[JAVA-22519] Created new module libraries-stream and added 5 articles (#15403)

2023-12-13 09:40:13 +02:00
parent 0323a8168c
commit 8daf19c9ec
92 changed files with 718 additions and 430 deletions
@@ -0,0 +1,17 @@
+package com.baeldung.airline;
+
+import com.github.rvesse.airline.annotations.Cli;
+import com.github.rvesse.airline.help.Help;
+
+@Cli(name = "baeldung-cli", 
+description = "Baeldung Airline Tutorial",
+defaultCommand = Help.class, 
+commands = { DatabaseSetupCommand.class, LoggingCommand.class, Help.class })
+public class CommandLine {
+
+    public static void main(String[] args) {
+        com.github.rvesse.airline.Cli<Runnable> cli = new com.github.rvesse.airline.Cli<>(CommandLine.class);
+        Runnable cmd = cli.parse(args);
+        cmd.run();
+    }
+}
@@ -0,0 +1,77 @@
+package com.baeldung.airline;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.inject.Inject;
+
+import com.github.rvesse.airline.HelpOption;
+import com.github.rvesse.airline.annotations.Command;
+import com.github.rvesse.airline.annotations.Option;
+import com.github.rvesse.airline.annotations.OptionType;
+import com.github.rvesse.airline.annotations.restrictions.AllowedRawValues;
+import com.github.rvesse.airline.annotations.restrictions.MutuallyExclusiveWith;
+import com.github.rvesse.airline.annotations.restrictions.Pattern;
+import com.github.rvesse.airline.annotations.restrictions.RequiredOnlyIf;
+
+@Command(name = "setup-db", description = "Setup our database")
+public class DatabaseSetupCommand implements Runnable {
+    @Inject
+    private HelpOption<DatabaseSetupCommand> help;
+
+    @Option(type = OptionType.COMMAND,
+      name = {"-d", "--database"},
+      description = "Type of RDBMS.",
+      title = "RDBMS type: mysql|postgresql|mongodb")
+    @AllowedRawValues(allowedValues = { "mysql", "postgres", "mongodb" })
+    protected String rdbmsMode = "mysql";
+
+    @Option(type = OptionType.COMMAND,
+      name = {"--rdbms:url", "--url"},
+      description = "URL to use for connection to RDBMS.",
+      title = "RDBMS URL")
+    @MutuallyExclusiveWith(tag="mode")
+    @Pattern(pattern="^(http://.*):(d*)(.*)u=(.*)&p=(.*)")
+    protected String rdbmsUrl = "";
+
+    @Option(type = OptionType.COMMAND,
+      name = {"--rdbms:host", "--host"},
+      description = "Host to use for connection to RDBMS.",
+      title = "RDBMS host")
+    @MutuallyExclusiveWith(tag="mode")
+    protected String rdbmsHost = "";
+
+    @RequiredOnlyIf(names={"--rdbms:host", "--host"})
+    @Option(type = OptionType.COMMAND,
+      name = {"--rdbms:user", "-u", "--user"},
+      description = "User for login to RDBMS.",
+      title = "RDBMS user")
+    protected String rdbmsUser;
+
+    @RequiredOnlyIf(names={"--rdbms:host", "--host"})
+    @Option(type = OptionType.COMMAND,
+      name = {"--rdbms:password", "--password"},
+      description = "Password for login to RDBMS.",
+      title = "RDBMS password")
+    protected String rdbmsPassword;
+
+    @Option(type = OptionType.COMMAND,
+      name = {"--driver", "--jars"},
+      description = "List of drivers",
+      title = "--driver <PATH_TO_YOUR_JAR> --driver <PATH_TO_YOUR_JAR>")
+    protected List<String> jars = new ArrayList<>();
+
+    @Override
+    public void run() {
+        //skipping store our choices...
