经典设计模式之策略模式【如何重构聚合支付平台，对接【支付宝，微信，银联支付】】

梦里梦外; 2022-01-22 04:41 324阅读 0赞

# **写在前面：设计模式源于生活，而又高于生活！** #

**为什么要使用设计模式重构代码**

使用设计模式可以重构整体架构代码、提高代码复用性、扩展性、减少代码冗余问题。
    
    Java高级工程师装逼的技能！

**什么是策略模式**

策略模式是对算法的包装，是把使用算法的责任和算法本身分割开来，委派给不同的对象管理，最终可以实现**解决多重if判断问题**。

1.环境（Context）角色：持有一个Strategy的引用
    2.抽象策略（Strategy）角色：这是一个抽象角色，通常由一个接口或抽象类实现。此角色给出所有的具体策略类所需的接口。
    3.具体策略（ContextStrategy）角色：包装了相关的算法或行为。

**策略模式应用场景**

比如搭建聚合支付平台的时候，这时候需要对接很多第三方支付接口，比如支付宝、微信支付、银联支付等。通过传统if代码判断的，后期的维护性非常差！

public  String toPayHtml2(String payCode){
        if(payCode.equals("ali_pay")){
            return  "调用支付宝接口...";
        }
        if(payCode.equals("union_pay")){
            return  "调用银联支付接口";
        }
        if(payCode.equals("weChat_pay")){
            return  "调用微信支付接口...";
        }
        return  "未找到该接口...";
    }

这时候可以通过策略模式解决多重if判断问题。

**版权[@须臾之余][Link 1]**[https://my.oschina.net/u/3995125][Link 1]

## **策略模式架构图** ##

**![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE0MTg1MzA_size_16_color_FFFFFF_t_70][]**

## **策略模式环境搭建** ##

**Maven依赖信息**

<parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.1.RELEASE</version>
        </parent>
        <dependencies>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.16.10</version>
            </dependency>
            <dependency>
                <groupId>commons-lang</groupId>
                <artifactId>commons-lang</artifactId>
                <version>2.6</version>
            </dependency>
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>1.1.1</version>
            </dependency>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
            </dependency>
        </dependencies>

**PayStrategy(抽象角色)**

/**
     * @title: PayStrategy  共同算法定义的骨架
     */
    public interface PayStrategy {
        /**
         *  策略模式共同算法的骨架
         */
        String toPayHtml();
    }

**ConcreteStrategy (具体实现角色)**

/**
     * @title: AliPayStrategy
     */
    @Component
    public class AliPayStrategy implements PayStrategy {
    
        @Override
        public String toPayHtml() {
            return "调用支付宝支付接口...";
        }
    }

@Component
    public class UnionPayStrategy implements PayStrategy {
        @Override
        public String toPayHtml() {
            return "调用银联支付接口...";
        }
    }

@Component
    public class WeChatPayStrategy implements PayStrategy {
        @Override
        public String toPayHtml() {
            return "调用微信支付接口";
        }
    }

**PayContextService (上下文)**

/**
     * @title: PayContextStrategy
     */
    @Component
    public class PayContextStrategy {
        @Autowired
        private PaymentChannelMapper paymentChannelMapper;
        @Autowired
        private SpringUtils springUtils;
    
        public String toPayHtml(String payCode){
            //1.使用payCode参数查询数据库获取beanid
            PaymentChannelEntity paymentChannel = paymentChannelMapper.getPaymentChannel(payCode);
            if(paymentChannel==null){
                return BaseReturnInfo.PAYMENTCHANNEL_IS_NULL;
            }
            //2.获取到beanid之后，使用spring容器获取实例对象
            String strategyBeanId = paymentChannel.getStrategyBeanId();
            if(StringUtils.isBlank(strategyBeanId)){
                return BaseReturnInfo.STRATEGYBEANID_IS_BLANK;
            }
            // 3.执行该实现的方法即可.... aliPayStrategy
            PayStrategy payStrategy = springUtils.getBean(strategyBeanId, PayStrategy.class);
            // 4.执行具体策略算法
            return payStrategy.toPayHtml();
        }
    }

**SpringUtils**

/**
     *  使用beanid 获取spring容器中的bean对象
     */
    @Component
    public class SpringUtils implements ApplicationContextAware {
    
        private static ApplicationContext applicationContext;
    
        @Override
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
            this.applicationContext = applicationContext;
        }
    
        //获取applicationContext
        public static ApplicationContext getApplicationContext() {
            return applicationContext;
        }
    
        //通过name获取 Bean.
        public static Object getBean(String name){
            return getApplicationContext().getBean(name);
        }
    
        //通过class获取Bean.
        public static <T> T getBean(Class<T> clazz){
            return getApplicationContext().getBean(clazz);
        }
    
        //通过name,以及Clazz返回指定的Bean
        public static <T> T getBean(String name,Class<T> clazz){
            return getApplicationContext().getBean(name, clazz);
        }
    
