关于rust:利用springboot初始化机制三种实现策略模式的应用

面试时总被问，spring中应用了哪些设计模式，你在理论开发中又应用哪些设计模式。给他手指一个方向跟他说，这就是一个模式：go out!。
这就是一种模式：策略模式，一个接口的多个实现形式(算法)。本文梳理了应用springboot实现的三种实现策略模式的利用
咱们晓得，springboot利用初始化的过程是通过事件机制进行的。次要是通过 EventPublishingRunListener 在不同的初始化阶段发送不同的 SpringApplicationEvent (不同的子)事件，触发相应逻辑(这里的逻辑指class的加载)的加载和初始化。
当 ApplicationPreparedEvent 事件发送后，对于利用来讲，阐明整个初始化过程已实现，也意味着所有的类已放入spring ioc 中。
这时咱们就能够联合本人的业务逻辑实现策略模式的利用，咱们通过以下三种形式实现策略的利用
形式一：应用ApplicationListener 和 ContextRefreshedEvent
外围应用的是 ApplicationContext.getBeanNamesForAnnotation(Class annotationType)办法，基于注解类，获取标有指定注解类的所有实例
咱们的业务逻辑是这样的：利用Api接管规定参数(authType)，Api 依据authType 值的不同，应用不同的auth service，执行相应的规定业务逻辑。
public interface UserValidator<D, R> {

String check(D data, R rule);œ

}
@Service
@Validator(authType = AuthType.B_USER)
public class BUserValidator implements UserValidator<String, String> {

@Overridepublic String check(String data, String rule) {    System.out.println("客官，这里B端用户逻辑");    return "";}

}
@Service
@Validator(authType = AuthType.C_USER)
public class CUserValidator implements UserValidator<String, String> {

@Overridepublic String check(String data, String rule) {    System.out.println("客官，这里C端用户逻辑");    return "";}

}
public enum AuthType {

B_USER(1, "b端用户"),C_USER(2, "c端用户");public final int type;public final String code;AuthType(int type, String code) {    this.type = type;    this.code = code;}

}
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
@Inherited
public @interface Validator {

AuthType authType();

}
@Component
public class AuthContainer implements ApplicationListener<ContextRefreshedEvent> {

private ConcurrentHashMap<Integer, UserValidator> validatorMap = new ConcurrentHashMap<>();@Overridepublic void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {    String[] names = context.getBeanNamesForAnnotation(Validator.class);    if (names.length > 0) {        for (String name : names) {            System.out.println("UserValidator:" + name);            UserValidator userValidator = context.getBean(name, UserValidator.class);            Validator validator = userValidator.getClass().getAnnotation(Validator.class);            validatorMap.put(validator.authType().type, userValidator);        }    }}public ConcurrentHashMap<Integer, UserValidator> getValidatorMap() {    return validatorMap;}

}
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Api 接口定义如下，依据不同的authType 值，执行不同的auth service
@RequestMapping("/client_auth")
@RestController
public class Client3 {

@Autowiredprivate AuthContainer authContainer;@RequestMapping("getAuth")public String getRule(@RequestParam("authType") Integer authType) {    // if authType=1，B_USER; if authType=2，C_USER;    ConcurrentHashMap<Integer, UserValidator> map = authContainer.getValidatorMap();    UserValidator userValidator = map.get(authType);    String res = userValidator.check("hi", "看看什么规定");    return res;}

}
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形式二：应用ApplicationContextAware 和 @PostConstruct
咱们的业务逻辑是这样的：利用Api接管规定参数(ruleType)，Api 依据ruleType 值的不同，应用不同的rule service，执行相应的规定业务逻辑。
外围应用的是 ApplicationContext.getBeanNamesForAnnotation(Class annotationType)办法，基于注解类，获取标有指定注解类的所有实例
代码构造：

外围代码如下：
public abstract class RuleValidator<D, R> {

public abstract String check(D data, R rule);

}
@RuleMapping(ruleCodeEnum = RuleCodeEnum.COUNT)
@Service
public class CountRuleValidator extends RuleValidator<String, String> {

@Overridepublic String check(String data, String rule) {    System.out.println("客官，这里是数量规定区域");    return "";}

}
@RuleMapping(ruleCodeEnum = RuleCodeEnum.PRICE)
@Service
public class PriceRuleValidator extends RuleValidator<String, String> {