+        if (!help.showHelpIfRequested()) {
+            if(!"".equals(rdbmsHost)) {
+                System.out.println("Connecting to database host: " + rdbmsHost);
+                System.out.println("Credential: " + rdbmsUser + " / " + rdbmsPassword);
+            } else {
+                System.out.println("Connecting to database url: " + rdbmsUrl);
+            }
+            System.out.println(jars.toString());
+        }
+    }
+}
@@ -0,0 +1,24 @@
+package com.baeldung.airline;
+
+import javax.inject.Inject;
+
+import com.github.rvesse.airline.HelpOption;
+import com.github.rvesse.airline.annotations.Command;
+import com.github.rvesse.airline.annotations.Option;
+
+@Command(name = "setup-log", description = "Setup our log")
+public class LoggingCommand implements Runnable {
+
+    @Inject
+    private HelpOption<LoggingCommand> help;
+
+    @Option(name = { "-v", "--verbose" }, description = "Set log verbosity on/off")
+    private boolean verbose = false;
+
+    @Override
+    public void run() {
+        //skipping store user choice
+        if (!help.showHelpIfRequested())
+            System.out.println("Verbosity: " + verbose);
+    }
+}
@@ -0,0 +1,37 @@
+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;
+    }
+}
@@ -0,0 +1,23 @@
+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);
+  }
+}
@@ -0,0 +1,68 @@
+package com.baeldung.jcommander.usagebilling.cli;
+
+import static com.baeldung.jcommander.usagebilling.cli.UsageBasedBilling.FETCH_CMD;
+import static com.baeldung.jcommander.usagebilling.service.FetchCurrentChargesService.getDefault;
+
+import java.util.List;
+
+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;
+
+@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);
+    }
+}
@@ -0,0 +1,97 @@
+package com.baeldung.jcommander.usagebilling.cli;
+
+import static com.baeldung.jcommander.usagebilling.cli.UsageBasedBilling.SUBMIT_CMD;
+import static com.baeldung.jcommander.usagebilling.service.SubmitUsageService.getDefault;
+
+import java.math.BigDecimal;
+import java.time.Instant;
+
+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;
+
+@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);
+    }
+}
@@ -0,0 +1,80 @@
+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));
+    }
+}
@@ -0,0 +1,33 @@
+package com.baeldung.jcommander.usagebilling.cli.converter;
+
+import static java.lang.String.format;
+
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
+
+import com.beust.jcommander.ParameterException;
+import com.beust.jcommander.converters.BaseConverter;
+
+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())));
+        }
+    }
+}
@@ -0,0 +1,15 @@
+package com.baeldung.jcommander.usagebilling.cli.splitter;
+
+import static java.util.Arrays.asList;
+
+import java.util.List;
+
+import com.beust.jcommander.converters.IParameterSplitter;
+
+public class ColonParameterSplitter implements IParameterSplitter {
+
+    @Override
+    public List<String> split(String value) {
+        return asList(value.split(":"));
+    }
+}
@@ -0,0 +1,26 @@
+package com.baeldung.jcommander.usagebilling.cli.validator;
+
+import java.util.regex.Pattern;
+
+import com.beust.jcommander.IParameterValidator;
+import com.beust.jcommander.ParameterException;
+
+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();
+    }
+}
@@ -0,0 +1,20 @@
+package com.baeldung.jcommander.usagebilling.model;
+
+import java.util.List;
+
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@NoArgsConstructor(access = AccessLevel.PACKAGE)
+@AllArgsConstructor(access = AccessLevel.PACKAGE)
+@Builder
+@Getter
+public class CurrentChargesRequest {
+
+    private String customerId;
+    private List<String> subscriptionIds;
+    private boolean itemized;
+}
@@ -0,0 +1,60 @@
+package com.baeldung.jcommander.usagebilling.model;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import java.util.List;
+
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@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;
+    }
+}
@@ -0,0 +1,54 @@
+package com.baeldung.jcommander.usagebilling.model;
+
+import java.math.BigDecimal;
+import java.time.Instant;
+
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@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
+    }
+}
@@ -0,0 +1,68 @@
+package com.baeldung.jcommander.usagebilling.service;
+
+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;
+
+import java.math.BigDecimal;
+import java.util.List;
