通过SecurityUtils获取Subject详解

我不是女神ヾ 2023-06-27 05:42 34阅读 0赞

### 文章目录 ###

*   *  获取Subject
     *  猜想
     *  源码分析
     *  ThreadContext是什么时候跟Subject绑定的呢?
     *  猜想ThreadLocal是跟当前线程绑定的,如果我springmvc里面使用异步方法执行,在异步处理过程中能获取到subject吗?
     *  验证:

## 获取Subject ##

使用shiro获取Subject的方法:

Subject subject = SecurityUtils.getSubject();

为什么,不管在哪通过SecurityUtils获取的Subject 都是同一个呢?  
而且Subject 里面还有用户的信息.

## 猜想 ##

首先,能在各个地方获取Subject 只有一种办法,就是通过ThreadLocal类来实现,那么SecurityUtils肯定维护了一个ThreadLocal.

## 源码分析 ##

首先看getSubject方法:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70]  
点到ThreadContext类:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 1]  
说明是ThreadContext类维护了一个ThreadLocal;

## ThreadContext是什么时候跟Subject绑定的呢? ##

我们发现有个方法:bind(Subject subject),  
看谁掉了这个方法:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 2]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 3]  
是SubjectCallable里面就开始绑定了,我们只要看是谁新建了SubjectCallable这个类就好了,发现在Subject里面执行execute的时候新建的,同时将subject也就是this传进去了.  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 4]  
现在明了了,上篇讲到[subject创建详解][subject]  
里面有一张图:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 5]  
在创建了subject的时候就通过execute来执行过滤器链的方法,这时候将创建好的subject跟ThreadContext进行了绑定,所以我们在任何地方都可以通过SecurityUtils.getSubject()来获取Subject.

## 猜想ThreadLocal是跟当前线程绑定的,如果我springmvc里面使用异步方法执行,在异步处理过程中能获取到subject吗? ##

是可以的,我们看ThreadContext里的的ThreadLocal具体实现就知道了:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 6]  
主要功劳就是InheritableThreadLocal实现,这个实现大概做的事情就是如果父线程里面使用ThreadLocal了,然后在父线程里面又创建子线程,这是会将父线程的ThreadLocal拷贝到子线程里面,所以在异步线程里面是可以获取到subject的.  
这时候就会想如果是异步线程池呢,这一块比较复杂,因为  
InheritableThreadLocal实现的时候,如果是异步线程池,在一开始设置了ThreadLocal,他是有缓存的,详情见:[解决父子线程ThreadLocal中的缓存问题][ThreadLocal]

## 验证: ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 7]

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[subject]: https://blog.csdn.net/qq_38366063/article/details/103822382
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[ThreadLocal]: https://github.com/alibaba/transmittable-thread-local
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