Drools学习笔记2—Conditions / LHS 匹配模式&条件元素
- Rule的LHS由条件元素（Conditional Elements—CE）和匹配模式（Patterns）组成
- Patterns被用来指示出fact的字段约束
- 每个约束必须为true才能让RHS的actions fire
测试代码，测试用获取KnowledgeBase方法：
/** * 获取KnowledgeBase * @return * @throws Exception */ private static KnowledgeBase readKnowledgeBase(String ruleName) throws Exception { KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource(ruleName, RuleTest.class), ResourceType.DRL); KnowledgeBuilderErrors errors = kbuilder.getErrors(); if (errors.size() > 0) { for (KnowledgeBuilderError error: errors) { System.err.println(error); } throw new IllegalArgumentException("Could not parse knowledge."); } KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages(kbuilder.getKnowledgePackages()); return kbase; }
使用到的fact对象
package com.bean; import java.util.ArrayList; import java.util.List; public class Customer { private String name; private String Company; private Integer age; private String gender; private String city; private List<Account> accounts = new ArrayList<Account>(); //省略set、get、toString方法 }
package com.bean; public class Account { private String name; private String status; private int num; }
匹配模式（Patterns）
- 没有字段约束的Pattern
Person()
/**规则文件.drl**/ package com.sample import com.bean.Customer; rule "No args" when Customer() then System.out.println( "no massage" ); end /**java测试代码，采用Junit测试**/ /** * 没有字段约束的Pattern * @throws Exception */ @Test public void testNoParam() throws Exception { KnowledgeBase kbase = readKnowledgeBase("NoParam.drl"); StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test"); Customer customer = new Customer(); ksession.insert(customer); ksession.fireAllRules(); logger.close(); }
- 有文本字段约束的Pattern
Person( name == “bob” )
/**规则文件.drl**/ package com.sample import com.bean.Customer; rule "Binding Param" when Customer($name:name=="七夜雪") then System.out.println( "Binding Param Rule and Customer is " + $name ); end /**java测试代码，采用Junit测试**/ /** * 有文本字段约束的Pattern * @throws Exception */ Customer customer = new Customer(); customer.setName("七夜雪"); ksession.insert(customer); ksession.fireAllRules();
- 字段绑定的Pattern
Person( $name : name == “bob” )
变量名称可以是任何合法的java变量，$是可选的，可由于区分字段和变量
//drl规则文件 package com.sample import com.bean.Customer; rule "Binding Fact" when $customer:Customer(name=="七夜雪") then System.out.println( "Binding Fact Rule ：" + $customer ); end
/** * java测试方法 * 字段绑定的Pattern * @throws Exception */ @Test public void testBindingParam() throws Exception { KnowledgeBase kbase = readKnowledgeBase("HaveParam.drl"); StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test"); Customer customer = new Customer(); customer.setName("七夜雪"); ksession.insert(customer); ksession.fireAllRules(); logger.close(); }
- Fact绑定的Pattern
$bob : Person( name == “bob” )字段绑定的Pattern
//drl文件 package com.sample import com.bean.Customer; rule "Binding Fact" when $customer:Customer(name=="七夜雪") //绑定变量$customer变量名
then
System.out.println( "Binding Fact Rule ：" + $customer );
end
/** * Fact绑定的Pattern * @throws Exception */ @Test public void testBindingFact() throws Exception { KnowledgeBase kbase = readKnowledgeBase("BindingFact.drl"); StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test"); Customer customer = new Customer(); customer.setName("七夜雪"); customer.setCompany("听雪楼"); ksession.insert(customer); ksession.fireAllRules(); logger.close(); }
- 变量约束的Pattern
Person( name == $name )
package com.sample import com.bean.Customer; import com.bean.Account; rule "Param Limit" when Customer($name:name=="七夜雪") Account(name==$name) then System.out.println( "Param Limit Rule" ); end
/** * 变量约束的Pattern * @throws Exception */ @Test public void testParamLimit() throws Exception { KnowledgeBase kbase = readKnowledgeBase("ParamLimit.drl"); StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test"); Customer customer = new Customer(); customer.setName("七夜雪"); customer.setCompany("听雪楼"); Account account = new Account(); account.setName("七夜雪"); ksession.insert(customer); ksession.insert(account); ksession.fireAllRules(); logger.close(); }
条件元素（Conditional Elements）
and
- 对于顶级（非嵌套）patterns是隐式成立的
- 可以显示add
- 使用关键字’and’（不推荐使用 &&）
package com.sample import com.bean.Customer; import com.bean.Account; rule "And" when Customer(name=="七夜雪" ) and Account(name=="七夜雪") then System.out.println( "And Rule" ); end rule "Default" when Customer(name=="七夜雪" ) Account(name=="七夜雪") then System.out.println( "default is and" ); end rule "&&" when Customer(name=="七夜雪" ) && Account(name=="七夜雪") then System.out.println( "And && Rule" ); end
