本文主要是介绍Spring Acegi框架授权的实现，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
原文网址：http://www.bianceng.cn/Programming/Java/201103/25348.htm
我们从FilterSecurityInterceptor我们从入手看看怎样进行授权的：
Java代码
//这里是拦截器拦截HTTP请求的入口
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
FilterInvocation fi = new FilterInvocation(request, response, chain);
invoke(fi);
}
//这是具体的拦截调用
public void invoke(FilterInvocation fi) throws IOException, ServletException {
if ((fi.getRequest() != null) && (fi.getRequest ().getAttribute(FILTER_APPLIED) != null)
&& observeOncePerRequest) {
//在第一次进行过安全检查之后就不会再做了
fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
} else {
//这是第一次收到相应的请求，需要做安全检测，同时把标志为设置好 - FILTER_APPLIED，下次就再有请求就不会作相同的安全检查了
if (fi.getRequest() != null) {
fi.getRequest().setAttribute(FILTER_APPLIED, Boolean.TRUE);
}
//这里是做安全检查的地方
InterceptorStatusToken token = super.beforeInvocation(fi);
//接着向拦截器链执行
try {
fi.getChain().doFilter(fi.getRequest(), fi.getResponse ());
} finally {
super.afterInvocation(token, null);
}
}
}
我们看看在AbstractSecurityInterceptor是怎样对HTTP请求作安全检测的：
Java代码
protected InterceptorStatusToken beforeInvocation(Object object) {
Assert.notNull(object, "Object was null");
if (!getSecureObjectClass().isAssignableFrom(object.getClass())) {
throw new IllegalArgumentException("Security invocation attempted for object "
+ object.getClass().getName()
+ " but AbstractSecurityInterceptor only configured to support secure objects of type: "
+ getSecureObjectClass());
}
//这里读取配置FilterSecurityInterceptor的ObjectDefinitionSource属性 ，这些属性配置了资源的安全设置
ConfigAttributeDefinition attr = this.obtainObjectDefinitionSource ().getAttributes(object);
if (attr == null) {
if(rejectPublicInvocations) {
throw new IllegalArgumentException(
"No public invocations are allowed via this AbstractSecurityInterceptor. "
+ "This indicates a configuration error because the "
+ "AbstractSecurityInterceptor.rejectPublicInvocations property is set to 'true'");
}
if (logger.isDebugEnabled()) {
logger.debug("Public object - authentication not attempted");
}
publishEvent(new PublicInvocationEvent(object));
return null; // no further work post-invocation
}
if (logger.isDebugEnabled()) {
logger.debug("Secure object: " + object.toString() + "; ConfigAttributes: " + attr.toString());
}
//这里从SecurityContextHolder中去取Authentication对象，一般在登录时 会放到SecurityContextHolder中去
if (SecurityContextHolder.getContext().getAuthentication() == null) {
credentialsNotFound(messages.getMessage ("AbstractSecurityInterceptor.authenticationNotFound",
"An Authentication object was not found in the SecurityContext"), object, attr);
}
// 如果前面没有处理鉴权，这里需要对鉴权进行处理
Authentication authenticated;
if (!SecurityContextHolder.getContext().getAuthentication ().isAuthenticated() || alwaysReauthenticate) {
try {//调用配置好的AuthenticationManager处理鉴权，如果鉴权不成 功，抛出异常结束处理
authenticated = this.authenticationManager.authenticate (SecurityContextHolder.getContext()
.getAuthentication());
} catch (AuthenticationException authenticationException) {
throw authenticationException;
}
// We don't authenticated.setAuthentication(true), because each provider should do that
if (logger.isDebugEnabled()) {
logger.debug("Successfully Authenticated: " + authenticated.toString());
}
//这里把鉴权成功后得到的Authentication保存到 SecurityContextHolder中供下次使用
SecurityContextHolder.getContext().setAuthentication (authenticated);
