Support compression (gzip content encoding)

README.md

@@ -30,6 +30,7 @@ Flak components    | Description
          * [Query argument](#query-argument)
          * [Form argument](#form-argument)
          * [Custom arguments](#custom-arguments)
+      * [Compression](#compression)
       * [Managing apps](#managing-apps)
       * [To be continued....](#to-be-continued)
    * [Why Flak?](#why-flak)
@@ -39,7 +40,7 @@ Flak components    | Description
       * [How to publish locally](#how-to-publish-locally)
 
 <!-- Created by https://github.com/ekalinin/github-markdown-toc -->
-<!-- Added by: pcdv, at: Sat Sep 10 06:05:40     2022 -->
+<!-- Added by: pcdv, at: Sun Dec 31 19:04:56     2023 -->
 
 <!--te-->
 <!-- to update TOC:
@@ -208,6 +209,17 @@ You can accept other argument types if you:
   }
 ```
 
+### Compression
+
+Gzip compression can be enabled for a given endpoint or all endpoints of a 
+class by using the `@Compress` annotation.
+
+Files served with `FlakResourceImpl` will be automatically compressed 
+according to their content type and size.
+
+It is possible to tune compression behavior:
+ * file size threshold (using system property `flak.compressThreshold`)
+ * eligible content types (using a custom `ContentTypeProvider`)
 
 ### Managing apps
 

flak-api/src/main/java/flak/Response.java

@@ -11,6 +11,11 @@ public interface Response {
 
   void addHeader(String header, String value);
 
+  /**
+   * Checks whether specified response header is set.
+   */
+  boolean hasResponseHeader(String name);
+
   /**
    * Warning: must be called after addHeader().
    *
@@ -27,4 +32,16 @@ public interface Response {
    * location.
    */
   void redirect(String path);
+
+  /**
+   * Configures whether gzip compression can be applied automatically according
+   * to Accept-Encoding request header and absence of Content-Encoding response
+   * header (false by default).
+   */
+  void setCompressionAllowed(boolean compressionAllowed);
+
+  /**
+   * @see #setCompressionAllowed(boolean)
+   */
+  boolean isCompressionAllowed();
 }

flak-api/src/main/java/flak/annotations/Compress.java

@@ -0,0 +1,15 @@
+package flak.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Enables compression on an endpoint, or all endpoints of a class.
+ */
+@Target({ElementType.METHOD, ElementType.TYPE})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Compress {
+  int COMPRESS_THRESHOLD = Integer.getInteger("flak.compressThreshold", 1024);
+}

flak-backend-jdk/src/main/java/flak/backend/jdk/HeaderList.java

@@ -16,4 +16,8 @@ void addHeadersInto(HttpExchange exchange) {
       exchange.getResponseHeaders().add(arr[0], arr[1]);
     }
   }
+
+  public boolean has(String name) {
+    return list.stream().anyMatch(arr -> name.equals(arr[0]));
+  }
 }

flak-backend-jdk/src/main/java/flak/backend/jdk/JdkRequest.java

@@ -16,9 +16,10 @@
 import flak.Request;
 import flak.Response;
 import flak.spi.SPRequest;
+import flak.spi.SPResponse;
 import flak.spi.util.IO;
 
-public class JdkRequest implements SPRequest, Response {
+public class JdkRequest implements SPRequest, SPResponse {
 
   private static final String[] EMPTY = {};
 
@@ -32,14 +33,15 @@ public class JdkRequest implements SPRequest, Response {
 
   private final String appRelativePath;
 
-  private BufferedOutputStream outputStream;
+  private OutputStream outputStream;
 
   private Form form;
   private final HeaderList headers = new HeaderList();
   private int status;
   private boolean statusFlushed;
 
   private Method handler;
+  private boolean compressionAllowed;
 
   public JdkRequest(App app,
                     String appRelativePath,
@@ -175,6 +177,11 @@ public void addHeader(String header, String value) {
     headers.add(header, value);
   }
 
+  @Override
+  public boolean hasResponseHeader(String name) {
+    return headers.has(name);
+  }
+
   public void setStatus(int status) {
     if (statusFlushed && status != this.status)
