JAVA规则引擎[Drools]--实例篇
随着互联网应用的飞速发展，各种业务需求也应运而生，对于不断变更和革新的业务规则而言，项目的开发就很有必要把规则部分独立提取出来，此时Drools的价值就得到了体现。废话不多说，看一个简单的例子。
这里举一个手机话费的例子。
一、定义规则：
首先要分析自己的业务逻辑，根据业务而制定出不同的规则，这里我们假设有3个规则。
1、对于新开户的手机用户送20元话费。
2、在2014年10月到12期间充值的用户，不论金额多少充值满3次就赠送5元话费。
3、当月充值金额达到100以上，每达到一次赠送话费10元。
二、创建Fact对象：
分析这些规则，并把他们抽象成一个Fact对象。
package com.core.drools;
import java.util.UUID;
/**
* EntityRule-Model
* @author Candy
*
*/
public class EntityRule {
private String username;
/** Whether for new account. */
private boolean account;
/** The number of add. */
private int addtime;
/** The sum of the current account. */
private double currentmoney;
/** The totail amount added. */
private double totailaddmoney;
/**
* Record the serial number of the operation.
* @param username
* @param currentmoney
*/
public void getSerialnumber(String username,double currentmoney){
System.out.println("Account："+username+" Balance：￥"+currentmoney);
System.out.println("Serial Number："+UUID.randomUUID().toString());
}
三、定义规则引擎：
业务和规则都整理清楚了我们就可以开始规则引擎的核心部分啦，这里我定义的是接口和实现类。
package com.core.drools;
/**
* RuleEngine-Interface
* @author Candy
*
*/
public interface RuleEngine {
/**
* Initializes the rules engine.
*/
public void init();
/**
* Refresh the rules engine.
*/
public void refresh();
/**
* Execute the rules engine.
*/
public void execute(final EntityRule entityRule);
}
package com.core.drools;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
import java.util.List;
import org.drools.RuleBase;
import org.drools.StatefulSession;
import org.drools.compiler.DroolsParserException;
import org.drools.compiler.PackageBuilder;
import org.drools.rule.Package;
import org.drools.spi.Activation;
/**
* RuleEngine-Implements
* @author Candy
*
*/
public class RuleEngineImpl implements RuleEngine{
private RuleBase ruleBase;
/*
* (non-Javadoc)
* @see com.core.drools.RuleEngine#init()
*/
@Override
public void init() {
/** Sets the system time format. */
System.setProperty("drools.dateformat", "yyyy-MM-dd HH:mm:ss");
/** Get the base factory. */
ruleBase =SingleRuleFactory.getRuleBase();
try {
/** Get the rule files has bean read. */
PackageBuilder backageBuilder = getPackageBuilderFile();
/** Add the package to the 'RuleBase'. */
ruleBase.addPackages(backageBuilder.getPackages());
} catch (DroolsParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
/*
* (non-Javadoc)
* @see com.core.drools.RuleEngine#refresh()
*/
@Override
public void refresh() {
ruleBase = SingleRuleFactory.getRuleBase();
Package[] packages = ruleBase.getPackages();
for(Package items :packages){
ruleBase.removePackage(items.getName());
}
init();
}
/*
* (non-Javadoc)
* @see com.core.drools.RuleEngine#execute(com.core.drools.EntityRule)
*/
@Override
public void execute(final EntityRule entityRule) {
if(null == ruleBase.getPackages() || 0 == ruleBase.getPackages().length) {
return;
}
StatefulSession statefulSession = ruleBase.newStatefulSession();
statefulSession.insert(entityRule);
statefulSession.fireAllRules(new org.drools.spi.AgendaFilter() {
public boolean accept(Activation activation) {
return !activation.getRule().getName().contains("_test");
}
});
statefulSession.dispose();
}
/**
* Read the rule files.
* @return
* @throws Exception
*/
private PackageBuilder getPackageBuilderFile()throws Exception {
/** Get the rule files. */
List<String> drlFilePath = getRuleFile();
/** Sets the file to 'readers'. */
List<Reader> readers = loadRuleFile(drlFilePath);
/** To create the 'backageBuilder'. */
PackageBuilder backageBuilder = new PackageBuilder();
for (Reader r : readers) {
backageBuilder.addPackageFromDrl(r);
}
/** Check if the script has a problem. */
if(backageBuilder.hasErrors()) {
throw new Exception(backageBuilder.getErrors().toString());
}
return backageBuilder;
}
/**
* Load the script files.
