概述
前不久刚学会使用权限注解()，开始思索了一番。最开始猜测实现方式是注解@Aspect，具体实现方式类似如下所示(切面记录审计日志)。后来发现并非如此，所以特地分析一下源码。
@Component
@Aspect
public class AuditLogAspectConfig {
@Pointcut("@annotation(com.ygsoft.ecp.mapp.basic.audit.annotation.AuditLog) || @annotation(com.ygsoft.ecp.mapp.basic.audit.annotation.AuditLogs)")
public void pointcut() {
}
@After(value="pointcut()")
public void after(JoinPoint joinPoint) {
//执行的逻辑
}
...
}权限注解的源码分析
DefaultAdvisorAutoProxyCreator这个类实现了BeanProcessor接口,当ApplicationContext读取所有的Bean配置信息后，这个类将扫描上下文，寻找所有的Advistor(一个Advisor是一个切入点和一个通知的组成)，将这些Advisor应用到所有符合切入点的Bean中。
@Configuration
public class ShiroAnnotationProcessorConfiguration extends AbstractShiroAnnotationProcessorConfiguration{
@Bean
@DependsOn("lifecycleBeanPostProcessor")
protected DefaultAdvisorAutoProxyCreator defaultAdvisorAutoProxyCreator() {
return super.defaultAdvisorAutoProxyCreator();
}
@Bean
protected AuthorizationAttributeSourceAdvisor authorizationAttributeSourceAdvisor(SecurityManager securityManager) {
return super.authorizationAttributeSourceAdvisor(securityManager);
}
}AuthorizationAttributeSourceAdvisor继承了StaticMethodMatcherPointcutAdvisor，如下代码所示，只匹配五个注解，也就是说只对这五个注解标注的类或者方法增强。StaticMethodMatcherPointcutAdvisor是静态方法切点的抽象基类，默认情况下它匹配所有的类。StaticMethodMatcherPointcut包括两个主要的子类分别是NameMatchMethodPointcut和AbstractRegexpMethodPointcut，前者提供简单字符串匹配方法前面，而后者使用正则表达式匹配方法前面。动态方法切点：DynamicMethodMatcerPointcut是动态方法切点的抽象基类，默认情况下它匹配所有的类，而且也已经过时，建议使用DefaultPointcutAdvisor和DynamicMethodMatcherPointcut动态方法代替。另外还需关注构造器中的传入的AopAllianceAnnotationsAuthorizingMethodInterceptor。
public class AuthorizationAttributeSourceAdvisor extends StaticMethodMatcherPointcutAdvisor {
private static final Logger log = LoggerFactory.getLogger(AuthorizationAttributeSourceAdvisor.class);
private static final Class<? extends Annotation>[] AUTHZ_ANNOTATION_CLASSES =
new Class[] {
RequiresPermissions.class, RequiresRoles.class,
RequiresUser.class, RequiresGuest.class, RequiresAuthentication.class
};
protected SecurityManager securityManager = null;
public AuthorizationAttributeSourceAdvisor() {
setAdvice(new AopAllianceAnnotationsAuthorizingMethodInterceptor());
}
public SecurityManager getSecurityManager() {
return securityManager;
}
public void setSecurityManager(org.apache.shiro.mgt.SecurityManager securityManager) {
this.securityManager = securityManager;
}
public boolean matches(Method method, Class targetClass) {
Method m = method;
if ( isAuthzAnnotationPresent(m) ) {
return true;
}
if ( targetClass != null) {
try {
m = targetClass.getMethod(m.getName(), m.getParameterTypes());
if ( isAuthzAnnotationPresent(m) ) {
return true;
}
} catch (NoSuchMethodException ignored) {
}
}
return false;
}
private boolean isAuthzAnnotationPresent(Method method) {
for( Class<? extends Annotation> annClass : AUTHZ_ANNOTATION_CLASSES ) {
Annotation a = AnnotationUtils.findAnnotation(method, annClass);
if ( a != null ) {
return true;
}
}
return false;
}
}AopAllianceAnnotationsAuthorizingMethodInterceptor在初始化时，interceptors添加了5个方法拦截器(都继承自AuthorizingAnnotationMethodInterceptor)，这5个拦截器分别对5种权限验证的方法进行拦截，执行invoke方法。
public class AopAllianceAnnotationsAuthorizingMethodInterceptor
extends AnnotationsAuthorizingMethodInterceptor implements MethodInterceptor {
public AopAllianceAnnotationsAuthorizingMethodInterceptor() {
List<AuthorizingAnnotationMethodInterceptor> interceptors =
new ArrayList<AuthorizingAnnotationMethodInterceptor>(5);
AnnotationResolver resolver = new SpringAnnotationResolver();
interceptors.add(new RoleAnnotationMethodInterceptor(resolver));
interceptors.add(new PermissionAnnotationMethodInterceptor(resolver));
interceptors.add(new AuthenticatedAnnotationMethodInterceptor(resolver));
interceptors.add(new UserAnnotationMethodInterceptor(resolver));
interceptors.add(new GuestAnnotationMethodInterceptor(resolver));
setMethodInterceptors(interceptors);
}
public Object invoke(MethodInvocation methodInvocation) throws Throwable {
org.apache.shiro.aop.MethodInvocation mi = createMethodInvocation(methodInvocation);
return super.invoke(mi);
}
...
