Merge branch 'master' of https://github.com/eugenp/tutorials

algorithms-miscellaneous-6/README.md

@@ -9,4 +9,5 @@
 - [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
 - [Implementing a 2048 Solver in Java](https://www.baeldung.com/2048-java-solver)
 - [Finding Top K Elements in an Array](https://www.baeldung.com/java-array-top-elements)
+- [Reversing a Linked List in Java](https://www.baeldung.com/java-reverse-linked-list)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-5)

apache-spark/src/main/java/com/baeldung/differences/dataframe/dataset/rdd/TouristData.java

@@ -0,0 +1,75 @@
+package com.baeldung.differences.dataframe.dataset.rdd;
+
+
+public class TouristData {
+
+    private String region;
+    private String country;
+    private String year;
+    private String series;
+    private Double value;
+    private String footnotes;
+    private String source;
+
+    public String getRegion() {
+        return region;
+    }
+
+    public void setRegion(String region) {
+        this.region = region;
+    }
+
+    public String getCountry() {
+        return country;
+    }
+
+    public void setCountry(String country) {
+        this.country = country;
+    }
+
+    public String getYear() {
+        return year;
+    }
+
+    public void setYear(String year) {
+        this.year = year;
+    }
+
+    public String getSeries() {
+        return series;
+    }
+
+    public void setSeries(String series) {
+        this.series = series;
+    }
+
+    public Double getValue() {
+        return value;
+    }
+
+    public void setValue(Double value) {
+        this.value = value;
+    }
+
+    public String getFootnotes() {
+        return footnotes;
+    }
+
+    public void setFootnotes(String footnotes) {
+        this.footnotes = footnotes;
+    }
+
+    public String getSource() {
+        return source;
+    }
+
+    public void setSource(String source) {
+        this.source = source;
+    }
+
+    @Override
+    public String toString() {
+        return "TouristData [region=" + region + ", country=" + country + ", year=" + year + ", series=" + series + ", value=" + value + ", footnotes=" + footnotes + ", source=" + source + "]";
+    }
+
+}

apache-spark/src/test/java/com/baeldung/differences/rdd/ActionsUnitTest.java

@@ -0,0 +1,67 @@
+package com.baeldung.differences.rdd;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.List;
+
+import org.apache.spark.SparkConf;
+import org.apache.spark.api.java.JavaPairRDD;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import scala.Tuple2;
+
+public class ActionsUnitTest {
+    private static JavaRDD<String> tourists;
+    private static JavaSparkContext sc;
+    public static final String COMMA_DELIMITER = ",(?=([^\"]*\"[^\"]*\")*[^\"]*$)";
+    
+    @BeforeClass
+    public static void init() {
+        SparkConf conf = new SparkConf().setAppName("reduce")
+            .setMaster("local[*]");
+        sc = new JavaSparkContext(conf);
+        tourists = sc.textFile("data/Tourist.csv").filter(line -> !line.startsWith("Region"));
+    }
+    
+    @AfterClass
+    public static void cleanup() {
+        sc.close();
+    }
+
+    @Test
+    public void whenDistinctCount_thenReturnDistinctNumRecords() {
+        JavaRDD<String> countries = tourists.map(line -> {
+            String[] columns = line.split(COMMA_DELIMITER);
+            return columns[1];
+        })
+            .distinct();
+        Long numberOfCountries = countries.count();
+        System.out.println("Count: " + numberOfCountries);
+        
+        assertEquals(Long.valueOf(220), numberOfCountries);
+    }
+    
+    @Test
+    public void whenReduceByKeySum_thenTotalValuePerKey() {
+        JavaRDD<String> touristsExpenditure = tourists.filter(line -> line.split(COMMA_DELIMITER)[3].contains("expenditure"));
+
+        JavaPairRDD<String, Double> expenditurePairRdd = touristsExpenditure.mapToPair(line -> {
+            String[] columns = line.split(COMMA_DELIMITER);
+            return new Tuple2<>(columns[1], Double.valueOf(columns[6]));
+        });
+        List<Tuple2<String, Double>> totalByCountry = expenditurePairRdd.reduceByKey((x, y) -> x + y)
+            .collect();
+        System.out.println("Total per Country: " + totalByCountry);
+        
+        for(Tuple2<String, Double> tuple : totalByCountry) {
+            if (tuple._1.equals("Mexico")) {
+                assertEquals(Double.valueOf(99164), tuple._2);
+            }
+        }
+    }
+
+}

