Shiro的Filter机制详解---源码分析

Shiro的Filter机制详解

首先从spring-shiro.xml的filter配置说起，先回答两个问题：

1， 为什么相同url规则，后面定义的会覆盖前面定义的(执行的时候只执行最后一个)。

2， 为什么两个url规则都可以匹配同一个url，只执行第一个呢。

 

下面分别从这两个问题入手，最终阅读源码得到解答。

问题一解答

相同url但定义在不同的行，后面覆盖前面

如

/usr/login.do=test3/usr/login.do=test1,test2不会执行test3的filter

要解答第一个问题，需要知道shiro（或者说是spring）是如何扫描这些url规则并保存的。

Web.xml配置shiro以及spring-shiro.xml的核心配置

在web.xml中定义shiroFilter

<filter>        <filter-name>shiroFilter</filter-name>        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>        <init-param>            <!-- 该值缺省为false,表示生命周期由SpringApplicationContext管理,设置为true则表示由ServletContainer管理 -->            <param-name>targetFilterLifecycle</param-name>            <param-value>true</param-value>        </init-param>    </filter>    <filter-mapping>        <filter-name>shiroFilter</filter-name>        <url-pattern>/*</url-pattern>    </filter-mapping>

在spring-shiro.xml中定义shiroFilter

（要和web.xml中的名称一样，因为spring就是依靠名称来获取这个bean的） 

<bean id="shiroFilter" class="org.apache.shiro.spring.web.ShiroFilterFactoryBean">        <property name="securityManager" ref="securityManager" />        <property name="loginUrl" value="/login.jsp" />        <property name="unauthorizedUrl" value="/WEB-INF/405.html" />        <property name="filters">            <map>                <entry key="kickout" value-ref="kickoutSessionControlFilter" />            </map>        </property>        <property name="filterChainDefinitions">            <value>                /**=kickout                /usr/login.do=anon                /security/*=anon                /usr/login.do=authc                /usr/test/*=authc            </value>        </property>    </bean>

都定义好之后，分析org.springframework.web.filter.DelegatingFilterProxy发现该filter类的任务是：将具体工作分派给org.apache.shiro.spring.web.ShiroFilterFactoryBean这个类中的静态内部类SpringShiroFilter做。

具体spring内部是怎么将工作委派的，暂时没有分析。

现在关注的是当spring把具体工作委派给ShiroFilterFactoryBean后，该类是怎么工作的。

Spring将配置注入到ShiroFilterFactoryBean

在这之前，spring通过bean注入，将ShiroFilterFactoryBean的相关成员通过set方法注入进去。

前面已经配置了filters和filterChainDefinitions，再次贴出如下所示：

<property name="filters">            <map>                <entry key="kickout" value-ref="kickoutSessionControlFilter" />            </map>        </property>        <property name="filterChainDefinitions">            <value>                /**=kickout                /usr/login.do=anon                /security/*=anon                /usr/login.do=authc                /usr/test/*=authc            </value>        </property>

看一下ShiroFilterFactoryBean是怎么接收他们的。

 

Filters很简单，只需要map接收就自动完成了。

public void setFilters(Map<String, Filter> filters) {        this.filters = filters;    }

但是filterChainDefinitions是String类型的，需要转换（使用了ini转换方法，内部使用LinkedHashMap保存url和filter的映射关系，保证了顺序）

public void setFilterChainDefinitions(String definitions) {        Ini ini = new Ini();        ini.load(definitions);        //did they explicitly state a 'urls' section?  Not necessary, but just in case:        Ini.Section section = ini.getSection(IniFilterChainResolverFactory.URLS);        if (CollectionUtils.isEmpty(section)) {            //no urls section.  Since this _is_ a urls chain definition property, just assume the            //default section contains only the definitions:            section = ini.getSection(Ini.DEFAULT_SECTION_NAME);        }        setFilterChainDefinitionMap(section);    }