+import java.util.UUID;
+
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesRequest;
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesResponse;
+import com.baeldung.jcommander.usagebilling.model.CurrentChargesResponse.LineItem;
+
+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);
+    }
+}
@@ -0,0 +1,16 @@
+package com.baeldung.jcommander.usagebilling.service;
+
+import java.util.UUID;
+
+import com.baeldung.jcommander.usagebilling.model.UsageRequest;
+
+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();
+    }
+}
@@ -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);
+}
@@ -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);
+}
@@ -0,0 +1,43 @@
+package com.baeldung.picocli.git;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+import com.baeldung.picocli.git.commands.programmative.GitCommand;
+import com.baeldung.picocli.git.commands.subcommands.GitAddCommand;
+import com.baeldung.picocli.git.commands.subcommands.GitCommitCommand;
+import com.baeldung.picocli.git.commands.subcommands.GitConfigCommand;
+
+import picocli.CommandLine;
+
+@SpringBootApplication
+public class Application implements CommandLineRunner {
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+
+    private GitCommand gitCommand;
+    private GitAddCommand addCommand;
+    private GitCommitCommand commitCommand;
+    private GitConfigCommand configCommand;
+
+    @Autowired
+    public Application(GitCommand gitCommand, GitAddCommand addCommand, GitCommitCommand commitCommand, GitConfigCommand configCommand) {
+        this.gitCommand = gitCommand;
+        this.addCommand = addCommand;
+        this.commitCommand = commitCommand;
+        this.configCommand = configCommand;
+    }
+
+    @Override
+    public void run(String... args) {
+        CommandLine commandLine = new CommandLine(gitCommand);
+        commandLine.addSubcommand("add", addCommand);
+        commandLine.addSubcommand("commit", commitCommand);
+        commandLine.addSubcommand("config", configCommand);
+
+        commandLine.parseWithHandler(new CommandLine.RunLast(), args);
+    }
+}
@@ -0,0 +1,33 @@
+package com.baeldung.picocli.git.commands.declarative;
+
+import static picocli.CommandLine.*;
+import static picocli.CommandLine.Command;
+
+import com.baeldung.picocli.git.commands.subcommands.GitAddCommand;
+import com.baeldung.picocli.git.commands.subcommands.GitCommitCommand;
+import com.baeldung.picocli.git.commands.subcommands.GitConfigCommand;
+import com.baeldung.picocli.git.model.ConfigElement;
+
+import picocli.CommandLine;
+
+@Command(
+  name = "git",
+  subcommands = {
+    GitAddCommand.class,
+    GitCommitCommand.class,
+    GitConfigCommand.class
+  }
+)
+public class GitCommand implements Runnable {
+    public static void main(String[] args) {
+        CommandLine commandLine = new CommandLine(new GitCommand());
+        commandLine.registerConverter(ConfigElement.class, ConfigElement::from);
+
+        commandLine.parseWithHandler(new RunLast(), args);
+    }
+
+    @Override
+    public void run() {
+        System.out.println("The popular git command");
+    }
+}
@@ -0,0 +1,27 @@
+package com.baeldung.picocli.git.commands.methods;
+
+import static picocli.CommandLine.Command;
+
+import picocli.CommandLine;
+
+@Command(name = "git")
+public class GitCommand implements Runnable {
+    public static void main(String[] args) {
+        CommandLine.run(new GitCommand(), args);
+    }
+
+    @Override
+    public void run() {
+        System.out.println("The popular git command");
+    }
+
+    @Command(name = "add")
+    public void addCommand() {
+        System.out.println("Adding some files to the staging area");
+    }
+
+    @Command(name = "commit")
+    public void commitCommand() {
+        System.out.println("Committing files in the staging area, how wonderful?");
+    }
+}
@@ -0,0 +1,28 @@
+package com.baeldung.picocli.git.commands.programmative;
+
+import static picocli.CommandLine.Command;
+import static picocli.CommandLine.RunLast;
+
+import org.springframework.stereotype.Component;
+
+import com.baeldung.picocli.git.commands.subcommands.GitAddCommand;
+import com.baeldung.picocli.git.commands.subcommands.GitCommitCommand;
+
+import picocli.CommandLine;
+
+@Command(name = "git")
+@Component
+public class GitCommand implements Runnable {
+    public static void main(String[] args) {
+        CommandLine commandLine = new CommandLine(new GitCommand());