    }

**数据库访问层**

**![20190605094953537.jpg][]**

/*
     Navicat MySQL Data Transfer
    
     Source Server         : MySQL
     Source Server Type    : MySQL
     Source Server Version : 50720
     Source Host           : localhost:3306
     Source Schema         : design_pattern
    
     Target Server Type    : MySQL
     Target Server Version : 50720
     File Encoding         : 65001
    
     Date: 08/05/2019 09:20:48
    */
    
    SET NAMES utf8mb4;
    SET FOREIGN_KEY_CHECKS = 0;
    
    -- ----------------------------
    -- Table structure for payment_channel
    -- ----------------------------
    DROP TABLE IF EXISTS `payment_channel`;
    CREATE TABLE `payment_channel`  (
      `ID` int(11) NOT NULL AUTO_INCREMENT COMMENT 'ID',
      `CHANNEL_NAME` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '渠道名称',
      `CHANNEL_ID` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '渠道ID',
      `strategy_bean_id` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '策略执行beanid',
      PRIMARY KEY (`ID`, `CHANNEL_ID`) USING BTREE
    ) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '支付渠道 ' ROW_FORMAT = Dynamic;
    
    -- ----------------------------
    -- Records of payment_channel
    -- ----------------------------
    INSERT INTO `payment_channel` VALUES (4, '支付宝渠道', 'ali_pay', 'aliPayStrategy');
    INSERT INTO `payment_channel` VALUES (5, '银联支付渠道', 'union_pay', 'unionPayStrategy');
    INSERT INTO `payment_channel` VALUES (6, '微信支付渠道', 'wechat_pay', 'weChatPayStrategy');
    
    SET FOREIGN_KEY_CHECKS = 1;

**数据库访问层**

@Data
    public class PaymentChannelEntity {
       /** ID */
       private Integer id;
       /** 渠道名称 */
       private String channelName;
       /** 渠道ID */
       private String channelId;
       /**
        * 策略执行beanId
        */
       private String strategyBeanId;
    
    }

**Mapper层**

public interface PaymentChannelMapper {
         @Select("\n" +
                 "SELECT  id as id ,CHANNEL_NAME as CHANNELNAME ,CHANNEL_ID as CHANNELID,strategy_bean_id AS strategybeanid\n" +
                 "FROM payment_channel where CHANNEL_ID=#{payCode}")
         public PaymentChannelEntity getPaymentChannel(String payCode);
    }

**BaseReturnInfo **

public interface BaseReturnInfo {
    
        String  PAYMENTCHANNEL_IS_NULL="没有该渠道信息";
    
        String STRATEGYBEANID_IS_BLANK="该渠道没有配置beanid";
    
        String PAYCODE_IS_BLANK="渠道code不能为空";
    }

**Controller层**

/**
     * @title: PayController
     */
    @RestController
    public class PayController {
        @Autowired
        private PayContextStrategy payContextStrategy;
    
        @RequestMapping("/toPayHtml")
        public  String toPayHtml(String payCode){
            if(StringUtils.isBlank(payCode)){
                return BaseReturnInfo.PAYCODE_IS_BLANK;
            }
            return payContextStrategy.toPayHtml(payCode);
        }
    }

**application.yml**

###服务启动端口号
    server:
      port: 8080
    spring:
    ###数据库相关连接      
      datasource:
        username: root
        password: root
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://127.0.0.1:3306/design_pattern?useUnicode=true&characterEncoding=UTF-8&useSSL=true
    ####打印MyBatias日志    
    logging:
      level:
      ### 开发环境使用DEBUG 生产环境info或者error
       com.xuyu.mapper: DEBUG

**启动类**

@SpringBootApplication
    @MapperScan("com.xuyu.mapper")
    @EnableAutoConfiguration
    public class AppSpringBoot {
        public static void main(String[] args) {
            SpringApplication.run(AppSpringBoot.class);
        }
    }

**效果**

**![20190605095135408.jpg][]**

![20190605095147874.jpg][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE0MTg1MzA_size_16_color_FFFFFF_t_70 1][]

优点：策略模式最终帮助我们解决在实际开发中多重if判断问题、提高扩展性、维护性增强、提高代码可读性。

缺点：后期维护不同策略类是非常多、定义类比较多、代码量增大。 优点大于缺点。

转载至：[https://my.oschina.net/u/3995125/blog/3046848][https_my.oschina.net_u_3995125_blog_3046848]

[Link 1]: https://my.oschina.net/u/3995125
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[20190605094953537.jpg]: /images/20220122/d601c41e4d68483ca78560f03b260047.png
[20190605095135408.jpg]: /images/20220122/99e1368d0f4a42ec83a9b4c7684b021c.png
[20190605095147874.jpg]: /images/20220122/8d03c0fd8af0401b8f0cf3de6a8fd38f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE0MTg1MzA_size_16_color_FFFFFF_t_70 1]: /images/20220122/c10a58c04bce4c6fb0f831bd18215bc2.png
[https_my.oschina.net_u_3995125_blog_3046848]: https://my.oschina.net/u/3995125/blog/3046848