fix(diagram-converter): handle FileCountLimitExceededException

diagram-converter/webapp/src/main/java/io/camunda/migration/diagram/converter/webapp/ConverterExceptionHandler.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH under
+ * one or more contributor license agreements. See the NOTICE file distributed
+ * with this work for additional information regarding copyright ownership.
+ * Licensed under the Camunda License 1.0. You may not use this file
+ * except in compliance with the Camunda License 1.0.
+ */
+package io.camunda.migration.diagram.converter.webapp;
+
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import org.apache.tomcat.util.http.fileupload.impl.FileCountLimitExceededException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.multipart.MultipartException;
+
+@ControllerAdvice
+public class ConverterExceptionHandler {
+
+  private static final Logger LOG = LoggerFactory.getLogger(ConverterExceptionHandler.class);
+
+  @Value("${server.tomcat.max-part-count:50}")
+  private int maxPartCount;
+
+  @ExceptionHandler(MultipartException.class)
+  public void handleMultipartException(MultipartException ex, HttpServletResponse response)
+      throws IOException {
+    Throwable rootCause = getRootCause(ex);
+
+    if (rootCause instanceof FileCountLimitExceededException) {
+      LOG.warn("File count limit exceeded: {}", rootCause.getMessage());
+      writeJsonError(
+          response, HttpStatus.PAYLOAD_TOO_LARGE, "FILE_COUNT_LIMIT_EXCEEDED", maxPartCount);
+      return;
+    }
+
+    LOG.error("Multipart request processing failed", ex);
+    writeJsonError(response, HttpStatus.BAD_REQUEST, "MULTIPART_ERROR", -1);
+  }
+
+  private void writeJsonError(
+      HttpServletResponse response, HttpStatus status, String errorCode, int limit)
+      throws IOException {
+    response.setStatus(status.value());
+    response.setContentType(MediaType.APPLICATION_JSON_VALUE);
+
+    String json =
+        "{\"errorCode\":\""
+            + errorCode
+            + "\",\"status\":"
+            + status.value()
+            + ",\"limit\":"
+            + limit
+            + "}";
+    response.getWriter().write(json);
+  }
+
+  private Throwable getRootCause(Throwable throwable) {
+    Throwable cause = throwable;
+    while (cause.getCause() != null && cause.getCause() != cause) {
+      cause = cause.getCause();
+    }
+    return cause;
+  }
+}

diagram-converter/webapp/src/main/javascript/src/App.jsx

@@ -11,7 +11,7 @@ import {
   ProgressIndicator,
   ProgressStep,
   Button,
-  Callout,
+  ActionableNotification,
   DataTable,
   Table,
   TableHead,
@@ -46,6 +46,9 @@ function App() {
   const [previewTableHeader, setPreviewTableHeader] = useState([]);
   const [previewTableRows, setPreviewTableRows] = useState([]);
 
+  const [downloadError, setDownloadError] = useState(null);
+  const [downloadErrorTitle, setDownloadErrorTitle] = useState("");
+
   const [showConfig, setShowConfig] = useState(false);
   const [configOptions, setConfigOptions] = useState({
     defaultJobType: "camunda-7-job",
@@ -199,41 +202,72 @@ function App() {
     setValidFiles(validFiles);
   }
 
