spring aop 拦截业务方法，实现权限控制示例

难点：aop类是普通的java类，session是无法注入的，那么在有状态的系统中如何获取用户相关信息呢，session是必经之路啊，获取session就变的很重要。思索很久没有办法，后来在网上看到了解决办法。

思路是：

i. SysContext  成员变量 request,session,response

ii. Filter 目的是给 SysContext 中的成员赋值

iii.然后在AOP中使用这个SysContext的值

要用好，需要理解  ThreadLocal和  和Filter 执行顺序

1.aop获取request，response，session等

public class SysContext {
  private static ThreadLocal<HttpServletRequest> requestLocal=new ThreadLocal<HttpServletRequest>();
  private static ThreadLocal<HttpServletResponse> responseLocal=new ThreadLocal<HttpServletResponse>(); 

  public static HttpServletRequest getRequest(){
   return requestLocalget();
  } 

  public static void setRequest(HttpServletRequest request){
   requestLocalset(request);
  } 

  public static HttpServletResponse getResponse(){
   return responseLocalget();
  } 

  public static void setResponse(HttpServletResponse response){
   responseLocalset(response);
  } 

  public static HttpSession getSession(){
   return (HttpSession)(getRequest())getSession();
  }
 }

2.添加过滤器

public class GetContextFilter implements Filter{ 

  @Override
  public void destroy() { 

  } 

  @Override
  public void doFilter(ServletRequest request, ServletResponse response,
    FilterChain chain) throws IOException, ServletException {
   SysContextsetRequest((HttpServletRequest)request);
   SysContextsetResponse((HttpServletResponse)response);
   chaindoFilter(request, response);
  } 

  @Override
  public void init(FilterConfig config) throws ServletException { 

  } 

 }

3.配置web.xml

将这部分放置在最前面，这样可以过滤到所有的请求

<filter>
  <filter-name>sessionFilter</filter-name>
  <filter-class>comuneifilterGetContextFilter</filter-class>
 </filter> 

 <filter-mapping>
  <filter-name>sessionFilter</filter-name>
  <url-pattern>*</url-pattern>
 </filter-mapping> 

4.spring aop before

从session中取出用户名，如果不存在，抛出异常跳转，将错误信息放到request中

@Aspect
 public class AdminAspect {
  ActionContext context = ActionContextgetContext();
  HttpServletRequest request;
  HttpServletResponse response; 

  @Before("execution(* comuneiActionAdminActiongetPrivileges())")
  public void adminPrivilegeCheck()
    throws Throwable {
   HttpSession session = SysContextgetSession();
   request = SysContextgetRequest();
   response = SysContextgetResponse();
   String userName = ""; 

   try {
    userName = sessiongetAttribute("userName")toString();
    if(userName==null||userNameequals(""))
     throw new Exception("no privilege");
   } catch (Exception ex) {
    requestsetAttribute("msg", "{\"res\":\"" + "无权限" + "\"}");
    try {
     requestgetRequestDispatcher("/jsp/jsonjsp")forward(
       request, response);
    } catch (ServletException e) {
     eprintStackTrace();
    } catch (IOException e) {
     eprintStackTrace();
    }
   }
  }
 }

5.applicationContext.xml

<bean id="adminAspect" class="comuneiaopAdminAspect"></bean> 

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