设计模式-策略模式

悠悠 2024-03-26 11:07 6阅读 0赞

1.  ## 简单策略模式 ##

假设业务：查询快递状态，给快递类型和快递单号。

### 1.1 策略分发类 ###

public interface Express{
        String selectExpressStatus(long expressNo);
    }

### 1.2 策略对外接收类 ###

public class ExpressStrategy{
        private Express express;
        public ExpressStrategy(Express express){
            this.express = express;
        }
        public String selectExpressstatus(long expressNo){
            return express.selectExpressStatus(expressNo);
        }
    }

#### 1.3 各种策略实现类 ####

public class ShunfengExpress implements Express{
        @0verride
        public String selectExpressStatus (long expressNo){
            // String status = shunfengMapper.selectById(expressNo).getResult();
            return "deliver express by Shunfeng";
        }
    }

public class YuantongExpress implements Express{
        @0verride
        public String selectExpressStatus (long expressNo）{
            // String status = yuantongMapper.selectById(expressNo).getResult();
            return "deliver express by Yuantong";
        }
    }

public class ZhongtongExpress implements Express{
        @Override
        public String selectExpressStatus (long expressNo){
        // String status = zhongtongHapper.selectById(expressNo).getResult();
        return "deliver express by Zhongtong";
        }
    }

### 1.4 测试 ###

public class ExpressTest {
        @Test
        public void selectExpressStatusTest(){
            Expressstrategy expressService = new ExpressStrategy(new ShunfengExpress());
            String status = expressService.selectExpressStatus(123456L);
            System.out.println(status);
        }
    }

### 1.5 测试结果 ###

为了安全就拍屏幕了

![d9558918a278d6c64ea993770c8fc5fa.png][]

## 2. Spring+策略模式+工厂模式 ##

### 2.1 策略分发类 ###

public interface ExpressStrategy{
        String selectExpressStatus(ExpressStrategyDTO dto);
    }

### 2.2 策略类型枚举 ###

code用于类型标识；className是Bean名称

@Getter
    public enum ExpressEnum {
        /**
         * sf
         */
        SHUNFENG("sf","shunfeng"),
        /**
         * yt
         */
        YUANTONG("yt","yuantong" ),
        /**
         * zt
         */
        ZHONGTONG("zt","zhongtong");
    
        private final String code;
    
        private final String className;
        
        ExpressEnum(String code,String className){
            this.code = code;
            this.className = className;
        }
    }

### 2.3 各种策略实现类 ###

@Service后面的内容对应上面枚举类的className

@Service ("shunfeng")
    public class ShunfengExpressStrategyImpl implements ExpressStrategy {
        @0verride
        public String selectExpressStatus(ExpressStrategyDT0 dto){
            // String status = shunfengMapper.selectById(dto.getExpressNo()).getResult();
            return "deliver express by Shunfeng";
        }
    }

@Service ("yuantong")
    public class YuantongExpressStrategyImpl implements ExpressStrategy {
        @0verride
        public String selectExpressStatus(ExpressStrategyDT0 dto){
            // String status = yuantongMapper.selectById(dto.getExpressNo()).getResult();
            return "deliver express by Yuantong";
        }
    }

@Service ("zhongtong")
    public class ZhongtongExpressStrategyImpl implements ExpressStrategy {
        @0verride
        public String selectExpressStatus(ExpressStrategyDT0 dto){
            // String status = zhongtongMapper.selectById(dto.getExpressNo()).getResult();
            return "deliver express by Zhongtong";
        }
    }

### 2.4 工厂类 ###

把map注入到Spring

> 这里工厂类的逻辑是利用了Spring容器的处理方式，如果有 **多种类同时实现了某个接口，那么可以使用Map集合接收**，Map对应的泛型，String是Bean名称，ExpressStrategy是每个具体实现类，这样我们就可以使用Bean类型去指定具体的策略类了，然后建立一个快递策略枚举去管理这些Bean名称。同时，也可以将Bean名称与客户端定义的类型进行关联。

@Component
    public class ExpressStrategyFactory {
        @Resource
        public Map<String,ExpressStrategy> strategywap = new HashMap<>();
    
        /**
         * 获取策略Bean
         *
         * @param expressEnum 快递策略枚举
         * @return Bean
         */
        public ExpressStrategy getStrategyBean(ExpressEnum expressEnum) {
            return strategyMap.get(expressEnum.getCode());
        }
    }

