设计模式-责任链模式

这里举一个demo

public class ValidateHandler extends Handler {
    public void doHandler(Member member) {
        if(StringUtils.isEmpty(member.getLoginName()) ||
                StringUtils.isEmpty(member.getLoginPass())){
            System.out.println("用户名和密码为空");
            return;
        }
        System.out.println("用户名和密码不为空，可以往下执行");
        if(null != next) {
            next.doHandler(member);
        }
    }
}
public class LoginHandler extends Handler {
    public void doHandler(Member member) {
        System.out.println("登录成功！");
        member.setRoleName("管理员");
        if(null != next) {
            next.doHandler(member);
        }
    }
}
public class AuthHandler extends Handler {
    public void doHandler(Member member) {
        if(!"管理员".equals(member.getRoleName())){
            System.out.println("您不是管理员，没有操作权限");
            return;
        }
        System.out.println("允许操作");
    }
}

public abstract class Handler<T> {
    protected Handler next;
    
    public void next(Handler next){ 
        this.next = next;
    }

    public abstract void doHandler(Member member);

    public static class Builder<T>{
        private Handler<T> head;
        private Handler<T> tail;

        public Builder<T> addHandler(Handler handler){
                if (this.head == null) {
                    this.head = this.tail = handler;
                    return this;
                }
                this.tail.next(handler);
                this.tail = handler;
            return this;
        }

        public Handler<T> build(){
            return this.head;
        }

    }
}

public class MemberService {
    public void login(String loginName,String loginPass){
        Handler.Builder builder = new Handler.Builder();
        builder.addHandler(new ValidateHandler())
                .addHandler(new LoginHandler())
                .addHandler(new AuthHandler());
        builder.build().doHandler(new Member(loginName,loginPass));
    }
}
public class Test {
    public static void main(String[] args) {
        MemberService memberService = new MemberService();
        memberService.login("xiaofeng","123456");
    }
}

当最后一个addHandler(new AuthHandler())走完之后，调试结果：