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How to configure jbpm5 to store and retrieve Knowledge Sessions from the database
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created by <a href="http://community.jboss.org/people/MicheleMauro">Michele Mauro</a> in <i>jBPM</i> - <a href="http://community.jboss.org/message/587992#587992">View the full discussion</a>
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<div class="jive-rendered-content"><p>I'm trying to setup a web application to work with jbpm5 processes, but I'm stuck at the jbpm5 configuration. I use spring, and I can write up (messing a bit with the various examples) a test case that can create and launch a process, with a configuration along these lines in the applicationContext.xml:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><drools:ksession id="jpaSingleSessionCommandService" type="stateful" kbase="knowledgeBase"></p><p>     <drools:configuration></p><p>            <drools:work-item-handlers></p><p>                <drools:work-item-handler name="Human Task" ref="humanTaskHandler" /></p><p>            </drools:work-item-handlers></p><p>           <drools:jpa-persistence load="1"></p><p>                <drools:transaction-manager ref="transactionManager" /></p><p>                <drools:entity-manager-factory ref="entityManagerFactory" /></p><p>            </drools:jpa-persistence></p><p>    </drools:configuration></p><p></drools:ksession></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>However, this setup creates a new ksession each time the application is loaded. In my case, I need to load a specific ksession by id, work with the process instance contained in it, inspect it for current status and results, and then persist it back.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I've tried setting up something more basic in Spring, that is building only the KnowledgeBase and then getting the session with:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>StatefulKnowledgeSession ks = JPAKnowledgeService.loadStatefulKnowledgeSession(id, kbase, null, env);</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>but I keep getting strange NPEs and errors. In particular, I found that, while the documentation states (jBPM 5.0.0 manual, chapter 8) that you should build the environment to pass the JPAKnowledgeService in this way:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><a class="jive-link-anchor-small"><span class="java_type" style="color: #000000;">Environment</span><span class="java_plain" style="color: #000000;"> env </span><span class="java_operator" style="color: #000000;">=</span><span class="java_plain" style="color: #000000;"> </span><span class="java_type" style="color: #000000;">KnowledgeBaseFactory</span><span class="java_separator" style="color: #000000;">.</span><span class="java_plain" style="color: #000000;">newEnvironment</span><span class="java_separator" style="color: #000000;">();</span><br/><span class="java_plain" style="color: #000000;">env</span><span class="java_separator" style="color: #000000;">.</span><span class="java_plain" style="color: #000000;">set</span><span class="java_separator" style="color: #000000;">(</span><span class="java_plain" style="color: #000000;"> </span><span class="java_type" style="color: #000000;">EnvironmentName</span><span class="java_separator" style="color: #000000;">.</span><span class="java_plain" style="color: #000000;">ENTITY_MANAGER_FACTORY</span><span class="java_separator" style="color: #000000;">,</span><span class="java_plain" style="color: #000000;"> emf </span><span class="java_separator" style="color: #000000;">);</span><br/><span class="java_plain" style="color: #000000;">env</span><span class="java_separator" style="color: #000000;">.</span><span class="java_plain" style="color: #000000;">set</span><span class="java_separator" style="color: #000000;">(</span><span class="java_plain" style="color: #000000;"> </span><span class="java_type" style="color: #000000;">EnvironmentName</span><span class="java_separator" style="color: #000000;">.</span><span class="java_plain" style="color: #000000;">TRANSACTION_MANAGER</span><span class="java_separator" style="color: #000000;">,</span><br/><span class="java_plain" style="color: #000000;">         </span><span class="java_type" style="color: #000000;">TransactionManagerServices</span><span class="java_separator" style="color: #000000;">.</span><span class="java_plain" style="color: #000000;">getTransactionManager</span><span class="java_separator" style="color: #000000;">()</span><span class="java_plain" style="color: #000000;"> </span><span class="java_separator" style="color: #000000;">);</span></a></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>the SingleSessionCommandService, that is the final implementation of the KnowledgeSession that gets called, wants a different environment:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><a class="jive-link-external-small" href="https://github.com/droolsjbpm/droolsjbpm/blob/master/drools-persistence-jpa/src/main/java/org/drools/persistence/SingleSessionCommandService.java">https://github.com/droolsjbpm/droolsjbpm/blob/master/drools-persistence-jpa/src/main/java/org/drools/persistence/SingleSessionCommandService.java</a></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>line 56:</p><p class="line" id="LC56" style="padding-left: 1em; line-height: 1.4em;"><span class="k" style="line-height: 1.4em; font-weight: bold;">if</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">(</span> <span class="n" style="line-height: 1.4em;">env</span><span class="o" style="line-height: 1.4em; font-weight: bold;">.</span><span class="na" style="line-height: 1.4em; color: #008080;">get</span><span class="o" style="line-height: 1.4em; font-weight: bold;">(</span> <span class="n" style="line-height: 1.4em;">EnvironmentName</span><span class="o" style="line-height: 1.4em; font-weight: bold;">.</span><span class="na" style="line-height: 1.4em; color: #008080;">ENTITY_MANAGER_FACTORY</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">)</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">==</span> <span class="kc" style="line-height: 1.4em; font-weight: bold;">null</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">&&</span></p><p class="line" id="LC57" style="padding-left: 1em; line-height: 1.4em;">             <span class="n" style="line-height: 1.4em;">env</span><span class="o" style="line-height: 1.4em; font-weight: bold;">.</span><span class="na" style="line-height: 1.4em; color: #008080;">get</span><span class="o" style="line-height: 1.4em; font-weight: bold;">(</span> <span class="n" style="line-height: 1.4em;">EnvironmentName</span><span class="o" style="line-height: 1.4em; font-weight: bold;">.</span><span class="na" style="line-height: 1.4em; color: #008080;">PERSISTENCE_CONTEXT_MANAGER</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">)</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">==</span> <span class="kc" style="line-height: 1.4em; font-weight: bold;">null</span>  <span class="o" style="line-height: 1.4em; font-weight: bold;">)</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">{</span></p><p class="line" id="LC58" style="padding-left: 1em; line-height: 1.4em;">            <span class="k" style="line-height: 1.4em; font-weight: bold;">throw</span> <span class="k" style="line-height: 1.4em; font-weight: bold;">new</span> <span class="nf" style="line-height: 1.4em; color: #990000; font-weight: bold;">IllegalArgumentException</span><span class="o" style="line-height: 1.4em; font-weight: bold;">(</span> <span class="s" style="line-height: 1.4em; color: #dd1144;">"Environment must have an EntityManagerFactory "</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">+</span></p><p class="line" id="LC59" style="padding-left: 1em; line-height: 1.4em;">                                                  <span class="s" style="line-height: 1.4em; color: #dd1144;">"or a PersistenceContextManager instance"</span> <span class="o" style="line-height: 1.4em; font-weight: bold;">);</span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Now I'm completely confused. How does this work?</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Michele</p></div>
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