Java 如何将BasicPermission子类化以添加操作

我想创建BasicPermission的一个子类来添加操作，根据java文档的描述，这应该是可能的：

如果需要，子类可以在BasicPermission之上实现操作

以下是我的初步尝试：

public class BasicPermissionWithActions extends BasicPermission {

String        actions;
String[]      actionList;
String        name;

public BasicPermissionWithActions(String name, String actions) {
    super(name, actions);
    this.actions = actions;
    this.actionList = actions.split("\\,");
    this.name = name;
}

private static final long serialVersionUID = 7608854273379948062L;

@Override
public boolean implies(Permission p) {
    // name and class check can be done by super
    if (!super.implies(p))
        return false;

    // now check actions
    String requestedActions = p.getActions();
    String[] requestedActionList = requestedActions.split("\\,");
    for (String requestedAction : requestedActionList) {
        if (!hasRequestedAction(requestedAction))
            return false;
    }

    return true;
}

private boolean hasRequestedAction(String requestedAction) {
    for (String action : actionList) {
        if (action.equals(requestedAction))
            return true;
    }
    return false;
}

@Override
public String getActions() {
    return actions;
}

@Override
public int hashCode() {
    final int prime = 31;
    int result = super.hashCode();
    result = prime * result + ((actions == null) ? 0 : actions.hashCode());
    result = prime * result + ((name == null) ? 0 : name.hashCode());
    return result;
}

@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (!super.equals(obj))
        return false;
    if (getClass() != obj.getClass())
        return false;
    BasicPermissionWithActions other = (BasicPermissionWithActions) obj;
    if (actions == null) {
        if (other.actions != null)
            return false;
    } else if (!actions.equals(other.actions))
        return false;
    if (name == null) {
        if (other.name != null)
            return false;
    } else if (!name.equals(other.name))
        return false;
    return true;
}

@Override
public String toString() {
    return "(\"" + this.getClass().getName() + "\" \"" + name + "\" \"" + actions + "\")"; 
}

以及策略文件中的一个条目，用于使用此权限授予访问权限（在本例中，我指定的权限应不足以允许所需的操作）：

以及检查权限的代码：

        rep.getAccessControlContext().checkPermission(new BasicPermissionWithActions(getName(), "write"));

我预计此检查将失败，因为策略仅指定了读取操作。然而支票悄悄地通过了

问题是，每当策略文件中的权限名为“*”时，都不会检查操作。在调试模式下运行表明从未调用方法BasicPermissionWithActions.implies

---

如果我从策略文件中忽略了权限，我将获得预期的安全异常，但我无法使操作正常工作。

问题与PermissionCollection有关。BasicPermission实现自己的PermissionCollection以获得更好的性能。不幸的是，这个实现做出了一些简化的假设，这些假设破坏了子类的语义。具体来说，它为“*”实现了一个快捷方式，该快捷方式绕过Permission.implies方法并始终返回true

解决方案是实现一个自定义PermissionCollection，它只调用其成员的Permission.implies方法：

    private class CustomPermissionCollection extends PermissionCollection {

    private static final long serialVersionUID = 5654758059940546018L;

    Collection<Permission> perms = new ArrayList<Permission>();

    @Override
    public void add(Permission permission) {
        perms.add(permission);
    }

    @Override
    public boolean implies(Permission permission) {
        for (Permission p : perms) {
            if (p.implies(permission))
                return true;
        }
        return false;
    }

    @Override
    public Enumeration<Permission> elements() {
        return Collections.enumeration(perms);
    }

}

    private class CustomPermissionCollection extends PermissionCollection {

    private static final long serialVersionUID = 5654758059940546018L;

    Collection<Permission> perms = new ArrayList<Permission>();

    @Override
    public void add(Permission permission) {
        perms.add(permission);
    }

    @Override
    public boolean implies(Permission permission) {
        for (Permission p : perms) {
            if (p.implies(permission))
                return true;
        }
        return false;
    }

    @Override
    public Enumeration<Permission> elements() {
        return Collections.enumeration(perms);
    }

}

@Override
public PermissionCollection newPermissionCollection() {
    return new CustomPermissionCollection();
}