59 lines
2.4 KiB
Text
59 lines
2.4 KiB
Text
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[[_config_spi_providers]]
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=== Configure SPI Providers
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The specifics of each configuration setting is discussed elsewhere in
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context with that setting. However, it is useful to understand the format used
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to declare settings on SPI providers.
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{{book.project.name}} is a highly modular system that allows great
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flexibility. There are more than 50 service provider interfaces (SPIs), and
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you are allowed to swap out implementations of each SPI. An implementation of
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an SPI is known as a _provider_.
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All elements in an SPI declaration are optional, but a full SPI declaration
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looks like this:
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[source,xml]
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----
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<spi name="dblock">
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<default-provider>mongo</default-provider>
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<provider name="jpa" enabled="true">
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<properties>
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<property name="lockWaitTimeout" value="800"/>
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</properties>
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</provider>
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<provider name="mongo" enabled="true">
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<properties>
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<property name="lockRecheckTime" value="2"/>
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<property name="lockWaitTimeout" value="600"/>
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</properties>
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</provider>
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</spi>
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----
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Here we have two providers defined for the SPI `dblock`. The `default-provider`
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is listed as `mongo`. However it is up to the SPI to decide how it will treat
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this setting. Some SPIs allow more than one provider and some do not. So
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`default-provider` can help the SPI to choose.
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Also notice that each provider defines its own set of configuration properties.
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The fact that both providers above have a property called `lockWaitTimeout` is just a
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coincidence.
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The type of each property value is interpreted by the provider. However, there
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is one exception. Consider the `jpa` provider for the `eventStore` API:
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[source,xml]
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----
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<spi name="eventsStore">
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<provider name="jpa" enabled="true">
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<properties>
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<property name="exclude-events" value="["EVENT1",
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"EVENT2"]"/>
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</properties>
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</provider>
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</spi>
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----
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We see that the value begins and ends with square brackets. That means that
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the value will be passed to the provider as a list. In this example, the system will pass the
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provider a list with two element values _EVENT1_ and _EVENT2_. To add more values
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to the list, just separate each list element with a comma. Unfortunately,
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you do need to escape the quotes surrounding each list element with `\"`.
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