apache-spark/src/test/java/com/baeldung/differences/rdd/DataFrameUnitTest.java

@@ -0,0 +1,74 @@
+package com.baeldung.differences.rdd;
+
+import static org.apache.spark.sql.functions.col;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.spark.sql.DataFrameReader;
+import org.apache.spark.sql.Dataset;
+import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SparkSession;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class DataFrameUnitTest {
+    private static SparkSession session;
+    private static Dataset<Row> data;
+
+    @BeforeClass
+    public static void init() {
+        session = SparkSession.builder()
+            .appName("TouristDataFrameExample")
+            .master("local[*]")
+            .getOrCreate();
+        DataFrameReader dataFrameReader = session.read();
+        data = dataFrameReader.option("header", "true")
+            .csv("data/Tourist.csv");
+    }
+
+    @AfterClass
+    public static void cleanup() {
+        session.stop();
+    }
+
+    @Test
+    public void whenSelectSpecificColumns_thenColumnsFiltered() {
+        Dataset<Row> selectedData = data.select(col("country"), col("year"), col("value"));
+        selectedData.show();
+        
+        List<String> resultList = Arrays.asList(selectedData.columns());
+        assertTrue(resultList.contains("country"));
+        assertTrue(resultList.contains("year"));
+        assertTrue(resultList.contains("value"));
+        assertFalse(resultList.contains("Series"));
+
+    }
+
+    @Test
+    public void whenFilteringByCountry_thenCountryRecordsSelected() {
+        Dataset<Row> filteredData = data.filter(col("country").equalTo("Mexico"));
+        filteredData.show();
+        
+        filteredData.foreach(record -> {
+            assertEquals("Mexico", record.get(1));
+        });
+        
+    }
+
+    @Test
+    public void whenGroupCountByCountry_thenContryTotalRecords() {
+        Dataset<Row> recordsPerCountry = data.groupBy(col("country"))
+            .count();
+        recordsPerCountry.show();
+        
+        Dataset<Row> filteredData = recordsPerCountry.filter(col("country").equalTo("Sweden"));
+        assertEquals(new Long(12), filteredData.first()
+            .get(1));
+    }
+
+}

apache-spark/src/test/java/com/baeldung/differences/rdd/DatasetUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.differences.rdd;
+
+import static org.apache.spark.sql.functions.col;
+import static org.apache.spark.sql.functions.sum;
+import static org.junit.Assert.assertEquals;
+
+import org.apache.spark.api.java.function.FilterFunction;
+import org.apache.spark.sql.DataFrameReader;
+import org.apache.spark.sql.Dataset;
+import org.apache.spark.sql.Encoders;
+import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SparkSession;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import com.baeldung.differences.dataframe.dataset.rdd.TouristData;
+
+public class DatasetUnitTest {
+    private static SparkSession session;
+    private static Dataset<TouristData> typedDataset;
+
+    @BeforeClass
+    public static void init() {
+        session = SparkSession.builder()
+            .appName("TouristDatasetExample")
+            .master("local[*]")
+            .getOrCreate();
+        DataFrameReader dataFrameReader = session.read();
+        Dataset<Row> data = dataFrameReader.option("header", "true")
+            .csv("data/Tourist.csv");
+        Dataset<Row> responseWithSelectedColumns = data.select(col("region"), 
+            col("country"), col("year"), col("series"), col("value").cast("double"), 
+            col("footnotes"), col("source"));
+        typedDataset = responseWithSelectedColumns.as(Encoders.bean(TouristData.class));
+    }
+
+    @AfterClass
+    public static void cleanup() {
+        session.stop();
+    }
+
+    @Test
+    public void whenFilteringByCountry_thenCountryRecordsSelected() {
+        Dataset<TouristData> selectedData = typedDataset
+            .filter((FilterFunction<TouristData>) record -> record.getCountry()
+            .equals("Norway"));
+        selectedData.show();
+
+        selectedData.foreach(record -> {
+            assertEquals("Norway", record.getCountry());
+        });
+    }
+
+    @Test
+    public void whenGroupCountByCountry_thenContryTotalRecords() {
+        Dataset<Row> countriesCount = typedDataset.groupBy(typedDataset.col("country"))
+            .count();
+        countriesCount.show();
+
+        assertEquals(Long.valueOf(220), Long.valueOf(countriesCount.count()));
+    }
+
+    @Test
+    public void whenFilteredByPropertyRange_thenRetreiveValidRecords() {
+        // Filter records with existing data for years between 2010 and 2017
+        typedDataset.filter((FilterFunction<TouristData>) record -> record.getYear() != null 
+            && (Long.valueOf(record.getYear()) > 2010 && Long.valueOf(record.getYear()) < 2017))
+            .show();
+    }
+    
+    @Test
+    public void whenSumValue_thenRetreiveTotalValue() {
+        // Total tourist expenditure by country
+        typedDataset.filter((FilterFunction<TouristData>) record -> record.getValue() != null 
+            && record.getSeries()
+            .contains("expenditure"))
+            .groupBy("country")
+            .agg(sum("value"))
+            .show();
+    }
+
+}

