codeconsole opened a new pull request, #15715:
URL: https://github.com/apache/grails-core/pull/15715
## Summary
Adds null-safe, typed conversion methods to the `session`, `request`,
`flash` and `servletContext` objects, mirroring the existing `params.int('id',
1)` API. Also adds a missing `string`/`getString` converter to
`TypeConvertingMap` itself.
```groovy
Integer page = request.int('page', 1)
String tz = session.string('userTimeZoneId', 'America/Los_Angeles')
Boolean active = session.boolean('active', false)
String notice = flash.string('notice')
int uploads = servletContext.int('maxUploads', 10)
```
The full converter set is available — `string`, `byte`, `char`, `short`,
`int`, `long`, `double`, `float`, `boolean`, `list`, `date` — each with an
optional default-value overload, exactly as on `params`.
## Motivation
Under `@CompileStatic` / `@GrailsCompileStatic`, dynamic attribute access
such as `session.userTimeZoneId` does not compile, and the explicit form
requires a cast at every call site:
```groovy
String tz = (session.getAttribute('userTimeZoneId') as String) ?:
'America/Los_Angeles'
```
These converters give the same null-safe, typed, default-aware ergonomics as
`params`, and they compile under static compilation. They are equally useful in
dynamic code for the parsing/defaulting behaviour (just like `params.int(...)`).
## Design
- Conversion logic is extracted into an internal helper,
`org.grails.util.TypeConverters`, which converts a raw `Object` value to the
target type (with an optional default). Both `TypeConvertingMap`'s instance
`getX` methods and the new attribute extensions delegate to it, so the logic
lives in a single place and no new conversion methods are added to the public
`TypeConvertingMap` API.
- The extensions call the converters directly on the attribute value,
avoiding any per-access allocation.
- The instance `getX(name, default)` semantics are preserved, so `params`
behaviour is unchanged (verified by `GrailsParameterMapBindingSpec`).
- The one deliberate exception is the `boolean` default: "is the value
present" differs by holder (map `containsKey` vs. attribute set), which cannot
be expressed from a value alone, so it stays per-site and is documented inline.
- The `string` converter returns the first element when the attribute is an
array, mirroring the single-value semantics of the other converters; use `list`
for all values.
## Tests & docs
- Unit tests for the internal converters (incl. default-value coercion) and
for `getString`/`string`.
- A Spock spec per holder (`HttpSessionExtensionSpec`,
`HttpServletRequestExtensionSpec`, `ServletContextExtensionSpec`,
`FlashScopeExtensionSpec`) covering conversion, null-safety, defaults, and a
`@CompileStatic` static-resolution guard.
- `GrailsParameterMapBindingSpec` passes unchanged (regression guard for the
core refactor).
- New "Type Conversion of Attributes" section in the controllers guide.
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