Add basic support for thread interruption, and add protection for long running requests in web app

core/src/main/java/com/google/zxing/MultiFormatReader.java

@@ -169,6 +169,9 @@ public final class MultiFormatReader implements Reader {
   private Result decodeInternal(BinaryBitmap image) throws NotFoundException {
     if (readers != null) {
       for (Reader reader : readers) {
+        if (Thread.currentThread().isInterrupted()) {
+          throw NotFoundException.getNotFoundInstance();
+        }
         try {
           return reader.decode(image, hints);
         } catch (ReaderException re) {
@@ -179,6 +182,9 @@ public final class MultiFormatReader implements Reader {
         // Calling all readers again with inverted image
         image.getBlackMatrix().flip();
         for (Reader reader : readers) {
+          if (Thread.currentThread().isInterrupted()) {
+            throw NotFoundException.getNotFoundInstance();
+          }
           try {
             return reader.decode(image, hints);
           } catch (ReaderException re) {

zxingorg/src/main/java/com/google/zxing/web/DecodeServlet.java

@@ -391,7 +391,7 @@ public final class DecodeServlet extends HttpServlet {
         savedException = re;
       }
 
-      if (results.isEmpty()) {
+      if (results.isEmpty() && !Thread.currentThread().isInterrupted()) {
         try {
           // Look for pure barcode
           Result theResult = reader.decode(bitmap, HINTS_PURE);
@@ -403,7 +403,7 @@ public final class DecodeServlet extends HttpServlet {
         }
       }
 
-      if (results.isEmpty()) {
+      if (results.isEmpty() && !Thread.currentThread().isInterrupted()) {
         try {
           // Look for normal barcode in photo
           Result theResult = reader.decode(bitmap, HINTS);
@@ -415,7 +415,7 @@ public final class DecodeServlet extends HttpServlet {
         }
       }
 
-      if (results.isEmpty()) {
+      if (results.isEmpty() && !Thread.currentThread().isInterrupted()) {
         try {
           // Try again with other binarizer
           BinaryBitmap hybridBitmap = new BinaryBitmap(new HybridBinarizer(source));

zxingorg/src/main/java/com/google/zxing/web/TimeoutFilter.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2022 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.web;
+
+import com.google.common.util.concurrent.SimpleTimeLimiter;
+import com.google.common.util.concurrent.TimeLimiter;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.FilterConfig;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.annotation.WebFilter;
+import javax.servlet.annotation.WebInitParam;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Protect the decode endpoint from long-running requests.
+ */
+@WebFilter(urlPatterns = {"/w/decode"}, initParams = {
+  @WebInitParam(name = "timeoutSec", value = "10"),
+})
+public final class TimeoutFilter implements Filter {
+
+  private ExecutorService executorService;
+  private TimeLimiter timeLimiter;
+  private int timeoutSec;
+
+  @Override
+  public void init(FilterConfig filterConfig) {
+    executorService = Executors.newCachedThreadPool();
+    timeLimiter = SimpleTimeLimiter.create(executorService);
+    timeoutSec = Integer.parseInt(filterConfig.getInitParameter("timeoutSec"));
+  }
+
+  @Override
+  public void doFilter(ServletRequest request,
+                       ServletResponse response,
+                       FilterChain chain) throws IOException, ServletException {
+    try {
+      timeLimiter.callWithTimeout(new Callable<Void>() {
+        @Override
+        public Void call() throws Exception {
+          chain.doFilter(request, response);
+          return null;
+        }
+      }, timeoutSec, TimeUnit.SECONDS);
+    } catch (TimeoutException | InterruptedException e) {
+      HttpServletResponse servletResponse = (HttpServletResponse) response;
+      servletResponse.setStatus(HttpServletResponse.SC_REQUEST_TIMEOUT);
+      servletResponse.getWriter().write("Request took too long");
+    } catch (ExecutionException e) {
+      if (e.getCause() instanceof ServletException) {
+        throw (ServletException) e.getCause();
+      }
+      if (e.getCause() instanceof IOException) {
+        throw (IOException) e.getCause();
+      }
+      throw new ServletException(e.getCause());
+    }
+  }
+
+  @Override
+  public void destroy() {
+    if (executorService != null) {
+      executorService.shutdownNow();
+    }
+  }
+
+}

zxingorg/src/test/java/com/google/zxing/web/TimeoutFilterTestCase.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2022 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.web;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.springframework.mock.web.MockFilterChain;
+import org.springframework.mock.web.MockFilterConfig;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.GenericServlet;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * Tests {@link TimeoutFilter}.
+ */
+public final class TimeoutFilterTestCase extends Assert {
+
+  @Test
+  public void testTimeout() throws Exception {
+    MockFilterConfig config = new MockFilterConfig();
+    config.addInitParameter("timeoutSec", "1");
+    Filter filter = new TimeoutFilter();
+    filter.init(config);
+
+    FilterChain chain = new MockFilterChain(new GenericServlet() {
+      @Override
+      public void service(ServletRequest req, ServletResponse res) {
+        try {
+          Thread.sleep(2000);
+        } catch (InterruptedException e) {
+          // continue
+        }
+      }
+    });
+    HttpServletResponse response = new MockHttpServletResponse();
+    filter.doFilter(new MockHttpServletRequest(), response, chain);
+    filter.destroy();
+    assertEquals(HttpServletResponse.SC_REQUEST_TIMEOUT, response.getStatus());
+  }
+
+}