Design and Implementation of a Java Rule Engine with AND/OR Logic

The article introduces a rule engine refactoring scenario where existing trial‑user application rules need to be extended, highlighting the need for short‑circuit evaluation and maintainable logic.

if (是否海外用户) {
    return false;
}

if (刷单用户) {
    return false;
}

if (未付费用户 && 不再服务时段) {
    return false;
}

if (转介绍用户 || 付费用户 || 内推用户) {
    return true;
}

To address this, a rule executor is designed with a V1 version that separates rule abstraction, templates, and concrete implementations. The core abstractions include a RuleDto data class, a BaseRule interface, and an AbstractRule class that handles conversion and delegation.

// Business data
@Data
public class RuleDto {
    private String address;
    private int age;
}

// Rule abstraction
public interface BaseRule {
    boolean execute(RuleDto dto);
}

// Rule template
public abstract class AbstractRule implements BaseRule {
    protected <T> T convert(RuleDto dto) {
        return (T) dto;
    }
    @Override
    public boolean execute(RuleDto dto) {
        return executeRule(convert(dto));
    }
    protected <T> boolean executeRule(T t) {
        return true;
    }
}

// Concrete rule – example 1
public class AddressRule extends AbstractRule {
    @Override
    public boolean execute(RuleDto dto) {
        System.out.println("AddressRule invoke!");
        if (dto.getAddress().startsWith(MATCH_ADDRESS_START)) {
            return true;
        }
        return false;
    }
}

// Concrete rule – example 2
public class NationalityRule extends AbstractRule {
    @Override
    protected <T> T convert(RuleDto dto) {
        NationalityRuleDto nationalityRuleDto = new NationalityRuleDto();
        if (dto.getAddress().startsWith(MATCH_ADDRESS_START)) {
            nationalityRuleDto.setNationality(MATCH_NATIONALITY_START);
        }
        return (T) nationalityRuleDto;
    }
    @Override
    protected <T> boolean executeRule(T t) {
        System.out.println("NationalityRule invoke!");
        NationalityRuleDto nationalityRuleDto = (NationalityRuleDto) t;
        if (nationalityRuleDto.getNationality().startsWith(MATCH_NATIONALITY_START)) {
            return true;
        }
        return false;
    }
}

// Constants
public class RuleConstant {
    public static final String MATCH_ADDRESS_START = "北京";
    public static final String MATCH_NATIONALITY_START = "中国";
}

The executor is built with a fluent API that stores rule lists under AND (synchronous) or OR (short‑circuit) keys and iterates through them during execution.

public class RuleService {
    private Map<Integer, List<BaseRule>> hashMap = new HashMap<>();
    private static final int AND = 1;
    private static final int OR = 0;

    public static RuleService create() {
        return new RuleService();
    }
    public RuleService and(List<BaseRule> ruleList) {
        hashMap.put(AND, ruleList);
        return this;
    }
    public RuleService or(List<BaseRule> ruleList) {
        hashMap.put(OR, ruleList);
        return this;
    }
    public boolean execute(RuleDto dto) {
        for (Map.Entry<Integer, List<BaseRule>> item : hashMap.entrySet()) {
            List<BaseRule> ruleList = item.getValue();
            switch (item.getKey()) {
                case AND:
                    System.out.println("execute key = " + 1);
                    if (!and(dto, ruleList)) {
                        return false;
                    }
                    break;
                case OR:
                    System.out.println("execute key = " + 0);
                    if (!or(dto, ruleList)) {
                        return false;
                    }
                    break;
                default:
                    break;
            }
        }
        return true;
    }
    private boolean and(RuleDto dto, List<BaseRule> ruleList) {
        for (BaseRule rule : ruleList) {
            boolean execute = rule.execute(dto);
            if (!execute) {
                return false;
            }
        }
        return true;
    }
    private boolean or(RuleDto dto, List<BaseRule> ruleList) {
        for (BaseRule rule : ruleList) {
            boolean execute = rule.execute(dto);
            if (execute) {
                return true;
            }
        }
        return false;
    }
}

A test class demonstrates how to instantiate concrete rules, create a RuleDto with sample data, and execute the composed rule chain using the fluent API.

public class RuleServiceTest {
    @org.junit.Test
    public void execute() {
        // Define rules
        AgeRule ageRule = new AgeRule();
        NameRule nameRule = new NameRule();
        NationalityRule nationalityRule = new NationalityRule();
        AddressRule addressRule = new AddressRule();
        SubjectRule subjectRule = new SubjectRule();

        // Build DTO
        RuleDto dto = new RuleDto();
        dto.setAge(5);
        dto.setName("张三");
        dto.setAddress("北京");
        dto.setSubject("数学");

        // Execute with fluent builder
        boolean ruleResult = RuleService
                .create()
                .and(Arrays.asList(nationalityRule, nameRule, addressRule))
                .or(Arrays.asList(ageRule, subjectRule))
                .execute(dto);
        System.out.println("this student rule execute result :" + ruleResult);
    }
}

The conclusion lists the advantages of this approach—simplicity, modularity, and extensibility via the convert method—and its drawbacks, mainly the tight coupling to a shared DTO, suggesting that data should be prepared in advance for better decoupling.