fix(bindings): validate native packages and Java requirements

CHANGELOG.md

@@ -16,6 +16,9 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- Android packaging rejects ABI directories missing either native library or
+  containing empty libraries. JNI jar configuration now requires its actual JDK 17 minimum.
+
 - Java `Measure`, `DrawingPath` and `DrawingTransform` equality now agrees with
   hashing for signed zero and is reflexive for NaN, following `Double` semantics.
 

android/build.gradle.kts

@@ -77,12 +77,21 @@ val checkNative =
         dependsOn(buildNative)
         val jniLibs = layout.projectDirectory.dir("native/prebuilt/jniLibs").asFile
         doLast {
-            if (jniLibs.list().isNullOrEmpty()) {
+            val abiDirectories = jniLibs.listFiles()?.filter { it.isDirectory }.orEmpty()
+            if (abiDirectories.isEmpty()) {
                 throw GradleException(
                     "nothing in $jniLibs — run android/build_native.py, " +
                         "or pass -Podr.abis=<abis> to have the build run it"
                 )
             }
+            for (directory in abiDirectories) {
+                for (name in listOf("libodr_jni.so", "libc++_shared.so")) {
+                    val library = directory.resolve(name)
+                    if (!library.isFile || library.length() == 0L) {
+                        throw GradleException("missing or empty native library: $library")
+                    }
+                }
+            }
         }
     }
 

jni/CMakeLists.txt

@@ -32,7 +32,7 @@ endif ()
 # quietly shipping half a package.
 option(ODR_JNI_JAR "Build the java half, `odr-core-java.jar`" ON)
 if (ODR_JNI_JAR)
-    find_package(Java 11 REQUIRED COMPONENTS Development)
+    find_package(Java 17 REQUIRED COMPONENTS Development)
     include(UseJava)
 endif ()