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INT-2218 - Chain Parser Validation Improvements

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Components within Chain: Add parser validation

For reference see: https://jira.springsource.org/browse/INT-2218

INT-2218 - Code review changes

INT-2218 - Fix HttpOutboundGatewayParserTests

INT-2218 - Remove input-channel validation

Was already covered by PR #592
This commit is contained in:
Gunnar Hillert
2012-09-12 10:07:18 -04:00
committed by Gary Russell
parent c9f73a8a49
commit 7055845424
10 changed files with 455 additions and 7 deletions
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51
src/reference/docbook/chain.xml
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@@ -13,10 +13,10 @@
progression. For example, it is fairly common to provide a Transformer before other components. Similarly, when
providing a <emphasis>Filter</emphasis> before some other component in a chain, you are essentially creating a
<ulink url="http://www.eaipatterns.com/MessageSelector.html">Selective Consumer</ulink>. In either case, the
chain only requires a single <code>input-channel</code> and a single <code>output-channel</code> eliminating
chain only requires a single <code>input-channel</code> and a single <code>output-channel</code> eliminating
the need to define channels for each individual component.
<tip>
Spring Integration's <interfacename>Filter</interfacename> provides a boolean property <methodname>throwExceptionOnRejection</methodname>.
Spring Integration's <interfacename>Filter</interfacename> provides a boolean property <methodname>throwExceptionOnRejection</methodname>.
When providing multiple Selective Consumers on the same point-to-point channel with different acceptance criteria,
this value should be set to 'true' (the default is false) so that the dispatcher will know that the Message was
rejected and as a result will attempt to pass the Message on to other subscribers. If the Exception were not
@@ -68,7 +68,7 @@
</para>
<para>
The &lt;header-enricher&gt; element used in the above example will set a message header named "foo" with a value
of "bar" on the message. A header enricher is a specialization of <interfacename>Transformer</interfacename>
of "bar" on the message. A header enricher is a specialization of <interfacename>Transformer</interfacename>
that touches only header values. You could obtain the same result by implementing a MessageHandler that did the
header modifications and wiring that as a bean, but the header-enricher is obviously a simpler option.
</para>
@@ -84,11 +84,52 @@
<int:logging-channel-adapter level="INFO" log-full-message="true"/>
</int:chain>]]></programlisting>
</para>
<para>
<para><emphasis>Disallowed Attributes and Elements</emphasis></para>
<para>
It is important to note that certain attributes, such as
<emphasis role="bold">order</emphasis> and <emphasis role="bold">input-channel</emphasis>
are not allowed to be specified on components used within a
<emphasis>chain</emphasis>. The same is true for the <emphasis role="bold">poller</emphasis>
sub-element.
</para>
<important>
<para>
For the <emphasis>Spring Integration</emphasis> core components, the
XML Schema itself will enforce some of these constraints. However, for non-core
components or your own custom components, these constraints are enforced
by the XML namespace parser, not by the XML Schema.
</para>
<para>
These XML namespace parser constraints were added with
<emphasis>Spring Integration 2.2</emphasis>. The XML namespace parser
will throw an <classname>BeanDefinitionParsingException</classname> if you try to use disallowed
attributes and elements.
</para>
</important>
<para>
The <emphasis>id</emphasis> attribute, however, is allowed to be specified.
In fact, the <link linkend='delayer'><emphasis>Delayer</emphasis></link>
component actually requires the <emphasis>id</emphasis> attribute to be present.
</para>
<para>
In most other cases, the <emphasis>id</emphasis> will generally be
ignored but may still add value for documentation purposes, and may also
be used for providing more meaningful log messages.
</para>
<note>
Currently, the XML Schema of the <emphasis>Spring Integration</emphasis> Core module
prevents you from setting the <emphasis>id</emphasis> attribute for
Core components within a Message Handler Chain. This may be relaxed in future,
to provide the benefits described above.
</note>
<para><emphasis>Calling a Chain from within a Chain</emphasis></para>
<para>
Sometimes you need to make a nested call to another chain from within a chain and then come
back and continue execution within the original chain.
To accomplish this you can utilize a Messaging Gateway by including a &lt;gateway&gt; element.
For example:
</para>
<programlisting language="xml"><![CDATA[ <int:chain id="main-chain" input-channel="in" output-channel="out">
<int:header-enricher>
<int:header name="name" value="Many" />
@@ -117,7 +158,7 @@
<bean class="org.foo.SampleService" />
</int:service-activator>
</int:chain>]]></programlisting>
<para>
In the above example the <emphasis>nested-chain-a</emphasis> will be called at the end of
<emphasis>main-chain</emphasis> processing by the 'gateway' element configured there. While in
<emphasis>nested-chain-a</emphasis> a call to a <emphasis>nested-chain-b</emphasis> will be made