apache-spark/src/test/java/com/baeldung/differences/rdd/TransformationsUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.differences.rdd;
+
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.spark.SparkConf;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class TransformationsUnitTest {
+    
+    public static final String COMMA_DELIMITER = ",(?=([^\"]*\"[^\"]*\")*[^\"]*$)";
+    private static JavaSparkContext sc;
+    private static JavaRDD<String> tourists;
+    
+    @BeforeClass
+    public static void init() {
+        SparkConf conf = new SparkConf().setAppName("uppercaseCountries")
+            .setMaster("local[*]");
+        sc = new JavaSparkContext(conf);
+        tourists = sc.textFile("data/Tourist.csv")
+            .filter(line -> !line.startsWith("Region")); //filter header row
+    }
+    
+    @AfterClass
+    public static void cleanup() {
+        sc.close();
+    }
+
+    @Test
+    public void whenMapUpperCase_thenCountryNameUppercased() {
+        JavaRDD<String> upperCaseCountries = tourists.map(line -> {
+            String[] columns = line.split(COMMA_DELIMITER);
+            return columns[1].toUpperCase();
+        })
+            .distinct();
+        
+        upperCaseCountries.saveAsTextFile("data/output/uppercase.txt");
+        
+        upperCaseCountries.foreach(country -> {
+            //replace non alphanumerical characters
+            country = country.replaceAll("[^a-zA-Z]", "");
+            assertTrue(StringUtils.isAllUpperCase(country));
+        });
+    }
+
+    @Test
+    public void whenFilterByCountry_thenShowRequestedCountryRecords() {
+        JavaRDD<String> touristsInMexico = tourists.filter(line -> line.split(COMMA_DELIMITER)[1].equals("Mexico"));
+        
+        touristsInMexico.saveAsTextFile("data/output/touristInMexico.txt");
+        
+        touristsInMexico.foreach(record -> {
+            assertEquals("Mexico", record.split(COMMA_DELIMITER)[1]);
+        });
+    }
+
+}

core-java-modules/core-java-collections-3/README.md

@@ -13,3 +13,4 @@
 - [Quick Guide to the Java Stack](https://www.baeldung.com/java-stack)
 - [Convert an Array of Primitives to a List](https://www.baeldung.com/java-primitive-array-to-list)
 - [A Guide to BitSet in Java](https://www.baeldung.com/java-bitset)
+- [Get the First Key and Value From a HashMap](https://www.baeldung.com/java-hashmap-get-first-entry)

core-java-modules/core-java-io-3/README.md

@@ -11,4 +11,5 @@ This module contains articles about core Java input and output (IO)
 - [Java Files Open Options](https://www.baeldung.com/java-file-options)
 - [Creating Temporary Directories in Java](https://www.baeldung.com/java-temp-directories)
 - [Reading a Line at a Given Line Number From a File in Java](https://www.baeldung.com/java-read-line-at-number)
+- [Find the Last Modified File in a Directory with Java](https://www.baeldung.com/java-last-modified-file)
 - [[<-- Prev]](/core-java-modules/core-java-io-2)

core-java-modules/core-java-io-3/src/test/java/com/baeldung/createfile/CreateFileUnitTest.java

