org.kie.internal.runtime.helper

## Class BatchExecutionHelper

- java.lang.Object
- - org.kie.internal.runtime.helper.BatchExecutionHelper

-     public class BatchExecutionHelper
      extends Object

  Provides a configured XStream instance to support the marshalling of BatchExecutions, where the resulting xml can be used as a message format. Configured converters only exist for the commands supported via the CommandFactory. The user may add other converters for their user objects.

  This is very useful for scripting stateless of stateful knowledge sessions, especially when services are involved.

  There is current no xsd for schema validation, however we will try to outline the basic format here and the drools-pipeline module has an illustrative unit test in the XStreamBatchExecutionTest unit test. The root element is <batch-execution> and it can contain zero or more commands elements.

       <batch-execution>
       ...
       </batch-execution>

  This contains a list of elements that represent commands, the supported commands is limited to those Commands provided by the CommandFactory. The most basic of these is the <insert> element, which inserts objects. The contents of the insert element is the user object, as dictated by XStream.

       <batch-execution>
           <insert>
           ....
           </insert>
       </batch-execution>

  The insert element supports an 'out-identifier' attribute, this means the inserted object's FactHandle will be returned and optionally the object itself as part of the <batch-execution-results> payload. To return the object use the attribute 'return-object' which takes a boolean 'true'|'false' value, by default this is true. The

       <batch-execution >
           <insert out-identifier='userVar' >
           ....
           </insert>
       </batch-execution>

  It's also possible to insert a collection of objects using the <insert-elements> element, here each element is inserted in turn. This command also support's an 'out-identifier' attribute which returns the FactHandle's in a Collection, of the same order that the objects where inserted. 'return-object' is also supported to optionally return the inserted objects, again they will be in a collection of the same order they where inserted. The org.domain.UserClass is just an illustrative user object that xstream would serialise.

       <batch-execution>
           <insert-elements>
               <org.domain.UserClass>
               ...
               </org.domain.UserClass>
               <org.domain.UserClass>
               ...
               </org.domain.UserClass>
               <org.domain.UserClass>
               ...
               </org.domain.UserClass>
           </insert-elements>
       </batch-execution>

  Next there is the <set-global> element, which sets a global for the session.

       <batch-execution>
           <set-global identifier='userVar'>
               <org.domain.UserClass>
               ...
               </org.domain.UserClass>
           </set-global>
       </batch-execution>

  <set-global> also supports two other optional attributes 'out' and 'out-identifier'. 'out' is a boolean and when set the global will be added to the <batch-execution-results> payload using the name from the 'identifier' attribute. 'out-identifier' works like 'out' but additionally allows you to override the identifier used in the <batch-execution-results> payload.

       <batch-execution>
           <set-global identifier='userVar1' out='true'>
               <org.domain.UserClass>
               ...
               </org.domain.UserClass>
           </set-global>
           <set-global identifier='userVar2' out-identifier='alternativeUserVar2'>
               <org.domain.UserClass>
               ...
               </org.domain.UserClass>
           </set-global>
       </batch-execution>

  There is also a <get-global> element, which has no contents but does support an 'out-identifier' attribute, there is no need for an 'out' attribute as we assume that a <get-global> is always an 'out'.

       <batch-execution>
           <get-global identifier='userVar1' />
           <get-global identifier='userVar2' out-identifier='alternativeUserVar2'/>
       </batch-execution>

  Specific objects can be retrieved using the FactHandle:

       <batch-execution>
           <get-object out-identifier='outStilton' factHandle='" + factHandle.toExternalForm() + "' />
       </batch-execution>

  While the 'out' attribute is useful in returning specific instances as a result payload, we often wish to run actual querries. Both parameter and parameterless querries are supported. The 'name' attribute is the name of the query to be called, and the 'out-identifier' is the identifier to be used for the query results in the <batch-execution-results> payload.

       <batch-execution>
           <query out-identifier='cheeses' name='cheeses'/>
           <query out-identifier='cheeses2' name='cheesesWithParams'>
               <string>stilton</string>
               <string>cheddar</string>
           </query>;
       </batch-execution>

  The <start-process> command is also supported and accepts optional parameters:

       <batch-execution>
        <startProcess processId='org.kie.actions'>
          <parameter identifier='person'>
             <org.kie.TestVariable>
               <name>John Doe</name>
             </org.kie.TestVariable>
          </parameter>
        </startProcess>
       </batch-execution>

  SignelEvent

       <signal-event process-instance-id='1' event-type='MyEvent'>
           <string>MyValue</string>
       </signal-event>

  CompleteWorkItem

       <complete-work-item id='" + workItem.getId() + "' >
          <result identifier='Result'>
               <string>SomeOtherString</string>
           </result>
       </complete-work-item>

  AbortWorkItem

       <abort-work-item id='21' />

  Support for more commands will be added over time.

  The following is a simple insert batch-execution command:

       <batch-execution>
         <insert out-identifier='outStilton'>
           <org.kie.Cheese>
             <type>stilton</type>
             <price>25</price>
             <oldPrice>0</oldPrice>
           </org.kie.Cheese>
         </insert>
       </batch-execution>

  The pipeline can be used to handle this end to end, notice the part where the configured XStream instance is passed "BatchExecutionHelper.newXStreamMarshaller()". This will take a given xml, transform it and then execute it as a BatchExecution Command. Notice the Pipeline also handles the marshalling of the ExecutionResults back out to XML.

       Action executeResultHandler = PipelineFactory.newExecuteResultHandler();

       Action assignResult = PipelineFactory.newAssignObjectAsResult();
       assignResult.setReceiver( executeResultHandler );

       Transformer outTransformer = PipelineFactory.newXStreamToXmlTransformer( BatchExecutionHelper.newXStreamMarshaller() );
       outTransformer.setReceiver( assignResult );

       KnowledgeRuntimeCommand batchExecution = PipelineFactory.newBatchExecutor();
       batchExecution.setReceiver( outTransformer );

       Transformer inTransformer = PipelineFactory.newXStreamFromXmlTransformer( BatchExecutionHelper.newXStreamMarshaller() );
       inTransformer.setReceiver( batchExecution );

       Pipeline pipeline = PipelineFactory.newStatelessKnowledgeSessionPipeline( ksession );
       pipeline.setReceiver( inTransformer );

  The results would look like following xml:

       <execution-results>
         <result identifier='outStilton'>
           <org.kie.Cheese>
             <type>stilton</type>
             <oldPrice>0</oldPrice>
             <price>30</price>
           </org.kie.Cheese>
         </result>
       </execution-results>

  This api is experimental and thus the classes and the interfaces returned are subject to change.

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `BatchExecutionHelper()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static com.thoughtworks.xstream.XStream` | `newJSonMarshaller()`
    `static com.thoughtworks.xstream.XStream` | `newXStreamMarshaller()`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### BatchExecutionHelper

          public BatchExecutionHelper()

  - ### Method Detail

    - #### newXStreamMarshaller

          public static com.thoughtworks.xstream.XStream newXStreamMarshaller()

    - #### newJSonMarshaller

          public static com.thoughtworks.xstream.XStream newJSonMarshaller()

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