       throw new IllegalStateException("Status has already been sent: " + this.status);
@@ -190,7 +197,8 @@ public OutputStream getOutputStream() {
     if (outputStream == null) {
       this.outputStream = new BufferedOutputStream(exchange.getResponseBody(), 8192) {
         @Override
-        public void close() {
+        public void close() throws IOException {
+          super.flush();
           // disable close, we will do it in finish()
         }
 
@@ -210,10 +218,22 @@ public void redirect(String location) {
     setStatus(HttpURLConnection.HTTP_MOVED_TEMP);
   }
 
+  @Override
+  public void setCompressionAllowed(boolean compressionAllowed) {
+    this.compressionAllowed = compressionAllowed;
+
+  }
+
+  @Override
+  public boolean isCompressionAllowed() {
+    return compressionAllowed;
+  }
+
   void finish() throws IOException {
     flushStatus();
-    if (outputStream != null)
-      outputStream.flush();
+    if (outputStream != null) {
+      outputStream.close();
+    }
     exchange.getResponseBody().close();
   }
 
@@ -231,4 +251,9 @@ private void flushStatus() throws IOException {
   boolean hasOutputStream() {
     return outputStream != null;
   }
+
+  @Override
+  public void setOutputStream(OutputStream out) {
+    this.outputStream = out;
+  }
 }

flak-backend-jdk/src/main/java/flak/backend/jdk/MethodHandler.java

@@ -1,12 +1,15 @@
 package flak.backend.jdk;
 
 import flak.Response;
+import flak.annotations.Compress;
 import flak.spi.AbstractMethodHandler;
+import flak.spi.CompressionHelper;
 import flak.spi.SPRequest;
 import flak.spi.util.IO;
 import flak.spi.util.Log;
 
 import java.io.InputStream;
+import java.io.OutputStream;
 import java.lang.reflect.Method;
 import java.net.HttpURLConnection;
 import java.nio.charset.StandardCharsets;
@@ -57,33 +60,41 @@ protected boolean isApplicable(SPRequest req) {
 
   @SuppressWarnings({"StatementWithEmptyBody", "unchecked"})
   protected void processResponse(Response r, Object res) throws Exception {
+    if (allowCompress)
+      r.setCompressionAllowed(true);
     if (outputFormat != null) {
       outputFormat.convert(res, r);
     }
     else if (res instanceof Response) {
       // do nothing: status and headers should already be set
     }
-    else if (res instanceof String) {
-      r.setStatus(HttpURLConnection.HTTP_OK);
-      r.getOutputStream().write(((String) res).getBytes(StandardCharsets.UTF_8));
-    }
-    else if (res instanceof byte[]) {
-      r.setStatus(HttpURLConnection.HTTP_OK);
-      r.getOutputStream().write((byte[]) res);
-    }
-    else if (res instanceof InputStream) {
-      r.setStatus(HttpURLConnection.HTTP_OK);
-      IO.pipe((InputStream) res, r.getOutputStream(), false);
-    }
-    else if (res == null) {
-      if (!r.isStatusSet())
-        r.setStatus(200);
-    }
-    else
-      throw new RuntimeException("Unexpected return value: " + res + " from " + javaMethod
-        .toGenericString());
+    else {
+      OutputStream out = r.getOutputStream();
+      if (res instanceof String) {
+        r.setStatus(HttpURLConnection.HTTP_OK);
+        if (((String) res).length() > Compress.COMPRESS_THRESHOLD)
+          out = CompressionHelper.maybeCompress(r);
+        out.write(((String) res).getBytes(StandardCharsets.UTF_8));
+      }
+      else if (res instanceof byte[]) {
+        r.setStatus(HttpURLConnection.HTTP_OK);
+        if (((byte[]) res).length > Compress.COMPRESS_THRESHOLD)
+          out = CompressionHelper.maybeCompress(r);
+        out.write((byte[]) res);
+      }
+      else if (res instanceof InputStream) {
+        r.setStatus(HttpURLConnection.HTTP_OK);
+        out = CompressionHelper.maybeCompress(r);
+        IO.pipe((InputStream) res, out, false);
+      }
+      else if (res == null) {
+        if (!r.isStatusSet())
+          r.setStatus(200);
+      }
+      else
+        throw new RuntimeException("Unexpected return value: " + res + " from " + javaMethod
+          .toGenericString());
 
+    }
   }
-
-
 }

