在我的系统中,我有一个单一的类,其中有大量(20?)final
booleans
,定义了该用户类型拥有的权限。
有没有更好的方法来实现这个功能呢?
我相信有很多关于这方面的例子,但我不知道关键词是什么。
在我的系统中,我有一个单一的类,其中有大量(20?)final
booleans
,定义了该用户类型拥有的权限。
有没有更好的方法来实现这个功能呢?
我相信有很多关于这方面的例子,但我不知道关键词是什么。
你可以利用枚举类型,例如:
public enum Permission {
READ, WRITE;
}
public class User {
private final EnumSet<Permission> permissions;
public User(Permission... permissions) {
this.permissions = EnumSet.copyOf(Arrays.asList(permissions));
}
public boolean hasPermission(Permission permission) {
return permissions.contains(permission);
}
//...
}
User user = new User(Permission.READ, Permission.WRITE);
Permission
的类,并给每个User
分配一组它们。如果用户的权限集合中包含某个权限,则该用户拥有该权限,否则没有。Permission
类作为枚举类型(除非应用程序在动态创建角色方面做了一些不寻常的事情,否则它在概念上可能已经是这样了)。然后,通过调用类似于EnumSet.contains(Permission.ADMIN)
的东西,您可以获得非常清晰的代码。 - Andrzej Doylepublic interface IPersmisions {
public static final int NONE = 1 << 0;
public static final int LEVEL1 = 1 << 1;
public static final int LEVEL2 = 1 << 2;
public static final int LEVEL3 = 1 << 3;
public static final int LEVEL4 = 1 << 4;
public static final int LEVEL5 = 1 << 5;
public static final int LEVEL6 = 1 << 6;
public static final int LEVEL7 = 1 << 7;
public static final int LEVEL8 = 1 << 8;
public static final int LEVEL9 = 1 << 9;
}
in used You add
int permisions = IPersmisions.NONE;
public boolean checkPermission(int permission) {
return (permissions & permission) != 0;
}
public void addPermission(int permission) {
permissions = (permissions | permission);
}
public void removePermission(int permission) {
permissions = (permissions & ~permission);
}
public interface IPermisionGroup extends IPermisions {
public static final int LEVEL1_2_3 = LEVEL1 | LEVEL2 | LEVEL3;
public static final int LEVEL4_5_6 = LEVEL4 | LEVEL5 | LEVEL6;
public static final int LEVEL7_8_9 = LEVEL7 | LEVEL8 | LEVEL9;
}
在代码中,您可以使用以下方式:
user.addPermision(IPermisions.LEVEL1);
或者
user.addPermision(IPermisions.LEVEL1 | IPermision.LEVEL2);
或者
user.addPermision(IPermisionGroup.LEVEL1_2_3);
@tdammers提出的完整示例:
class enum Permission {
WRITE, READ, EXECUTE, GROUP, OWNER
}
public class User {
protected Set<Permission> permissions;
public User() {
permissions = new EnumSet<Permission>();
}
public boolean hasPermission(Permission p) {
return permissions.contains(p);
}
public void addPermisssion(Permission p) {
permissions.add(p);
}
public void removePermisssion(Permission p) {
permissions.remove(p);
}
}
//usage
User u = new User();
u.addPermission(Permission.READ);
System.out.writeln(u.hasPermission(Permission.WRITE));
u.removePermission(Permission.READ);
public class User {
private final boolean admin, superuser, guest;
public User(boolean admin, boolean superuser, boolean guest) {
this.admin = admin;
this.superuser = superuser;
this.guest = guest;
}
public boolean isAdmin() {
return admin;
}
public boolean isSuperuser() {
return superuser;
}
public boolean isGuest() {
return guest;
}
// and so on
}
多态性,而非条件语句。
class User {
final Print print;
User(Print print) {
this.print = print;
}
}
interface Print {
void print();
}
class CanPrint implements Print {
public void print() { do whatever it takes to print a user }
}
class CannotPrint implements Print {
public void print() { throw null; }
}