java 在 Spring Security 中将 List<Authority> 转换为 Collection<GrantedAuthority>
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Convert List<Authority> to Collection<GrantedAuthority> in Spring Security
提问by Mahmoud Saleh
My case is that i have a method that takes Collection and i have the value as a list when i tried to add the list value into collection parameter it doesn't work, so should i cast it ?
我的情况是，我有一个采用 Collection 的方法，当我尝试将列表值添加到集合参数中时，我将该值作为列表，但它不起作用，所以我应该转换它吗？
UPDATE:when i tried to create:
更新：当我尝试创建时：
new org.springframework.security.core.userdetails.User(
user.getEmail(), user.getPassword(), true, true, true, true,
user.getAuthorities());
where user.getAuthorities() returns an arraylist of my defined Authority object
其中 user.getAuthorities() 返回我定义的 Authority 对象的数组列表
above code gives error that the constructor is undefined, when i add collection casting it works fine.
上面的代码给出了构造函数未定义的错误，当我添加集合转换时它工作正常。
org.springframework.security.core.userdetails
Class UserConstructor
org.springframework.security.core.userdetails
类用户构造函数
User(java.lang.String username, java.lang.String password,
boolean enabled, boolean accountNonExpired,
boolean credentialsNonExpired, boolean accountNonLocked,
java.util.Collection<? extends GrantedAuthority> authorities)
回答by JB Nizet
The javadoc of the User constructortells you that the last argument must be a Collection<? extends GrantedAuthority>. So, you ArrayList will be accepted if it's an ArrayList<Something>, where Somethingis GrantedAuthorityor a class which implements GrantedAuthority.
User 构造函数的javadoc告诉您最后一个参数必须是Collection<? extends GrantedAuthority>. 因此，如果 ArrayList 是ArrayList<Something>, where SomethingisGrantedAuthority或实现GrantedAuthority.
You still haven't told us what was the exact type returned by the method user.getAuthorities(). Do you understand Generics? Have you read the Java tutorial about generics?
您仍然没有告诉我们方法返回的确切类型是什么user.getAuthorities()。你了解泛型吗？你读过关于泛型的Java 教程吗？
回答by NPE
A Listalready isa Collectionsince it's a sub-interface of Collection.
AList已经是aCollection因为它是Collection.
If you have a variable of type implementing List(e.g. ArrayList), you can use it anywhere a Collectionis expected. No conversion will be necessary, not even an explicit type cast.
如果您有一个实现类型的变量List（例如ArrayList），您可以在Collection预期的任何地方使用它。不需要转换，甚至不需要显式类型转换。
回答by Malcolm
Collection<SomeClass> collection = list; //Where list is a List<SomeClass>
However, List already is collection, so actually no conversion is required.
但是，List 已经是集合，所以实际上不需要转换。
