
+    @Parameter(names = "--help", help = true)
+    private boolean help;
+
+    @Parameter(
+      names = { "--customer", "-C" },
+      description = "Id of the Customer who's using the services",
+      validateWith = UUIDValidator.class,
+      order = 1,
+      required = true
+    )
+    private String customerId;
+
+    @Parameter(
+      names = { "--subscription", "-S" },
+      description = "Filter charges for specific subscription Ids, includes all subscriptions if no value is specified",
+      variableArity = true,
+      splitter = ColonParameterSplitter.class,
+      order = 2
+    )
+    private List<String> subscriptionIds;
+
+    @Parameter(
+      names = { "--itemized" },
+      description = "Whether the response should contain breakdown by subscription, only aggregate values are returned by default",
+      order = 3
+    )
+    private boolean itemized;
+
+    void fetch() {
+        CurrentChargesRequest req = CurrentChargesRequest.builder()
+          .customerId(customerId)
+          .subscriptionIds(subscriptionIds)
+          .itemized(itemized)
+          .build();
+
+        CurrentChargesResponse response = service.fetch(req);
+        System.out.println(response);
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/cli/SubmitUsageCommand.java

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+package com.baeldung.jcommander.usagebilling.cli;
+
+import com.baeldung.jcommander.usagebilling.cli.converter.ISO8601TimestampConverter;
+import com.baeldung.jcommander.usagebilling.cli.validator.UUIDValidator;
+import com.baeldung.jcommander.usagebilling.model.UsageRequest;
+import com.baeldung.jcommander.usagebilling.model.UsageRequest.PricingType;
+import com.baeldung.jcommander.usagebilling.service.SubmitUsageService;
+import com.beust.jcommander.Parameter;
+import com.beust.jcommander.Parameters;
+import lombok.Getter;
+
+import java.math.BigDecimal;
+import java.time.Instant;
+
+import static com.baeldung.jcommander.usagebilling.cli.UsageBasedBilling.*;
+import static com.baeldung.jcommander.usagebilling.service.SubmitUsageService.getDefault;
+
+@Parameters(
+  commandNames = { SUBMIT_CMD },
+  commandDescription = "Submit usage for a given customer and subscription, accepts one usage item"
+)
+@Getter
+class SubmitUsageCommand {
+
+    SubmitUsageCommand() {
+    }
+
+    private SubmitUsageService service = getDefault();
+
+    @Parameter(names = "--help", help = true)
+    private boolean help;
+
+    @Parameter(
+      names = { "--customer", "-C" },
+      description = "Id of the Customer who's using the services",
+      validateWith = UUIDValidator.class,
+      order = 1,
+      required = true
+    )
+    private String customerId;
+
+    @Parameter(
+      names = { "--subscription", "-S" },
+      description = "Id of the Subscription that was purchased",
+      order = 2,
+      required = true
+    )
+    private String subscriptionId;
+
+    @Parameter(
+      names = { "--pricing-type", "-P" },
+      description = "Pricing type of the usage reported",
+      order = 3,
+      required = true
+    )
+    private PricingType pricingType;
+
+    @Parameter(
+      names = { "--quantity" },
+      description = "Used quantity; reported quantity is added over the billing period",
+      order = 3,
+      required = true
+    )
+    private Integer quantity;
+
+    @Parameter(
+      names = { "--timestamp" },
+      description = "Timestamp of the usage event, must lie in the current billing period",
+      converter = ISO8601TimestampConverter.class,
+      order = 4,
+      required = true
+    )
+    private Instant timestamp;
+
+    @Parameter(
+      names = { "--price" },
+      description = "If PRE_RATED, unit price to be applied per unit of usage quantity reported",
+      order = 5
+    )
+    private BigDecimal price;
+
+    void submit() {
+        
+        UsageRequest req = UsageRequest.builder()
+          .customerId(customerId)
+          .subscriptionId(subscriptionId)
+          .pricingType(pricingType)
+          .quantity(quantity)
+          .timestamp(timestamp)
+          .price(price)
+          .build();
+
+        String reqId = service.submit(req);
+        System.out.println("Generated Request Id for reference: " + reqId);
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/cli/UsageBasedBilling.java