@@ -6,6 +6,7 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 import java.io.File;
+import java.io.FileOutputStream;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -37,6 +38,12 @@ public class CreateFileUnitTest {
         assertTrue(success);
     }
 
+    @Test
+    void givenUsingFileOutputStream_whenCreatingFile_thenCorrect() throws IOException {
+        try(FileOutputStream fileOutputStream = new FileOutputStream(FILE_NAME)){
+        }
+    }
+
     @Test
     public void givenUsingGuava_whenCreatingFile_thenCorrect() throws IOException {
         com.google.common.io.Files.touch(new File(FILE_NAME));

core-java-modules/core-java-lang-3/README.md

@@ -6,4 +6,5 @@ This module contains articles about core features in the Java language
 - [Converting a Java String Into a Boolean](https://www.baeldung.com/java-string-to-boolean)
 - [When are Static Variables Initialized in Java?](https://www.baeldung.com/java-static-variables-initialization)
 - [Checking if a Class Exists in Java](https://www.baeldung.com/java-check-class-exists)
+- [The Difference Between a.getClass() and A.class in Java](https://www.baeldung.com/java-getclass-vs-class)
 - [[<-- Prev]](/core-java-modules/core-java-lang-2)

core-java-modules/core-java-reflection-2/src/main/java/com/baeldung/reflection/check/abstractclass/AbstractExample.java

@@ -0,0 +1,15 @@
+package com.baeldung.reflection.check.abstractclass;
+
+import java.time.LocalDate;
+import java.time.LocalTime;
+
+public abstract class AbstractExample {
+
+    public static String getAuthorName() {
+        return "Umang Budhwar";
+    }
+
+    public abstract LocalDate getLocalDate();
+
+    public abstract LocalTime getLocalTime();
+}

core-java-modules/core-java-reflection-2/src/test/java/com/baeldung/reflection/check/abstractclass/AbstractExampleUnitTest.java

@@ -0,0 +1,16 @@
+package com.baeldung.reflection.check.abstractclass;
+
+import java.lang.reflect.Modifier;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class AbstractExampleUnitTest {
+
+    @Test
+    void givenAbstractClass_whenCheckModifierIsAbstract_thenTrue() throws Exception {
+        Class<AbstractExample> clazz = AbstractExample.class;
+        Assertions.assertTrue(Modifier.isAbstract(clazz.getModifiers()));
+    }
+
+}

core-java-modules/core-java-security-2/README.md

@@ -10,4 +10,6 @@ This module contains articles about core Java Security
 - [SHA-256 and SHA3-256 Hashing in Java](https://www.baeldung.com/sha-256-hashing-java)
 - [Checksums in Java](https://www.baeldung.com/java-checksums)
 - [How to Read PEM File to Get Public and Private Keys](https://www.baeldung.com/java-read-pem-file-keys)
+- [Listing the Available Cipher Algorithms](https://www.baeldung.com/java-list-cipher-algorithms)
+- [Get a List of Trusted Certificates in Java](https://www.baeldung.com/java-list-trusted-certificates)
 - More articles: [[<-- prev]](/core-java-modules/core-java-security)

core-kotlin-modules/core-kotlin/src/main/kotlin/com/baeldung/arguments/DefaultArguments.kt