flak-backend-netty/src/main/java/flak/backend/netty/NettyResponse.java

@@ -1,7 +1,7 @@
 package flak.backend.netty;
 
 import flak.Request;
-import flak.Response;
+import flak.spi.SPResponse;
 import io.netty.buffer.Unpooled;
 import io.netty.handler.codec.http.DefaultFullHttpResponse;
 import io.netty.handler.codec.http.DefaultHttpHeaders;
@@ -13,7 +13,7 @@
 import java.net.HttpURLConnection;
 import java.nio.charset.StandardCharsets;
 
-public class NettyResponse implements Response {
+public class NettyResponse implements SPResponse {
   private final NettyRequest req;
   private final DefaultHttpHeaders headers;
   private int status = 200;
@@ -33,6 +33,11 @@ public void addHeader(String header, String value) {
     headers.add(header, value);
   }
 
+  @Override
+  public boolean hasResponseHeader(String name) {
+    return headers.contains(name);
+  }
+
   @Override
   public void setStatus(int status) {
     this.status = status;
@@ -54,6 +59,16 @@ public void redirect(String location) {
     setStatus(HttpURLConnection.HTTP_MOVED_TEMP);
   }
 
+  @Override
+  public void setCompressionAllowed(boolean compressionAllowed) {
+
+  }
+
+  @Override
+  public boolean isCompressionAllowed() {
+    return false;
+  }
+
   public int getStatus() {
     return status;
   }
@@ -67,4 +82,9 @@ public HttpResponse toHttpResponse() {
     //HttpUtil.setKeepAlive(r, false);
     //return r;
   }
+
+  @Override
+  public void setOutputStream(OutputStream out) {
+    throw new RuntimeException("TODO");
+  }
 }

flak-jackson/src/main/java/flak/jackson/JsonOutputFormatter.java

@@ -3,6 +3,7 @@
 import com.fasterxml.jackson.databind.ObjectWriter;
 import flak.OutputFormatter;
 import flak.Response;
+import flak.spi.CompressionHelper;
 
 /**
  * An output formatter using an ObjectWriter, which is the recommended way of
@@ -25,7 +26,6 @@ public JsonOutputFormatter(ObjectWriter writer) {
   @Override
   public void convert(T data, Response resp) throws Exception {
     resp.addHeader("Content-Type", "application/json");
-    resp.setStatus(200);
-    writer.writeValue(resp.getOutputStream(), data);
+    writer.writeValue(CompressionHelper.maybeCompress(resp), data);
   }
 }

flak-resource/src/main/java/flak/plugin/resource/AbstractResourceHandler.java

@@ -7,7 +7,9 @@
 
 import flak.HttpException;
 import flak.Request;
+import flak.spi.CompressionHelper;
 import flak.spi.RestrictedTarget;
+import flak.spi.SPResponse;
 import flak.spi.util.IO;
 import flak.spi.util.Log;
 
@@ -47,17 +49,20 @@ public void doGet(Request r, String ignored) throws Exception {
 
     InputStream in;
 
+    OutputStream out = r.getResponse().getOutputStream();
     try {
-      in = openPath(path);
+      in = openPath(path, (SPResponse) r.getResponse());
       String contentType = mime.getContentType(path);
-      if (contentType != null)
+      if (contentType != null) {
         r.getResponse().addHeader("Content-Type", contentType);
+        if (mime.shouldCompress(contentType))
+          out = CompressionHelper.maybeCompress(r.getResponse());
+      }
     }
     catch (FileNotFoundException e) {
       throw new HttpException(404, "Not found");
     }
 
-    OutputStream out = r.getResponse().getOutputStream();
     if (in != null) {
       r.getResponse().setStatus(200);
       try {
@@ -76,5 +81,5 @@ public void doGet(Request r, String ignored) throws Exception {
     }
   }
 
-  protected abstract InputStream openPath(String p) throws FileNotFoundException;
+  protected abstract InputStream openPath(String p, SPResponse resp) throws IOException;
 }

flak-resource/src/main/java/flak/plugin/resource/ContentTypeProvider.java

@@ -13,4 +13,11 @@ public interface ContentTypeProvider {
    */
   String getContentType(String path);
 
+  /**
+   * Used when serving resources, to help determine if a document should be
+   * compressed.
+   */
+  default boolean shouldCompress(String contentType) {
+    return contentType.contains("text") || contentType.contains("/json");
+  }
 }