fix(ci): add Maven Wrapper and fix compilation/test errors

- Add Maven Wrapper (mvnw, mvnw.cmd, .mvn/wrapper/) targeting Maven 3.9.9
- Fix RestClientConfig: connectTimeout/readTimeout → setConnectTimeout/setReadTimeout
- Fix SparkEtlExample: add explicit casts for lambda ambiguity with Scala types
- Fix MockitoFeaturesTest: avoid spying on JDK classes for byte-buddy compat
- Bump java.version 17 → 21 (switch patterns require 21+)
- Bump Mockito 5.11.0 → 5.23.0, add byte-buddy 1.17.7 override for JDK 25

Author: jyatesdotdev

.mvn/wrapper/maven-wrapper.properties

@@ -0,0 +1,3 @@
+wrapperVersion=3.3.4
+distributionType=only-script
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.9/apache-maven-3.9.9-bin.zip

examples/etl/src/main/java/com/example/template/etl/spark/SparkEtlExample.java

@@ -3,6 +3,9 @@
 import org.apache.spark.SparkConf;
 import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
+import org.apache.spark.api.java.function.FilterFunction;
+import org.apache.spark.api.java.function.MapFunction;
+import org.apache.spark.api.java.function.MapGroupsFunction;
 import org.apache.spark.sql.Dataset;
 import org.apache.spark.sql.Encoders;
 import org.apache.spark.sql.Row;
@@ -145,9 +148,9 @@ public record SalesRecord(String product, String region, double revenue) impleme
     public static Dataset<SalesRecord> typedDatasetExample(SparkSession spark, List<SalesRecord> data) {
         Dataset<SalesRecord> ds = spark.createDataset(data, Encoders.bean(SalesRecord.class));
 
-        return ds.filter(r -> r.revenue() > 100.0)
-                .groupByKey(SalesRecord::region, Encoders.STRING())
-                .mapGroups((region, iter) -> {
+        return ds.filter((FilterFunction<SalesRecord>) r -> r.revenue() > 100.0)
+                .groupByKey((MapFunction<SalesRecord, String>) SalesRecord::region, Encoders.STRING())
+                .mapGroups((MapGroupsFunction<String, SalesRecord, SalesRecord>) (region, iter) -> {
                     double total = 0;
                     int count = 0;
                     while (iter.hasNext()) {

examples/restful-api/src/main/java/com/example/template/restfulapi/client/RestClientConfig.java

@@ -29,8 +29,8 @@ public class RestClientConfig {
     @Bean
     public RestTemplate restTemplate(RestTemplateBuilder builder) {
         return builder
-                .connectTimeout(Duration.ofSeconds(5))
-                .readTimeout(Duration.ofSeconds(10))
+                .setConnectTimeout(Duration.ofSeconds(5))
+                .setReadTimeout(Duration.ofSeconds(10))
                 .build();
     }
 

examples/testing/src/test/java/com/example/template/testing/mockito/MockitoFeaturesTest.java

@@ -125,16 +125,15 @@ void bddStyle() {
     @Test
     @DisplayName("Spy wraps a real object, allowing selective stubbing")
     void spyExample() {
-        var realList = new java.util.ArrayList<>(List.of("a", "b", "c"));
-        var spiedList = spy(realList);
+        var spiedService = spy(new UserService(repository));
 
-        // Real method is called
-        assertThat(spiedList.get(0)).isEqualTo("a");
+        // Real method is called by default
+        when(repository.findById(1L)).thenReturn(Optional.of(ALICE));
+        assertThat(spiedService.getById(1L)).isEqualTo(ALICE);
 
-        // Override specific behavior
-        doReturn("MOCKED").when(spiedList).get(1);
-        assertThat(spiedList.get(1)).isEqualTo("MOCKED");
-        assertThat(spiedList.size()).isEqualTo(3); // real size
+        // Override specific behavior on the spy
+        doReturn(ALICE).when(spiedService).getById(2L);
+        assertThat(spiedService.getById(2L)).isEqualTo(ALICE);
     }
 
     // ── Exception Stubbing ─────────────────────────────────────────────