Data Binder: Add support for auto-instantiating null values in nested paths [SPR-6032]

[spring-projects-issues]

Keith Donald opened SPR-6032 and commented

Grails, SpEL, and the new PresentationModel support in development for 3.1 all have native support for this. We should consider building this capability natively into DataBinder for consistency, and so Grails no longer has to maintain its own DataBinder extension.

Scenario:
Assume we are binding to an instance of object Foo
Assume the expression of the property we are binding to is 'bar.baz', so a nested binding
If the bar property value is null, this feature will cause a new value of bar's propertyType to be created via its default constructor and set for bar.

As a developer, this alleviates me from having to make sure all the property paths are instantiated ahead of time; I can simply rely on what the client is binding along with the property metadata to drive population of the object graph. This is convenient.

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Affects: 3.0 M4

Issue Links:

• Option to expose empty value instead of NullValueInNestedPathException [SPR-1671] #6368 Option to expose empty value instead of NullValueInNestedPathException
• Null property values in nested paths relating to <spring:bind> tag, <form:xxx> tags, and ServletRequestDataBinder [SPR-1860] #6554 Null property values in nested paths relating to spring:bind tag, form:xxx tags, and ServletRequestDataBinder

Referenced from: commits 3fa533d

2 votes, 3 watchers

[spring-projects-issues]

Keith Donald commented

Discussed in team planning call:

• Default behavior is turned on with ability to turn off

[spring-projects-issues]

Keith Donald commented

Added "autoGrowNestedPaths" flag to BeanWrapper.

Default for BeanWrapper is false for compatibility reasons. Higher-level BeanWrapper users like DataBinder can set default to true. Enabling that will be done in a separate ticket.