Checking if a document is readOnly protected results in a NPE

[Gábor Lipták]

I was developing a unit test for my docx4j code, and I discovered this bug.

Lets suppose we have a docx, which is readonly protected by a password. Then we try to check its protection type:

WordprocessingMLPackage mergedDocument = load(anyProtectedDocumentAsByteArray);
assertThat(mergedDocument.getMainDocumentPart().getDocumentSettingsPart()
		.isRestrictEditingWith(STDocProtect.READ_ONLY)).isTrue();

Then we get an NPE:

java.lang.NullPointerException: Cannot invoke "org.docx4j.wml.CTSettings.getDocumentProtection()" because "this.jaxbElement" is null
	at org.docx4j.openpackaging.parts.WordprocessingML.DocumentSettingsPart.isRestrictEditingWith(DocumentSettingsPart.java:290)

I noticed, that if I first check the password in my test using org.docx4j.openpackaging.packages.ProtectDocument#validateProtectionPassword, then the assertion passes. So the validateProtectionPassword changes the state of DocumentSettingsPart by initializing the jaxbElement field. If I trigger the safeGetDocumentProtection method with the debugger before calling isRestrictEditingWith, then my test also passes.

Without fully understanding the code, I think if the org.docx4j.openpackaging.parts.WordprocessingML.DocumentSettingsPart#isRestrictEditingWith method would look like below, no error would happen:

    public boolean isRestrictEditingWith(STDocProtect editValue) {
        CTDocProtect ctDocProtect = **safeGetDocumentProtection()**;

        if (ctDocProtect == null) {
            return false;
        }

        return ctDocProtect.isEnforcement() && ctDocProtect.getEdit().equals(editValue);
    }

Please note, that in this DocumentSettingsPart there are a lot of code places, where this.jaxbElement is read, probably some other places should also be replaced by safeGetDocumentProtection.