java - 如何从 javax.servlet.filter doFilter 方法返回 JSON 响应消息和 HTTP 错误代码？

Question

我已经为我们的应用程序创建了一个处理 REST 请求的 servlet 过滤器。我已经注释了 web.xml 并创建了我的过滤器。该过滤器运行良好，但仅返回 JSON 文本消息。我还需要返回 405 HTTP 状态代码。当我执行测试并且测试失败时，我有一个简单的 PrintWriter 来打印错误消息:

public class MyFilter implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse apiResponse = (HttpServletResponse) response;
        apiResponse.setContentType("application/json");
        htmlOut = apiResponse.getWriter();
        mainErrorObject = new JSONObject();
        if(true){
            htmlOut.println(mainErrorObject.toString());
        }
        htmlOut.close();
    }
}

那么，就像我说的，如何返回 JSON 文本消息和 HTTP 错误代码？

Answer 1

ServletResponse 实现 HttpServletResponse 并且它有一个 setStatus 方法，用于设置响应的状态代码。

setStatus

void setStatus(int sc)

Sets the status code for this response. This method is used to set the return status code when there is no error (for example, for the status codes SC_OK or SC_MOVED_TEMPORARILY). If there is an error, and the caller wishes to invoke an error-page defined in the web application, the sendError method should be used instead.The container clears the buffer and sets the Location header, preserving cookies and other headers.