set Java cross compile target to Java 8 (#53)

* java cross compile

* loosen up distribution req

* use 17 in ci

* ditto

* add back distribution: "temurin"

* downgrade to java 8

Author: jimexist

.github/workflows/build.yml

@@ -20,10 +20,10 @@ jobs:
           toolchain: stable
           components: rustfmt, clippy
 
-      - name: Set up JDK 11
+      - name: Set up JDK 17
         uses: actions/setup-java@v2
         with:
-          java-version: "11"
+          java-version: "17"
           distribution: "temurin"
 
       - name: Validate Gradle wrapper
@@ -66,10 +66,10 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
-      - name: Set up JDK 11
+      - name: Set up JDK 17
         uses: actions/setup-java@v2
         with:
-          java-version: 11
+          java-version: 17
           distribution: "temurin"
 
       - name: Validate Gradle wrapper

.github/workflows/release.yml

@@ -20,10 +20,10 @@ jobs:
           toolchain: stable
           components: rustfmt, clippy
 
-      - name: Set up JDK 11
+      - name: Set up JDK 17
         uses: actions/setup-java@v2
         with:
-          java-version: "11"
+          java-version: "17"
           distribution: "temurin"
 
       - name: Validate Gradle wrapper
@@ -66,10 +66,10 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
-      - name: Set up JDK 11
+      - name: Set up JDK 17
         uses: actions/setup-java@v2
         with:
-          java-version: 11
+          java-version: 17
           distribution: "temurin"
 
       - name: Validate Gradle wrapper

buildSrc/src/main/groovy/datafusion.java-conventions.gradle

@@ -11,6 +11,11 @@ repositories {
 
 java {
     toolchain {
-        languageVersion = JavaLanguageVersion.of(11)
+        languageVersion = JavaLanguageVersion.of(15)
     }
 }
+
+tasks.withType(JavaCompile) {
+    // down-compile to minimal version
+    options.release.set(8)
+}

datafusion-java/src/main/java/org/apache/arrow/datafusion/JNILoader.java

@@ -4,7 +4,6 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -23,8 +22,6 @@ private enum OsName {
     Linux
   }
 
-  private static final Map<OsName, String> OS_NAME_STRING_MAP =
-      Map.of(OsName.Linux, "so", OsName.Osx, "dylib", OsName.Windows, "dll");
   private static final String libraryName = "datafusion_jni";
 
   private static final String ERROR_MSG =
@@ -49,7 +46,15 @@ private static String getResourceName() {
   }
 
   private static String getExtension() {
-    return OS_NAME_STRING_MAP.get(getOsName());
+    OsName osName = getOsName();
+    if (osName == OsName.Linux) {
+      return "so";
+    } else if (osName == OsName.Osx) {
+      return "dylib";
+    } else if (osName == OsName.Windows) {
+      return "dll";
+    }
+    throw new IllegalStateException("Cannot determin extension for " + osName);
   }
 
   static synchronized void load() {