@@ -0,0 +1,37 @@
+package com.baeldung.arguments
+
+fun main() {
+
+    // Skip both the connectTimeout and enableRetry arguments
+    connect("http://www.baeldung.com")
+
+    // Skip only the enableRetry argument:
+    connect("http://www.baeldung.com", 5000)
+
+    // Skip only the middle argument connectTimeout
+    // connect("http://www.baeldung.com", false) // This results in a compiler error
+
+    // Because we skipped the connectTimeout argument, we must pass the enableRetry as a named argument
+    connect("http://www.baeldung.com", enableRetry = false)
+
+    // Overriding Functions and Default Arguments
+    val realConnector = RealConnector()
+    realConnector.connect("www.baeldung.com")
+    realConnector.connect()
+}
+
+fun connect(url: String, connectTimeout: Int = 1000, enableRetry: Boolean = true) {
+    println("The parameters are url = $url, connectTimeout = $connectTimeout, enableRetry = $enableRetry")
+}
+
+open class AbstractConnector {
+    open fun connect(url: String = "localhost") {
+        // function implementation
+    }
+}
+
+class RealConnector : AbstractConnector() {
+    override fun connect(url: String) {
+        println("The parameter is url = $url")
+    }
+}

core-kotlin-modules/core-kotlin/src/main/kotlin/com/baeldung/arguments/NamedArguments.kt

@@ -0,0 +1,28 @@
+package com.baeldung.arguments
+
+fun main() {
+    resizePane(newSize = 10, forceResize = true, noAnimation = false)
+
+    // Swap the order of last two named arguments
+    resizePane(newSize = 11, noAnimation = false, forceResize = true)
+
+    // Named arguments can be passed in any order
+    resizePane(forceResize = true, newSize = 12, noAnimation = false)
+
+    // Mixing Named and Positional Arguments
+    // Kotlin 1.3 would allow us to name only the arguments after the positional ones
+    resizePane(20, true, noAnimation = false)
+
+    // Using a positional argument in the middle of named arguments (supported from Kotlin 1.4.0)
+    // resizePane(newSize = 20, true, noAnimation = false)
+
+    // Only the last argument as a positional argument (supported from Kotlin 1.4.0)
+    // resizePane(newSize = 30, forceResize = true, false)
+
+    // Use a named argument in the middle of positional arguments (supported from Kotlin 1.4.0)
+    // resizePane(40, forceResize = true, false)
+}
+
+fun resizePane(newSize: Int, forceResize: Boolean, noAnimation: Boolean) {
+    println("The parameters are newSize = $newSize, forceResize = $forceResize, noAnimation = $noAnimation")
+}

gradle/gradle-wrapper/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Guide to the Gradle Wrapper](https://www.baeldung.com/gradle-wrapper)

httpclient-2/README.md

@@ -8,5 +8,7 @@ The "REST With Spring" Classes: http://bit.ly/restwithspring
 
 ### Relevant Articles: 
 
-- [How to Set TLS Version in Apache HttpClient](https://www.baeldung.com/TODO)
+- [How to Set TLS Version in Apache HttpClient](https://www.baeldung.com/apache-httpclient-tls)
+- [Reading an HTTP Response Body as a String in Java](https://www.baeldung.com/java-http-response-body-as-string)
+- [How To Get Cookies From the Apache HttpClient Response](https://www.baeldung.com/java-apache-httpclient-cookies)
 - More articles: [[<-- prev]](../httpclient)

persistence-modules/jooq/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Getting Started with jOOQ](https://www.baeldung.com/jooq-intro)

persistence-modules/spring-boot-persistence-h2/src/main/resources/application-persistent-on.properties

@@ -0,0 +1,10 @@
+#spring.datasource.url=jdbc:h2:file:C:/data/demodb
+#spring.datasource.url=jdbc:h2:file:~/demodb
+spring.datasource.url=jdbc:h2:file:./src/main/resources/db/demodb
+spring.datasource.driverClassName=org.h2.Driver
+spring.datasource.username=sa
+spring.datasource.password=
+spring.h2.console.enabled=true
+spring.jpa.hibernate.ddl-auto=create-drop
+spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
+spring.h2.console.path=/h2-console

persistence-modules/spring-boot-persistence-h2/src/test/java/com/baeldung/persistent/FilesLocationUnitTest.java