}AopAllianceAnnotationsAuthorizingMethodInterceptor的invoke方法，又会调用超类AuthorizingMethodInterceptor的invoke方法，在该方法中先执行assertAuthorized方法，进行权限校验，校验不通过，抛出AuthorizationException异常，中断方法；校验通过，则执行methodInvocation.proceed()，该方法也就是被拦截并且需要权限校验的方法。
public abstract class AuthorizingMethodInterceptor extends MethodInterceptorSupport {
public Object invoke(MethodInvocation methodInvocation) throws Throwable {
assertAuthorized(methodInvocation);
return methodInvocation.proceed();
}
protected abstract void assertAuthorized(MethodInvocation methodInvocation) throws AuthorizationException;
}assertAuthorized方法最终执行的还是AuthorizingAnnotationMethodInterceptor.assertAuthorized，而AuthorizingAnnotationMethodInterceptor有5中的具体的实现类(RoleAnnotationMethodInterceptor, PermissionAnnotationMethodInterceptor, AuthenticatedAnnotationMethodInterceptor, UserAnnotationMethodInterceptor, GuestAnnotationMethodInterceptor)。
public abstract class AnnotationsAuthorizingMethodInterceptor extends AuthorizingMethodInterceptor {
protected void assertAuthorized(MethodInvocation methodInvocation) throws AuthorizationException {
//default implementation just ensures no deny votes are cast:
Collection<AuthorizingAnnotationMethodInterceptor> aamis = getMethodInterceptors();
if (aamis != null && !aamis.isEmpty()) {
for (AuthorizingAnnotationMethodInterceptor aami : aamis) {
if (aami.supports(methodInvocation)) {
aami.assertAuthorized(methodInvocation);
}
}
}
}
...
