Drools 官方例子代码解读（一）：高尔夫球员位置问题

Drools 官方例子代码解读（一）：高尔夫球员位置问题

从本篇开始，逐步的研读下Drools中自带的一些经典的例子。今天先来看下高尔夫球员位置问题：

已知有四个高尔夫球员，他们的名字是Fred,Joe,Bob,Tom;今天他们分别穿着红色，蓝色，橙色，以及格子衣服，并且他们按照从左往右的顺序站成一排。我们将最左边的位置定为1，最右边的位置定为4，中间依次是2,3位置。现在我们了解的情况是： 1.高尔夫球员Fred,目前不知道他的位置和衣服颜色 2.Fred右边紧挨着的球员穿蓝色衣服 3.Joe排在第2个位置 4.Bob穿着格子短裤 5.Tom没有排在第1位或第4位，也没有穿橙色衣服请问,这四名球员的位置和衣服颜色。 

        

 

因为Drools规则引擎的强大，我们只需要把已知条件写成规则，然后由规则引擎去筛选符合条件的结果。

 

代码清单：

GolfExample.java

package org.drools.examples;import org.drools.KnowledgeBase;import org.drools.KnowledgeBaseFactory;import org.drools.builder.KnowledgeBuilder;import org.drools.builder.KnowledgeBuilderFactory;import org.drools.builder.ResourceType;import org.drools.io.ResourceFactory;import org.drools.runtime.StatefulKnowledgeSession;public class GolfingExample {/** * @param args */public static void main(final String[] args) throws Exception {final KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();kbuilder.add(ResourceFactory.newClassPathResource("golf.drl",GolfingExample.class), ResourceType.DRL);final KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());final StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();String[] names = new String[] { "Fred", "Joe", "Bob", "Tom" };String[] colors = new String[] { "red", "blue", "plaid", "orange" };int[] positions = new int[] { 1, 2, 3, 4 };for (int n = 0; n < names.length; n++) {for (int c = 0; c < colors.length; c++) {for (int p = 0; p < positions.length; p++) {ksession.insert(new Golfer(names[n], colors[c],positions[p]));}}}ksession.fireAllRules();ksession.dispose();}public static class Golfer {private String name;private String color;private int position;public Golfer() {}public Golfer(String name, String color, int position) {super();this.name = name;this.color = color;this.position = position;}/** * @return the color */public String getColor() {return this.color;}/** * @return the name */public String getName() {return this.name;}/** * @return the name */public int getPosition() {return this.position;}}} 

golf.drl

package org.drools.examples;dialect "mvel"import org.drools.examples.GolfingExample.Golfer;rule "find solution" when //Fred的位置和颜色未知 $fred : Golfer( name == "Fred" ) // Joe 排在第2个位置,并且他的位置和颜色与Fred的位置不相同 $joe : Golfer( name == "Joe", position == 2, position != $fred.position, color != $fred.color ) // Bob穿着格子短裤,位置和颜色与Fred和Joe都不相同 $bob : Golfer( name == "Bob", position != $fred.position, position != $joe.position, color == "plaid", color != $fred.color, color != $joe.color ) //Tom的位置既不在第1位,也不在第4位,并且没有穿橙色衣服 $tom : Golfer( name == "Tom", position != 1, position != 4, position != $fred.position, position != $joe.position, position != $bob.position, color != "orange", //color != "blue", color != $fred.color, color != $joe.color, color != $bob.color ) //Fred右边紧挨着的球员穿蓝色衣服 Golfer( position == ( $fred.position + 1 ), color == "blue", this in ( $joe, $bob, $tom ) )then System.out.println( "Fred " + $fred.getPosition() + " " + $fred.getColor() ); System.out.println( "Joe " + $joe.getPosition() + " " + $joe.getColor() ); System.out.println( "Bob " + $bob.getPosition() + " " + $bob.getColor() ); System.out.println( "Tom " + $tom.getPosition() + " " + $tom.getColor() );end 

运行结果：

Fred 1 orangeJoe 2 blueBob 4 plaidTom 3 red