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Polish SpEL selection/projection in ref docs

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Sam Brannen 2021-04-28 15:54:39 +02:00
parent 59015344a7
commit 8456eaca8e
1 changed files with 17 additions and 17 deletions
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src/docs/asciidoc/core/core-expressions.adoc
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@ -1804,7 +1804,7 @@ Selection is a powerful expression language feature that lets you transform a
source collection into another collection by selecting from its entries. source collection into another collection by selecting from its entries.
Selection uses a syntax of `.?[selectionExpression]`. It filters the collection and Selection uses a syntax of `.?[selectionExpression]`. It filters the collection and
returns a new collection that contain a subset of the original elements. For example, returns a new collection that contains a subset of the original elements. For example,
selection lets us easily get a list of Serbian inventors, as the following example shows: selection lets us easily get a list of Serbian inventors, as the following example shows:
[source,java,indent=0,subs="verbatim,quotes",role="primary"] [source,java,indent=0,subs="verbatim,quotes",role="primary"]
@ -1820,14 +1820,14 @@ selection lets us easily get a list of Serbian inventors, as the following examp
"members.?[nationality == 'Serbian']").getValue(societyContext) as List<Inventor> "members.?[nationality == 'Serbian']").getValue(societyContext) as List<Inventor>
---- ----
Selection is actually supported for arrays and anything that implements `java.lang.Iterable` or `java.util.Map`. Selection is supported for arrays and anything that implements `java.lang.Iterable` or
For a list or array, the selection criteria is evaluated against each individual element. Against a map, the `java.util.Map`. For a list or array, the selection criteria is evaluated against each
selection criteria is evaluated against each map entry (objects of the Java type individual element. Against a map, the selection criteria is evaluated against each map
`Map.Entry`). Each map entry has its key and value accessible as properties for use in entry (objects of the Java type `Map.Entry`). Each map entry has its `key` and `value`
the selection. accessible as properties for use in the selection.
The following expression returns a new map that consists of those elements of the original map The following expression returns a new map that consists of those elements of the
where the entry value is less than 27: original map where the entry's value is less than 27:
[source,java,indent=0,subs="verbatim,quotes",role="primary"] [source,java,indent=0,subs="verbatim,quotes",role="primary"]
.Java .Java
@ -1840,9 +1840,8 @@ where the entry value is less than 27:
val newMap = parser.parseExpression("map.?[value<27]").getValue() val newMap = parser.parseExpression("map.?[value<27]").getValue()
---- ----
In addition to returning all the selected elements, you can retrieve only the first or
In addition to returning all the selected elements, you can retrieve only the the last element. To obtain the first element matching the selection, the syntax is
first or the last value. To obtain the first entry matching the selection, the syntax is
`.^[selectionExpression]`. To obtain the last matching selection, the syntax is `.^[selectionExpression]`. To obtain the last matching selection, the syntax is
`.$[selectionExpression]`. `.$[selectionExpression]`.
@ -1851,11 +1850,11 @@ first or the last value. To obtain the first entry matching the selection, the s
[[expressions-collection-projection]] [[expressions-collection-projection]]
=== Collection Projection === Collection Projection
Projection lets a collection drive the evaluation of a sub-expression, and the Projection lets a collection drive the evaluation of a sub-expression, and the result is
result is a new collection. The syntax for projection is `.![projectionExpression]`. For a new collection. The syntax for projection is `.![projectionExpression]`. For example,
example, suppose we have a list of inventors but want the list of suppose we have a list of inventors but want the list of cities where they were born.
cities where they were born. Effectively, we want to evaluate 'placeOfBirth.city' for Effectively, we want to evaluate 'placeOfBirth.city' for every entry in the inventor
every entry in the inventor list. The following example uses projection to do so: list. The following example uses projection to do so:
[source,java,indent=0,subs="verbatim,quotes",role="primary"] [source,java,indent=0,subs="verbatim,quotes",role="primary"]
.Java .Java
@ -1870,7 +1869,8 @@ every entry in the inventor list. The following example uses projection to do so
val placesOfBirth = parser.parseExpression("members.![placeOfBirth.city]") as List<*> val placesOfBirth = parser.parseExpression("members.![placeOfBirth.city]") as List<*>
---- ----
You can also use a map to drive projection and, in this case, the projection expression is Projection is supported for arrays and anything that implements `java.lang.Iterable` or
`java.util.Map`. When using a map to drive projection, the projection expression is
evaluated against each entry in the map (represented as a Java `Map.Entry`). The result evaluated against each entry in the map (represented as a Java `Map.Entry`). The result
of a projection across a map is a list that consists of the evaluation of the projection of a projection across a map is a list that consists of the evaluation of the projection
expression against each map entry. expression against each map entry.