这两步完成后，filters被注入

filterChianDefinitions也被注入，但是注入方法通过shiro自定义了ini方式，

该方式通过LinkedHashMap保存url规则和对应的权限（键值对）,所以当写了相同的url规则，后者会覆盖前者(------现在对HashMap的存储规则遗忘了，需要再看一下)

问题一解答完成

 

问题二解答：

同一个url可以匹配不同的规则，但只执行首行/usr/* =test1,test2/usr/login.do=test3url = /usr/login.do请求来了，不会执行test3，因为已经匹配了/usr/* =test1,test2要解答该问题，需要知道每个url的FilterChain是如何获取的

接上分析:

有了filter和filterChainDefinitionMap的数据后，下面的工作是构造FilterChainManager

构造FilterChainManager

为什么到这一步呢？

查看spring委托机制，最终找到ShiroFilterFactoryBean的createInstance()方法(这个方法是shiro的filter构造机制的主线)，由于ShiroFilterFactoryBean 实现了FactoryBean，spring就是通过这个接口的createInstance方法获取到filter实例的，下面是该方法在ShiroFilterFactoryBean中的实现：

protected AbstractShiroFilter createInstance() throws Exception {        log.debug("Creating Shiro Filter instance.");        SecurityManager securityManager = getSecurityManager();        if (securityManager == null) {            String msg = "SecurityManager property must be set.";            throw new BeanInitializationException(msg);        }        if (!(securityManager instanceof WebSecurityManager)) {            String msg = "The security manager does not implement the WebSecurityManager interface.";            throw new BeanInitializationException(msg);        }        FilterChainManager manager = createFilterChainManager();               PathMatchingFilterChainResolver chainResolver = new PathMatchingFilterChainResolver();        chainResolver.setFilterChainManager(manager);               return new SpringShiroFilter((WebSecurityManager) securityManager, chainResolver);    }

从这里可以知道，首先获取filterChainManager，具体方法如下

protected FilterChainManager createFilterChainManager() {        DefaultFilterChainManager manager = new DefaultFilterChainManager();        Map<String, Filter> defaultFilters = manager.getFilters();        //apply global settings if necessary:        for (Filter filter : defaultFilters.values()) {            applyGlobalPropertiesIfNecessary(filter);        }        //Apply the acquired and/or configured filters:        Map<String, Filter> filters = getFilters();        if (!CollectionUtils.isEmpty(filters)) {            for (Map.Entry<String, Filter> entry : filters.entrySet()) {                String name = entry.getKey();                Filter filter = entry.getValue();                applyGlobalPropertiesIfNecessary(filter);                if (filter instanceof Nameable) {                    ((Nameable) filter).setName(name);                }                //'init' argument is false, since Spring-configured filters should be initialized                //in Spring (i.e. 'init-method=blah') or implement InitializingBean:                manager.addFilter(name, filter, false);            }        }        //build up the chains:        Map<String, String> chains = getFilterChainDefinitionMap();        if (!CollectionUtils.isEmpty(chains)) {            for (Map.Entry<String, String> entry : chains.entrySet()) {                String url = entry.getKey();                String chainDefinition = entry.getValue();                manager.createChain(url, chainDefinition);            }        }        return manager;    }

分析后得知，首先在createFilterChainManager()方法中，创建一个DefaultFilterChainManager对象，而这个对象的构造函数在最后会将DefaultFilter中定义的shiro默认的filter映射加入到该对象中。如下代码就是DefaultFilter的定义。

 

在DefaultFilterChainManager中还做了一件事就是url-filter的映射变成filterChain，这句代码就是执行这个任务（将我们在xml文件中定义的filterChainDefinitions变成filterChain）。

manager.createChain(url, chainDefinition);

作用是将权限分割：如

"authc, roles[admin,user], perms[file:edit]"