/**
* 条件元素 and、&&，不写默认为and
* @throws Exception
*/
@Test
public void testAndRule() throws Exception {
KnowledgeBase kbase = readKnowledgeBase("And.drl");
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test");
Customer customer = new Customer();
customer.setName("七夜雪");
Account account = new Account();
account.setName("七夜雪");
ksession.insert(customer);
ksession.insert(account);
ksession.fireAllRules();
logger.close();
}
or
- 列能被显式or
- 使用关键字’or’（不推荐使用 ||）
package com.sample
import com.bean.Customer;
import com.bean.Account;
rule "Or"
when
Customer(name=="七夜雪" ) or
Account(name=="七夜雪")
then
System.out.println( "And Rule" );
end
/**
* 条件元素 or，不写默认为and
* 注：每个条件符合，then的内容都会执行一次
* @throws Exception
*/
@Test
public void testOrRule() throws Exception {
KnowledgeBase kbase = readKnowledgeBase("Or.drl");
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test");
Customer customer = new Customer();
customer.setName("七夜雪");
Account account = new Account();
account.setName("七夜雪");
ksession.insert(customer);
ksession.insert(account);
ksession.fireAllRules();
logger.close();
}
exists 、Not
package com.sample
import com.bean.Customer;
import com.bean.Account;
rule "Exists"
when
exists Customer() //工作空间存在customer对象
then
System.out.println( "Customer Exists" );
end
rule "Not"
when
not Account() //工作空间不存在Account对象
then
System.out.println( "Account Not Exists" );
end
/**
* 条件元素 exist、not，两个刚好相反
*
* @throws Exception
*/
@Test
public void testExistsAndNotRule() throws Exception {
KnowledgeBase kbase = readKnowledgeBase("From.drl");
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test");
Customer customer = new Customer();
Account account = new Account();
account.setName("七夜雪");
Account account1 = new Account();
account.setName("碧落");
customer.getAccounts().add(account);
customer.getAccounts().add(account1);
ksession.insert(customer);
ksession.fireAllRules();
logger.close();
}
from
package com.sample import com.bean.Customer; import com.bean.Account; rule "from" when $customer:Customer( )
//customer中的accounts列表中存在name="碧落"的account对象 Account(name=="碧落") from $customer.accounts then System.out.println( "from element test success" ); end
/** * 条件元素 from * * @throws Exception */ @Test public void testFromRule() throws Exception { KnowledgeBase kbase = readKnowledgeBase("From.drl"); StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test"); Customer customer = new Customer(); ksession.insert(customer); ksession.fireAllRules(); logger.close(); }
collect
package com.sample import com.bean.Customer; import com.bean.Account; import java.util.ArrayList; rule "collect" when $customer:Customer( )
//列表中status="Y"的Account对象大于等于4个， $accounts:ArrayList(size >= 4) from collect (Account(status == "Y")) then System.out.println( "collect element test success" ); end
/** * 条件元素 collect * * @throws Exception */ @Test public void testCollectRule() throws Exception { KnowledgeBase kbase = readKnowledgeBase("Collect.drl"); StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test"); Customer customer = new Customer(); Account account1 = new Account(); account1.setStatus("Y"); Account account2 = new Account(); account2.setStatus("Y"); Account account3= new Account(); account3.setStatus("Y"); Account account4 = new Account(); account4.setStatus("Y"); ksession.insert(customer); ksession.insert(account1); ksession.insert(account2); ksession.insert(account3); ksession.insert(account4); ksession.fireAllRules(); logger.close(); }
Accumulate 聚合函数
package com.sample import com.bean.Customer; import com.bean.Account; rule "accumulate" when
//工作空间中，account对象的num属性之和大于400时符合规则 $total:Number( intValue > 400) from accumulate (Account($num:num),sum($num)) then System.out.println( "accumulate element test success" ); end
/** * 条件元素 Accumulate * 聚合函数 * @throws Exception */ @Test public void testAccumulateRule() throws Exception { KnowledgeBase kbase = readKnowledgeBase("Accumulate.drl"); StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession(); KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test"); Customer customer = new Customer(); Account account1 = new Account(); account1.setNum(100); Account account2 = new Account(); account2.setNum(100); Account account3= new Account(); account3.setNum(100); Account account4 = new Account(); account4.setNum(200); ksession.insert(customer); ksession.insert(account1); ksession.insert(account2); ksession.insert(account3); ksession.insert(account4); ksession.fireAllRules(); logger.close(); }
