6.2. Building and Deploying

6.2.1. KnowledgePackage

A Knowledge Package is a collection of Knowledge Definitions, such as rules and processes. It is created by the Knowledge Builder. Knowledge Packages are self-contained and serializable, and they currently form the basic deployment unit.
A chart demonstrating the KnowledgePackage interface.

Figure 6.1. KnowledgePackage interface

Note

A Knowledge Package instance cannot be reused once it's added to the Knowledge Base. If you need to add it to another Knowledge Base, serialize it and use the "cloned" result.
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6.2.2. Creating a new KnowledgeBase

Procedure 6.2. Task

  1. Use this default configuration to create a new KnowledgeBase: 
    KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
  2. If a custom class loader was used with the KnowledgeBuilder to resolve types not in the default class loader, then that must also be set on the KnowledgeBase. The technique for this is the same as with the KnowledgeBuilder and is shown below: 
    KnowledgeBaseConfiguration kbaseConf =
    KnowledgeBaseFactory.createKnowledgeBaseConfiguration( null, cl );
KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase( kbaseConf );
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6.2.3. Add KnowledgePackages to a KnowledgeBase

In-process building is the simplest form of deployment. It compiles the knowledge definitions and adds them to the Knowledge Base in the same JVM. This approach requires drools-core.jar and drools-compiler.jar to be on the classpath.

Procedure 6.3. Task

  • To add KnowledgePackages to a KnowledgeBase, use this code: 
    Collection<KnowledgePackage> kpkgs = kbuilder.getKnowledgePackages();

KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
kbase.addKnowledgePackages( kpkgs );
    The addKnowledgePackages(kpkgs) method can be called iteratively to add additional knowledge.
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6.2.4. Building and Deployment in Separate Processes

Both the KnowledgeBase and the KnowledgePackage are units of deployment and serializable. This means you can have one machine do any necessary building, requiring drools-compiler.jar, and have another machine deploy and execute everything, needing only drools-core.jar.
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6.2.5. Writing the KnowledgePackage to an OutputStream

This is the code for writing the KnowledgePackage to an OutputStream: 
 ObjectOutputStream out = new ObjectOutputStream( new FileOutputStream( fileName ) );
out.writeObject( kpkgs );
out.close();
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6.2.6. Reading the KnowledgePackage from an InputStream

Use this code for reading the KnowledgePackage from an InputStream: 
ObjectInputStream in = new ObjectInputStream( new FileInputStream( fileName ) );
// The input stream might contain an individual
// package or a collection.
@SuppressWarnings( "unchecked" )
Collection<KnowledgePackage> kpkgs =
    ()in.readObject( Collection<KnowledgePackage> );
in.close();

KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
kbase.addKnowledgePackages( kpkgs );
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6.2.7. StatefulknowledgeSessions and KnowledgeBase Modifications

The KnowledgeBase creates and returns StatefulKnowledgeSession objects and can optionally keep references to them.
When KnowledgeBase modifications occur, they are applied against the data in the sessions. This reference is a weak reference and it is also optional. It is controlled by a boolean flag.
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