Decorator for @Nullable annotations

[bjansen]

Hi,

I was wondering if you would consider adding a new decorator to the codegen that adds a @Nullable annotation on getters that might return a null value, based on the cardinality defined in the XSD.

For example,

<xs:element name="Foo" type="xs:string" minOccurs="0"/>

would generate the following getter:

@javax.annotation.Nullable
public String getFoo() { }

Also, things like choices would also result in nullable getters:

<xs:sequence>
    <xs:choice>
        <xs:element name="foo" type="xs:string"/>
        <xs:element name="bar" type="xs:string"/>
    </xs:choice>
</xs:sequence>

would result in:

@javax.annotation.Nullable
public String getFoo() { }

@javax.annotation.Nullable
public String getBar() { }

I started working on such a decorator, I think I have something that works pretty well on my XSD but I'm not sure it's 100% correct, and I would rather use an officiel decorator that is bundled with JiBX.