Chapter 5. Rules

• In JBoss Rules, 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.
  

  Figure 5.1. The DSL editor

Procedure 5.1. Task

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

   Figure 5.2. Dialog box

1. This wizard can be opened by double-clicking a line in the table of language message mappings or by clicking the Edit button.
   

   Figure 5.3. Editing options

2. To change the mapping, edit the appropriate options and click the OK button.

1. Ruleflows can only be set by using the graphical flow editor which is part of the JBoss Rules plug-in for JBoss Developer Studio. Once you have set up a JBoss Rules 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.

1. To create breakpoints in the Package Explorer view or Navigator view of the JBoss Rules 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

     Rule breakpoints can only be created in the consequence of a rule. Double-clicking on a line where no breakpoint is allowed does nothing.
   • Right-click the ruler. Select the Toggle Breakpoint action in the context menu. Choosing this action adds 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. JBoss Rules breakpoints are only enabled if you debug your application as a JBoss Rules 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 JBoss Rules Application .
   • Alternatively, select Debug As Debug Configuration to open a new dialog window for creating, managing and running debug configurations.
     Select the JBoss Rules Application item in the left tree and click the New launch configuration button (leftmost icon in the toolbar above the tree). This creates 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 halts if any breakpoint is encountered. This can be a JBoss Rules rule breakpoint, or any other standard Java breakpoint. Whenever a JBoss Rules 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).