On Tue, Nov 20, 2012 at 2:01 PM, Benedikt Ritter <benerit...@gmail.com>wrote:
> Hi,
>
> Gary and I did some work on CSV-68 Use the Builder Pattern to create
> CSVFormats [1].
> We have implemented a builder for CSVFormats in trunk. It is capable of...
>
> ...creating a CSVFormat from scratch by only passing in a delimiter:
> CSVFormat format = CSVFormat.newBuilder(',').build();
>
> ...creating a CSVFormat from the commons-csv defaults (RFC4180 but ignoring
> empty lines)
> CSVFormat format = CSVFormat.defaults().build();
>
> ...creating a CSVFormat based on a
> CSVFormat copyOfRFC4180 = CSVFormat.newBuilder(CSVFormat.RFC4180).build();
>
> The builders provides the same fluent API like CSVFormat did before by
> returning itself:
> CSVFormat format =
>
> CSVFormat.newBuilder(',').withRecordSeparator('\n').withIgnoreEmptyLines(true).build();
>
> Using a builder has several advantages:
> - the construction of CSVFormats can be separated from the CSVFormat itself
> - the interface of CSVFormat is now much smaller
> - if we want to add another parameter to CSVFormat we only have to change
> CSVFormat's private ctor, and the build method. We had to change every
> withXXX method before.
> - CSVFormats can only be created into a valid state, because the builder
> internally uses the validate method, which was package visible before and
> therefore not accessible to users.
>
> However there are also disadvantages:
> - the builder is more verbose; it forces users to the build() method, where
> every withXXX method returned a CSVFormat before.
>
I'm not crazy about the extra method call but I see the value of the
pattern, especially always having a valid state (which we also had before
right?)
The build() method could also be called toCSVFormat().
Like StringBuilder has toString(), a FooBuilder can say "toFoo()" so you
know what to expect.
Gary
- it has been argued that using the builder pattern only to make sure
> CSVFormats are valid is overengineered. No other library has this kind of
> validation.
>
> Please share your thoughts about the builder.
>
> Regards,
> Benedikt
>
> [1] https://issues.apache.org/jira/browse/CSV-68
>
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