Fix for #667 Illegal Access for JDK 9 or greater

.github/workflows/build-matrix.yml

@@ -22,12 +22,12 @@ jobs:
         with:
           java-version: ${{ matrix.java_version }}
       - name: Install
-        run: mvn clean install -DskipTests
+        run: mvn clean install -DskipTests --batch-mode --no-transfer-progress
         env:
           BUILD_PORT: 0
           BUILD_SECURE_PORT: 0
       - name: Build
-        run: mvn clean package
+        run: mvn clean package --batch-mode --no-transfer-progress
         env:
           BUILD_PORT: 0
           BUILD_SECURE_PORT: 0

handlebars/src/main/java/com/github/jknack/handlebars/context/MemberValueResolver.java

@@ -78,7 +78,7 @@ private Map<String, M> cache(final Class<?> clazz) {
       Set<M> members = members(clazz);
       for (M m : members) {
         // Mark as accessible.
-        if (m instanceof AccessibleObject) {
+        if (isUseSetAccessible(m) && m instanceof AccessibleObject) {
           ((AccessibleObject) m).setAccessible(true);
         }
         mcache.put(memberName(m), m);
@@ -88,6 +88,31 @@ private Map<String, M> cache(final Class<?> clazz) {
     return mcache;
   }
 
+  /**
+   * Determines whether or not to call
+   * {@link AccessibleObject#setAccessible(boolean)} on members before they are
+   * cached.
+   *
+   * Calling setAccessible on JDK 9 or later on private or protected declaring
+   * classes in modules will result in errors so the default implementation checks
+   * to see if the declared class cannonical name starts with "java." or "sun." to
+   * prevent most of these errors.
+   *
+   * Modular applications should create their own resolvers and override this
+   * method to prevent encapsulation violation errors.
+   *
+   * @param member Not null.
+   * @return true will cause setAccessible(true) to be called.
+   */
+  protected boolean isUseSetAccessible(final M member) {
+    Class<?> dc = member.getDeclaringClass();
+    String dn = dc == null ? null : dc.getCanonicalName();
+    if (dn != null && (dn.startsWith("java.") || dn.startsWith("sun."))) {
+      return false;
+    }
+    return true;
+  }
+
   /**
    * Invoke the member in the given context.
    *

handlebars/src/test/java/com/github/jknack/handlebars/context/SetAccessibleValueResolverTest.java

@@ -0,0 +1,58 @@
+package com.github.jknack.handlebars.context;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+import static org.junit.Assume.assumeTrue;
+
+import java.lang.reflect.Method;
+import java.util.Collections;
+
+import org.junit.Test;
+
+public class SetAccessibleValueResolverTest {
+
+  /*
+   * The following tests require JDK 9 or greater.
+   * To keep the tests from failing we use junit assume.
+   */
+
+  @Test
+  public void testSetAccessibleOnJDK9OrGreater() throws Exception {
+    assumeTrue(getJavaVersion() >= 9);
+    MethodValueResolver mv = new MethodValueResolver() {
+
+      @Override
+      protected boolean isUseSetAccessible(Method m) {
+        return true;
+      }
+    };
+    try {
+      mv.resolve(Collections.emptyMap(), "doesNotMatter");
+      fail("Expect InaccessibleObjectException");
+    } catch (/* InaccessibleObjectException */ Exception e) {
+    }
+
+    mv = new MethodValueResolver();
+    mv.resolve(Collections.emptyMap(), "doesNotMatter");
+    Object result = mv.resolve(Collections.emptyMap(), "isEmpty");
+    assertEquals(Boolean.TRUE, result);
+  }
+
+  static int getJavaVersion() {
+    String version = System.getProperty("java.version");
+    if (version.startsWith("1.")) {
+      version = version.substring(2, 3);
+    } else {
+      int dot = version.indexOf(".");
+      if (dot != -1) {
+        version = version.substring(0, dot);
+      }
+    }
+    try {
+      return Integer.parseInt(version);
+    } catch (NumberFormatException e) {
+      return 8;
+    }
+  }
+
+}