将会被分割为

{ "authc", "roles[admin,user]", "perms[file:edit]" }

具体的源代码如下：

public void createChain(String chainName, String chainDefinition) {      //。。。。。。。。        //parse the value by tokenizing it to get the resulting filter-specific config entries        //        //e.g. for a value of        //        //     "authc, roles[admin,user], perms[file:edit]"        //        // the resulting token array would equal        //        //     { "authc", "roles[admin,user]", "perms[file:edit]" }        //        String[] filterTokens = splitChainDefinition(chainDefinition);        for (String token : filterTokens) {            String[] nameConfigPair = toNameConfigPair(token);            addToChain(chainName, nameConfigPair[0], nameConfigPair[1]);        }    }

并且通过toNameConfigPair(token)将如：roles[admin,user]形式的变成roles，admin,user形式的分割

然后根据url规则 映射 权限和角色

可以发现，每次分割一个token，都会通过addToChain方法接受

分析public void addToChain(String chainName, String filterName, String chainSpecificFilterConfig)方法

public void addToChain(String chainName, String filterName, String chainSpecificFilterConfig) {        if (!StringUtils.hasText(chainName)) {            throw new IllegalArgumentException("chainName cannot be null or empty.");        }        Filter filter = getFilter(filterName);        if (filter == null) {            throw new IllegalArgumentException("There is no filter with name '" + filterName +                    "' to apply to chain [" + chainName + "] in the pool of available Filters.  Ensure a " +                    "filter with that name/path has first been registered with the addFilter method(s).");        }        applyChainConfig(chainName, filter, chainSpecificFilterConfig);        NamedFilterList chain = ensureChain(chainName);        chain.add(filter);    }

分析applyChainConfig(chainName, filter, chainSpecificFilterConfig);

protected void applyChainConfig(String chainName, Filter filter, String chainSpecificFilterConfig) {      //………………………….        if (filter instanceof PathConfigProcessor) {            ((PathConfigProcessor) filter).processPathConfig(chainName, chainSpecificFilterConfig);        } else {            if (StringUtils.hasText(chainSpecificFilterConfig)) {                //they specified a filter configuration, but the Filter doesn't implement PathConfigProcessor                //this is an erroneous config:                String msg = "chainSpecificFilterConfig was specified, but the underlying " +                        "Filter instance is not an 'instanceof' " +                        PathConfigProcessor.class.getName() + ".  This is required if the filter is to accept " +                        "chain-specific configuration.";                throw new ConfigurationException(msg);            }        }}

由于我们自定义的filter都是PathMatchingFilter的子类，所以在applyChainConfig方法中完成的就是将url添加到filter的url表中。

在PathMatchingFilter中可以发现

protected Map<String, Object> appliedPaths = new LinkedHashMap<String, Object>();

processPathConfig 方法的实现如下

public Filter processPathConfig(String path, String config) {        String[] values = null;        if (config != null) {            values = split(config);        }        this.appliedPaths.put(path, values);        return this;}

基本上在spring-shiro.xml中定义filter的载入过程已经阅读完成，

1， 定义一个DefaultFilterChainManager对象

2， 首先加载默认的filter

3， 加载xml文件中定义的filter

4， 加载xml文件定义的url和filter映射关系

5， 将映射关系解析为以url为键，NamedFilterList为值的键值对。

6， 在解析的过程中，对每个url和对应的过滤条件，都会放到对应filter的appliedPaths中（在PathMatchingFilter中定义）。

现在FilterChainManager的对象已经创建完毕，并且每个filter也已经实例化完毕。

构造SpingShiroFilter

在创建SpringShiroFilter之前还要将刚才创建的FilterChainManager对象包装成一个PathMatchingFilterChainResolver对象（注释的意思是：不直接将FilterChainManager对象暴露给AbstractShiroFilter的实现者，在这里就是SpringShiroFilter。）

 

 

PathMatchingFilterChainResolver最重要的作用是：当请求url来的时候，他担任匹配工作（调用该类的getChain方法做匹配，暂时先不分析该方法，等知道在哪里调用该方法时候再分析。其实问题二此时已经可以解答，通过该方法就可以知道，某个url匹配到过滤链的第一个规则时就return了。）

上图最后一句话执行完成后，一个SpringShiroFilter创建完毕。

请求过滤过程分析(上)

下面分析当url请求到来的时候，shiro是如何完成过滤的。首先通过图片大致的了解一下。

 

 

现在分析AbstractShiroFilter的doFilterInternal()方法

protected void doFilterInternal(ServletRequest servletRequest, ServletResponse servletResponse, final FilterChain chain)            throws ServletException, IOException {        Throwable t = null;        try {            final ServletRequest request = prepareServletRequest(servletRequest, servletResponse, chain);            final ServletResponse response = prepareServletResponse(request, servletResponse, chain);            final Subject subject = createSubject(request, response);            subject.execute(new Callable() {                public Object call() throws Exception {                    updateSessionLastAccessTime(request, response);                    executeChain(request, response, chain);                    return null;                }            });        } catch (ExecutionException ex) {            t = ex.getCause();        } catch (Throwable throwable) {            t = throwable;        }        //…………    }

暂时不关心subject相关的创建等过程，只关心这行代码

executeChain(request, response, chain);

具体实现如下

protected void executeChain(ServletRequest request, ServletResponse response, FilterChain origChain)            throws IOException, ServletException {        FilterChain chain = getExecutionChain(request, response, origChain);        chain.doFilter(request, response);}

再看getExecutionChain(request, response, origChain);具体实现如下：

protected FilterChain getExecutionChain(ServletRequest request, ServletResponse response, FilterChain origChain) {        FilterChain chain = origChain;        FilterChainResolver resolver = getFilterChainResolver();        if (resolver == null) {            log.debug("No FilterChainResolver configured.  Returning original FilterChain.");            return origChain;        }        FilterChain resolved = resolver.getChain(request, response, origChain);        if (resolved != null) {            log.trace("Resolved a configured FilterChain for the current request.");            chain = resolved;        } else {            log.trace("No FilterChain configured for the current request.  Using the default.");        }        return chain;    }

可以发现，这里用到了我们在创建SpringShiroFilter时传递的FilterChainResolver，至此，我们终于找到了getChain()方法在这里被调用了。其源码实现如下

public FilterChain getChain(ServletRequest request, ServletResponse response, FilterChain originalChain) {        FilterChainManager filterChainManager = getFilterChainManager();        if (!filterChainManager.hasChains()) {            return null;        }        String requestURI = getPathWithinApplication(request);        //the 'chain names' in this implementation are actually path patterns defined by the user.  We just use them        //as the chain name for the FilterChainManager's requirements        for (String pathPattern : filterChainManager.getChainNames()) {            // If the path does match, then pass on to the subclass implementation for specific checks:            if (pathMatches(pathPattern, requestURI)) {                if (log.isTraceEnabled()) {                    log.trace("Matched path pattern [" + pathPattern + "] for requestURI [" + requestURI + "].  " +                            "Utilizing corresponding filter chain...");                }                return filterChainManager.proxy(originalChain, pathPattern);            }        }        return null;    }

从for循环可以看出，当匹配到第一个url规则，则return一个代表这个url规则的FilterChain给web容器执行。

 

问题二解答：每个url在匹配他的FilterChain时，当匹配到第一个URL规则时，就返回。

 

 

请求过滤过程分析(下)

FilterChain的实现类为org.apache.shiro.web.servlet.ProxiedFilterChain

从该类的doFilter方法可以知道，它会将Filter链的Filter的doFilter方法顺序执行一遍。下图展示了这一过程

 

现在只需要分析每个Filter的doFilter方法就行了。

先看一下shiro整个filter框架继承关系(图片来自第八章 拦截器机制——《跟我学Shiro》)

 

上面是它的继承关系：最终的doFilter方法在OncePerRequestFilter中实现，具体代码如下：

public final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)            throws ServletException, IOException {        String alreadyFilteredAttributeName = getAlreadyFilteredAttributeName();        if ( request.getAttribute(alreadyFilteredAttributeName) != null ) {            log.trace("Filter '{}' already executed.  Proceeding without invoking this filter.", getName());            filterChain.doFilter(request, response);        } else //noinspection deprecation            if (/* added in 1.2: */ !isEnabled(request, response) ||                /* retain backwards compatibility: */ shouldNotFilter(request) ) {            log.debug("Filter '{}' is not enabled for the current request.  Proceeding without invoking this filter.",                    getName());            filterChain.doFilter(request, response);        } else {            // Do invoke this filter...            log.trace("Filter '{}' not yet executed.  Executing now.", getName());            request.setAttribute(alreadyFilteredAttributeName, Boolean.TRUE);            try {                doFilterInternal(request, response, filterChain);            } finally {                // Once the request has finished, we're done and we don't                // need to mark as 'already filtered' any more.                request.removeAttribute(alreadyFilteredAttributeName);            }        }    }

可以发现该方法最终会调用doFilterInternal(request, response, filterChain);来完成具体的过滤操作，doFilterInternal方法在 SpringShiroFilter的直接父类AbstractShiroFilter的具体实现过程已经在上面分析过了：具体的就是shiro真正验证授权前的subject，session等初始化的工作，使得后面的过滤以及验证授权工作可以得到subject等然后正常工作。完成后调用其他shiro filter进行继续过滤

 

而除了shiroFilter之外，其余的filter都是AdviceFilter分支的子类。刚才看了AbstractShiroFilter的doFilterInternal方法，现在看一下AdviceFilter对该方法的实现：

public void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain)            throws ServletException, IOException {        Exception exception = null;        try {            boolean continueChain = preHandle(request, response);            if (log.isTraceEnabled()) {                log.trace("Invoked preHandle method.  Continuing chain?: [" + continueChain + "]");            }            if (continueChain) {                executeChain(request, response, chain);            }            postHandle(request, response);            if (log.isTraceEnabled()) {                log.trace("Successfully invoked postHandle method");            }        } catch (Exception e) {            exception = e;        } finally {            cleanup(request, response, exception);        }    }

与AbstractShiroFilter的doFilterInternal方法不同的是，这里通过continueChain变量来判断到底后续的filter会不会被继续执行。而该变量的值由preHandle（）函数决定。

 

基本上所有在系统中用到的filter都是继承PathMatchingFilter类的。看一下该类的preHandle()函数实现,可以发现，我们在xml文件中定义的url匹配，在这里面可以看到匹配原则了:

protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {        if (this.appliedPaths == null || this.appliedPaths.isEmpty()) {            if (log.isTraceEnabled()) {                log.trace("appliedPaths property is null or empty.  This Filter will passthrough immediately.");            }            return true;        }        for (String path : this.appliedPaths.keySet()) {            // If the path does match, then pass on to the subclass implementation for specific checks            //(first match 'wins'):            if (pathsMatch(path, request)) {                log.trace("Current requestURI matches pattern '{}'.  Determining filter chain execution...", path);                Object config = this.appliedPaths.get(path);                return isFilterChainContinued(request, response, path, config);            }        }        //no path matched, allow the request to go through:        return true;    }

继续调用isFilterChainContinued(request, response, path, config)--> onPreHandle(request, response, pathConfig);

分析onPreHandle()，PathMatchingFilter自己并没有实现，只是简单的返回true。所以当我们自定义filter的时候，要将具体的逻辑实现在该方法中,或者实现该类的子类AccessControlFilter(该类对onPreHandle()方法进行了更细致的划分，大部分一般会继承该类)

有兴趣的可以分析一下shiro自带的这些filter