如何在java中以json格式使jetty ErrorHandler顯示錯誤

Question

我通過下面的示例代碼以這種方式啟動了jetty服務器，我編寫了自己的errorHandler類。 通過一些研究，我在這里得到了一些信息。 但似乎還不足以讓我得到我想要的東西。 我設置為由服務器調用的類的名稱是HandleClient。

因此，如果出現錯誤404，則顯示{"message":"HTTP error 404"} 。 程序運行正常但是響應是文本/純文本格式。

我的問題是：如何配置類以格式化並顯示MIME MediaType中的錯誤：application / json。

我已經度過了這個不眠之夜。 將非常感謝所有的幫助。

    public class MVCPattern{

    public MVCPattern(){
    }

    public static void main(String args[]) throws JSONException, IOException{
        MVCPattern mvcPattern = new MVCPattern();


        ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
        context.setContextPath("/");

        Server jettyServer = new Server(9000);
        jettyServer.setHandler(context);
        context.setErrorHandler(new ErrorHandler());
        // default error handler for resources out of "context" scope
        jettyServer.addBean(new ErrorHandler());

        ServletHolder jerseyServlet = context.addServlet(org.glassfish.jersey.servlet.ServletContainer.class, "/*");
        jerseyServlet.setInitOrder(0);

        // Tells the Jersey Servlet which REST service/class to load.
        jerseyServlet.setInitParameter("jersey.config.server.provider.classnames",
                HandleClient.class.getCanonicalName() );

        try {
            jettyServer.start();            
            jettyServer.join();

        } catch (Exception ex) {
            Logger.getLogger(HandleClient.class.getName()).log(Level.SEVERE, null, ex);
        } finally {
            jettyServer.destroy();
        }
    }
    /**
     * Dummy error handler that disables any error pages or jetty related messages and returns our
     * ERROR status JSON with plain HTTP status instead. All original error messages (from our code) are preserved
     * as they are not handled by this code.
     */
    static class ErrorHandler extends ErrorPageErrorHandler {
        @Override
        public void handle(String target, org.eclipse.jetty.server.Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException {
            response.getWriter()
            .append("{\"message\":\"HTTP error ")
            .append(String.valueOf(response.getStatus()))
            .append("\"}");
        }
    }

}

Answer 1

您應該檢查HttpServletRequest.getHeader("Accept")的Accept標頭，以首先查看客戶端是否可以接受該類型。

然后使用HttpServletResponse.setContentType("text/json")設置響應的內容類型。

或者，如果您使用的是Jetty 9.3.11.v20160721（或更新版本），則可以覆蓋ErrorHandler.generateAcceptableResponse(Request baseRequest, HttpServletRequest request, HttpServletResponse response, int code, String message, String mimeType)方法並相應地處理它。

請參閱： https ： //github.com/eclipse/jetty.project/blob/jetty-9.3.11.v20160721/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ErrorHandler.java#例如L196-L226在其上的使用。

Answer 2

這不是什么大問題。

默認情況下，Jetty使用ErrorPageErrorHandler，您可以檢查Jetty的WebAppContext（）構造函數，默認情況下看起來像這樣（jetty 9.4.19.v20190610）：

public WebAppContext()
    {
        this(null,null,null,null,null,new ErrorPageErrorHandler(),SESSIONS|SECURITY);
    }

https://github.com/eclipse/jetty.project/blob/jetty-9.4.x/jetty-webapp/src/main/java/org/eclipse/jetty/webapp/WebAppContext.java

您可以擴展ErrorPageErrorHandler並寫入JSON中的響應錯誤。

例：

import com.fasterxml.jackson.databind.ObjectMapper;
import com.igorkhromov.dto.Errors;
import org.eclipse.jetty.http.MimeTypes;
import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.servlet.ErrorPageErrorHandler;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.Writer;
import java.nio.charset.StandardCharsets;


public class ErrorHandler extends ErrorPageErrorHandler {

    /*
        Messages to error made based on:
        Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
        https://tools.ietf.org/html/rfc7231
    */

    private static final String ERROR_404_MESSAGE = "Target resource not found";

    private static final String ERROR_501_MESSAGE = "Server functionality to process request is not implemented";

    private static final String ERROR_502_MESSAGE = "Server cannot proxy request";

    private static final String ERROR_503_MESSAGE = "Server is currently unable to handle the request";

    private static final String ERROR_504_MESSAGE = "Server did not receive a timely response from an upstream server";

    private static final String ERROR_UNEXPECTED_MESSAGE = "Unexpected error occurs";

    private static final ObjectMapper MAPPER = new ObjectMapper();

    @Override
    protected void generateAcceptableResponse(Request baseRequest, HttpServletRequest request, HttpServletResponse response, int code, String message, String mimeType)
            throws IOException
    {

            baseRequest.setHandled(true);
            Writer writer = getAcceptableWriter(baseRequest, request, response);
            if (null != writer) {
                response.setContentType(MimeTypes.Type.APPLICATION_JSON.asString());
                response.setStatus(code);
                handleErrorPage(request, writer, code, message);
            }

    }

    @Override
    protected Writer getAcceptableWriter(Request baseRequest, HttpServletRequest request, HttpServletResponse response)
            throws IOException
    {

            response.setCharacterEncoding(StandardCharsets.UTF_8.name());
            return response.getWriter();
    }

    @Override
    protected void writeErrorPage(HttpServletRequest request, Writer writer, int code, String message, boolean showStacks)
            throws IOException
    {

            try {
                writer.write(MAPPER.writeValueAsString(new Errors(getMessage(code))));
            }
            catch (Exception e) {
                // Log if needed
            }
    }

    private boolean isRestRequest(HttpServletRequest request) {
        return request.getServletPath().startsWith("/api/");
    }

    private String getMessage(int code) {
        switch (code) {
            case 404 : return ERROR_404_MESSAGE;
            case 501 : return ERROR_501_MESSAGE;
            case 502 : return ERROR_502_MESSAGE;
            case 503 : return ERROR_503_MESSAGE;
            case 504 : return ERROR_504_MESSAGE;
            default  : return ERROR_UNEXPECTED_MESSAGE;
        }
    }
}

我的GitHub倉庫中的代碼： https ： //github.com/xrom888/blog_jetty-display-errors-in-json

自定義ErrorHandler： https ： //github.com/xrom888/blog_jetty-display-errors-in-json/blob/master/src/main/java/com/igorkhromov/ErrorHandler.java

MIT許可下的所有代碼，享受））。