if - Java代码多分支语句优化

Question

1.项目背景 一个controller，一个serivce，多个dao层 service里面更具用户的不同参数调用不同的dao进行实例化，时候在调用方法。2.不要问为什么设计，那是因为一个模块对应37张表，用户根据下拉选择输入不同的表...

PHP中文网 · Answer

I think it would be good to call the Dao layer through reflection without repeating the name of dao from the front end;
Just a thought.

黄舟 · Answer

Since your question already contains several affirmative sentences such as "don't ask" and "definitely", it's hard to say anything else. You can try factory mode or manager mode to get the corresponding dao instance based on the flag value (actually, you just move this ugly code to a dark corner).

高洛峰 · Answer

Polymorphism, or table-driven mode (refer to Chapter 18 of the Code Collection)

ringa_lee · Answer

Obviously it’s a design problem, it’s still a bit stubborn

迷茫 · Answer

Project structure problem. Think about the characteristics of java. Encapsulation. Inheritance polymorphism

迷茫 · Answer

Since you mentioned the word injection, I assume that you are using the Spring framework, and Spring's applicationContext can get all the beans that have been initialized by the container. Usually there is a data access layer abstraction such as BaseDao in the framework. Then you can use baseDao=applicationContext.getBean("beanName"), and then you can do whatever you want

巴扎黑 · Answer

I will build a map
map.put("dao1",dao1);
map.put("dao2",dao2);
map.put("dao3",dao3);
Then select the map through the parameters of the page Key, get dao
Of course, if you are using spring, this map can be directly configured in spring xml

PHPz · Answer

I remember that both if else and switch case statements can be reconstructed using command mode

interface dao
{
    crdu() ;
}

class ConcreteDao implements dao
{
    crdu(){...} ;
}

class Service
{
    private Dao dao ;

    public void set(Dao dao){}

    public void service(){dao.service();}
}

class ServiceControl
{
    private HashMap map ;
    private Service service ;

    public ServiceControl()
    {
        //读xml表初始化标识与dao的对应
    }

    public void service(int flag)
    {
        //根据flag来选择不同的dao注入到service中
        Dao dao = map.get(flag) ;
        service.set(dao) ;
        service.service() ;
    }
}

Then the control layer can directly use servicecontrol, so that the control layer is decoupled from the dao, and the modifications on both sides do not affect each other and are coordinated through xml

if - Java代码多分支语句优化

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