如何从ServletFilter的ServletResponse中获取HTTP状态码？

Question

我试图报告从我的webapp返回的每个HTTP状态代码。然而，状态码似乎无法通过ServletResponse访问，或者即使我将它转换为HttpServletResponse。有没有办法在ServletFilter中访问这个值？

Answer 1

首先，您需要将状态码保存在可访问的位置。最好的包装您的实现的响应，并保持它有：

public class StatusExposingServletResponse extends HttpServletResponseWrapper { 

    private int httpStatus; 

    public StatusExposingServletResponse(HttpServletResponse response) { 
     super(response); 
    } 

    @Override 
    public void sendError(int sc) throws IOException { 
     httpStatus = sc; 
     super.sendError(sc); 
    } 

    @Override 
    public void sendError(int sc, String msg) throws IOException { 
     httpStatus = sc; 
     super.sendError(sc, msg); 
    } 


    @Override 
    public void setStatus(int sc) { 
     httpStatus = sc; 
     super.setStatus(sc); 
    } 

    public int getStatus() { 
     return httpStatus; 
    } 

} 

为了使用这种包装，您需要添加一个Servlet过滤器，是你可以做你的报告：

public class StatusReportingFilter implements Filter { 

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { 
     StatusExposingServletResponse response = new StatusExposingServletResponse((HttpServletResponse)res); 
     chain.doFilter(req, response); 
     int status = response.getStatus(); 
     // report 
    } 

    public void init(FilterConfig config) throws ServletException { 
     //empty 
    } 

    public void destroy() { 
     // empty 
    } 

} 

Answer 2

编写HttpServletResponseWrapper并覆盖所有的setStatus（），sendError（）和sendRedirect（）方法来记录所有内容。编写一个过滤器，用于在每个请求中为您的包装器交换响应对象。

Answer 3

有一两件事从上面大卫的回答缺少的是你也应该重写sendError的其它形式：

@Override 
public void sendError(int sc, String msg) throws IOException { 
    httpStatus = sc; 
    super.sendError(sc, msg); 
} 

Answer 4

由于Servlet的3.0，有一个HttpServletResponse#getStatus()。因此，如果有升级空间，请升级到Servlet 3.0（Tomcat 7，Glassfish 3，JBoss AS 6等），并且不需要封装。

chain.doFilter(request, response); 
int status = ((HttpServletResponse) response).getStatus(); 

Answer 5

还需要包括用于#sendRedirect的包装，它会更好，如果你坚持使用旧的容器，然后初始化状态为“200”，而不是“0”

private int httpStatus = SC_OK; 

... 

@Override 
public void sendRedirect(String location) throws IOException { 
    httpStatus = SC_MOVED_TEMPORARILY; 
    super.sendRedirect(location); 
} 

Answer 6

给David拉比诺维茨一个替代的解决方案，它使用的实际状态代码（在它正在使用的包装器设置后它的变化的情况下）是：

public class StatusExposingServletResponse extends HttpServletResponseWrapper { 

    public StatusExposingServletResponse(HttpServletResponse response) { 
     super(response); 
    } 

    @Override 
    public void sendError(int sc) throws IOException { 
     super.sendError(sc); 
    } 

    @Override 
    public void sendError(int sc, String msg) throws IOException { 
     super.sendError(sc, msg); 
    } 

    @Override 
    public void setStatus(int sc) { 
     super.setStatus(sc); 
    } 

    public int getStatus() { 
     try { 
      ServletResponse object = super.getResponse(); 

      // call the private method 'getResponse' 
      Method method1 = object.getClass().getMethod("getResponse"); 
      Object servletResponse = method1.invoke(object, new Object[] {}); 

      // call the parents private method 'getResponse' 
      Method method2 = servletResponse.getClass().getMethod("getResponse"); 
      Object parentResponse = method2.invoke(servletResponse, new Object[] {}); 

      // call the parents private method 'getResponse' 
      Method method3 = parentResponse.getClass().getMethod("getStatus"); 
      int httpStatus = (Integer) method3.invoke(parentResponse, new Object[] {}); 

      return httpStatus; 
     } 
     catch (Exception e) { 
      e.printStackTrace(); 
      return HttpServletResponse.SC_ACCEPTED; 
     } 
    } 

    public String getMessage() { 
     try { 
      ServletResponse object = super.getResponse(); 

      // call the private method 'getResponse' 
      Method method1 = object.getClass().getMethod("getResponse"); 
      Object servletResponse = method1.invoke(object, new Object[] {}); 

      // call the parents private method 'getResponse' 
      Method method2 = servletResponse.getClass().getMethod("getResponse"); 
      Object parentResponse = method2.invoke(servletResponse, new Object[] {}); 

      // call the parents private method 'getResponse' 
      Method method3 = parentResponse.getClass().getMethod("getReason"); 
      String httpStatusMessage = (String) method3.invoke(parentResponse, new Object[] {}); 

      if (httpStatusMessage == null) { 
       int status = getStatus(); 
       java.lang.reflect.Field[] fields = HttpServletResponse.class.getFields(); 

       for (java.lang.reflect.Field field : fields) { 
        if (status == field.getInt(servletResponse)) { 
         httpStatusMessage = field.getName(); 
         httpStatusMessage = httpStatusMessage.replace("SC_", ""); 
         if (!"OK".equals(httpStatusMessage)) { 
          httpStatusMessage = httpStatusMessage.toLowerCase(); 
          httpStatusMessage = httpStatusMessage.replace("_", " "); 
          httpStatusMessage = capitalizeFirstLetters(httpStatusMessage); 
         } 

         break; 
        } 
       } 
      } 

      return httpStatusMessage; 
     } 
     catch (Exception e) { 
      e.printStackTrace(); 
      return ""; 
     } 
    } 

    private static String capitalizeFirstLetters(String s) { 

     for (int i = 0; i < s.length(); i++) { 
      if (i == 0) { 
       // Capitalize the first letter of the string. 
       s = String.format("%s%s", Character.toUpperCase(s.charAt(0)), s.substring(1)); 
      } 

      if (!Character.isLetterOrDigit(s.charAt(i))) { 
       if (i + 1 < s.length()) { 
        s = String.format("%s%s%s", s.subSequence(0, i + 1), 
          Character.toUpperCase(s.charAt(i + 1)), 
          s.substring(i + 2)); 
       } 
      } 
     } 

     return s; 

    } 

    @Override 
    public String toString() { 
     return this.getMessage() + " " + this.getStatus(); 
    } 

} 

警告：大量的类层次结构的假设的使用SNE时aky反思和内省去获得私人数据价值。

Answer 7

除了大卫的回答，您还需要重写复位方法：

@Override 
public void reset() { 
    super.reset(); 
    this.httpStatus = SC_OK; 
} 

...以及已过时setStatus（INT，字符串）

@Override 
public void setStatus(int status, String string) { 
    super.setStatus(status, string); 
    this.httpStatus = status; 
}