Servlet 过滤器修改标头值，而 Servlet 请求包装器不起作用答案

【问题标题】：Servlet Filter modify header value with servlet request wrapper not workingServlet 过滤器修改标头值，而 Servlet 请求包装器不起作用
【发布时间】：2016-11-19 20:26:46
【问题描述】：

我正在尝试更改请求中的 Content-Type 标头，并在它到达我的 spring rest 控制器之前将其更改为“application/json”。我创建了一个 servlet 请求包装器来更改值，但是当请求到达控制器时，它仍然是“文本/纯文本”。日志显示，在点击 doFilter() 之前，标头值已更改；

这是我的类扩展 HttpServletRequestWrapper

class HttpServletRequestWritableWrapper extends HttpServletRequestWrapper {
private final Logger logger = org.slf4j.LoggerFactory.getLogger(HttpServletRequestWritableWrapper.class);
private final ByteArrayInputStream decryptedBody;

HttpServletRequestWritableWrapper(HttpServletRequest request, byte[] decryptedData) {
    super(request);
    decryptedBody = new ByteArrayInputStream(decryptedData);
}



@Override
public String getHeader(String name) {
    String headerValue = super.getHeader(name);
    if("Accept".equalsIgnoreCase(name))
    {
        logger.debug("Accept header changing :");
        return headerValue.replaceAll(
                MediaType.TEXT_PLAIN_VALUE, MediaType.APPLICATION_JSON_VALUE
        );
    }
    else if ("Content-Type".equalsIgnoreCase(name))
    {
        logger.debug("Content type change: ");
        return headerValue.replaceAll(MediaType.TEXT_PLAIN_VALUE, MediaType.APPLICATION_JSON_VALUE);
    }
    return headerValue;
}

@Override
public Enumeration<String> getHeaderNames() {
    return super.getHeaderNames();
}

@Override
public String getContentType() {
    String contentTypeValue = super.getContentType();
    if (MediaType.TEXT_PLAIN_VALUE.equalsIgnoreCase(contentTypeValue)) {
        logger.debug("Changing on getContentType():");
        return MediaType.APPLICATION_JSON_VALUE;
    }
    return contentTypeValue;
}


@Override
public BufferedReader getReader() throws UnsupportedEncodingException {
    return new BufferedReader(new InputStreamReader(decryptedBody, UTF_8));
}

@Override
public ServletInputStream getInputStream() throws IOException {
    return new ServletInputStream() {
        @Override
        public int read() {
            return decryptedBody.read();
        }
    };
}

这是我的过滤器：

@WebFilter(displayName = "EncryptionFilter", urlPatterns = "/*")
public class EncryptionFilter implements Filter {
private final Logger logger = org.slf4j.LoggerFactory.getLogger(EncryptionFilter.class);

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

}

@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    byte[] data = "{\"currentClientVersion\":{\"majorElement\":\"1\",\"minorElement\":\"2\"}}".getBytes();

    logger.debug("data string " + data.toString());

    logger.debug("Content-type before: " + servletRequest.getContentType());

    HttpServletRequest request = (HttpServletRequest) servletRequest;
    HttpServletRequestWritableWrapper requestWrapper = new HttpServletRequestWritableWrapper(request, data);
    //logger.debug("Accept Header: " + requestWrapper.getHeader("Accept"));
    //logger.debug("Content-Type: " + requestWrapper.getHeader("Content-Type"));
    //logger.debug("Contenttype" + requestWrapper.getContentType());

    filterChain.doFilter(requestWrapper, servletResponse);


}

@Override
public void destroy() {

}


}

【问题讨论】：

标签： spring servlet-filters

【解决方案1】：

似乎在我的过滤器之后在其他地方调用了 getHeaders 方法，并且没有返回带有我更新值的标题。

我在我的 HttpServletRequestWrapper 中添加了这个覆盖，它现在可以工作了：

@Override
public Enumeration<String> getHeaders(String name) {
    List<String> headerVals = Collections.list(super.getHeaders(name));
    int index = 0;
    for (String value : headerVals) {
        if ("Content-Type".equalsIgnoreCase(name)) {
            logger.debug("Content type change: ");
            headerVals.set(index, MediaType.APPLICATION_JSON_VALUE);
        }

        index++;
    }

    return Collections.enumeration(headerVals);
}

【讨论】：