### 2.5 上下文类 ###

根据dto中的类型拿到具体策略类

@Component
    public class ExpressStrategyContext {
        @Autowired
        private ExpressStrategyFactory expressStrategyFactory;
    
        public String select(ExpressStrategyDT0 dto){
            ExpressEnum expressEnum =
                Arrays.stream( ExpressEnum.class.getEnumConstants())
                    .filter(e -> e.getCode( ).equals(dto.getExpressType())).findAny().get();
            ExpressStrategy expressStrategy = expressStrategyFactory.getStrategyBean(expressEnum);
            return expressStrategy.selectExpressStatus(dto);
        }
    }

### 2.6 传参dto ###

@Data
    public class ExpressStrategyDTO {
        /**
         * 快递类型
         */
        private String expressType;
        /**
         * 快递单号
         */
        private Long expressNo;
    }

### 2.7 测试 ###

@Runwith(SpringRunner.class)
    @SpringBootTest
    public class FactoryExpressTest {
        @Autowired
        private ExpressStrategyContext expressStrategyContext;
    
        @Test
        public void selectExpressStatusTest();
            ExpressStrategyDTO dto = new ExpressStrategyDTO();
            dto.setExpressType(ExpressEnum.SHUNFENG.getcode());
            dto.setExpressNo(123456L);
            string s = expressStrategyContext.select(dto);
            System.out.println(s);
        }
    }

![8fa4118ced61438d8e9b12109d5de812.png][]

### 2.8 扩展 ###

虽然这个和策略模式没关系，但也是对Bean重命名的一种场景，就放到扩展了。

只需要保留上面的“2.3 各种策略实现类”，我这里把bean重命名了一下，改为：

@Service("shunfengExprossStrategy")、@Service("yuantongExprossStrategy")、@Service("zhongtongExprossStrategy")

#### 2.8.1 全部分发场景接口 ####

public interface ExpressService{
        String selectExpressStatus(ExpressStrategyDTO dto);
    }

#### 2.8.2 全部分发场景实现类 ####

@Service(value = "ExpressService")
    public class ExpressserviceImpl implements ExpressService {
    
        private ShunfengExpressstrategyImpl shunfengExpressStrategy;
    
        private YuantongExpressStrategyImpl yuantongExpressStrategy;
    
        private ZhongtongExpressStrategyImpl zhongtongExpjessstrategy;
    
        public ExpressServiceImpl(
    @Qualifier("shunfengExpressStrategy") ShunfengExpressstrategyImpl shunfengExpressStrategy,
    @Qualifier("yuantongExpressStrategy") YuantongExpressStrategyImpl yuantongExpressStrategy,
    @Qualifier("zhongtongExpressStrategy") ZhongtongExpressStrategyImpl zhongtongExpressStrategy){
            this.shunfengExpressstrategy = shunfengExpressStrategy;
            this.yuantongExpressstrategy = yuantongExpressStrategy;
            this.zhongtongExpressstrategy = zhongtongExpressStrategy;
        }
    
        @Override
        public String selectExpressStatus(ExpressStrategyDT0 dto) {
            return shunfengExpressStrategy.selectExpressStatus(dto)
                +yuantongExpressStrategy.selectExpressStatus(dto)
                +zhongtongExpressStrategy.selectExpressStatus(dto);
        }
    }

#### 2.8.3 测试 ####

@Runwith(SpringRunner.class)
    @SpringBootTest
    public class FactoryExpressTest {
        @Autowired
        private ExpressStrategyContext expressStrategyContext;
    
        @Autowired
        private ExpressService expressService;
    
        @Test
        public void selectExpressStatusTest();
    //        ExpressStrategyDTO dto = new ExpressStrategyDTO();
    //        dto.setExpressType(ExpressEnum.SHUNFENG.getcode());
    //        dto.setExpressNo(123456L);
    //        string s = expressStrategyContext.select(dto);
    //        System.out.println(s);
            
            String s1 = expressService.selectExpressStatus(new ExpressStrategyDTO());
            System.out.println(s1);
        }
    }

![1b304ec809a57d63804ec786fe6889de.png][]

## 3. Spring+策略模式+工厂模式+自定义注解 ##

个人浅显的见解：这种写法比第二种更优雅一些，不用注入map。

### 3.1 策略分发类 ###

public interface ExpressStrategy{
        String selectExpressStatus(ExpressStrategyDTO dto);
    }

### 3.2 策略类型枚举 ###

这里直接用属性的.name()了，没啥区别

@Getter
    public enum ExpressEnum {
        /**
         * sf
         */
        SHUNFENG,
        /**
         * yt
         */
        YUANTONG,
        /**
         * zt
         */
        ZHONGTONG;
    }

