Merge pull request #21 from brunobaiano/tip-18

tip-18

_posts/2023-11-16-daily-tip-18.md

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+---
+title: "Daily tip #18"
+date: 2023-11-16
+---
+
+## Tip of the day #18
+
+Use the groupingBy collector to create a `Map<?, List<?>> from a List<?>`.
+
+### What is it?
+
+The groupingBy collector is a static method in the Collectors class that returns a Collector implementing a "group by" operation on input elements of type T, grouping elements according to a classification function, and returning the results in a Map.
+
+Let's see how it works:
+
+Imagine that you have an Account class:
+
+```java
+class Account {
+   UUID id,
+    Card card
+}
+
+class Card {
+    UUID id,
+    String number,
+    String flag
+}
+```
+
+Then you can group by card.getFlag() ( master, visa, others).
+
+```java
+Map<String, List<Account>> accountMap = 
+        accountList.stream().collect(Collectors.groupingBy(account -> account.getCard().getFlag()));
+```
+
+Easy right?
+
+### How to
+
+Take a look in [repo-tip-18](https://github.com/brunobaiano/tip-of-the-day/tree/main/tip-18) to see a real example of today's tip.

tip-18/.dockerignore

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+*
+!target/*-runner
+!target/*-runner.jar
+!target/lib/*
+!target/quarkus-app/*

tip-18/.gitignore

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+#Maven
+target/
+pom.xml.tag
+pom.xml.releaseBackup
+pom.xml.versionsBackup
+release.properties
+.flattened-pom.xml
+
+# Eclipse
+.project
+.classpath
+.settings/
+bin/
+
+# IntelliJ
+.idea
+*.ipr
+*.iml
+*.iws
+
+# NetBeans
+nb-configuration.xml
+
+# Visual Studio Code
+.vscode
+.factorypath
+
+# OSX
+.DS_Store
+
+# Vim
+*.swp
+*.swo
+
+# patch
+*.orig
+*.rej
+
+# Local environment
+.env
+
+# Plugin directory
+/.quarkus/cli/plugins/
+/.idea/

tip-18/.mvn/wrapper/.gitignore

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+maven-wrapper.jar

tip-18/.mvn/wrapper/MavenWrapperDownloader.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.Authenticator;
+import java.net.PasswordAuthentication;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardCopyOption;
+
+public final class MavenWrapperDownloader
+{
+    private static final String WRAPPER_VERSION = "3.2.0";
+
+    private static final boolean VERBOSE = Boolean.parseBoolean( System.getenv( "MVNW_VERBOSE" ) );
+
+    public static void main( String[] args )
+    {
+        log( "Apache Maven Wrapper Downloader " + WRAPPER_VERSION );
+
+        if ( args.length != 2 )
+        {
+            System.err.println( " - ERROR wrapperUrl or wrapperJarPath parameter missing" );
+            System.exit( 1 );
+        }
+
+        try
+        {
+            log( " - Downloader started" );
+            final URL wrapperUrl = new URL( args[0] );
+            final String jarPath = args[1].replace( "..", "" ); // Sanitize path
+            final Path wrapperJarPath = Paths.get( jarPath ).toAbsolutePath().normalize();
+            downloadFileFromURL( wrapperUrl, wrapperJarPath );
+            log( "Done" );
+        }
+        catch ( IOException e )
+        {
+            System.err.println( "- Error downloading: " + e.getMessage() );
+            if ( VERBOSE )
+            {
+                e.printStackTrace();
+            }
+            System.exit( 1 );
+        }
+    }
+
+    private static void downloadFileFromURL( URL wrapperUrl, Path wrapperJarPath )
+        throws IOException
+    {
+        log( " - Downloading to: " + wrapperJarPath );
+        if ( System.getenv( "MVNW_USERNAME" ) != null && System.getenv( "MVNW_PASSWORD" ) != null )
+        {
+            final String username = System.getenv( "MVNW_USERNAME" );
+            final char[] password = System.getenv( "MVNW_PASSWORD" ).toCharArray();
+            Authenticator.setDefault( new Authenticator()
+            {
+                @Override
+                protected PasswordAuthentication getPasswordAuthentication()
+                {
+                    return new PasswordAuthentication( username, password );
+                }
+            } );
+        }
+        try ( InputStream inStream = wrapperUrl.openStream() )
+        {
+            Files.copy( inStream, wrapperJarPath, StandardCopyOption.REPLACE_EXISTING );
+        }
+        log( " - Downloader complete" );
+    }
+
+    private static void log( String msg )
+    {
+        if ( VERBOSE )
+        {
+            System.out.println( msg );
+        }
+    }
+
+}

tip-18/.mvn/wrapper/maven-wrapper.properties

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+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.5/apache-maven-3.9.5-bin.zip
+wrapperUrl=https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.2.0/maven-wrapper-3.2.0.jar

tip-18/README.md

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+# tip-18
+
+This project uses Quarkus, the Supersonic Subatomic Java Framework.
+
+If you want to learn more about Quarkus, please visit its website: https://quarkus.io/ .
+
+## Running the application in dev mode
+
+You can run your application in dev mode that enables live coding using:
+```shell script
+./mvnw compile quarkus:dev
+```
+
+> **_NOTE:_**  Quarkus now ships with a Dev UI, which is available in dev mode only at http://localhost:8080/q/dev/.
+
+## Packaging and running the application
+
+The application can be packaged using:
+```shell script
+./mvnw package
+```
+It produces the `quarkus-run.jar` file in the `target/quarkus-app/` directory.
+Be aware that it’s not an _über-jar_ as the dependencies are copied into the `target/quarkus-app/lib/` directory.
+
+The application is now runnable using `java -jar target/quarkus-app/quarkus-run.jar`.
+
+If you want to build an _über-jar_, execute the following command:
+```shell script
+./mvnw package -Dquarkus.package.type=uber-jar
+```
+
+The application, packaged as an _über-jar_, is now runnable using `java -jar target/*-runner.jar`.
+
+## Creating a native executable
+
+You can create a native executable using: 
+```shell script
+./mvnw package -Dnative
+```
+
+Or, if you don't have GraalVM installed, you can run the native executable build in a container using: 
+```shell script
+./mvnw package -Dnative -Dquarkus.native.container-build=true
+```
+
+You can then execute your native executable with: `./target/tip-18-1.0.0-SNAPSHOT-runner`
+
+If you want to learn more about building native executables, please consult https://quarkus.io/guides/maven-tooling.
+
+## Provided Code
+
+### RESTEasy Reactive
+
+Easily start your Reactive RESTful Web Services
+
+[Related guide section...](https://quarkus.io/guides/getting-started-reactive#reactive-jax-rs-resources)