@Overridepublic String check(String data, String rule) {    System.out.println("客官，这里是价格规定区域");    return "";}

}
public enum RuleCodeEnum {

/** 价格规定 */PRICE(1, "price"),/** 数量规定 */COUNT(2, "count");public final int type;public final String code;RuleCodeEnum(int type, String code) {    this.type = type;    this.code = code;}

}
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
@Inherited
public @interface RuleMapping {

String ruleCode() default "";String ruleDesc() default "";RuleCodeEnum ruleCodeEnum();

}

@Component
public class RuleValidatorInit implements ApplicationContextAware {

private static ApplicationContext context;private Map<Integer, RuleValidator> validatorMap = new HashMap<>();@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {    this.context = applicationContext;}public Map<Integer, RuleValidator> getValidatorMap() {    return validatorMap;}@PostConstructpublic void afterPropertiesSet() {    String[] names = context.getBeanNamesForAnnotation(RuleMapping.class);    if (names.length > 0) {        for (String name : names) {            RuleValidator ruleValidator = context.getBean(name, RuleValidator.class);            RuleMapping ruleMapping = ruleValidator.getClass().getAnnotation(RuleMapping.class);            validatorMap.put(ruleMapping.ruleCodeEnum().type, ruleValidator);        }    }}

}
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Api 接口定义如下，依据不同的ruleType 值，执行不同的rule service
@RequestMapping("/client")
@RestController
public class Client {

@Autowiredprivate RuleValidatorInit ruleValidatorInit;@RequestMapping("getRule")public String getRule(@RequestParam("ruleType") Integer ruleType) {    Map<Integer, RuleValidator> map = ruleValidatorInit.getValidatorMap();    System.out.println(map);    RuleValidator<String, String> ruleValidator = map.get(ruleType);    String res = ruleValidator.check("hi", "看看什么规定");    return res;}

}
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形式三：应用ApplicationContextAware
比照形式一，这里不须要定义指定注解了
外围应用的是 ApplicationContext.getBeansOfType(classType)办法，获取接口 classType 的所有子类实例
代码构造：

外围代码如下：
public interface RoleValidator<D, R> {

String check(D data, R rule);RoleCodeEnum source();

}
@Service
public class BRoleValidator implements RoleValidator<String, String> {

@Overridepublic String check(String data, String rule) {    System.out.println("客官，这里B端用户逻辑");    return "";}@Overridepublic RoleCodeEnum source() {    return RoleCodeEnum.B_USER;}

}
@Service
public class CRoleValidator implements RoleValidator<String, String> {

@Overridepublic String check(String data, String rule) {    System.out.println("客官，这里C端用户逻辑");    return "";}@Overridepublic RoleCodeEnum source() {    return RoleCodeEnum.C_USER;}

}
public enum RoleCodeEnum {

B_USER(1, "b端用户"),C_USER(2, "c端用户");public final int type;public final String code;RoleCodeEnum(int type, String code) {    this.type = type;    this.code = code;}

}
@Component
public class RoleValidatorInit implements ApplicationContextAware {

private static Map<RoleCodeEnum, RoleValidator> builderMap = new HashMap<>();@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {    for (RoleValidator roleValidator : applicationContext.getBeansOfType(RoleValidator.class).values()) {        builderMap.put(roleValidator.source(), roleValidator);    }}public static RoleValidator getRoleValidator(RoleCodeEnum role) {    return builderMap.get(role);}

}
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Api 接口定义如下，依据不同的roleType 值，执行不同的role service
@RequestMapping("/client_role")
@RestController
public class Client2 {

@Autowiredprivate RoleValidatorInit roleValidatorInit;@RequestMapping("getRole")public String getRule(@RequestParam("roleType") Integer roleType) {    // if roleType=1，B_USER; if roleType=2，C_USER;    RoleValidator roleValidator = roleValidatorInit.getRoleValidator(RoleCodeEnum.B_USER);    String res = roleValidator.check("hi", "看看什么规定");    return res;}

}
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总结
通过三种形式的比照，对于外围局部，其实就是几行代码的不同。无论是利用 Event 事件还是通过 Aware，实质都是拿到或利用 ApplicationContext 去解析接口，拿到实现类的实例，放入汇合，而后在客户端(或其余)获取汇合，依据枚举标识拿到对应的子类，执行对应的业务逻辑。