PreQuery (Google App Engine API for Java)
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@Target(value=METHOD)
@Retention(value=RUNTIME)
public @interface PreQuery
Identifies a callback method to be invoked before a
Query
for any of the specified kinds
is executed against the datastore. If
kinds()
is not provided the callback will execute
for queries against all kinds, including kind-less queries. Methods with this annotation must
return
void
, must accept a single argument of type
PreQueryContext
, must not
throw any checked exceptions, must not be static, and must belong to a class with a no-arg
constructor. Neither the method nor the no-arg constructor of the class to which it belongs are
required to be public. Methods with this annotation are free to throw any unchecked exception
they like. Throwing an unchecked exception will prevent callbacks that have not yet been executed
from running, and the exception will propagate to the code that invoked the datastore operation
that resulted in the invocation of the callback. Throwing an unchecked exception from a callback
will prevent the datastore operation from executing.
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Optional Element Summary
Optional Elements
Modifier and Type |
Optional Element and Description |
java.lang.String[] |
kinds
The kinds to which this callback applies.
|
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Last updated 2025-06-16 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-06-16 UTC."],[[["`@PreQuery` is an annotation used to mark a method as a callback to be executed before a datastore `Query` is run."],["The callback method must return `void`, accept a `PreQueryContext` argument, and cannot throw checked exceptions or be static."],["The `kinds` element of the `@PreQuery` annotation specifies the datastore kinds to which the callback applies; if unspecified, it applies to all kinds."],["Throwing an unchecked exception within a callback method will halt any further callbacks and prevent the datastore operation."]]],[]]