今天看了教程的第三章...是关于授权的......和以前一样.....自己也研究了下....我觉得看那篇教程怎么说呢.....总体上是为数不多的精品教程了吧....但是有些地方确实是讲的太少了....而这些地方又是蛮难的..比如3.5节Authorizer、PermissionResolver及RolePermissionResolver...可能作者觉得讲清楚要花太多的篇幅涉及太多的类吧.....但是我看起来就很不爽0.0....既然提到了就想弄明白.....不然太纠结了....所以就有了这篇学习记录...记录我对Shiro授权的理解
Subject
我是从subject.isPermittedAll("system:view")这里开始研究的...
和我的上一篇学习记录写到的一样Subject只是一个接口,它的实现类是DelegatingSubject类.
public boolean isPermittedAll(String... permissions) {
return hasPrincipals() && securityManager.isPermittedAll(getPrincipals(), permissions);
}
授权和认证太像啦,这里subject其实也是委托securityManager来具体处理的(第2行).
SecurityManager
securityManager的实现类是DefaultSecurityManager...DefaultSecurityManager的N层父类AuthorizingSecurityManager里有isPermitted方法
public boolean isPermittedAll(PrincipalCollection principals, String... permissions) {
return this.authorizer.isPermittedAll(principals, permissions);
}
从中可以看出....Shiro的认证和授权真的是太像了...这里授权是委托授权器authorizer来做具体的授权,就像我学习认证那篇文章讲的,认证是委托authenticator来做一样.
ModularRealmAuthorizer
我想再吐槽一下.....ModularRealmAuthorizer和ModularRealmAuthenticator真是亲兄弟啊......我差点就看错名字了....
public boolean isPermittedAll(PrincipalCollection principals, String... permissions) {
assertRealmsConfigured();
if (permissions != null && permissions.length > 0) {
for (String perm : permissions) {
if (!isPermitted(principals, perm)) {
return false;
}
}
}
return true;
}
这里就是把permissions一个一个取出来,调用isPermitted(principals, perm)方法去看看用户是否有每一个传入的权限perm(第5行)...........
全部包含就是返回true,否则返回false.
那我们就去看看isPermitted方法好了
public boolean isPermitted(PrincipalCollection principals, String permission) {
assertRealmsConfigured();
for (Realm realm : getRealms()) {
if (!(realm instanceof Authorizer)) continue;
if (((Authorizer) realm).isPermitted(principals, permission)) {
return true;
}
}
return false;
}
从这里(第5行)可以看出其实ModularRealmAuthorizer是调用了Realm的isPermitted的....
AuthorizingRealm
public boolean isPermitted(PrincipalCollection principals, String permission) {
Permission p = getPermissionResolver().resolvePermission(permission);
return isPermitted(principals, p);
}
public boolean isPermitted(PrincipalCollection principals, Permission permission) {
AuthorizationInfo info = getAuthorizationInfo(principals);
return isPermitted(permission, info);
}
private boolean isPermitted(Permission permission, AuthorizationInfo info) {
Collection<Permission> perms = getPermissions(info);
if (perms != null && !perms.isEmpty()) {
for (Permission perm : perms) {
if (perm.implies(permission)) {
return true;
}
}
}
return false;
}
那么Realm又是怎么处理的呢?
在第一个方法中调用PermissionResolver去把要验证的字符串的permission转化成了实实在在的Permission对象...这是很重要的一步(但是PermissionResolver在第三个方法中也有用到,所以这里就不提了)....
然后再第二个方法中根据传入的principals调用Realm的getAuthorizationInfo(principals)得到AuthorizationInfo ....这里大家一定很熟悉...因为自己写Realm的话一定会去覆盖这个getAuthorizationInfo方法..返回的AuthenorizationInfo里可以得到用户的权限...只不过也是字符串形式......
然后就到了第三个方法....第12行,把info再转化成Permission对象的集合...然后遍历这个集合,去和传入的permission比较,看看用户的permission是否包含(implies)传入的permission....
private Collection<Permission> getPermissions(AuthorizationInfo info) {
Set<Permission> permissions = new HashSet<Permission>();
if (info != null) {
Collection<Permission> perms = info.getObjectPermissions();
if (!CollectionUtils.isEmpty(perms)) {
permissions.addAll(perms);
}
perms = resolvePermissions(info.getStringPermissions());
if (!CollectionUtils.isEmpty(perms)) {
permissions.addAll(perms);
}
perms = resolveRolePermissions(info.getRoles());
if (!CollectionUtils.isEmpty(perms)) {
permissions.addAll(perms);
}
}
if (permissions.isEmpty()) {
return Collections.emptySet();
} else {
return Collections.unmodifiableSet(permissions);
}
}
AuthorizationInfo对象(包含用户字符串形式的权限)是如何提取出Permission对象的呢?