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+package com.baeldung.jcommander.usagebilling.cli;
+
+import com.beust.jcommander.JCommander;
+import com.beust.jcommander.ParameterException;
+import com.beust.jcommander.UnixStyleUsageFormatter;
+
+public class UsageBasedBilling {
+
+    static final String SUBMIT_CMD = "submit";
+    static final String FETCH_CMD = "fetch";
+
+    private JCommander jCommander;
+    private SubmitUsageCommand submitUsageCmd;
+    private FetchCurrentChargesCommand fetchChargesCmd;
+
+    public UsageBasedBilling() {
+        this.submitUsageCmd = new SubmitUsageCommand();
+        this.fetchChargesCmd = new FetchCurrentChargesCommand();
+        jCommander = JCommander.newBuilder()
+          .addObject(this)
+          .addCommand(submitUsageCmd)
+          .addCommand(fetchChargesCmd)
+          .build();
+
+        setUsageFormatter(SUBMIT_CMD);
+        setUsageFormatter(FETCH_CMD);
+    }
+
+    public void run(String[] args) {
+        String parsedCmdStr;
+        try {
+            jCommander.parse(args);
+            parsedCmdStr = jCommander.getParsedCommand();
+            
+            switch (parsedCmdStr) {
+                case SUBMIT_CMD:
+                    if (submitUsageCmd.isHelp()) {
+                        getSubCommandHandle(SUBMIT_CMD).usage();
+                    }
+                    System.out.println("Parsing usage request...");
+                    submitUsageCmd.submit();
+                    break;
+
+                case FETCH_CMD:
+                    if (fetchChargesCmd.isHelp()) {
+                        getSubCommandHandle(SUBMIT_CMD).usage();
+                    }
+                    System.out.println("Preparing fetch query...");
+                    fetchChargesCmd.fetch();
+                    
+                    break;
+                    
+                default:
+                    System.err.println("Invalid command: " + parsedCmdStr);
+            }
+        } catch (ParameterException e) {
+            System.err.println(e.getLocalizedMessage());
+            parsedCmdStr = jCommander.getParsedCommand();
+            if (parsedCmdStr != null) {
+                getSubCommandHandle(parsedCmdStr).usage();
+            } else {
+                jCommander.usage();
+            }
+        }
+    }
+
+    private JCommander getSubCommandHandle(String command) {
+        JCommander cmd = jCommander.getCommands().get(command);
+
+        if (cmd == null) {
+            System.err.println("Invalid command: " + command);
+        }
+        return cmd;
+    }
+
+    private void setUsageFormatter(String subCommand) {
+        JCommander cmd = getSubCommandHandle(subCommand);
+        cmd.setUsageFormatter(new UnixStyleUsageFormatter(cmd));
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/cli/converter/ISO8601TimestampConverter.java

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+package com.baeldung.jcommander.usagebilling.cli.converter;
+
+import com.beust.jcommander.ParameterException;
+import com.beust.jcommander.converters.BaseConverter;
+
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
+
+import static java.lang.String.format;
+
+public class ISO8601TimestampConverter extends BaseConverter<Instant> {
+
+    private static final DateTimeFormatter TS_FORMATTER = DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss");
+
+    public ISO8601TimestampConverter(String optionName) {
+        super(optionName);
+    }
+
+    @Override
+    public Instant convert(String value) {
+        try {
+            return LocalDateTime
+              .parse(value, TS_FORMATTER)
+              .atOffset(ZoneOffset.UTC)
+              .toInstant();
+        } catch (DateTimeParseException e) {
+            throw new ParameterException(getErrorString(value, format("an ISO-8601 formatted timestamp (%s)", TS_FORMATTER.toString())));
+        }
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/cli/splitter/ColonParameterSplitter.java

@@ -0,0 +1,15 @@
+package com.baeldung.jcommander.usagebilling.cli.splitter;
+
+import com.beust.jcommander.converters.IParameterSplitter;
+
+import java.util.List;
+
+import static java.util.Arrays.asList;
+
+public class ColonParameterSplitter implements IParameterSplitter {
+
+    @Override
+    public List<String> split(String value) {
+        return asList(value.split(":"));
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/cli/validator/UUIDValidator.java

@@ -0,0 +1,26 @@
+package com.baeldung.jcommander.usagebilling.cli.validator;
+
+import com.beust.jcommander.IParameterValidator;
+import com.beust.jcommander.ParameterException;
+
+import java.util.regex.Pattern;
+
+public class UUIDValidator implements IParameterValidator {
+
+    private static final String UUID_REGEX = 
+      "[0-9a-fA-F]{8}(-[0-9a-fA-F]{4}){3}-[0-9a-fA-F]{12}";
+
+    @Override
+    public void validate(String name, String value) throws ParameterException {
+        if (!isValidUUID(value)) {
+            throw new ParameterException(
+              "String parameter " + value + " is not a valid UUID.");
+        }
+    }
+
+    private boolean isValidUUID(String value) {
+        return Pattern
+          .compile(UUID_REGEX)
+          .matcher(value).matches();
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/model/CurrentChargesRequest.java

