add java sources to maveb

spring-5-mvc/pom.xml

@@ -1,5 +1,6 @@
 <?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"
+<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</groupId>
@@ -51,12 +52,10 @@
         <dependency>
             <groupId>org.jetbrains.kotlin</groupId>
             <artifactId>kotlin-stdlib-jre8</artifactId>
-            <version>${kotlin.version}</version>
         </dependency>
         <dependency>
             <groupId>org.jetbrains.kotlin</groupId>
             <artifactId>kotlin-reflect</artifactId>
-            <version>${kotlin.version}</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.module</groupId>
@@ -91,7 +90,6 @@
     </dependencies>
 
     <build>
-        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
         <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
         <plugins>
             <plugin>
@@ -132,11 +130,43 @@
                     </dependency>
                 </dependencies>
             </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>build-helper-maven-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>add-source</goal>
+                        </goals>
+                        <configuration>
+                            <sources>
+                                <source>${basedir}/src/main/java</source>
+                                <source>${basedir}/src/main/kotlin</source>
+                            </sources>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>test-compile</id>
+                        <phase>test-compile</phase>
+                        <goals>
+                            <goal>add-test-source</goal>
+                        </goals>
+                        <configuration>
+                            <sources>
+                                <source>${basedir}/src/test/java</source>
+                                <source>${basedir}/src/test/kotlin</source>
+                            </sources>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
     </build>
-    
+
     <properties>
         <jayway-rest-assured.version>2.9.0</jayway-rest-assured.version>
         <kotlin.version>1.1.2</kotlin.version>
+        <start-class>com.baeldung.Spring5Application</start-class>
     </properties>
 </project>