INT-2725/26 MongoDb Adapter Docs
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Oleg Zhurakousky
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Gary Russell
Gary Russell
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@@ -112,5 +112,167 @@
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<classname>MongoDbFactory</classname> as a constructor argument.
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</para>
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</section>
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<section id="mongodb-inbound-channel-adapter">
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<title>MongoDB Inbound Channel Adapter</title>
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<para>
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The <emphasis>MongoDb Inbound Channel Adapter</emphasis> is a polling consumer that reads data
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from MongoDb and sends it as a Message payload.
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</para>
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<programlisting lang="xml"><![CDATA[<int-mongodb:inbound-channel-adapter id="mongoInboundAdapter"
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channel="replyChannel"
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query="{'name' : 'Bob'}"
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entity-class="java.lang.Object"
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auto-startup="false">
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<int:poller fixed-rate="100"/>
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</int-mongodb:inbound-channel-adapter>]]></programlisting>
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<para>
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As you can see from the configuration above, you configure a <emphasis>MongoDb Inbound Channel Adapter</emphasis> using
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the <code>inbound-channel-adapter</code> element, providing values for various attributes such as:
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<itemizedlist>
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<listitem>
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<para><code>query</code> or <code>query-expression</code> - a
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JSON query (see <ulink url="http://www.mongodb.org/display/DOCS/Querying">MongoDb Querying</ulink>) </para>
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</listitem>
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<listitem>
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<para><code>entity-class</code> - the type of the payload object; if not supplied, a
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<classname>com.mongodb.DBObject</classname> will be returned.</para>
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</listitem>
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<listitem>
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<para><code>collection-name</code> or <code>collection-name-expression</code> -
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Identifies the name of the MongoDb collection to use. </para>
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</listitem>
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<listitem>
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<para><code>mongodb-factory</code> -
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reference to an instance of <classname>org.springframework.data.mongodb.MongoDbFactory</classname> </para>
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</listitem>
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<listitem>
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<para><code>mongo-template</code> -
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reference to an instance of <classname>org.springframework.data.mongodb.core.MongoTemplate</classname>
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</para>
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</listitem>
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</itemizedlist>
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and other attributes that are common across all other inbound adapters (e.g., 'channel').
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</para>
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<note>
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You cannot set both <code>mongo-template</code> and <code>mongodb-factory</code>.
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</note>
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<para>
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The example above is relatively simple and static since it has a literal value for the <code>query</code> and uses
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the default name for a <code>collection</code>. Sometimes you may need to change those values at runtime, based on some condition.
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To do that, simply use their <code>-expression</code> equivalents (<code>query-expression</code> and
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<code>collection-name-expression</code>) where the provided expression can be any valid SpEL expression.
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</para>
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<para>
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Also, you may wish to do some post-processing to the successfully processed data that was read from the MongoDb.
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For example; you may want to move or remove a document after its been processed.
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You can do this using Transaction Synchronization feature that was added with Spring Integration 2.2.
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</para>
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<programlisting lang="xml"><![CDATA[<int-mongodb:inbound-channel-adapter id="mongoInboundAdapter"
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channel="replyChannel"
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query="{'name' : 'Bob'}"
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entity-class="java.lang.Object"
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auto-startup="false">
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<int:poller fixed-rate="200" max-messages-per-poll="1">
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<int:transactional synchronization-factory="syncFactory"/>
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</int:poller>
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</int-mongodb:inbound-channel-adapter>
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<int:transaction-synchronization-factory id="syncFactory">
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<int:after-commit expression="@documentCleaner.remove(#mongoTemplate, payload, headers.mongo_collectionName)" channe="someChannel"/>
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</int:transaction-synchronization-factory>
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<bean id="documentCleaner" class="foo.bar.DocumentCleaner"/>
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<bean id="transactionManager" class="org.springframework.integration.transaction.PseudoTransactionManager"/>]]></programlisting>
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<programlisting lang="java"><![CDATA[public class DocumentCleaner {
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public void remove(MongoOperations mongoOperations, Object target, String collectionName) {
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if (target instanceof List<?>){
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List<?> documents = (List<?>) target;
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for (Object document : documents) {
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mongoOperations.remove(new BasicQuery(JSON.serialize(document)), collectionName);
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}
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}
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}
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}]]></programlisting>
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<para>
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As you can see from the above, all you need to do is declare your poller to be transactional with a <code>transactional</code> element.
