tdf#121925 test for URLClassPath.ClassPathURLCheck

Adds a configure test to check for the enabled ClassPathURLCheck.
Should be reverted, if our jars pass it.

Change-Id: I040b41f329ccae21b92118fd58270682e50e95c1
Reviewed-on: https://gerrit.libreoffice.org/64709
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

configure.ac

@@ -7308,6 +7308,58 @@ if test -n "$ENABLE_JAVA" -a -z "$JAVAINC"; then
 fi
 SOLARINC="$SOLARINC $JAVAINC"
 
+if test "$ENABLE_JAVA" != "" -a "x" != "x$JAVACOMPILER"; then
+    url_check_unknown=0
+    java_base="testurlcheck"
+    java_src="${java_base}.java"
+    java_cls="${java_base}.class"
+    cat > "${java_src}" <<_ACEOF
+[import jdk.internal.loader.URLClassPath;
+import java.lang.reflect.Field;
+import java.net.URL;
+
+class ${java_base}
+{
+    public static void main(String args[])
+    {
+        try {
+            URLClassPath cp = new URLClassPath(new URL[0], null);
+            Field field = cp.getClass().getDeclaredField("DISABLE_CP_URL_CHECK");
+            field.setAccessible(true);
+            System.out.println(field.get(cp).toString());
+        } catch(Exception e) {
+            System.out.println("unknown");
+        }
+    }
+}]
+_ACEOF
+    AC_MSG_CHECKING([if jdk.net.URLClassPath.ClassPathURLCheck is disabled])
+    java_cmd="$JAVACOMPILER --add-exports java.base/jdk.internal.loader=ALL-UNNAMED ${java_src} 1>&2"
+    AC_TRY_EVAL(java_cmd)
+    if test $? = 0 -a -f "./${java_cls}"; then
+        java_res=`$JAVAINTERPRETER --add-opens java.base/jdk.internal.loader=ALL-UNNAMED ${java_base} 2>/dev/null`
+        if test $? = 0; then
+            case "${java_res}" in
+            true) AC_MSG_RESULT([yes]) ;;
+            false)
+                rm -f "./${java_src}" "./${java_cls}"
+                AC_MSG_ERROR([no - Java unit tests will break!])
+                ;;
+            *) url_check_unknown=1 ;;
+            esac
+        else
+            url_check_unknown=1
+        fi
+    else
+        url_check_unknown=1
+    fi
+    if test $url_check_unknown -eq 1; then
+        AC_MSG_RESULT([unknown - assuming yes])
+        add_warning "Unable to find the default value for jdk.net.URLClassPath.ClassPathURLCheck - java tests might fail!"
+    fi
+    rm -f "./${java_src}" "./${java_cls}"
+fi
+
 AC_SUBST(JAVACOMPILER)
 AC_SUBST(JAVADOC)
 AC_SUBST(JAVAINTERPRETER)