fix(jni): require a jdk for the jar rather than shipping without it

CHANGELOG.md

@@ -18,6 +18,9 @@ The release run heads these entries with the version and opens a fresh
 
 - A pdf that nests parentheses inside a string opens, and keeps its document
   metadata — `cairo` and `pdfTeX` write their `/Producer` that way.
+- A jni build without a JDK fails instead of shipping a package missing
+  `odr-core-java.jar`. `ODR_JNI_JAR=OFF` is how the AAR build asks for the
+  native half alone.
 
 ## v6.9.0 - 2026-08-18
 

android/build_native.py

@@ -93,6 +93,8 @@ def build(architecture: str, conan: str, build_profile: str, output: Path) -> No
          # rather than shipped as a second .so the app would have to load
          "-DBUILD_SHARED_LIBS=OFF",
          "-DODR_JNI=ON",
+         # the AAR compiles `jni/java/` itself, so no jar and no JDK here
+         "-DODR_JNI_JAR=OFF",
          "-DODR_CLI=OFF",
          "-DODR_TEST=OFF",
          "-DODR_WITH_HTTP_SERVER=ON"])

jni/AGENTS.md

@@ -8,7 +8,7 @@ package `app.opendocument.core`. Mirrors the surface of the python bindings
 
 | Path | What |
 |------|------|
-| `CMakeLists.txt` | Builds `libodr_jni` + `odr-core-java.jar`; included from the root build via `ODR_JNI`, or standalone against an installed `odrcore`. |
+| `CMakeLists.txt` | Builds `libodr_jni` + `odr-core-java.jar`; included from the root build via `ODR_JNI`, or standalone against an installed `odrcore`. `ODR_JNI_JAR=OFF` builds the native half alone — what `../android` does, and the only build needing no JDK. |
 | `pom.xml` | Maven distribution of the Java classes only (`app.opendocument:odr-core-java`); published to Maven Central (the `central` profile) and GitHub Packages on release via `.github/workflows/maven.yml`. Keep `--release`/`-Xlint` in sync with `CMAKE_JAVA_COMPILE_FLAGS`. |
 | `src/` | JNI sources, one `jni_*` unit per public-API area; `odr_jni.hpp` (strings, exceptions, handles) and `jni_convert.hpp` (struct/POJO marshalling) are the helpers. |
 | `java/app/opendocument/core/` | Java API: enums, POJOs (styles, metas, `HtmlConfig`), and handle-backed wrappers extending `NativeResource`. Also compiled as-is into the AAR (`../android`) — which is kotlin, but this stays java: `add_jar` below has no kotlin toolchain. |

jni/CMakeLists.txt

@@ -21,18 +21,18 @@ else ()
 endif ()
 
 # On android the NDK sysroot ships `jni.h` and the JNI symbols come from the
-# runtime, so there is nothing to find or link against. A JDK stays optional
-# there rather than unused: the android odrcore package ships
-# `odr-core-java.jar` next to `libodr_jni.so` and OpenDocument.droid takes both
-# out of it, while `android/` (the AAR) builds the native half alone, with the
-# android toolchain compiling `java/` itself.
-if (ANDROID)
-    find_package(Java 11 COMPONENTS Development)
-else ()
-    find_package(Java 11 REQUIRED COMPONENTS Development)
+# runtime, so there is nothing to find or link against.
+if (NOT ANDROID)
     find_package(JNI REQUIRED)
 endif ()
-if (Java_FOUND)
+
+# Android is no reason to skip the jar — the android odrcore package ships it
+# next to `libodr_jni.so` for OpenDocument.droid. Only the AAR build wants the
+# native half alone, and asks for it, so a missing JDK fails rather than
+# 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)
     include(UseJava)
 endif ()
 
@@ -56,7 +56,7 @@ endif ()
 
 install(TARGETS odr_jni LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}" COMPONENT jni)
 
-if (NOT Java_FOUND)
+if (NOT ODR_JNI_JAR)
     return()
 endif ()
 

jni/README.md

@@ -71,6 +71,12 @@ This produces `build/jni/libodr_jni.dylib` (or `.so`) and
 `build/jni/odr-core-java.jar`. `jni/CMakeLists.txt` can also be configured
 standalone against an installed `odrcore` package.
 
+`ODR_JNI_JAR=OFF` builds the native library alone. That is what the AAR build
+(`android/build_native.py`) asks for, since it compiles `jni/java/` with the
+android toolchain instead, and it is the only build needing no JDK — on android
+the headers come from the NDK sysroot. Otherwise a missing JDK fails the
+configure step rather than producing a package without the jar in it.
+
 ## Runtime data
 
 There is none. The renderer's CSS/JS are part of the library and detection needs