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 accounts = new ArrayList();
//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();
}