void postParse()
    {
        if (packageName == null)
        {
            setPackageName("");
        }

        String javaPkg = (String) extraOptions.get("java_package");
        String javaPackageName = javaPkg == null || javaPkg.length() == 0 ?
                packageName.getValue() : javaPkg;
        this.javaPackageName = new Mutable<String>(javaPackageName);

        // Cache all fully-qualified message names and enum group names so we
        // can look them up quickly
        for (Message m : getMessages())
            m.cacheFullyQualifiedNames();
        for (EnumGroup eg : getEnumGroups())
            eg.cacheFullyQualifiedName();

        for (Message m : getMessages())
            m.resolveReferences(m);

        for (Service s : getServices())
            s.resolveReferences();

        for (Extension e : getExtensions())
            e.resolveReferences();

        for (ConfiguredReference r : references)
            r.resolve(this);

        if (!standardOptions.isEmpty())
            ConfiguredReference.resolve(this, standardOptions, extraOptions, getPackageName());
    }
Returns the java package name that was configured in the proto. Note that {@link #getJavaPackageName()} will have
the same value as this, if the compiler options did not have entries that override it.
protostuff-parser/src/main/java/io/protostuff/parser/Proto.java