allow to write to PathURLConnection

jimfs/src/main/java/com/google/common/jimfs/PathURLConnection.java

@@ -27,6 +27,7 @@
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
@@ -60,6 +61,7 @@ final class PathURLConnection extends URLConnection {
   private static final String DEFAULT_CONTENT_TYPE = "application/octet-stream";
 
   private InputStream stream;
+  private OutputStream outStream;
   private ImmutableListMultimap<String, String> headers = ImmutableListMultimap.of();
 
   PathURLConnection(URL url) {
@@ -122,6 +124,16 @@ public InputStream getInputStream() throws IOException {
     return stream;
   }
 
+  @Override
+  public OutputStream getOutputStream() throws IOException {
+    if (outStream == null) {
+      Path path = Paths.get(toUri(url));
+      Files.createDirectories(path.getParent());
+      outStream = Files.newOutputStream(path);
+    }
+    return outStream;
+  }
+
   @SuppressWarnings("unchecked") // safe by specification of ListMultimap.asMap()
   @Override
   public Map<String, List<String>> getHeaderFields() {

jimfs/src/test/java/com/google/common/jimfs/UrlTest.java

@@ -19,11 +19,13 @@
 import static com.google.common.base.StandardSystemProperty.LINE_SEPARATOR;
 import static com.google.common.truth.Truth.assertThat;
 import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.junit.Assert.assertEquals;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Range;
 import com.google.common.io.Resources;
 import java.io.IOException;
+import java.io.OutputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLConnection;
@@ -61,6 +63,33 @@ public void readFromUrl() throws IOException {
         .isEqualTo("Hello World" + LINE_SEPARATOR.value());
   }
 
+  @Test
+  public void writeToUrl() throws IOException {
+    String content = "Hello World" + LINE_SEPARATOR.value();
+    URL url = path.toUri().toURL();
+    URLConnection connection = url.openConnection();
+    try (OutputStream os = connection.getOutputStream()) {
+        os.write(content.getBytes(UTF_8));
+    }
+    assertThat(Resources.asCharSource(url, UTF_8).read())
+        .isEqualTo("Hello World" + LINE_SEPARATOR.value());
+  }
+
+  @Test
+  public void writeToUrlSameOutputStream() throws IOException {
+    //similar to sockets, expect same OutputStream (see AbstractPlainSocketImpl)
+    URL url = path.toUri().toURL();
+    URLConnection connection = url.openConnection();
+    OutputStream os = connection.getOutputStream();
+    os.write("ABC".getBytes(UTF_8));
+    OutputStream os2 = connection.getOutputStream();
+    os2.write("DEF".getBytes(UTF_8));
+    os2.close();
+    assertEquals(os, os2);
+    assertThat(Resources.asCharSource(url, UTF_8).read())
+        .isEqualTo("ABCDEF");
+  }
+
   @Test
   public void readDirectoryContents() throws IOException {
     Files.createDirectory(path);