CleanCode TIL (2022.02.15)

public Service getService() {
    if (service == null)
        service = new MyServiceImpl(...); // 모든 상황에 적합한 기본값일까? 
    return service;
}

MyService myService = (MyService)(jndiContext.lookup("NameOfMyService"));

// Bank.java (패키지 이름을 감춘다)
import java.util.*;
// 은행 추상화
public interface Bank {
    Collection < Account > getAccounts();
    void setAccounts(Collection < Account > accounts);
}
// BankImpl.java 
import java.util.*;
// 추상화를 위한 POJO("Plain Old Java Object") 구현
public class BankImpl implements Bank {
    private List < Account > accounts;
    public Collection < Account > getAccounts() {
        return accounts;
    }
    public void setAccounts(Collection < Account > accounts) {
        this.accounts = new ArrayList < Account > ();
        for (Account account: accounts) {
            this.accounts.add(account);
        }
    }
}
// BankProxyHandler.java 
import java.lang.reflect.*;
import java.util.*;
// 프록시 API가 필요한 "InvocationHandler"
public class BankProxyHandler implements InvocationHandler {
    private Bank bank;
    public BankProxyHandler(Bank bank) {
        this.bank = bank;
    }
    // InvocationHandler에 정의된 메서드
    public Object invoke(Object proxy, Method method, Object[] args)
    throws Throwable {
        String methodName = method.getName();
        if (methodName.equals("getAccounts")) {
            bank.setAccounts(getAccountsFromDatabase());
            return bank.getAccounts();
        } else if (methodName.equals("setAccounts")) {
            bank.setAccounts((Collection < Account > ) args[0]);
            setAccountsToDatabase(bank.getAccounts());
            return null;
        } else { ...
        }
    }
    // 세부사항은 여기에 이어진다.
    protected Collection < Account > getAccountsFromDatabase() { ...
    }
    protected void setAccountsToDatabase(Collection < Account > accounts) { ...
    }
}
// 다른 곳에 위치하는 코드
Bank bank = (Bank) Proxy.newProxyInstance(Bank.class.getClassLoader(),
    new Class[] {
        Bank.class
    },
    new BankProxyHandler(new BankImpl()));