} else {//这里处理前面已经通过鉴权的请求，先从SecurityContextHolder 中去取得Authentication
authenticated = SecurityContextHolder.getContext ().getAuthentication();
if (logger.isDebugEnabled()) {
logger.debug("Previously Authenticated: " + authenticated.toString());
}
}
// 这是处理授权的过程
try {
//调用配置好的AccessDecisionManager来进行授权
this.accessDecisionManager.decide(authenticated, object, attr);
} catch (AccessDeniedException accessDeniedException) {
//授权不成功向外发布事件
AuthorizationFailureEvent event = new AuthorizationFailureEvent(object, attr, authenticated,
accessDeniedException);
publishEvent(event);
throw accessDeniedException;
}
if (logger.isDebugEnabled()) {
logger.debug("Authorization successful");
}
AuthorizedEvent event = new AuthorizedEvent(object, attr, authenticated);
publishEvent(event);
// 这里构建一个RunAsManager来替代当前的Authentication对象，默认情况 下使用的是NullRunAsManager会把SecurityContextHolder中的Authentication对象清空
Authentication runAs = this.runAsManager.buildRunAs(authenticated, object, attr);
if (runAs == null) {
if (logger.isDebugEnabled()) {
logger.debug("RunAsManager did not change Authentication object");
}
// no further work post-invocation
return new InterceptorStatusToken(authenticated, false, attr, object);
} else {
if (logger.isDebugEnabled()) {
logger.debug("Switching to RunAs Authentication: " + runAs.toString());
}
SecurityContextHolder.getContext().setAuthentication (runAs);
// revert to token.Authenticated post-invocation
return new InterceptorStatusToken(authenticated, true, attr, object);
}
}
到这里我们假设配置AffirmativeBased作为AccessDecisionManager：
Java代码
//这里定义了决策机制，需要全票才能通过
public void decide(Authentication authentication, Object object, ConfigAttributeDefinition config)
throws AccessDeniedException {
//这里取得配置好的迭代器集合
Iterator iter = this.getDecisionVoters().iterator();
int deny = 0;
//依次使用各个投票器进行投票，并对投票结果进行计票
while (iter.hasNext()) {
AccessDecisionVoter voter = (AccessDecisionVoter) iter.next ();
int result = voter.vote(authentication, object, config);
//这是对投票结果进行处理，如果遇到其中一票通过，那就授权通过， 如果是弃权或者反对，那就继续投票
switch (result) {
case AccessDecisionVoter.ACCESS_GRANTED:
return;
case AccessDecisionVoter.ACCESS_DENIED:
//这里对反对票进行计数
deny++;
break;
default:
break;
}
}
//如果有反对票，抛出异常，整个授权不通过
if (deny > 0) {
throw new AccessDeniedException(messages.getMessage ("AbstractAccessDecisionManager.accessDenied",
"Access is denied"));
}
// 这里对弃权票进行处理，看看是全是弃权票的决定情况，默认是不通过， 由allowIfAllAbstainDecisions变量控制
checkAllowIfAllAbstainDecisions();
}
具体的投票由投票器进行，我们这里配置了RoleVoter来进行投票：
public int vote(Authentication authentication, Object object, ConfigAttributeDefinition config) {
int result = ACCESS_ABSTAIN;
//这里取得资源的安全配置
Iterator iter = config.getConfigAttributes();
while (iter.hasNext()) {
ConfigAttribute attribute = (ConfigAttribute) iter.next ();
if (this.supports(attribute)) {
result = ACCESS_DENIED;
// 这里对资源配置的安全授权级别进行判断，也就是匹配ROLE为前 缀的角色配置
// 遍历每个配置属性，如果其中一个匹配该主体持有的 GrantedAuthority,则访问被允许。
for (int i = 0; i < authentication.getAuthorities ().length; i++) {
if (attribute.getAttribute().equals (authentication.getAuthorities()[i].getAuthority())) {
return ACCESS_GRANTED;
}
}
}
}
return result;
}
上面就是对整个授权过程的一个分析，从FilterSecurityInterceptor拦截Http请求入 手，然后读取对资源的安全配置以后，把这些信息交由AccessDecisionManager来进行决 策，Spring为我们提供了若干决策器来使用，在决策器中我们可以配置投票器来完成投票 ，我们在上面具体分析了角色投票器的使用过程。
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