* @param drlFilePath
* @return
* @throws FileNotFoundException
*/
private List<Reader> loadRuleFile(List<String> drlFilePath)
throws FileNotFoundException {
if (null == drlFilePath || 0 == drlFilePath.size()) {
return null;
}
List<Reader> readers = new ArrayList<Reader>();
for (String ruleFilePath : drlFilePath) {
readers.add(new FileReader(new File(ruleFilePath)));
}
return readers;
}
/**
* Get the rule files.
* @return
*/
private List<String> getRuleFile(){
List<String> drlFilePath = new ArrayList<String>();
String path="D:/utils/my/DroolsProject/src/com/core/drools/drools_rule.drl";
drlFilePath.add(path);
return drlFilePath;
}
}
这里定义一个单例的RuleBase工厂类。
package com.core.drools;
import org.drools.RuleBase;
import org.drools.RuleBaseFactory;
/**
* To create a singleton factory.
* @author Candy
*
*/
public class SingleRuleFactory {
private static RuleBase ruleBase;
/**
* Get the base factory.
* @return
*/
public static RuleBase getRuleBase(){
return null != ruleBase ? ruleBase : RuleBaseFactory.newRuleBase();
}
}
四、编写规则文件：
规则文件可以根据自己的业务需求定义多个文件，这里我只定义了一个。
package com.core.drools
import com.core.drools.EntityRule;
rule accountEntity
//One
salience 100
lock-on-active true
when
$entityRule : EntityRule(account == true)
then
System.out.println("The new account:Present ￥20.0");
$entityRule.setCurrentmoney($entityRule.getCurrentmoney()+20);
$entityRule.getSerialnumber($entityRule.getUsername(),$entityRule.getCurrentmoney());
System.out.println("--------------------------------------------------");
end
rule billEntity
//two
salience 99
lock-on-active true
date-effective "2014-010-01 00:00:00"
date-expires "2014-012-31 23:59:59"
when
$entityRule : EntityRule(addtime >= 3)
then
System.out.println("Prepaid phone number reach "+$entityRule.getAddtime()
+" times:Present ￥"+$entityRule.getAddtime()/3*5);
$entityRule.setCurrentmoney($entityRule.getCurrentmoney()+$entityRule.getAddtime()/3*5);
$entityRule.getSerialnumber($entityRule.getUsername(),$entityRule.getCurrentmoney());
System.out.println("--------------------------------------------------");
end
rule addMoney
//Three
salience 98
lock-on-active true
when
$entityRule : EntityRule(totailaddmoney >= 100)
then
System.out.println("The account for the month top-up totail amount is "
+$entityRule.getTotailaddmoney()+":Present ￥"+(int)$entityRule.getTotailaddmoney()/100*10);
$entityRule.setCurrentmoney($entityRule.getCurrentmoney()
+(int)$entityRule.getTotailaddmoney()/100 * 10);
$entityRule.getSerialnumber($entityRule.getUsername(),$entityRule.getCurrentmoney());
end
五、测试引擎：
package com.test;
import java.io.IOException;
import com.core.drools.EntityRule;
import com.core.drools.RuleEngine;
import com.core.drools.RuleEngineImpl;
/**
* Test Drools
* @author Candy
*
*/
public class DroolsTest {
public static void main(String[] args) throws IOException {
RuleEngine engineImpl =new RuleEngineImpl();
engineImpl.init();
final EntityRule entityRule= new EntityRule();
entityRule.setCurrentmoney(350d);
entityRule.setUsername("Candy");
entityRule.setAccount(true);
entityRule.setTotailaddmoney(350d);
entityRule.setAddtime(7);
engineImpl.execute(entityRule);
}
}
六、测试结果：
The new account:Present ￥20.0
Account：Candy Balance：￥370.0
Serial Number：0fd98593-caa2-444d-a4ff-b4001cfb3260
------------------------------------------------------------------------------
Prepaid phone number reach 7 times:Present ￥10
Account：Candy Balance：￥380.0
Serial Number：a118b211-c28e-4035-aa60-2f417f62b2f3
------------------------------------------------------------------------------
The account for the month top-up totail amount is 350.0: Present ￥30
Account：Candy Balance：￥410.0
Serial Number：2bfc02c2-267f-47a2-9cda-5a4196e2b7cf