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This element can reference a real transaction manager (for example if some other part of your flow invokes JDBC).
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If you don't have a 'real' transaction, you can use a
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<classname>org.springframework.integration.transaction.PseudoTransactionManager</classname> which is an implementation
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of the Spring's <classname>PlatformTransactionManager</classname> and enables the use of the transaction synchronization
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features of the mongo adapter when there is no actual transaction.
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</para>
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<important>
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This does NOT make MongoDB itself transactional, it simply allows the synchronization of actions to be taken before/after success (commit)
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or after failure (rollback).
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</important>
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<para>
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Once your poller is transactional all you need to do is set an instance of the
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<classname>org.springframework.integration.transaction.TransactionSynchronizationFactory</classname> on the <code>transactional</code> element.
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<classname>TransactionSynchronizationFactory</classname> will create an instance of the <classname>TransactioinSynchronization</classname>.
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For your convenience, we've exposed a default SpEL-based <classname>TransactionSynchronizationFactory</classname> which allows
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you to configure SpEL expressions, with their execution being coordinated (synchronized) with a transaction.
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Expressions for before-commit, after-commit, and after-rollback are supported, together with a channel for each where the
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evaluation result (if any) will be sent. For each sub-element you can specify <code>expression</code> and/or <code>channel</code>
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attributes. If only the <code>channel</code> attribute is present the received Message will be sent there as part of the particular
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synchronization scenario. If only the <code>expression</code> attribute is present and the result of an expression is a non-Null
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value, a Message with the result as the payload will be generated and sent to a default channel (NullChannel) and will appear in the
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logs (DEBUG). If you want the evaluation result to go to a specific channel add a <code>channel</code> attribute. If the result of an
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expression is null or void, no Message will be generated.
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</para>
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<para>
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For more information about transaction synchronization, see <xref linkend="transaction-synchronization"/>.
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</para>
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</section>
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<section id="mongodb-outbound-channel-adapter">
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<title>MongoDB Outbound Channel Adapter</title>
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<para>
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The <emphasis>MongoDb Outbound Channel Adapter</emphasis> allows you to write the Message payload to a MongoDb document store
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</para>
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<programlisting lang="xml"><![CDATA[<int-mongodb:outbound-channel-adapter id="fullConfigWithCollectionExpression"
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collection-name="myCollection"
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mongo-converter="mongoConverter"
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mongodb-factory="mongoDbFactory" />]]></programlisting>
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<para>
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As you can see from the configuration above, you configure a <emphasis>MongoDb Outbound Channel Adapter</emphasis> using
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the <code>outbound-channel-adapter</code> element while also providing values for various attributes such as:
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<itemizedlist>
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<listitem>
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<para><code>collection-name</code> or <code>collection-name-expression</code> -
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Identifies the name of the MongoDb collection to use. </para>
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</listitem>
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<listitem>
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<para><code>mongo-converter</code> -
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reference to an instance of <classname>org.springframework.data.mongodb.core.convert.MongoConverter</classname> to assist with
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converting a raw java object to a JSON document representation </para>
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</listitem>
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<listitem>
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<para><code>mongodb-factory</code> -
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reference to an instance of <classname>org.springframework.data.mongodb.MongoDbFactory</classname> </para>
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</listitem>
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<listitem>
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<para><code>mongo-template</code> -
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reference to an instance of <classname>org.springframework.data.mongodb.core.MongoTemplate</classname>
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(NOTE: you can not have both mongo-template and mongodb-factory set)</para>
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</listitem>
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</itemizedlist>
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and other attributes that are common across all other inbound adapters (e.g., 'channel').
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</para>
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<para>
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The example above is relatively simple and static since it has a literal value for the <code>collection-name</code>.
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Sometimes you may need to change this value at runtime based on some condition.
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To do that, simply use <code>collection-name-expression</code>
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where the provided expression can be any valid SpEL expression.
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</para>
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</section>
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</chapter>
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