added PushStateDispatcher for production and development to WebResourceServlet

scm-webapp/src/main/java/sonia/scm/ProxyPushStateDispatcher.java

@@ -0,0 +1,134 @@
+package sonia.scm;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.io.ByteStreams;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.HttpURLConnection;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * PushStateDispatcher which delegates the request to a different server. This dispatcher should only be used for
+ * development and never in production.
+ *
+ * @since 2.0.0
+ */
+public final class ProxyPushStateDispatcher implements PushStateDispatcher {
+
+  @FunctionalInterface
+  interface ConnectionFactory {
+
+    HttpURLConnection open(URL url) throws IOException;
+
+  }
+
+  private final String target;
+  private final ConnectionFactory connectionFactory;
+
+  /**
+   * Creates a new dispatcher for the given target. The target must be a valid url.
+   *
+   * @param target proxy target
+   */
+  public ProxyPushStateDispatcher(String target) {
+    this(target, ProxyPushStateDispatcher::openConnection);
+  }
+
+  /**
+   * This Constructor should only be used for testing.
+   *
+   * @param target proxy target
+   * @param connectionFactory factory for creating an connection from a url
+   */
+  @VisibleForTesting
+  ProxyPushStateDispatcher(String target, ConnectionFactory connectionFactory) {
+    this.target = target;
+    this.connectionFactory = connectionFactory;
+  }
+
+  @Override
+  public void dispatch(HttpServletRequest request, HttpServletResponse response, String uri) throws IOException {
+    try {
+      proxy(request, response, uri);
+    } catch (FileNotFoundException ex) {
+      response.setStatus(HttpServletResponse.SC_NOT_FOUND);
+    }
+  }
+
+  private void proxy(HttpServletRequest request, HttpServletResponse response, String uri) throws IOException {
+    URL url = createProxyUrl(uri);
+
+    HttpURLConnection connection = connectionFactory.open(url);
+    connection.setRequestMethod(request.getMethod());
+    copyRequestHeaders(request, connection);
+
+    if (request.getContentLength() > 0) {
+      copyRequestBody(request, connection);
+    }
+
+    int responseCode = connection.getResponseCode();
+    response.setStatus(responseCode);
+    copyResponseHeaders(response, connection);
+
+    appendProxyHeader(response, url);
+
+    copyResponseBody(response, connection);
+  }
+
+  private void appendProxyHeader(HttpServletResponse response, URL url) {
+    response.addHeader("X-Forwarded-Port", String.valueOf(url.getPort()));
+  }
+
+  private void copyResponseBody(HttpServletResponse response, HttpURLConnection connection) throws IOException {
+    try (InputStream input = connection.getInputStream(); OutputStream output = response.getOutputStream()) {
+      ByteStreams.copy(input, output);
+    }
+  }
+
+  private void copyResponseHeaders(HttpServletResponse response, HttpURLConnection connection) {
+    Map<String, List<String>> headerFields = connection.getHeaderFields();
+    for (Map.Entry<String, List<String>> entry : headerFields.entrySet()) {
+      if (entry.getKey() != null && !"Transfer-Encoding".equalsIgnoreCase(entry.getKey())) {
+        for (String value : entry.getValue()) {
+          response.addHeader(entry.getKey(), value);
+        }
+      }
+    }
+  }
+
+  private void copyRequestBody(HttpServletRequest request, HttpURLConnection connection) throws IOException {
+    connection.setDoOutput(true);
+    try (InputStream input = request.getInputStream(); OutputStream output = connection.getOutputStream()) {
+      ByteStreams.copy(input, output);
+    }
+  }
+
+  private void copyRequestHeaders(HttpServletRequest request, HttpURLConnection connection) {
+    Enumeration<String> headers = request.getHeaderNames();
+    while (headers.hasMoreElements()) {
+      String header = headers.nextElement();
+      Enumeration<String> values = request.getHeaders(header);
+      while (values.hasMoreElements()) {
+        String value = values.nextElement();
+        connection.setRequestProperty(header, value);
+      }
+    }
+  }
+
+  private URL createProxyUrl(String uri) throws MalformedURLException {
+    return new URL(target + uri);
+  }
+
+  private static HttpURLConnection openConnection(URL url) throws IOException {
+    return (HttpURLConnection) url.openConnection();
+  }
+}