@@ -0,0 +1,52 @@
+package com.baeldung.persistent;
+
+import static org.junit.Assert.assertTrue;
+
+import java.io.File;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.annotation.DirtiesContext.ClassMode;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import com.baeldung.h2db.auto.configuration.AutoConfigurationDemo;
+
+@ActiveProfiles("persistent-on")
+@RunWith(SpringRunner.class)
+@DirtiesContext(classMode = ClassMode.BEFORE_EACH_TEST_METHOD)
+@SpringBootTest(classes = AutoConfigurationDemo.class)
+public class FilesLocationUnitTest {
+
+    @BeforeClass
+    public static void beforeClass() {
+
+    }
+
+    @Test(expected = Test.None.class)
+    public void whenApplicationStarted_thenEmbeddedDbSubfolderCreated() {
+        File subdirectory = new File("src/main/resources/db");
+        System.out.println(subdirectory.getAbsolutePath());
+        assertTrue(subdirectory.exists());
+        assertTrue(subdirectory.isDirectory());
+    }
+
+    @Test(expected = Test.None.class)
+    public void whenApplicationStarted_thenEmbeddedDbFilesCreated() {
+        File dbFile = new File("src/main/resources/db/demodb.mv.db");
+        System.out.println(dbFile.getAbsolutePath());
+
+        assertTrue(dbFile.exists());
+        assertTrue(dbFile.isFile());
+    }
+
+    @AfterClass
+    public static void cleanUp() {
+        File dbFile = new File("src/main/resources/db/demodb.mv.db");
+        dbFile.deleteOnExit();
+    }
+}

spring-boot-modules/spring-boot-environment/README.md

@@ -4,4 +4,5 @@ This module contains articles about configuring the Spring Boot `Environment`
 
 ### Relevant Articles:			
  - [EnvironmentPostProcessor in Spring Boot](https://www.baeldung.com/spring-boot-environmentpostprocessor)
- - [Spring Properties File Outside jar](https://www.baeldung.com/spring-properties-file-outside-jar)
+ - [Spring Properties File Outside jar](https://www.baeldung.com/spring-properties-file-outside-jar)
+ - [Get the Running Port in Spring Boot](https://www.baeldung.com/spring-boot-running-port)

spring-boot-modules/spring-boot-keycloak/pom.xml

@@ -76,7 +76,7 @@
     </build>
 
     <properties>
-        <keycloak-adapter-bom.version>10.0.2</keycloak-adapter-bom.version>
+        <keycloak-adapter-bom.version>11.0.2</keycloak-adapter-bom.version>
     </properties>
 
 </project>

spring-boot-modules/spring-boot-mvc-3/README.md

@@ -8,4 +8,5 @@ This module contains articles about Spring Web MVC in Spring Boot projects.
 - [Download an Image or a File with Spring MVC](https://www.baeldung.com/spring-controller-return-image-file)
 - [Spring MVC Async vs Spring WebFlux](https://www.baeldung.com/spring-mvc-async-vs-webflux)
 - [Differences in @Valid and @Validated Annotations in Spring](https://www.baeldung.com/spring-valid-vs-validated)
+- [CharacterEncodingFilter In SpringBoot](https://www.baeldung.com/spring-boot-characterencodingfilter)
 - More articles: [[prev -->]](/spring-boot-modules/spring-boot-mvc-2)

spring-cloud/spring-cloud-netflix-feign/pom.xml

@@ -0,0 +1,71 @@
+<?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>
+    <groupId>com.baeldung.cloud</groupId>
+    <artifactId>spring-cloud-netlix-feign</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>spring-cloud-netflix-feign</name>
+    <description>Netflix Feign project for Spring Boot</description>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-boot-1</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-1</relativePath>
+    </parent>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.springframework.cloud</groupId>
+                <artifactId>spring-cloud-dependencies</artifactId>
+                <version>${spring-cloud.version}</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.cloud</groupId>
+            <artifactId>spring-cloud-starter-feign</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.netflix.feign</groupId>
+            <artifactId>feign-okhttp</artifactId>
+            <version>${feign-ok.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.httpcomponents</groupId>
+            <artifactId>httpcore</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <spring-cloud.version>Camden.SR7</spring-cloud.version>
+        <feign-ok.version>8.18.0</feign-ok.version>
+        <!--
+        <spring-cloud.version>Hoxton.SR8</spring-cloud.version>
+        -->
+        <!--
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        -->
+    </properties>
+
+</project>

spring-cloud/spring-cloud-netflix-feign/src/main/java/com/baeldung/cloud/netflix/feign/ExampleApplication.java

