Servlet 过滤器包装器 - 更改内容类型时遇到问题

Question

我有RESTful Web服务，它被javascript使用。 此服务返回内容类型"应用程序/json"。 但是，对于 IE，内容类型必须是"text/html"。 所以我写了一个过滤器和包装器，以便在检测到 IE 作为客户端时更改内容类型。 我的逻辑似乎对内容类型没有影响。 我做错了什么？

过滤器：

public class IE8Filter implements Filter {
    private Logger logger = LoggerHelper.getLogger();
    @Override
    public void destroy() {}
    @Override
    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {
         HttpServletRequest request = (HttpServletRequest) req;
         HttpServletResponse response = (HttpServletResponse) res;
         String userAgent = request.getHeader("User-Agent");
         logger.debugf("User Agent  = '%s'", userAgent);
         IE8FilterResponseWrapper wrapper = new IE8FilterResponseWrapper(response);

         chain.doFilter(req, wrapper);

         if (userAgent.contains("MSIE 8") || userAgent.contains("MSIE 7")) {
             wrapper.setContentType("text/html");
             logger.debugf("Content Type  = '%s'", wrapper.getContentType());
         }

    }
    @Override
    public void init(FilterConfig arg0) throws ServletException {}
}

包装器：

public class IE8FilterResponseWrapper extends HttpServletResponseWrapper {

    private String contentType;
    public IE8FilterResponseWrapper(HttpServletResponse response) {
        super(response);
    }
    public void setContentType(String type) { 
        this.contentType = type;
        super.setContentType(type); 
    } 
     public String getContentType() { 
         return contentType; 
     } 
}

Answer 1

我找到了答案。 诀窍是阻止我的 Web 服务使用我的包装器设置内容类型：

public class IE8FilterResponseWrapper extends HttpServletResponseWrapper {

    public IE8FilterResponseWrapper(HttpServletResponse response) {
        super(response);
    }
    public void forceContentType(String type) {
        super.setContentType(type); 
    }
    public void setContentType(String type) { 
    } 
    public void setHeader(String name, String value) {
        if (!name.equals("Content-Type")) {
            super.setHeader(name, value);
        }
    }
    public void addHeader(String name, String value) {
        if (!name.equals("Content-Type")) {
            super.addHeader(name, value);
        }
    }
     public String getContentType() { 
         return super.getContentType(); 
     } 
}

我的过滤器现在看起来像：

public class IE8Filter implements Filter {
    private Logger logger = LoggerHelper.getLogger();
    @Override
    public void destroy() {}
    @Override
    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {
         HttpServletRequest request = (HttpServletRequest) req;
         HttpServletResponse response = (HttpServletResponse) res;
         String userAgent = request.getHeader("User-Agent");
         logger.debugf("User Agent  = '%s'", userAgent);
         IE8FilterResponseWrapper wrapper = new IE8FilterResponseWrapper(response);
         if (userAgent.contains("MSIE 8") || userAgent.contains("MSIE 7")) {
             wrapper.forceContentType("text/html");
             chain.doFilter(req, wrapper);
         }
         else {
             chain.doFilter(req, res);
         }

    }
    @Override
    public void init(FilterConfig arg0) throws ServletException {}
}

我不确定这是否是包装器的使用方式，但哎呀它有效。