fix: JAVA_HOME points to JRE directory on OpenJDK8, should instead point to JDK directory

.github/workflows/ci-workflow.yml

@@ -18,13 +18,26 @@ jobs:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK 17
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           java-version: '17'
           distribution: 'adopt'
       - name: Build Rust with Cargo
         run: cargo build --verbose
       - name: Test Rust with Cargo
-        run: cargo test --verbose -- --nocapture
+        run: cargo test --verbose -- --nocapture
+
+  test-legacy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up JDK 8
+        uses: actions/setup-java@v4
+        with:
+          java-version: '8'
+          distribution: 'temurin'
+      - name: Test Rust with Cargo
+        run: JAVAM_HOME="" cargo test --features=legacy-java-compat --verbose -- --nocapture

Cargo.toml

@@ -26,4 +26,5 @@ glob = "0.3"
 docopt = { version = "1.1", optional = true }
 
 [features]
-build-binary = ["docopt"]
+build-binary = ["docopt"]
+legacy-java-compat = []

src/lib.rs

@@ -196,6 +196,17 @@ fn do_locate_java_home() -> Result<String> {
     home_path.pop();
     home_path.pop();
 
+    // Java 8(aka 1.8) has a slightly different directory structure,
+    // where java is in the ${JAVA_HOME}/jre/bin/java directory, and ${JAVA_HOME}/bin/java is just a symlink.
+    // Since we recursively follow symlinks, we end up in the wrong directory,
+    // so we need to pop one more time.
+    #[cfg(feature = "legacy-java-compat")]
+    if let Some(last_section) = home_path.file_name() {
+        if last_section == "jre" {
+            home_path.pop();
+        }
+    }
+
     home_path
         .into_os_string()
         .into_string()
@@ -276,4 +287,10 @@ mod unit_tests {
     fn locate_java_from_exec_test() {
         println!("do_locate_java_home: {}", do_locate_java_home().unwrap());
     }
+
+    #[test]
+    fn jni_headers_test() {
+        let java_home = do_locate_java_home().unwrap();
+        assert!(PathBuf::from(java_home).join("include").join("jni.h").exists());
+    }
 }