36 lines
1.5 KiB
ReStructuredText
36 lines
1.5 KiB
ReStructuredText
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.. _Custom Directives-java:
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Custom Directives
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=================
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Part of the power of akka-http directives comes from the ease with which it’s possible to define
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custom directives at differing levels of abstraction.
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There are essentially three ways of creating custom directives:
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1. By introducing new “labels” for configurations of existing directives
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2. By transforming existing directives
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3. By writing a directive “from scratch”
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Configuration Labeling
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______________________
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The easiest way to create a custom directive is to simply assign a new name for a certain configuration
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of one or more existing directives. In fact, most of the predefined akka-http directives can be considered
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named configurations of more low-level directives.
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The basic technique is explained in the chapter about Composing Directives, where, for example, a new directive
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``getOrPut`` is defined like this:
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.. includecode2:: ../../../code/docs/http/javadsl/server/directives/CustomDirectivesExamplesTest.java
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:snippet: labeling
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Multiple directives can be nested to produce a single directive out of multiple like this:
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.. includecode2:: ../../../code/docs/http/javadsl/server/directives/CustomDirectivesExamplesTest.java
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:snippet: composition
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Another example is the :ref:`MethodDirectives-java` which are simply instances of a preconfigured :ref:`-method-java-` directive.
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The low-level directives that most often form the basis of higher-level “named configuration” directives are grouped
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together in the :ref:`BasicDirectives-java` trait.
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