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GH-3998: Fix gateway docs for @Payload #4000

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Feb 1, 2023
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GH-3998: Fix gateway docs for @Payload #4000

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5b6820a
GH-3998: Fix gateway docs for `@Payload`
artembilan Feb 1, 2023
219a8df
* Cross link to `gateway-expressions` paragraph for better context
artembilan Feb 1, 2023
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27 changes: 14 additions & 13 deletions src/reference/asciidoc/gateway.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -158,6 +158,7 @@ IMPORTANT: If you specify, for example, the `requestChannel` in `<int:method/>`

NOTE: If a no-argument gateway is specified in XML, and the interface method has both a `@Payload` and `@Gateway` annotation (with a `payloadExpression` or a `payload-expression` in an `<int:method/>` element), the `@Payload` value is ignored.

[[gateway-expressions]]
===== Expressions and "`Global`" Headers

The `<header/>` element supports `expression` as an alternative to `value`.
Expand Down Expand Up @@ -225,10 +226,10 @@ public interface MyGateway {

void twoMapsAndOneAnnotatedWithPayload(@Payload Map<String, Object> payload, Map<String, Object> headers);

@Payload("#args[0] + #args[1] + '!'")
@Payload("args[0] + args[1] + '!'")
void payloadAnnotationAtMethodLevel(String a, String b);

@Payload("@someBean.exclaim(#args[0])")
@Payload("@someBean.exclaim(args[0])")
void payloadAnnotationAtMethodLevelUsingBeanResolver(String s);

void payloadAnnotationWithExpression(@Payload("toUpperCase()") String s);
Expand All @@ -254,17 +255,17 @@ public interface MyGateway {
<1> Note that, in this example, the SpEL variable, `#this`, refers to the argument -- in this case, the value of `s`.

The XML equivalent looks a little different, since there is no `#this` context for the method argument.
However, expressions can refer to method arguments by using the `#args` variable, as the following example shows:
However, expressions can refer to method arguments by using the `args` property for the `MethodArgsHolder` root object (see <<gateway-expressions>> for more information), as the following example shows:

====
[source,xml]
----
<int:gateway id="myGateway" service-interface="org.something.MyGateway">
<int:method name="send1" payload-expression="#args[0] + 'thing2'"/>
<int:method name="send2" payload-expression="@someBean.sum(#args[0])"/>
<int:method name="send3" payload-expression="#method"/>
<int:method name="send1" payload-expression="args[0] + 'thing2'"/>
<int:method name="send2" payload-expression="@someBean.sum(args[0])"/>
<int:method name="send3" payload-expression="method"/>
<int:method name="send4">
<int:header name="thing1" expression="#args[2].toUpperCase()"/>
<int:header name="thing1" expression="args[2].toUpperCase()"/>
</int:method>
</int:gateway>
----
Expand Down Expand Up @@ -515,23 +516,23 @@ Starting with version 5.0, the timeouts can be defined as expressions, as the fo
====
[source, java]
----
@Gateway(payloadExpression = "#args[0]", requestChannel = "someChannel",
requestTimeoutExpression = "#args[1]", replyTimeoutExpression = "#args[2]")
@Gateway(payloadExpression = "args[0]", requestChannel = "someChannel",
requestTimeoutExpression = "args[1]", replyTimeoutExpression = "args[2]")
String lateReply(String payload, long requestTimeout, long replyTimeout);
----
====

The evaluation context has a `BeanResolver` (use `@someBean` to reference other beans), and the `#args` array variable is available.

The evaluation context has a `BeanResolver` (use `@someBean` to reference other beans), and the `args` array property from the `#root` object is available.
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ditto

See <<gateway-expressions>> for more information about this root object.
When configuring with XML, the timeout attributes can be a long value or a SpEL expression, as the following example shows:

====
[source, xml]
----
<method name="someMethod" request-channel="someRequestChannel"
payload-expression="#args[0]"
payload-expression="args[0]"
request-timeout="1000"
reply-timeout="#args[1]">
reply-timeout="args[1]">
</method>
----
====
Expand Down