@@ -0,0 +1,16 @@
+package com.baeldung.jcommander.usagebilling.model;
+
+import lombok.*;
+
+import java.util.List;
+
+@NoArgsConstructor(access = AccessLevel.PACKAGE)
+@AllArgsConstructor(access = AccessLevel.PACKAGE)
+@Builder
+@Getter
+public class CurrentChargesRequest {
+
+    private String customerId;
+    private List<String> subscriptionIds;
+    private boolean itemized;
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/model/CurrentChargesResponse.java

@@ -0,0 +1,56 @@
+package com.baeldung.jcommander.usagebilling.model;
+
+import lombok.*;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import java.util.List;
+
+@NoArgsConstructor(access = AccessLevel.PACKAGE)
+@AllArgsConstructor(access = AccessLevel.PACKAGE)
+@Builder
+@Getter
+public class CurrentChargesResponse {
+
+    private String customerId;
+    private BigDecimal amountDue;
+    private List<LineItem> lineItems;
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        sb
+          .append("Current Month Charges: {")
+          .append("\n\tcustomer: ")
+          .append(this.customerId)
+          .append("\n\ttotalAmountDue: ")
+          .append(this.amountDue.setScale(2, RoundingMode.HALF_UP))
+          .append("\n\tlineItems: [");
+
+        for (LineItem li : this.lineItems) {
+            sb
+              .append("\n\t\t{")
+              .append("\n\t\t\tsubscription: ")
+              .append(li.subscriptionId)
+              .append("\n\t\t\tamount: ")
+              .append(li.amount.setScale(2, RoundingMode.HALF_UP))
+              .append("\n\t\t\tquantity: ")
+              .append(li.quantity)
+              .append("\n\t\t},");
+        }
+
+        sb.append("\n\t]\n}\n");
+        return sb.toString();
+    }
+
+    @NoArgsConstructor(access = AccessLevel.PACKAGE)
+    @AllArgsConstructor(access = AccessLevel.PACKAGE)
+    @Builder
+    @Getter
+    public static class LineItem {
+
+        private String subscriptionId;
+        private BigDecimal amount;
+        private Integer quantity;
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/model/UsageRequest.java

@@ -0,0 +1,50 @@
+package com.baeldung.jcommander.usagebilling.model;
+
+import lombok.*;
+
+import java.math.BigDecimal;
+import java.time.Instant;
+
+@NoArgsConstructor(access = AccessLevel.PACKAGE)
+@AllArgsConstructor(access = AccessLevel.PACKAGE)
+@Builder
+@Getter
+public class UsageRequest {
+
+    private String customerId;
+    private String subscriptionId;
+    private PricingType pricingType;
+    private Integer quantity;
+    private BigDecimal price;
+    private Instant timestamp;
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        sb
+          .append("\nUsage: {")
+          .append("\n\tcustomer: ")
+          .append(this.customerId)
+          .append("\n\tsubscription: ")
+          .append(this.subscriptionId)
+          .append("\n\tquantity: ")
+          .append(this.quantity)
+          .append("\n\ttimestamp: ")
+          .append(this.timestamp)
+          .append("\n\tpricingType: ")
+          .append(this.pricingType);
+
+        if (PricingType.PRE_RATED == this.pricingType) {
+            sb
+              .append("\n\tpreRatedAt: ")
+              .append(this.price);
+        }
+
+        sb.append("\n}\n");
+        return sb.toString();
+    }
+
+    public enum PricingType {
+        PRE_RATED, UNRATED
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/service/DefaultFetchCurrentChargesService.java