### 3.3 自定义注解类 ###

@Documented
    @Target
    @Retention
    @Component
    public @interface ExpressStrategyAnnotation {
        /** 快递类型 */
        ExpressEnum expressType();
    }

### 3.4 工厂类 ###

@Component
    public class ExpressStrategyFactory implements ApplicationListener<ContextRefreshedEvent> {
    
        /** 工厂map */
        private static final Map<String, ExpressStrategy> STRATEGY_MAP = new HashMap<>();
    
        /**
         * 获取@ExpressStrategyAnnotation标记过的类
         */
        @Override
        public void onApplicationEvent(ContextRefreshEvent event) {
            ApplicationContext applicationContext = event.getApplicationContext();
            Map<String, Object> beansWithAnnotation = applicationContext.getBeansWithAnnotation(ExpressStrategyAnnotation.class);
            if (beansWithAnnotation.isEmpty()) {
                return;
            }
            for (Map.Entry<String, Object> next : beansWithAnnotation.entrySet()) {
                Object bean = next.getValue();
                ExpressStrategyAnnotation annotation = AnnotationUtils.findAnnotaion(AopUtils.getTargetClass(bean), ExpressStrategyAnnotation.class);
                if (annotation != null) {
                    ExpressEnum expressType = annotation.expressType();
                    if (bean instanceof ExpressStrategy) {
                        STRATEGY_MAP.put(expressType.name(), (ExpressStrategy) bean);
                    }
                }
            }
        }
    
        /** 获取快递策略对象 */
        public ExpressStrategy getStrategyByName(String name) {
            return STRATEGY_MAP.get(name);
        }
    }

### 3.5 传参dto ###

@Data
    public class ExpressStrategyDTO {
        /**
         * 快递类型
         */
        private String expressType;
        /**
         * 快递单号
         */
        private Long expressNo;
    }

### 3.6 业务接口类 ###

public interface ExpressService{
        String selectExpressStatus(ExpressStrategyDTO dto);
    }

### 3.7 业务接口实现类 ###

@Service
    public class ExpressserviceImpl implements ExpressService {
    
        @Autowired
        private ExpressStrategyFactory expressStrategyFactory;
    
        @Override
        public String selectExpressStatus(ExpressStrategyDT0 dto) {
            ExpressStrategy strategy = expressStrategyFactory.getStrategyByName(dto.getExpressType)
            return strategy.
        }
    }

### 3.8 各种业务策略实现类 ###

@Service
    @ExpressStrategyAnnotation(expressType = ExpressEnum.SHUNFENG)
    public class ShunfengExpressStrategyImpl implements ExpressStrategy {
        @0verride
        public String selectExpressStatus(ExpressStrategyDT0 dto){
            // String status = shunfengMapper.selectById(dto.getExpressNo()).getResult();
            return "deliver express by Shunfeng";
        }
    }

@Service
    @ExpressStrategyAnnotation(expressType = ExpressEnum.YUANTONG)
    public class YuantongExpressStrategyImpl implements ExpressStrategy {
        @0verride
        public String selectExpressStatus(ExpressStrategyDT0 dto){
            // String status = yuantongMapper.selectById(dto.getExpressNo()).getResult();
            return "deliver express by Yuantong";
        }
    }

@Service
    @ExpressStrategyAnnotation(expressType = ExpressEnum.ZHONGTONG)
    public class ZhongtongExpressStrategyImpl implements ExpressStrategy {
        @0verride
        public String selectExpressStatus(ExpressStrategyDT0 dto){
            // String status = zhongtongMapper.selectById(dto.getExpressNo()).getResult();
            return "deliver express by Zhongtong";
        }
    }

### 3.9 测试 ###

@Runwith(SpringRunner.class)
    @SpringBootTest
    public class AnnotationStrategyTest {
        @Autowired
        private ExpressService expressService;
    
        @Test
        public void selectExpressStatusTest();
            ExpressStrategyDTO dto = new ExpressStrategyDTO();
            dto.setExpressType(ExpressEnum.SHUNFENG.getcode());
            dto.setExpressNo(123456L);
            string s = expressService.selectExpressStatus(dto);
            System.out.println(s);
        }
    }

![8fa4118ced61438d8e9b12109d5de812.png][]

[d9558918a278d6c64ea993770c8fc5fa.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/5cc5eadbe8df44628f5f1b32b99e0e66.png
[8fa4118ced61438d8e9b12109d5de812.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/2d04e82976f14b7baeca64616b0597a8.png
[1b304ec809a57d63804ec786fe6889de.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/fe76f953fff04b58bf9fdab7b61c83a2.png