設計模式原則之開放-封閉原則

　　程序擴展對外開放，修改對外封閉

ResolverUtil

其中有一個接口、兩個內部類，Class對象和Annotation對象被封裝成了Test對象

Test

兩個實現類，核心功能是匹配Class類型

IsA

public static class IsA implements Test {private Class<?> parent;/** Constructs an IsA test using the supplied Class as the parent class/interface. */public IsA(Class<?> parentType) {this.parent = parentType;}/** Returns true if type is assignable to the parent type supplied in the constructor. */@Overridepublic boolean matches(Class<?> type) {return type != null && parent.isAssignableFrom(type);}@Overridepublic String toString() {return "is assignable to " + parent.getSimpleName();} }

AnnotatedWith

public static class AnnotatedWith implements Test {private Class<? extends Annotation> annotation;/** Constructs an AnnotatedWith test for the specified annotation type. */public AnnotatedWith(Class<? extends Annotation> annotation) {this.annotation = annotation;}/** Returns true if the type is annotated with the class provided to the constructor. */@Overridepublic boolean matches(Class<?> type) {return type != null && type.isAnnotationPresent(annotation);}@Overridepublic String toString() {return "annotated with @" + annotation.getSimpleName();} }

使用

String packageName = "com/wjz/mybatis/type/scan"; ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<Class<?>>(); resolverUtil.find(new ResolverUtil.IsA(CommonService.class), packageName); Set<Class<? extends Class<?>>> handlerSet = resolverUtil.getClasses();

如此設計

我們可以實現Test接口，傳參find方法時傳入，而不用修改ResolverUtil的內部方法。

package com.wjz.mybatis.type.scan;import org.apache.ibatis.io.ResolverUtil.Test;public class Testtest implements Test {@Overridepublic boolean matches(Class<?> type) {if (type == Testtest.class) {return true;}return false;}}

?

轉載于:https://www.cnblogs.com/BINGJJFLY/p/9905198.html

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