Question

我正在尝试报告从我的webapp返回的每个HTTP状态代码。但是，状态代码似乎无法通过ServletResponse访问，或者即使我将其转换为HttpServletResponse也是如此。有没有办法在ServletFilter中访问这个值？

Answer 1

首先，您需要将状态代码保存在可访问的位置。最好用你的实现包装响应并保存在那里：

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;
    }

}

为了使用这个包装器，您需要添加一个servlet过滤器，如果您可以进行报告：

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

从Servlet 3.0开始，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），您不需要包装器。

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

Answer 3

还需要包含#sendRedirect的包装器，最好将状态初始化为'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 4

David的回答中缺少的一件事是你还应该覆盖另一种形式的sendError：

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

Answer 5

除了David的回答之外，您还需要覆盖重置方法：

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

...以及弃用的setStatus（int，String）

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

Answer 6

编写一个HttpServletResponseWrapper并覆盖所有setStatus（），sendError（）和sendRedirect（）方法来记录所有内容。编写一个过滤器，在每次请求时将包装器交换为响应对象。

Answer 7

如果您遇到旧容器，那么使用实际状态代码的David Rabinowitz的替代解决方案（如果在使用包装器设置后更改）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：在使用偷偷摸摸的反射和内省来获取私有数据值时，会对类层次结构进行大量假设。

如何从ServletFilter中的ServletResponse中获取HTTP状态代码？

7 个答案: