Spring Security3源码分析-Filter链排序分析
通过前面SpringSecurity提供的各种Filter的分析，大体上知道每个Filter具体的用途了。
SpringSecurity一共提供了20个Filter，我目前只分析了13个（如果http的auto-config="true"，那默认的filter列表都包含在这13个里面了），另外7个在后面的源码分析中碰到时会逐个讲解。
在分析http标签时，已经提到filter排序的问题了，但是没有深入。
现在再回头看filter是如何排序的。下面的代码片段截取自HttpSecurityBeanDefinitionParser类，
//定义未排序filter集合。该集合中的对象为OrderDecorator实例。
List<OrderDecorator> unorderedFilterChain = new ArrayList<OrderDecorator>();
//添加http、认证相关的filter集合
unorderedFilterChain.addAll(httpBldr.getFilters());
unorderedFilterChain.addAll(authBldr.getFilters());
//定义RequestCacheAwareFilter过滤器，并添加到unorderedFilterChain中
BeanDefinition requestCacheAwareFilter = new RootBeanDefinition(RequestCacheAwareFilter.class);
requestCacheAwareFilter.getPropertyValues().addPropertyValue("requestCache", authBldr.getRequestCache());
unorderedFilterChain.add(new OrderDecorator(requestCacheAwareFilter, REQUEST_CACHE_FILTER));
//添加自定义filter
unorderedFilterChain.addAll(buildCustomFilterList(element, pc));
//根据排序规则进行排序
Collections.sort(unorderedFilterChain, new OrderComparator());
//检查每个filter与前一个filter的位置是否相同
//这里的检查主要是防止自定义filter直接配置position属性，造成与默认的filter产生order冲突
checkFilterChainOrder(unorderedFilterChain, pc, source);
//重新定义filterChain，把经过排序的filter依次添加到filterChain集合中
List<BeanMetadataElement> filterChain = new ManagedList<BeanMetadataElement>();
for (OrderDecorator od : unorderedFilterChain) {
filterChain.add(od.bean);
}细心的同学会发现httpBldr.getFilters()、authBldr.getFilters()两个方法返回的就是OrderDecorator对象的集合列表。并且OrderDecorator对象已经将filter与SecurityFilters中的order关联了起来
unorderedFilterChain.addAll(httpBldr.getFilters());
unorderedFilterChain.addAll(authBldr.getFilters());顺便看一下创建自定义过滤器部分
List<OrderDecorator> buildCustomFilterList(Element element, ParserContext pc) {
List<Element> customFilterElts = DomUtils.getChildElementsByTagName(element, Elements.CUSTOM_FILTER);
List<OrderDecorator> customFilters = new ArrayList<OrderDecorator>();
final String ATT_AFTER = "after";
final String ATT_BEFORE = "before";
final String ATT_POSITION = "position";
//循环自定义标签列表custom-filter
for (Element elt: customFilterElts) {
String after = elt.getAttribute(ATT_AFTER);
String before = elt.getAttribute(ATT_BEFORE);
String position = elt.getAttribute(ATT_POSITION);
String ref = elt.getAttribute(ATT_REF);
if (!StringUtils.hasText(ref)) {
pc.getReaderContext().error("The '" + ATT_REF + "' attribute must be supplied", pc.extractSource(elt));
}
RuntimeBeanReference bean = new RuntimeBeanReference(ref);
if(WebConfigUtils.countNonEmpty(new String[] {after, before, position}) != 1) {
pc.getReaderContext().error("A single '" + ATT_AFTER + "', '" + ATT_BEFORE + "', or '" +
ATT_POSITION + "' attribute must be supplied", pc.extractSource(elt));
}
//如果指定了position，直接将filter与order产生关联关系
if (StringUtils.hasText(position)) {
customFilters.add(new OrderDecorator(bean, SecurityFilters.valueOf(position)));
//如果指定了after，将filter与after值加一产生关联关系
} else if (StringUtils.hasText(after)) {
SecurityFilters order = SecurityFilters.valueOf(after);
if (order == SecurityFilters.LAST) {
customFilters.add(new OrderDecorator(bean, SecurityFilters.LAST));
} else {
customFilters.add(new OrderDecorator(bean, order.getOrder() + 1));
}
//如果指定了before，将filter与before-1产生关联关系
} else if (StringUtils.hasText(before)) {
SecurityFilters order = SecurityFilters.valueOf(before);
if (order == SecurityFilters.FIRST) {
customFilters.add(new OrderDecorator(bean, SecurityFilters.FIRST));
} else {
customFilters.add(new OrderDecorator(bean, order.getOrder() - 1));
}
}
}
return customFilters;
}这里用到三个重要的与排序相关的类及枚举，分别是OrderDecorator、OrderComparator以及SecurityFilters枚举
首先看SecurityFilters枚举定义
enum SecurityFilters {
FIRST (Integer.MIN_VALUE),
//order=100
CHANNEL_FILTER,
//order=200
CONCURRENT_SESSION_FILTER,
//依次递增……
SECURITY_CONTEXT_FILTER,
LOGOUT_FILTER,
X509_FILTER,
PRE_AUTH_FILTER,
CAS_FILTER,
FORM_LOGIN_FILTER,
OPENID_FILTER,
LOGIN_PAGE_FILTER,
DIGEST_AUTH_FILTER,
BASIC_AUTH_FILTER,
REQUEST_CACHE_FILTER,
SERVLET_API_SUPPORT_FILTER,
REMEMBER_ME_FILTER,
ANONYMOUS_FILTER,
SESSION_MANAGEMENT_FILTER,
EXCEPTION_TRANSLATION_FILTER,
FILTER_SECURITY_INTERCEPTOR,
SWITCH_USER_FILTER,
LAST (Integer.MAX_VALUE);
//这里设置100，主要给自定义过滤器提供after、before的预留位置
//也就是说，在某个默认的过滤器前后只能自定义99个过滤器，虽然可能性几乎为0
private static final int INTERVAL = 100;
private final int order;
//返回的order值=序号*间隔100
private SecurityFilters() {
order = ordinal() * INTERVAL;
}
private SecurityFilters(int order) {
this.order = order;
}
//主要通过该方法返回Filter的位置
public int getOrder() {
return order;
}
}由此可见，该类维护了SpringSecurity中每个filter的顺序
接着看OrderDecorator类。这个类实现org.springframework.core.Ordered接口
class OrderDecorator implements Ordered {
BeanMetadataElement bean;
int order;
//构造函数传递两个参数1.bean定义；2.filter在链中的位置
public OrderDecorator(BeanMetadataElement bean, SecurityFilters filterOrder) {
this.bean = bean;
this.order = filterOrder.getOrder();
}
public OrderDecorator(BeanMetadataElement bean, int order) {
this.bean = bean;
this.order = order;
}
//实现接口方法getOrder
public int getOrder() {
return order;
}
public String toString() {
return bean + ", order = " + order;
}
}OrderComparator类的路径是org.springframework.core.OrderComparator，实际上是springcore包的一个比较器，可以顺便看下OrderComparator源码。下面截取的只是部分核心代码
public int compare(Object o1, Object o2) {
boolean p1 = (o1 instanceof PriorityOrdered);
boolean p2 = (o2 instanceof PriorityOrdered);
if (p1 && !p2) {
return -1;
}
else if (p2 && !p1) {
return 1;
}
//前面几行代码主要针对PriorityOrdered，这里不做分析
//分别获取Ordered接口实现类的getOrder方法得到order值
int i1 = getOrder(o1);
int i2 = getOrder(o2);
//对得到的order进行比较
return (i1 < i2) ? -1 : (i1 > i2) ? 1 : 0;
}
//获取Ordered接口的实现类，获取getOrder值
protected int getOrder(Object obj) {
return (obj instanceof Ordered ? ((Ordered) obj).getOrder() : Ordered.LOWEST_PRECEDENCE);
}通过以上的分析，可以总结如下
1.由SecurityFilters维持位置order
2.由OrderDecorator维持filter与order的对应关系
3.由OrderComparator负责比较OrderDecorator的先后顺序
附上默认的过滤器顺序列表
order过滤器名称100ChannelProcessingFilter200ConcurrentSessionFilter300SecurityContextPersistenceFilter400LogoutFilter500X509AuthenticationFilter600RequestHeaderAuthenticationFilter700CasAuthenticationFilter800UsernamePasswordAuthenticationFilter900OpenIDAuthenticationFilter1000DefaultLoginPageGeneratingFilter1100DigestAuthenticationFilter1200BasicAuthenticationFilter1300RequestCacheAwareFilter1400SecurityContextHolderAwareRequestFilter1500RememberMeAuthenticationFilter1600AnonymousAuthenticationFilter1700SessionManagementFilter1800ExceptionTranslationFilter1900FilterSecurityInterceptor2000SwitchUserFilter
以上标注红色的都已经分析完毕