Add JsonType.streamAsLines() supporting writing new line delimited content / application/x-json-stream (#391)

Co-authored-by: Rob Bygrave <robin.bygrave@gmail.com>

Author: rob-bygrave

blackbox-test/src/test/java/org/example/customer/stream/StreamBasicTest.java

@@ -22,6 +22,24 @@ void stream_toJson() {
     assertThat(asJson).isEqualTo("[{\"id\":1,\"name\":\"a\"},{\"id\":2,\"name\":\"b\"},{\"id\":3,\"name\":\"c\"}]");
   }
 
+  @Test
+  void streamAsLines_toJsonFromJson() {
+    JsonType<Stream<MyBasic>> streamType = type.streamAsLines();
+
+    String asJson = streamType.toJson(basics.stream());
+    String expected = "{\"id\":1,\"name\":\"a\"}\n{\"id\":2,\"name\":\"b\"}\n{\"id\":3,\"name\":\"c\"}\n";
+    assertThat(asJson)
+      .describedAs("expect new line delimited json content")
+      .isEqualTo(expected);
+
+    Stream<MyBasic> myBasicStream = streamType.fromJson(expected);
+    List<MyBasic> list = myBasicStream.toList();
+    assertThat(list).describedAs("reads new line delimited").isEqualTo(basics);
+
+    Stream<MyBasic> streamFromArray = streamType.fromJson("[{\"id\":1,\"name\":\"a\"},{\"id\":2,\"name\":\"b\"},{\"id\":3,\"name\":\"c\"}]");
+    assertThat(streamFromArray.toList()).describedAs("reads array as well").isEqualTo(basics);
+  }
+
   @Test
   void stream_traditionalArray() {
     String arrayJson = jsonb.toJson(basics);

jsonb/src/main/java/io/avaje/jsonb/JsonType.java

@@ -98,6 +98,15 @@ public interface JsonType<T> extends JsonView<T>, JsonMapper.Type<T> {
    */
   JsonType<Stream<T>> stream();
 
+  /**
+   * Support a stream of beans writing as new line delimited json (application/x-json-stream).
+   * <p>
+   * This type can read content that is either new lime delimited or in array form.
+   *
+   * @return The stream type for this base JsonType.
+   */
+  JsonType<Stream<T>> streamAsLines();
+
   /**
    * Return the set type for this JsonType.
    */

jsonb/src/main/java/io/avaje/jsonb/core/DJsonType.java

@@ -34,7 +34,16 @@ public final JsonView<T> view(String dsl) {
 
   @Override
   public JsonType<Stream<T>> stream() {
-    return new DJsonStreamType<>(jsonb, Types.newParameterizedType(Stream.class, type), new StreamAdapter<>(adapter));
+    return stream(false);
+  }
+
+  @Override
+  public JsonType<Stream<T>> streamAsLines() {
+    return stream(true);
+  }
+
+  private JsonType<Stream<T>> stream(boolean lineDelimited) {
+    return new DJsonStreamType<>(jsonb, Types.newParameterizedType(Stream.class, type), new StreamAdapter<>(adapter, lineDelimited));
   }
 
   @Override
@@ -125,7 +134,7 @@ private void close(Closeable outputStream) {
 
   @Override
   public final Stream<T> stream(JsonReader reader) {
-    return new StreamAdapter<>(adapter).fromJson(reader);
+    return new StreamAdapter<>(adapter, false).fromJson(reader);
   }
 
   @Override

jsonb/src/main/java/io/avaje/jsonb/core/StreamAdapter.java

@@ -14,16 +14,26 @@
 final class StreamAdapter<T> implements DJsonClosable<Stream<T>>, JsonAdapter<Stream<T>> {
 
   private final JsonAdapter<T> elementAdapter;
+  private final boolean lineDelimited;
 
-  StreamAdapter(JsonAdapter<T> elementAdapter) {
+  StreamAdapter(JsonAdapter<T> elementAdapter, boolean lineDelimited) {
     this.elementAdapter = elementAdapter;
+    this.lineDelimited = lineDelimited;
   }
 
   @Override
   public void toJson(JsonWriter writer, Stream<T> value) {
-    writer.beginArray();
-    value.forEach(bean -> elementAdapter.toJson(writer, bean));
-    writer.endArray();
+    if (lineDelimited) {
+      writer.pretty(false);
+      value.forEach(bean -> {
+        elementAdapter.toJson(writer, bean);
+        writer.writeNewLine();
+      });
+    } else {
+      writer.beginArray();
+      value.forEach(bean -> elementAdapter.toJson(writer, bean));
+      writer.endArray();
+    }
   }
 
   @Override