从上面的方法可以看出权限是来自3个方法和合并..info.getObjectPermissions().....resolvePermissions(info.getStringPermissions())和resolveRolePermissions(info.getRoles())....
第一个方法info.getObjectPermissions()我也不知道它是做啥的....看了源文档的注释还是不懂(%>_<%)......我Shiro也仅仅只写过一个demo.......实在是不了解......
第二个方法resolvePermissions(info.getStringPermissions())很重要..要提到WildcardPermissionResolver和WildcardPermission....等会再说....
第三个方法resolveRolePermissions(info.getRoles())我觉得是个预留的方法....要用到RolePermissionResolver接口的子类来做具体的处理....但是Shiro没有提供任何实现...大家可以去看看教程...开涛哥的教程里有他的实现.....我看了下源文档的注释....以我英语6级500都不到的渣渣功力来解读的话(=.=)大致意思就是说有些时候只能获取到subject的role,但是没有permission,这个时候用RolePermissionResolver可以根据role解读出permission...嗯....大致就是这么个意思...错了别打我....Σ( ° △ °|||)︴
然后重点自然就是第二个方法resolvePermissions(info.getStringPermissions())啦....
private Collection<Permission> resolvePermissions(Collection<String> stringPerms) {
Collection<Permission> perms = Collections.emptySet();
PermissionResolver resolver = getPermissionResolver();
if (resolver != null && !CollectionUtils.isEmpty(stringPerms)) {
perms = new LinkedHashSet<Permission>(stringPerms.size());
for (String strPermission : stringPerms) {
Permission permission = getPermissionResolver().resolvePermission(strPermission);
perms.add(permission);
}
}
return perms;
}
那么Shiro是如何把String的permission转化成实实在在的Permission对象的呢?
那就要用到PermissionResolver 的resolvePermission方法了(从上面第7行可以看出)...
WildcardPermissionResolver
WildcardPermissionResolver在Shiro里是PermissionResolver 的默认实现....
看看这个类名真是高大上...但是其实代码超级短....
public class WildcardPermissionResolver implements PermissionResolver {
/**
* Returns a new {@link WildcardPermission WildcardPermission} instance constructed based on the specified
* <tt>permissionString</tt>.
*
* @param permissionString the permission string to convert to a {@link Permission Permission} instance.
* @return a new {@link WildcardPermission WildcardPermission} instance constructed based on the specified
* <tt>permissionString</tt>
*/
public Permission resolvePermission(String permissionString) {
return new WildcardPermission(permissionString);
}
}
就是返回new了一个WildcardPermission仅此而已....
WildcardPermission
public WildcardPermission(String wildcardString) {
this(wildcardString, DEFAULT_CASE_SENSITIVE);
}
public WildcardPermission(String wildcardString, boolean caseSensitive) {
setParts(wildcardString, caseSensitive);
}
构造方法主要就是调用了setParts方法....另外稍微提一下....DEFAULT_CASE_SENSITIVE默认是false....那就是不区分字符串权限大小写咯~(system:view和System:vIew是一会事情)
protected void setParts(String wildcardString, boolean caseSensitive) {
if (wildcardString == null || wildcardString.trim().length() == 0) {
throw new IllegalArgumentException("Wildcard string cannot be null or empty. Make sure permission strings are properly formatted.");
}
wildcardString = wildcardString.trim();
List<String> parts = CollectionUtils.asList(wildcardString.split(PART_DIVIDER_TOKEN));
this.parts = new ArrayList<Set<String>>();
for (String part : parts) {
Set<String> subparts = CollectionUtils.asSet(part.split(SUBPART_DIVIDER_TOKEN));
if (!caseSensitive) {
subparts = lowercase(subparts);
}
if (subparts.isEmpty()) {
throw new IllegalArgumentException("Wildcard string cannot contain parts with only dividers. Make sure permission strings are properly formatted.");
}
this.parts.add(subparts);
}
if (this.parts.isEmpty()) {
throw new IllegalArgumentException("Wildcard string cannot contain only dividers. Make sure permission strings are properly formatted.");
}
}
那么setParts方法做了些什么呢?
