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INT-3927: Docs for IntegrationComponentScan

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JIRA: https://jira.spring.io/browse/INT-3927

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This commit is contained in:
Artem Bilan
2016-01-06 16:14:49 -05:00
committed by Gary Russell
parent 5b7c5b4b72
commit afc286a66a
4 changed files with 56 additions and 17 deletions
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28
spring-integration-core/src/main/java/org/springframework/integration/annotation/IntegrationComponentScan.java
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@@ -1,5 +1,5 @@
/*
* Copyright 2014 the original author or authors.
* Copyright 2014-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -22,15 +22,22 @@ import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
import org.springframework.core.annotation.AliasFor;
import org.springframework.integration.config.IntegrationComponentScanRegistrar;
/**
* Configures component scanning directives for use with @{@link org.springframework.context.annotation.Configuration} classes.
* Scan Spring Integration specific components.
* Configures component scanning directives for use with
* {@link org.springframework.context.annotation.Configuration} classes.
* <p>
* Scans for {@link MessagingGateway} on interfaces to create {@code GatewayProxyFactoryBean}s.
*
* @author Artem Bilan
* @since 4.0
*
* @see ComponentScan
* @see MessagingGateway
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@@ -41,28 +48,27 @@ public @interface IntegrationComponentScan {
/**
* Alias for the {@link #basePackages()} attribute.
* Allows for more concise annotation declarations e.g.:
* {@code @ComponentScan("org.my.pkg")} instead of
* {@code @ComponentScan(basePackages="org.my.pkg")}.
*
* {@code @IntegrationComponentScan("org.my.pkg")} instead of
* {@code @IntegrationComponentScan(basePackages="org.my.pkg")}.
* @return the array of 'basePackages'.
*/
@AliasFor("basePackages")
String[] value() default {};
/**
* Base packages to scan for annotated components.
* <p>{@link #value()} is an alias for (and mutually exclusive with) this attribute.
* <p>Use {@link #basePackageClasses()} for a type-safe alternative to String-based package names.
*
* The {@link #value()} is an alias for (and mutually exclusive with) this attribute.
* Use {@link #basePackageClasses()} for a type-safe alternative to String-based package names.
* @return the array of 'basePackages'.
*/
@AliasFor("value")
String[] basePackages() default {};
/**
* Type-safe alternative to {@link #basePackages()} for specifying the packages
* to scan for annotated components. The package of each class specified will be scanned.
* <p>Consider creating a special no-op marker class or interface in each package
* Consider creating a special no-op marker class or interface in each package
* that serves no purpose other than being referenced by this attribute.
*
* @return the array of 'basePackageClasses'.
*/
Class<?>[] basePackageClasses() default {};

18
spring-integration-core/src/main/java/org/springframework/integration/annotation/MessagingGateway.java
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@@ -1,5 +1,5 @@
/*
* Copyright 2014-2015 the original author or authors.
* Copyright 2014-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -27,9 +27,17 @@ import java.lang.annotation.Target;
* ({@code <gateway/>}) as an abstraction over the messaging API. The target
* application’s business logic may be completely unaware of the Spring Integration
* API, with the code interacting only via the interface.
* <p>
* Important: The {@link IntegrationComponentScan} annotation is required along with
* {@link org.springframework.context.annotation.Configuration}
* to scan interfaces annotated with {@link MessagingGateway}, because the
* standard {@link org.springframework.context.annotation.ComponentScan}
* ignores interfaces.
*
* @author Artem Bilan
* @since 4.0
*
* @see IntegrationComponentScan
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@@ -44,14 +52,16 @@ public @interface MessagingGateway {
String name() default "";
/**
* Identifies default channel the messages will be sent to upon invocation of methods of the gateway proxy.
* Identifies the default channel to which messages will be sent upon invocation
* of methods of the gateway proxy.
* @return the suggested channel name, if any
*/
String defaultRequestChannel() default "";
/**
* Identifies default channel the gateway proxy will subscribe to to receive reply {@code Message}s, which will then be
* converted to the return type of the method signature.
* Identifies the default channel the gateway proxy will subscribe to, to receive reply
* {@code Message}s, the payloads of
* which will be converted to the return type of the method signature.
* @return the suggested channel name, if any
*/
String defaultReplyChannel() default "";

20
src/reference/asciidoc/configuration.adoc
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@@ -256,6 +256,8 @@ Annotations available in Spring Integration include:
* @InboundChannelAdapter
* @BridgeFrom
* @BridgeTo
* @MessagingGateway
* @IntegrationComponentScan
The behavior of each is described in its own chapter or section within this reference.
@@ -438,6 +440,24 @@ public String foo() {
The first example requires that the default poller has been declared elsewhere in the application context.
*@MessagingGateway*
See <<messaging-gateway-annotation>>.
*@IntegrationComponentScan*
The standard Spring Framework `@ComponentScan` annotation doesn't scan interfaces for stereotype `@Component`
annotations.
To overcome this limitation and allow the configuration of `@MessagingGateway` (see <<messaging-gateway-annotation>>),
the `@IntegrationComponentScan` mechanism has been introduced.
This annotation must be placed along with a `@Configuration` annotation, and customized for the scanning options,
such as `basePackages` and `basePackageClasses`.
In this case all discovered interfaces annotated with `@MessagingGateway` will be parsed and registered
as a `GatewayProxyFactoryBean` s.
All other class-based components are parsed by the standard `@ComponentScan`.
In future, more scanning logic may be added to the `@IntegrationComponentScan`.
[[meta-annotations]]
==== Messaging Meta-Annotations

7
src/reference/asciidoc/gateway.adoc
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@@ -277,8 +277,11 @@ public interface TestGateway {
}
----
As with the XML version, Spring Integration creates the `proxy` implementation with its messaging infrastructure, when discovering these annotations during a component scan.
To perform this scan and register the `BeanDefinition` in the application context, add the `@IntegrationComponentScan` annotation to a `@Configuration` class - see also <<annotations>>.
IMPORTANT: As with the XML version, Spring Integration creates the `proxy` implementation with its messaging infrastructure, when discovering these annotations during a component scan.
To perform this scan and register the `BeanDefinition` in the application context, add the `@IntegrationComponentScan` annotation to a `@Configuration` class.
The standard `@ComponentScan` infrastructure doesn't deal with interfaces, therefore the custom `@IntegrationComponentScan` logic has been introduced
to determine `@MessagingGateway` annotation on the interfaces and register `GatewayProxyFactoryBean` s for them.
See also <<annotations>>
[[gateway-calling-no-argument-methods]]
==== Invoking No-Argument Methods