一个参数（@RequestParam 字符串选项卡）- 多种方法

Question

I get "tab" from front, his value can be 'profile', 'active', 'summary', 'votes' etc. Each value has its own method. How can I call a method based on the value of 'tab' without using switch and if . Are there any patterns for this case?

Answer 1

I think the Decorator Pattern is a good solution for that, see the solution bellow:

1. Create an interface to the Tab :

public interface Tab {
    String methodName();
}

2. Implement the classes for this interface: ActiveTab , ProfileTab , SummaryTab

3. Create an Enum to understand and convert the parameter:

public enum TabTypeEnum {
    PROFILE(ProfileTab.class), ACTIVE(ActiveTab.class), SUMMARY(SummaryTab.class);

    Class<? extends Tab> tabClazz;

    TabTypeEnum(Class<? extends Tab> tabClazz) {
        this.tabClazz = tabClazz;
    }

    public static Tab getTabClazz(String tab) throws IllegalAccessException, InstantiationException {
        return TabTypeEnum.valueOf(tab.toUpperCase()).tabClazz.newInstance();
    }
}

4. Create the Decorator:

public class TabDecorator implements Tab {
    protected Tab tab;

    public TabDecorator(String tab) {
        try {
            this.tab = TabTypeEnum.getTabClazz(tab);
        } catch (NullPointerException | IllegalArgumentException | IllegalAccessException | InstantiationException e) {
            throw new InvalidTabException(tab);
        }
    }

    @Override
    public String methodName() {
        return this.tab.methodName();
    }
}

5. Finally, use the decorator:

@GetMapping("/")
public String getByTabParam(@RequestParam String tab) {
    return new TabDecorator(tab).methodName();
}

Se the solution working: https://github.com/armandoalmeida/tab-problem-stackoverflow

Answer 2

With reflection?

MyClass c = new MyClass();
Method m = c.getClass().getMethod(value);
m.invoke(c);

Where MyClass contains methods with name correspond to the values.

Although I think this is discouraged because Java compiler wouldn't be able to detect errors.