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05579fd1
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05579fd1
编写于
12月 08, 2016
作者:
J
Juergen Hoeller
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差异文件
SpEL docs: supported literals, null comparisons
Issue: SPR-14361 Issue: SPR-14987
上级
6517c537
变更
1
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1 changed file
with
19 addition
and
6 deletion
+19
-6
src/asciidoc/core-expressions.adoc
src/asciidoc/core-expressions.adoc
+19
-6
未找到文件。
src/asciidoc/core-expressions.adoc
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05579fd1
...
...
@@ -220,6 +220,7 @@ example for Spring bean or Spring Web Flow definitions. In this case, the parser
evaluation context, root object and any predefined variables are all set up implicitly,
requiring the user to specify nothing other than the expressions.
====
As a final introductory example, the use of a boolean operator is shown using the
Inventor object in the previous example.
...
...
@@ -583,12 +584,13 @@ Autowired methods and constructors can also use the `@Value` annotation.
[[expressions-ref-literal]]
=== Literal expressions
The types of literal expressions supported are strings, dates, numeric values (int,
real, and hex), boolean and null. Strings are delimited by single quotes. To put a
single quote itself in a string use two single quote characters. The following listing
shows simple usage of literals. Typically they would not be used in isolation like this,
but as part of a more complex expression, for example using a literal on one side of a
logical comparison operator.
The types of literal expressions supported are strings, numeric values (int, real, hex),
boolean and null. Strings are delimited by single quotes. To put a single quote itself
in a string, use two single quote characters.
The following listing shows simple usage of literals. Typically they would not be used
in isolation like this but rather as part of a more complex expression, for example
using a literal on one side of a logical comparison operator.
[source,java,indent=0]
[subs="verbatim,quotes"]
...
...
@@ -777,6 +779,17 @@ and greater than or equal are supported using standard operator notation.
boolean
trueValue
=
parser
.
parseExpression
(
"'black' < 'block'"
).
getValue
(
Boolean
.
class
);
----
[
NOTE
]
====
Greater
/
less
-
than
comparisons
against
`
null
`
follow
a
simple
rule
:
`
null
`
is
treated
as
nothing
here
(
i
.
e
.
NOT
as
zero
).
As
a
consequence
,
any
other
value
is
always
greater
than
`
null
`
(`
X
>
null
`
is
always
`
true
`)
and
no
other
value
is
ever
less
than
nothing
(`
X
<
null
`
is
always
`
false
`).
If
you
prefer
numeric
comparisons
instead
,
please
avoid
number
-
based
`
null
`
comparisons
in
favor
of
comparisons
against
zero
(
e
.
g
.
`
X
>
0
`
or
`
X
<
0
`).
====
In
addition
to
standard
relational
operators
SpEL
supports
the
`
instanceof
`
and
regular
expression
based
`
matches
`
operator
.
...
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