+  function buildErrorMessage(errorBody) {
+    switch (errorBody.errorCode) {
+      case "FILE_COUNT_LIMIT_EXCEEDED":
+        return <>
+          Too many files uploaded. The online version supports up to {errorBody.limit} files per request.
+          {" "}To learn how to run the diagram converter locally with a custom file limit, consult the{" "}
+          <a href="https://docs.camunda.io/docs/guides/migrating-from-camunda-7/migration-tooling/diagram-converter/#local-web-application"
+            target="_blank" rel="noopener noreferrer">diagram converter guide</a>.
+        </>;
+      default:
+        return "Download failed. Please try again.";
+    }
+  }
+
+  async function handleDownloadResponse(filename, response, title) {
+    if (!response.ok) {
+      let errorMessage = "Download failed. Please try again.";
+      try {
+        const errorBody = await response.json();
+        errorMessage = buildErrorMessage(errorBody);
+      } catch {
+        // Response body is not JSON, use default message
+      }
+      setDownloadErrorTitle(title);
+      setDownloadError(errorMessage);
+      return;
+    }
+    setDownloadError(null);
+    await download1(filename, response);
+  }
+
   async function downloadXLS() {
     const formData = createFormData(validFiles);
-    //validFiles.forEach((file) => formData.append("file", file));
-    await download1("analysis.xlsx",
+    await handleDownloadResponse("analysis.xlsx",
       await fetch(baseUrl + "/check", {
         body: formData,
         method: "POST",
         headers: {
           Accept:
             "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
         },
-      })
+      }),
+      "Downloading XLSX failed"
     );
   }
   async function downloadCSV() {
     const formData = createFormData(validFiles);
-    //validFiles.forEach((file) => formData.append("file", file));
-    await download1("analysis.csv",
+    await handleDownloadResponse("analysis.csv",
       await fetch(baseUrl + "/check", {
         body: formData,
         method: "POST",
         headers: {
           Accept: "text/csv",
         },
-      })
+      }),
+      "Downloading CSV failed"
     );
   }
   async function downloadZIP() {
     const formData = createFormData(validFiles);
-    //validFiles.forEach((file) => formData.append("file", file));
-    await download1("converted-models.zip",
+    await handleDownloadResponse("converted-models.zip",
       await fetch(baseUrl + "/convertBatch", {
         body: formData,
         method: "POST",
-      })
+      }),
+      "Downloading ZIP failed"
     );
   }
 
@@ -522,6 +556,17 @@ function App() {
                   }
                 />
               ))}
+              {downloadError && (
+                <ActionableNotification
+                  kind="error"
+                  title={downloadErrorTitle}
+                  lowContrast
+                  onClose={() => setDownloadError(null)}
+                  className="download-error-notification"
+                >
+                  {downloadError}
+                </ActionableNotification>
+              )}
               <Button
                 kind="tertiary"
                 size="lg"

diagram-converter/webapp/src/main/javascript/src/index.css

@@ -303,6 +303,12 @@ th, td {
   stroke: #0dcaf0 !important; 
 }
 
+.download-error-notification {
+  width: 100%;
+  max-inline-size: 100%;
+  margin-bottom: 1rem;
+}
+
 .configBox {
   margin-top: 1rem;
   padding: 1rem;

diagram-converter/webapp/src/main/resources/application.yaml

@@ -1,3 +1,12 @@
+server:
+  tomcat:
+    max-part-count: 100
+
+spring:
+  servlet:
+    multipart:
+      resolve-lazily: true
+
 notification:
   slack:
     enabled: false

diagram-converter/webapp/src/test/java/io/camunda/migration/diagram/converter/webapp/ConverterExceptionHandlerTest.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH under
+ * one or more contributor license agreements. See the NOTICE file distributed
+ * with this work for additional information regarding copyright ownership.
+ * Licensed under the Camunda License 1.0. You may not use this file
+ * except in compliance with the Camunda License 1.0.
+ */
+package io.camunda.migration.diagram.converter.webapp;
+
+import static org.assertj.core.api.Assertions.*;
+
+import io.restassured.RestAssured;
+import io.restassured.http.ContentType;
+import io.restassured.response.Response;
+import java.io.File;
+import java.net.URISyntaxException;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.web.server.LocalServerPort;
+import org.springframework.test.context.TestPropertySource;
+
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+@TestPropertySource(
+    properties = {"server.tomcat.max-part-count=2", "spring.servlet.multipart.resolve-lazily=true"})
+public class ConverterExceptionHandlerTest {
+
+  @LocalServerPort int port;
+
+  @BeforeEach
+  void setup() {
+    RestAssured.port = port;
+  }
+
+  @Test
+  void convertBatchExceedingFileCountLimit() throws URISyntaxException {
+    Response response =
+        RestAssured.given()
+            .contentType(ContentType.MULTIPART)
+            .multiPart(
+                "file", new File(getClass().getClassLoader().getResource("example.bpmn").toURI()))
+            .multiPart(
+                "file", new File(getClass().getClassLoader().getResource("example2.bpmn").toURI()))
+            .formParam("appendDocumentation", true)
+            .accept("application/zip")
+            .post("/convertBatch");
+
+    assertThat(response.statusCode()).isEqualTo(413);
+    assertThat(response.jsonPath().getString("errorCode")).isEqualTo("FILE_COUNT_LIMIT_EXCEEDED");
+    assertThat(response.jsonPath().getInt("limit")).isEqualTo(2);
+  }
+}