+        commandLine.addSubcommand("add", new GitAddCommand());
+        commandLine.addSubcommand("commit", new GitCommitCommand());
+
+        commandLine.parseWithHandler(new RunLast(), args);
+    }
+
+    @Override
+    public void run() {
+        System.out.println("The popular git command");
+    }
+}
@@ -0,0 +1,31 @@
+package com.baeldung.picocli.git.commands.subcommands;
+
+import static picocli.CommandLine.*;
+
+import java.nio.file.Path;
+import java.util.List;
+
+import org.springframework.stereotype.Component;
+
+@Command(
+  name = "add"
+)
+@Component
+public class GitAddCommand implements Runnable {
+    @Option(names = "-A")
+    private boolean allFiles;
+
+    @Parameters(index = "0..*")
+    private List<Path> files;
+
+    @Override
+    public void run() {
+        if (allFiles) {
+            System.out.println("Adding all files to the staging area");
+        }
+
+        if (files != null) {
+            files.forEach(path -> System.out.println("Adding " + path + " to the staging area"));
+        }
+    }
+}
@@ -0,0 +1,26 @@
+package com.baeldung.picocli.git.commands.subcommands;
+
+import static picocli.CommandLine.Command;
+import static picocli.CommandLine.Option;
+
+import org.springframework.stereotype.Component;
+
+@Command(
+  name = "commit"
+)
+@Component
+public class GitCommitCommand implements Runnable {
+    @Option(names = {"-m", "--message"}, required = true)
+    private String[] messages;
+
+    @Override
+    public void run() {
+        System.out.println("Committing files in the staging area, how wonderful?");
+        if (messages != null) {
+            System.out.println("The commit message is");
+            for (String message : messages) {
+                System.out.println(message);
+            }
+        }
+    }
+}
@@ -0,0 +1,25 @@
+package com.baeldung.picocli.git.commands.subcommands;
+
+import static picocli.CommandLine.Command;
+import static picocli.CommandLine.Parameters;
+
+import org.springframework.stereotype.Component;
+
+import com.baeldung.picocli.git.model.ConfigElement;
+
+@Command(
+  name = "config"
+)
+@Component
+public class GitConfigCommand implements Runnable {
+    @Parameters(index = "0")
+    private ConfigElement element;
+
+    @Parameters(index = "1")
+    private String value;
+
+    @Override
+    public void run() {
+        System.out.println("Setting " + element.value() + " to " + value);
+    }
+}
@@ -0,0 +1,25 @@
+package com.baeldung.picocli.git.model;
+
+import java.util.Arrays;
+
+public enum ConfigElement {
+    USERNAME("user.name"),
+    EMAIL("user.email");
+
+    private final String value;
+
+    ConfigElement(String value) {
+        this.value = value;
+    }
+
+    public String value() {
+        return value;
+    }
+
+    public static ConfigElement from(String value) {
+        return Arrays.stream(values())
+          .filter(element -> element.value.equals(value))
+          .findFirst()
+          .orElseThrow(() -> new IllegalArgumentException("The argument " + value + " doesn't match any ConfigElement"));
+    }
+}
@@ -0,0 +1,20 @@
+package com.baeldung.picocli.helloworld;
+
+import static picocli.CommandLine.Command;
+
+import picocli.CommandLine;
+
+@Command(
+  name = "hello",
+  description = "Says hello"
+)
+public class HelloWorldCommand implements Runnable {
+    public static void main(String[] args) {
+        CommandLine.run(new HelloWorldCommand(), args);
+    }
+
+    @Override
+    public void run() {
+        System.out.println("Hello World!");
+    }
+}
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>
@@ -0,0 +1,29 @@
+package com.baeldung.jcommander.helloworld;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.beust.jcommander.JCommander;
+
+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());
+    }
+}
@@ -0,0 +1,62 @@
+package com.baeldung.jcommander.usagebilling.cli;
+
+import static org.hamcrest.collection.IsIterableContainingInOrder.contains;
+import static org.junit.Assert.assertThat;
+
+import org.junit.Test;
+
+import com.beust.jcommander.JCommander;
+
+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"));
+    }
+}
@@ -0,0 +1,63 @@
+package com.baeldung.jcommander.usagebilling.cli;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.Test;
+
+import com.beust.jcommander.JCommander;
+import com.beust.jcommander.ParameterException;
+
+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"
+        });
+    }
+}