这个方法主要就是为WildcardPermission的成员域List<Set<String>> parts去赋值....我们来看看分隔符....
protected static final String WILDCARD_TOKEN = "*";
protected static final String PART_DIVIDER_TOKEN = ":";
protected static final String SUBPART_DIVIDER_TOKEN = ",";
然后大家再看代码应该就没什么问题了...这个代码我觉得没啥好说的...我就举几个例子吧...可能更直观点....
如果用户的字符串权限是"system:user:create,view"
那么parts这个成员域List的size是3.第一个set包含system...第二个set包含user....第三个set的size是2,包含create和view
构造方法和setParts就做了这些事情! 其实一点也不多....
好了...现在要检测的传入的字符串权限被转化成了Permission对象....用户拥有的字符串权限也转化成了Permission对象....那么如何判断用户是否有传入的权限呢?
在前面AuthorizingRealm那小节里我看看到了是调用perm.implies(permission)来判断是否包含的....
请注意..perm是用户的权限...permission是传入要检测的权限...
我们来看看implies方法吧....
public boolean implies(Permission p) {
// By default only supports comparisons with other WildcardPermissions
if (!(p instanceof WildcardPermission)) {
return false;
}
WildcardPermission wp = (WildcardPermission) p;
List<Set<String>> otherParts = wp.getParts();
int i = 0;
for (Set<String> otherPart : otherParts) {
// If this permission has less parts than the other permission, everything after the number of parts contained
// in this permission is automatically implied, so return true
if (getParts().size() - 1 < i) {
return true;
} else {
Set<String> part = getParts().get(i);
if (!part.contains(WILDCARD_TOKEN) && !part.containsAll(otherPart)) {
return false;
}
i++;
}
}
// If this permission has more parts than the other parts, only imply it if all of the other parts are wildcards
for (; i < getParts().size(); i++) {
Set<String> part = getParts().get(i);
if (!part.contains(WILDCARD_TOKEN)) {
return false;
}
}
return true;
}
代码就这么点...但是解释起来可能要很多篇幅....所以我还是觉得举例子比较快......其实这个方法就是比较2个Permission的parts部分....
比较是一部分一部分进行的...先List[0]和List[0]比较(第一个for的第一次循环)...再List[1]和List[1]比较(第一个for的第二次循环)....
比如用户权限是"*:user,admin:view" 传入要检测的权限是"system:guest:view"
第一个for的第一轮比较...看代码第19行....因为用户parts的[0]是* !part.contains(WILDCARD_TOKEN)是false..所以继续下一轮for循环...意思就是*肯定包含system
然后进入for的第二轮!part.contains(WILDCARD_TOKEN)是true..所以要看!part.containsAll(otherPart)...
变量part是字符串user和admin的集合...otherPart是字符串guest的集合..!part.containsAll(otherPart)返回是true..所以if成立...所以return false..即用户是不包含传入检测的权限的(当然这里其实没有这么快就能得出这个结论..ModularRealmAuthorizer中如果有多个realm,要所有realm都返回false才能判断用户没有这个权限..因为程序可能会配置多个Realm...多个Realm可能会给一个用户取到不同的权限...所以每个Realm都要检测过来才知道用户到底包不包含传入要检测的权限...这个道理蛮简单的..大家都懂的..我就是稍微提醒一下..我只是假设我这里就配置了一个realm.....哈哈)...
看了这个implies方法的流程...我想大家也能明白为什么user:*是能匹配user:view:123而*:view不能匹配system:user:view的道理吧....
因为在用户权限长度m小于传入权限长度n的时候,implies方法的第一个for最多做m次就能知道返回是false还是true了..后面的n-m次比较是不会做的...
而用户权限长度m大于传入权限长度n的时候,先做implies方法的第一个for的n次比较,如果还是没结果...再做第2个for..检测用户权限patrs[n-m]到parts[m-1]的部分..这些部分只要有任意一个不是*那就说明用户不具有传入待检测的权限...
以上就是我今天对Shiro授权的理解了吧....