@@ -0,0 +1,16 @@
+package com.baeldung.cloud.netflix.feign;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cloud.netflix.feign.EnableFeignClients;
+
+@SpringBootApplication
+@EnableFeignClients
+public class ExampleApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(ExampleApplication.class, args);
+    }
+
+}
+

spring-cloud/spring-cloud-netflix-feign/src/main/java/com/baeldung/cloud/netflix/feign/client/JSONPlaceHolderClient.java

@@ -0,0 +1,25 @@
+package com.baeldung.cloud.netflix.feign.client;
+
+import com.baeldung.cloud.netflix.feign.config.ClientConfiguration;
+import com.baeldung.cloud.netflix.feign.hystrix.JSONPlaceHolderFallback;
+import com.baeldung.cloud.netflix.feign.model.Post;
+import org.springframework.cloud.netflix.feign.FeignClient;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+
+import java.util.List;
+
+@FeignClient(value = "jplaceholder",
+        url = "https://jsonplaceholder.typicode.com/",
+        configuration = ClientConfiguration.class,
+        fallback = JSONPlaceHolderFallback.class)
+public interface JSONPlaceHolderClient {
+
+    @RequestMapping(method = RequestMethod.GET, value = "/posts")
+    List<Post> getPosts();
+
+
+    @RequestMapping(method = RequestMethod.GET, value = "/posts/{postId}", produces = "application/json")
+    Post getPostById(@PathVariable("postId") Long postId);
+}

spring-cloud/spring-cloud-netflix-feign/src/main/java/com/baeldung/cloud/netflix/feign/config/ClientConfiguration.java

@@ -0,0 +1,38 @@
+package com.baeldung.cloud.netflix.feign.config;
+
+import feign.Logger;
+import feign.RequestInterceptor;
+import feign.codec.ErrorDecoder;
+import feign.okhttp.OkHttpClient;
+
+import org.apache.http.entity.ContentType;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class ClientConfiguration {
+
+    @Bean
+    public Logger.Level feignLoggerLevel() {
+        return Logger.Level.FULL;
+    }
+
+    @Bean
+    public ErrorDecoder errorDecoder() {
+        return new ErrorDecoder.Default();
+    }
+
+    @Bean
+    public OkHttpClient client() {
+        return new OkHttpClient();
+    }
+
+    @Bean
+    public RequestInterceptor requestInterceptor() {
+        return requestTemplate -> {
+            requestTemplate.header("user", "ajeje");
+            requestTemplate.header("password", "brazof");
+            requestTemplate.header("Accept", ContentType.APPLICATION_JSON.getMimeType());
+        };
+    }
+}

spring-cloud/spring-cloud-netflix-feign/src/main/java/com/baeldung/cloud/netflix/feign/config/CustomErrorDecoder.java

@@ -0,0 +1,21 @@
+package com.baeldung.cloud.netflix.feign.config;
+
+import com.baeldung.cloud.netflix.feign.exception.BadRequestException;
+import com.baeldung.cloud.netflix.feign.exception.NotFoundException;
+import feign.Response;
+import feign.codec.ErrorDecoder;
+
+public class CustomErrorDecoder implements ErrorDecoder {
+    @Override
+    public Exception decode(String methodKey, Response response) {
+
+        switch (response.status()){
+            case 400:
+                return new BadRequestException();
+            case 404:
+                return new NotFoundException();
+            default:
+                return new Exception("Generic error");
+        }
+    }
+}

spring-cloud/spring-cloud-netflix-feign/src/main/java/com/baeldung/cloud/netflix/feign/exception/BadRequestException.java

@@ -0,0 +1,21 @@
+package com.baeldung.cloud.netflix.feign.exception;
+
+public class BadRequestException extends Exception {
+
+    public BadRequestException() {
+    }
+
+    public BadRequestException(String message) {
+        super(message);
+    }
+
+    public BadRequestException(Throwable cause) {
+        super(cause);
+    }
+
+    @Override
+    public String toString() {
+        return "BadRequestException: "+getMessage();
+    }
+
+}