Add an integration test that runs on JDK-8

Signed-off-by: Andriy Redko <andriy.redko@aiven.io>

.github/workflows/test-jdk8-compat-unit.yml

@@ -0,0 +1,30 @@
+name: Unit
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macOS-latest]
+    steps:
+      - name: Checkout Java Client
+        uses: actions/checkout@v3
+
+      - name: Set up JDK 8
+        uses: actions/setup-java@v3
+        with:
+          java-version: 8
+          distribution: 'temurin'
+          cache: 'gradle'
+
+      - name: Set up JDK 11
+        uses: actions/setup-java@v3
+        with:
+          java-version: 11
+          distribution: 'temurin'
+          cache: 'gradle'
+
+      - name: Run Unit Test
+        run: ./gradlew clean unitTest -Pcheck-jdk8-compatibility=true

java-client/build.gradle.kts

@@ -32,6 +32,7 @@
 
 import com.github.jk1.license.ProjectData
 import com.github.jk1.license.render.ReportRenderer
+import org.gradle.api.tasks.testing.Test
 import java.io.FileWriter
 
 buildscript {
@@ -337,7 +338,9 @@ publishing {
     }
 }
 
-if (JavaVersion.current() >= JavaVersion.VERSION_11) {
+// Use `-Pcheck-jdk8-compatibility=true` to
+val jdk8compatibility = (project.findProperty("check-jdk8-compatibility") as String?).toBoolean()
+if (JavaVersion.current() >= JavaVersion.VERSION_11 && jdk8compatibility == false) {
   val java11: SourceSet = sourceSets.create("java11") {
     java {
       compileClasspath += sourceSets.main.get().output + sourceSets.test.get().output
@@ -369,5 +372,17 @@ if (JavaVersion.current() >= JavaVersion.VERSION_11) {
     testClassesDirs += java11.output.classesDirs
     classpath = sourceSets["java11"].runtimeClasspath
   }
-
-}
+} else if (jdk8compatibility == true) {
+    java {
+        toolchain {
+          languageVersion = JavaLanguageVersion.of(8)
+          vendor = JvmVendorSpec.ADOPTIUM
+        }
+    }
+
+    tasks.register<Test>("tests-jdk8") {
+      javaLauncher = javaToolchains.launcherFor {
+        languageVersion = JavaLanguageVersion.of(8)
+      }
+    }
+}

java-client/src/test/java/org/opensearch/client/opensearch/core/PutIndexTemplateRequestTest.java

@@ -2,8 +2,10 @@
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import jakarta.json.stream.JsonParser;
 import java.io.StringReader;
-import java.util.List;
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.Map;
 import org.junit.Assert;
 import org.junit.Test;
@@ -16,15 +18,19 @@ public class PutIndexTemplateRequestTest extends Assert {
     @Test
     public void deserialize_validFieldsIncluded_RequestIsBuilt() throws JsonProcessingException {
         final JsonpMapper mapper = new JsonbJsonpMapper();
-        final Map<String, Object> indexTemplateMap = Map.of("name", "test", "index_patterns", "*", "create", true, "priority", 1);
+        final Map<String, Object> indexTemplateMap = new HashMap<>();
+        indexTemplateMap.put("name", "test");
+        indexTemplateMap.put("index_patterns", "*");
+        indexTemplateMap.put("create", true);
+        indexTemplateMap.put("priority", 1);
 
         final String indexTemplate = new ObjectMapper().writeValueAsString(indexTemplateMap);
-        final var parser = mapper.jsonProvider().createParser(new StringReader(indexTemplate));
+        final JsonParser parser = mapper.jsonProvider().createParser(new StringReader(indexTemplate));
 
         final PutIndexTemplateRequest putIndexTemplateRequest = PutIndexTemplateRequest._DESERIALIZER.deserialize(parser, mapper);
 
         assertEquals(putIndexTemplateRequest.name(), "test");
-        assertEquals(putIndexTemplateRequest.indexPatterns(), List.of("*"));
+        assertEquals(putIndexTemplateRequest.indexPatterns(), Collections.singletonList("*"));
         assertEquals((int) putIndexTemplateRequest.priority(), 1);
     }
 

java-client/src/test/java/org/opensearch/client/opensearch/core/search/InnerHitsTest.java

@@ -9,7 +9,7 @@
 import jakarta.json.stream.JsonParser;
 import java.io.StringReader;
 import java.io.StringWriter;
-import java.util.List;
+import java.util.Arrays;
 import org.junit.Test;
 import org.opensearch.client.json.JsonpMapper;
 import org.opensearch.client.json.JsonpSerializable;
@@ -26,7 +26,7 @@ public class InnerHitsTest {
      */
     @Test
     public void testInnerHitStoredFields() {
-        InnerHits hits = InnerHits.of((it) -> it.storedFields(List.of("field1", "field2")));
+        InnerHits hits = InnerHits.of((it) -> it.storedFields(Arrays.asList("field1", "field2")));
         assertTrue(toJson(hits).contains("stored_fields"));
     }
 

settings.gradle.kts

@@ -30,6 +30,10 @@
  * GitHub history for details.
  */
 
+plugins {
+  id("org.gradle.toolchains.foojay-resolver-convention") version("0.7.0")
+}
+
 rootProject.name = "opensearch-java"
 include("java-client")
 include("samples")