@@ -0,0 +1,68 @@
+package com.baeldung.jcommander.usagebilling.service;
+
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesRequest;
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesResponse;
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesResponse.LineItem;
+
+import java.math.BigDecimal;
+import java.util.List;
+import java.util.UUID;
+
+import static java.lang.String.format;
+import static java.util.Arrays.asList;
+import static java.util.Arrays.fill;
+import static java.util.Collections.emptyList;
+import static java.util.concurrent.ThreadLocalRandom.current;
+import static java.util.stream.Collectors.toList;
+
+class DefaultFetchCurrentChargesService implements FetchCurrentChargesService {
+
+    @Override
+    public CurrentChargesResponse fetch(CurrentChargesRequest request) {
+        List<String> subscriptions = request.getSubscriptionIds();
+
+        if (subscriptions == null || subscriptions.isEmpty()) {
+            System.out.println("Fetching ALL charges for customer: " + request.getCustomerId());
+            subscriptions = mockSubscriptions();
+
+        } else {
+            System.out.println(format("Fetching charges for customer: %s and subscriptions: %s", request.getCustomerId(), subscriptions));
+        }
+
+        CurrentChargesResponse charges = mockCharges(request.getCustomerId(), subscriptions, request.isItemized());
+        System.out.println("Fetched charges...");
+        return charges;
+    }
+
+    private CurrentChargesResponse mockCharges(String customerId, List<String> subscriptions, boolean itemized) {
+        List<LineItem> lineItems = mockLineItems(subscriptions);
+        BigDecimal amountDue = lineItems
+          .stream()
+          .map(li -> li.getAmount())
+          .reduce(new BigDecimal("0"), BigDecimal::add);
+
+        return CurrentChargesResponse
+          .builder()
+          .customerId(customerId)
+          .lineItems(itemized ? lineItems : emptyList())
+          .amountDue(amountDue)
+          .build();
+    }
+
+    private List<LineItem> mockLineItems(List<String> subscriptions) {
+        return subscriptions
+          .stream()
+          .map(subscription -> LineItem.builder()
+            .subscriptionId(subscription)
+            .quantity(current().nextInt(20))
+            .amount(new BigDecimal(current().nextDouble(1_000)))
+            .build())
+          .collect(toList());
+    }
+
+    private List<String> mockSubscriptions() {
+        String[] subscriptions = new String[5];
+        fill(subscriptions, UUID.randomUUID().toString());
+        return asList(subscriptions);
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/service/DefaultSubmitUsageService.java

@@ -0,0 +1,16 @@
+package com.baeldung.jcommander.usagebilling.service;
+
+import com.baeldung.jcommander.usagebilling.model.UsageRequest;
+
+import java.util.UUID;
+
+class DefaultSubmitUsageService implements SubmitUsageService {
+
+    @Override
+    public String submit(UsageRequest request) {
+        System.out.println("Submitting usage..." + request);
+
+        System.out.println("Submitted usage successfully...");
+        return UUID.randomUUID().toString();
+    }
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/service/FetchCurrentChargesService.java

@@ -0,0 +1,13 @@
+package com.baeldung.jcommander.usagebilling.service;
+
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesRequest;
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesResponse;
+
+public interface FetchCurrentChargesService {
+
+    static FetchCurrentChargesService getDefault() {
+        return new DefaultFetchCurrentChargesService();
+    }
+
+    CurrentChargesResponse fetch(CurrentChargesRequest request);
+}

libraries-3/src/main/java/com/baeldung/jcommander/usagebilling/service/SubmitUsageService.java

@@ -0,0 +1,12 @@
+package com.baeldung.jcommander.usagebilling.service;
+
+import com.baeldung.jcommander.usagebilling.model.UsageRequest;
+
+public interface SubmitUsageService {
+
+    static SubmitUsageService getDefault() {
+        return new DefaultSubmitUsageService();
+    }
+
+    String submit(UsageRequest request);
+}

libraries-3/src/test/java/com/baeldung/jcommander/helloworld/HelloWorldAppUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.jcommander.helloworld;
+
+import com.beust.jcommander.JCommander;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class HelloWorldAppUnitTest {
+
+    @Test
+    public void whenJCommanderInvokedWithArgs_thenArgsParsed() {
+
+        HelloWorldArgs jArgs = new HelloWorldArgs();
+        JCommander helloCmd = JCommander
+          .newBuilder()
+          .addObject(jArgs)
+          .build();
+
+        // when
+        String[] argv = new String[] {
+          "--name", "JavaWorld"
+        };
+        helloCmd.parse(argv);
+
+        // then
+        assertEquals("JavaWorld", jArgs.getName());
+    }
+}

libraries-3/src/test/java/com/baeldung/jcommander/usagebilling/cli/FetchCurrentChargesCommandUnitTest.java

