多个if-else代码:

@RunWith(SpringRunner.class)
@SpringBootTest
public class EducationalBackgroundTest {
    private int year = 6;

    @Test
    public void normalIfElse(){
        if ( year == 6){
            System.out.println("小学毕业");
        }else if ( year == 9){
            System.out.println("初中毕业");
        }else if ( year == 12){
            System.out.println("高中毕业");
        }else {
            System.out.println("未知学习时间");
        }
    }
}

上面只统计了3个学习时间,如果我们要写其他的学习时间就需要继续添加if-else,如果业务很复杂,那么这个代码看起来会很乱,不方便维护;

 

下面用策略模式工厂模式优化该if-else;

1. 定义抽象策略角色(接口

public interface EducationalBackground {
    void process();
}

 

2. 编写具体策略角色(实现策略角色接口

小学毕业策略角色:

import org.springframework.beans.factory.InitializingBean;
import org.springframework.stereotype.Component;

@Component
public class Primary implements EducationalBackground,InitializingBean {


    @Override
    public void process() {
        System.out.println("小学毕业");
    }
    @Override
    public void afterPropertiesSet() throws Exception {
        EducationBackgroundFactory.put(6,this);
    }

}

 

这里的InitializingBean接口(具体看Spring Bean的生命周期)只有一个方法afterPropertiesSet,实现了该接口的bean初始化会调用这个方法;

再写一个策略角色“初中毕业”:

import org.springframework.beans.factory.InitializingBean;
import org.springframework.stereotype.Component;

@Component
public class Junior implements EducationalBackground,InitializingBean {

    @Override
    public void process() {
        System.out.println("初中毕业");
    }
    @Override
    public void afterPropertiesSet() throws Exception {
        EducationBackgroundFactory.put(9,this);
    }

}

 

3. 环境角色,内部持有一个策略类的引用

简单工厂模式

import java.util.HashMap;
import java.util.Map;
import java.util.Optional;

public class EducationBackgroundFactory {
    private static Map<Integer,EducationalBackground> educationMap = new HashMap<>();

    private EducationBackgroundFactory(){}

    private final static EducationalBackground EMPTY = new EmptyDesc();

    /**
     * 将对应年数的学历对象注册到Map中
     * @param year
     * @param educationalBackground
     */
    public static void put(int year,EducationalBackground educationalBackground){
        educationMap.put(year,educationalBackground);
    }

    /**
     *获得对应学历对象
     * @param year
     */
    public static EducationalBackground get(int year){
        EducationalBackground educationalBackground = educationMap.get(year);
        //没有对应year返回EMPTY
        return Optional.ofNullable(educationalBackground).orElse(EMPTY);
    }

    private static class EmptyDesc implements EducationalBackground{
        @Override
        public void process() {
            System.out.println("未知的学习时间year");
        }
    }

}

 

测试方法:

@RunWith(SpringRunner.class)
@SpringBootTest
public class EducationalBackgroundTest {
    private int year = 6;

    /**
     * 设计之后仅需两行代码
     */
    @Test
    public void design(){
        EducationalBackground educationalBackground = EducationBackgroundFactory.get(year);
        educationalBackground.process();
    }

}

 

有关于year的参数最好是配置在配置文件中,比如项目已上线,只需要修改配置文件中的内容即可修改对应的引用,而不需要修改代码(修改了代码需要发布)!

 

参考来源:

https://www.cnblogs.com/pfblog/p/7815238.html