}AuthorizingAnnotationMethodInterceptor的assertAuthorized，首先从子类获取AuthorizingAnnotationHandler，再调用该实现类的assertAuthorized方法。
public abstract class AuthorizingAnnotationMethodInterceptor extends AnnotationMethodInterceptor
{
public AuthorizingAnnotationMethodInterceptor( AuthorizingAnnotationHandler handler ) {
super(handler);
}
public AuthorizingAnnotationMethodInterceptor( AuthorizingAnnotationHandler handler,
AnnotationResolver resolver) {
super(handler, resolver);
}
public Object invoke(MethodInvocation methodInvocation) throws Throwable {
assertAuthorized(methodInvocation);
return methodInvocation.proceed();
}
public void assertAuthorized(MethodInvocation mi) throws AuthorizationException {
try {
((AuthorizingAnnotationHandler)getHandler()).assertAuthorized(getAnnotation(mi));
}
catch(AuthorizationException ae) {
if (ae.getCause() == null) ae.initCause(new AuthorizationException("Not authorized to invoke method: " + mi.getMethod()));
throw ae;
}
}
}
现在分析其中一种实现类PermissionAnnotationMethodInterceptor，也是用的最多的，但是这个类的实际代码很少，很明显上述分析的getHandler在PermissionAnnotationMethodInterceptor中返回值为PermissionAnnotationHandler。
public class PermissionAnnotationMethodInterceptor extends AuthorizingAnnotationMethodInterceptor {
public PermissionAnnotationMethodInterceptor() {
super( new PermissionAnnotationHandler() );
}
public PermissionAnnotationMethodInterceptor(AnnotationResolver resolver) {
super( new PermissionAnnotationHandler(), resolver);
}
}在PermissionAnnotationHandler类中，终于发现实际的检验逻辑，还是调用的Subject.checkPermission()进行校验。
public class PermissionAnnotationHandler extends AuthorizingAnnotationHandler {
public PermissionAnnotationHandler() {
super(RequiresPermissions.class);
}
protected String[] getAnnotationValue(Annotation a) {
RequiresPermissions rpAnnotation = (RequiresPermissions) a;
return rpAnnotation.value();
}
public void assertAuthorized(Annotation a) throws AuthorizationException {
if (!(a instanceof RequiresPermissions)) return;
RequiresPermissions rpAnnotation = (RequiresPermissions) a;
String[] perms = getAnnotationValue(a);
Subject subject = getSubject();
if (perms.length == 1) {
subject.checkPermission(perms[0]);
return;
}
if (Logical.AND.equals(rpAnnotation.logical())) {
getSubject().checkPermissions(perms);
return;
}
if (Logical.OR.equals(rpAnnotation.logical())) {
boolean hasAtLeastOnePermission = false;
for (String permission : perms) if (getSubject().isPermitted(permission)) hasAtLeastOnePermission = true;
if (!hasAtLeastOnePermission) getSubject().checkPermission(perms[0]);
}
}
}
实现类似编程式AOP
定义一个注解
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Log {
String value() default "";
}继承StaticMethodMatcherPointcutAdvisor类，并实现相关的方法。
@SuppressWarnings("serial")
@Component
public class HelloAdvisor extends StaticMethodMatcherPointcutAdvisor{
public HelloAdvisor() {
setAdvice(new LogMethodInterceptor());
}
public boolean matches(Method method, Class targetClass) {
Method m = method;
if ( isAuthzAnnotationPresent(m) ) {
return true;
}
if ( targetClass != null) {
try {
m = targetClass.getMethod(m.getName(), m.getParameterTypes());
return isAuthzAnnotationPresent(m);
} catch (NoSuchMethodException ignored) {
}
}
return false;
}
private boolean isAuthzAnnotationPresent(Method method) {
Annotation a = AnnotationUtils.findAnnotation(method, Log.class);
return a!= null;
}
}
实现MethodInterceptor接口，定义切面处理的逻辑
public class LogMethodInterceptor implements MethodInterceptor{
public Object invoke(MethodInvocation invocation) throws Throwable {
Log log = invocation.getMethod().getAnnotation(Log.class);
System.out.println("log: "+log.value());
return invocation.proceed();
}
}定义一个测试类，并添加Log注解
@Component
public class TestHello {
@Log("test log")
public String say() {
return "ss";
}
}编写启动类，并且配置DefaultAdvisorAutoProxyCreator
@Configuration
public class TestBoot {
public static void main(String[] args) {
ApplicationContext ctx = new AnnotationConfigApplicationContext("com.fzsyw.test");
TestHello th = ctx.getBean(TestHello.class);
System.out.println(th.say());
}
@Bean
public DefaultAdvisorAutoProxyCreator defaultAdvisorAutoProxyCreator(){
DefaultAdvisorAutoProxyCreator da = new DefaultAdvisorAutoProxyCreator();
da.setProxyTargetClass(true);
return da;
}
}最终打印的结果如下，证明编程式的AOP生效。
log: test log
ss总结与思考
Shiro的注解式权限，使用确实方便，通过源码也分析了它的实现原理，比较核心的是配置DefaultAdvisorAutoProxyCreator和继承StaticMethodMatcherPointcutAdvisor。其中的5中权限注解，使用了统一一套代码架构，用到了的模板模式，方便扩展。最后自己也简单做了一个小例子，加深对编程式AOP的理解。