@@ -0,0 +1,61 @@
+package com.baeldung.jcommander.usagebilling.cli;
+
+import com.beust.jcommander.JCommander;
+import org.junit.Test;
+
+import static org.hamcrest.collection.IsIterableContainingInOrder.contains;
+import static org.junit.Assert.assertThat;
+
+public class FetchCurrentChargesCommandUnitTest {
+
+    private JCommander jc = JCommander.newBuilder()
+      .addObject(new FetchCurrentChargesCommand())
+      .build();
+
+    @Test
+    public void whenParsedMultipleSubscriptionsParameter_thenParameterSubscriptionsIsPopulated() {
+        FetchCurrentChargesCommand cmd = (FetchCurrentChargesCommand) jc
+          .getObjects()
+          .get(0);
+        
+        jc.parse(new String[] {
+          "-C", "cb898e7a-f2a0-46d2-9a09-531f1cee1839",
+          "-S", "subscriptionA001",
+          "-S", "subscriptionA002",
+          "-S", "subscriptionA003",
+        });
+
+        assertThat(cmd.getSubscriptionIds(),
+          contains("subscriptionA001", "subscriptionA002", "subscriptionA003"));
+    }
+
+    @Test
+    public void whenParsedSubscriptionsColonSeparatedParameter_thenParameterSubscriptionsIsPopulated() {
+        FetchCurrentChargesCommand cmd = (FetchCurrentChargesCommand) jc
+          .getObjects()
+          .get(0);
+
+        jc.parse(new String[] {
+          "-C", "cb898e7a-f2a0-46d2-9a09-531f1cee1839",
+          "-S", "subscriptionA001:subscriptionA002:subscriptionA003",
+        });
+
+        assertThat(cmd.getSubscriptionIds(), 
+          contains("subscriptionA001", "subscriptionA002", "subscriptionA003"));
+    }
+
+    @Test
+    public void whenParsedSubscriptionsWithVariableArity_thenParameterSubscriptionsIsPopulated() {
+        FetchCurrentChargesCommand cmd = (FetchCurrentChargesCommand) jc
+          .getObjects()
+          .get(0);
+
+        jc.parse(new String[] {
+          "-C", "cb898e7a-f2a0-46d2-9a09-531f1cee1839",
+          "-S", "subscriptionA001", "subscriptionA002", "subscriptionA003",
+        });
+
+        assertThat(cmd.getSubscriptionIds(),
+          contains("subscriptionA001", "subscriptionA002", "subscriptionA003"));
+    }
+}

libraries-3/src/test/java/com/baeldung/jcommander/usagebilling/cli/SubmitUsageCommandUnitTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.jcommander.usagebilling.cli;
+
+import com.beust.jcommander.JCommander;
+import com.beust.jcommander.ParameterException;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class SubmitUsageCommandUnitTest {
+
+    private JCommander jc = JCommander.newBuilder()
+        .addObject(new SubmitUsageCommand())
+        .build();
+
+    @Test
+    public void whenParsedCustomerParameter_thenParameterOfTypeStringIsPopulated() {
+        jc.parse(new String[] {
+            "--customer", "cb898e7a-f2a0-46d2-9a09-531f1cee1839",
+            "--subscription", "subscriptionPQRMN001",
+            "--pricing-type", "PRE_RATED",
+            "--timestamp", "2019-10-03T10:58:00",
+            "--quantity", "7",
+            "--price", "24.56"
+        });
+        
+        SubmitUsageCommand cmd = (SubmitUsageCommand) jc
+          .getObjects()
+          .get(0);
+        assertEquals("cb898e7a-f2a0-46d2-9a09-531f1cee1839", cmd.getCustomerId());
+    }
+
+    @Test
+    public void whenParsedTimestampParameter_thenParameterOfTypeInstantIsPopulated() {
+        jc.parse(new String[] {
+            "--customer", "cb898e7a-f2a0-46d2-9a09-531f1cee1839",
+            "--subscription", "subscriptionPQRMN001",
+            "--pricing-type", "PRE_RATED",
+            "--timestamp", "2019-10-03T10:58:00",
+            "--quantity", "7",
+            "--price", "24.56"
+        });
+        
+        SubmitUsageCommand cmd = (SubmitUsageCommand) jc
+          .getObjects()
+          .get(0);
+        assertEquals("2019-10-03T10:58:00Z", cmd
+          .getTimestamp()
+          .toString());
+    }
+
+    @Test(expected = ParameterException.class)
+    public void whenParsedCustomerIdNotUUID_thenParameterException() {
+        jc.parse(new String[] {
+          "--customer", "customer001",
+          "--subscription", "subscriptionPQRMN001",
+          "--pricing-type", "PRE_RATED",
+          "--timestamp", "2019-10-03T10:58:00",
+          "--quantity", "7",
+          "--price", "24.56"
+        });
+    }
+}

pom.xml

@@ -541,6 +541,7 @@
                 <!-- <module>lagom</module> --> <!-- Not a maven project -->
                 <module>libraries</module>
                 <module>libraries-2</module>
+                <module>libraries-3</module>
                 <module>libraries-data</module>
                 <module>libraries-data-2</module>
                 <module>libraries-data-db</module>
@@ -1307,6 +1308,7 @@
 
                 <!-- <module>lagom</module> --> <!-- Not a maven project -->
                 <module>libraries</module>
+                <module>libraries-3</module>
                 <module>libraries-data</module>
                 <module>libraries-data-2</module>
                 <module>libraries-data-db</module>