如何在过滤器中获取servlet的元信息？

问题描述

我想以声明的方式向servlet方法添加权限，例如：

// servlet
@Perms("admin","finance")
public void doPost(servletRequest req,servletResponse res) {
   ...
}

// web filter
public void doFilter(ServletRequest req,ServletResponse res,FilterChain chain) {
   List<String> allowedRoles = ... // somehow get values from @Perms
} 

也许还有其他方法可以不带注释，但这只是我想要做什么的一个例子。

或更抽象的例子：

@WebServlet("/someaddress")

// servlet
@What("have a nice day")
public void doPost(servletRequest req,servletResponse res) {
   ...
}

@WebFilter("/*")
// web filter
public void doFilter(ServletRequest req,FilterChain chain) {
   String msg = ... // somehow get values from @What
} 

解决方法

这是解决方法

1. 声明注释

@Retention(RetentionPolicy.RUNTIME)
public @interface What {
    String[] value();
}

1. 在servlet中覆盖init方法（我认为声明另一个类，所有的servlet将被该init继承是有用的）

    @Override
    public void init() throws ServletException {
        ServletContext ctx = this.getServletContext();
        final Class[] sFormalArgs = {HttpServletRequest.class,HttpServletResponse.class};
        try {
            Method m = this.getClass().getDeclaredMethod("doGet",sFormalArgs); // do the same with other methods
            What a = m.getAnnotation(What.class);
            String[] value = a.value();
            ctx.setAttribute("someStuff",value);

        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }
    }

1. 向方法添加注释

    @What({"admin","finance"})
    @Override
    protected void doGet(HttpServletRequest req,HttpServletResponse resp)
    {
        ....
    }

1. 通过网络过滤器获取它

    @Override
    public void doFilter(ServletRequest servletRequest,ServletResponse servletResponse,FilterChain filterChain
    ) {
        HttpServletRequest req = (HttpServletRequest) servletRequest;
        ServletContext ctx = req.getServletContext();
        Object o = ctx.getAttribute("someStuff");
    }

别忘了处理错误和多方面的问题