Drools Tools Reference Guide

1. To create a new Drools project, click File → New → Project → Drools → Drools Project . This will open the New Drools Project wizard.
   Type the project name into the relevant field and click the Next button.
2. You will see a list of default artifacts to it like sample rules, decision tables or ruleflows and Java classes for them. Add the ones that are relevant to your project and click Next.
3. You will be asked to specify a Drools runtime. If you have not yet set it up, you should do this now by clicking the Configure Workspace Settings link.
   You should see the Preferences window where you can configure the workspace settings for Drools runtimes. To create a new runtime, click the Add button. It will prompt you to enter a name for a new runtime and a path to the Drools runtime on your file system.

   Note

   A Drools runtime is a collection of .jars on your file system that represent one specific release of the Drools project .jars. When creating a new runtime, you must either point to the release of your choice or create a new runtime on your file system from the .jars included in the Drools Eclipse plugin.
4. You can create a new Drools 5 runtime from the .jars embedded in the Drools Eclipse plugin. Click the Create a new Drools 5 runtime button, select the folder where you want the runtime to be created and click OK.
5. You will see the newly created runtime show up in your list of Drools runtimes. Check it and click the OK button.
6. Click the Finish to complete the project creation.
7. Now you have a basic structure, classpath, sample rules and test case to get you started.

1. To create a new project you can either create an empty text .drl file or utilize the New Rule Package wizard.
2. To open the wizard select File → New → Rule Resource or use the menu with the JBoss Drools icon on the toolbar.
3. On the wizard page, select rules as a top level directory to store your rules and enter a rule name. Next, specify the mandatory rule package name. This defines a namespace that groups rules together.
4. The wizard then generates a rule skeleton to get you started.

1. To create breakpoints in the Package Explorer view or Navigator view of the Drools perspective, double-click the selected .drl file to open it in the editor.
2. You can add and remove rule breakpoints in the .drl files in two ways:
   • Double-click the rule in the Rule editor at the line where you want to add a breakpoint. A breakpoint can be removed by double-clicking the rule once more.

     Note

     Note that rule breakpoints can only be created in the consequence of a rule. Double-clicking on a line where no breakpoint is allowed will do nothing.
   • Right-click the ruler. Select the Toggle Breakpoint action in the context menu. Choosing this action will add a breakpoint at the selected line or remove it if there is one already.
3. The Debug perspective contains a Breakpoints view which can be used to see all defined breakpoints, get their properties, enable/disable and remove them. You can switch to it by clicking Window → Perspective → Others → Debug .

1. Drools breakpoints are only enabled if you debug your application as a Drools Application. To do this you should perform one of two actions:
   • Select the main class of your application. Right-click on it and select Debug As → Drools Application .
   • Alternatively, select Debug As → Debug Configuration to open a new dialog window for creating, managing and running debug configurations.
     Select the Drools Application item in the left tree and click the New launch configuration button (leftmost icon in the toolbar above the tree). This will create a new configuration with a number of the properties already filled in based on main class you selected in the beginning. All properties shown here are the same as any standard Java program.

   Note

   Remember to change the name of your debug configuration to something meaningful.
2. Click the Debug button on the bottom to start debugging your application.
3. After enabling the debugging, the application starts executing and will halt if any breakpoint is encountered. This can be a Drools rule breakpoint, or any other standard Java breakpoint. Whenever a Drools rule breakpoint is encountered, the corresponding .drl file is opened and the active line is highlighted. The Variables view also contains all rule parameters and their value. You can then use the default Java debug actions to decide what to do next (resume, terminate, step over, etc). The debug views can also be used to determine the contents of the working memory and agenda at that time as well (the current executing working memory is automatically shown).

• In Drools, the DSL configuration is stored in .dsl files. These can be created selecting File → New → Other → Drools → Domain Specific Language from the projects context menu.
  

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  Figure 5.1. The DSL editor

1. This wizard can be opened by double clicking some line in the table of language message mappings or by clicking the Edit button. You can edit the language expressions, rule mapping, objects and scopes of instance.
   

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   Figure 5.2. Editing options

2. To change the mapping a user should edit the appropriate options and finally click the OK button.

Procedure 5.1. Task

1. Click on the Add button and a dialog box will appear.
2. Enter the details of your language mapping wizard into the relevant fields.
   

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   Figure 5.3. Dialog box

1. Ruleflows can only be set by using the graphical flow editor which is part of the Drools plugin for Eclipse. Once you have set up a Drools project, you can start adding ruleflows. Add a ruleflow file (.rf) by clicking on the project and selecting File → New → Other... → Flow File.
   By default these ruleflow files (.rf) are opened in the graphical Flow editor.
2. The Flow editor consists of a palette, a canvas and an outline view. Select the element you would like to create in the palette and then add it to the canvas by clicking on the preferred location.
3. Clicking on the Select option in the palette and then on the element in your ruleflow allows you to view and set the properties of that element in the Properties view.
4. The Outline view is useful for complex schemata where not all nodes are seen at one time. Using the Outline view allows you to easily navigate between parts of a schema.