Expose JacksonCodec private parse methods.

Motivation:

Parsing a vertx structure from a Jackson JsonParser should be a possible thing.

Changes:

Expose the parseObject/parseArray/parseAny private methods.

Author: vietj

vertx-core/src/main/java/io/vertx/core/json/jackson/JacksonCodec.java

@@ -220,7 +220,7 @@ public static <T> T fromParser(JsonParser parser, Class<T> type) throws DecodeEx
     JsonToken remaining;
     try {
       parser.nextToken();
-      res = parseAny(parser);
+      res = parseValue(parser);
       remaining = parser.nextToken();
     } catch (IOException e) {
       throw new DecodeException(e.getMessage(), e);
@@ -233,12 +233,19 @@ public static <T> T fromParser(JsonParser parser, Class<T> type) throws DecodeEx
     return cast(res, type);
   }
 
-  private static Object parseAny(JsonParser parser) throws IOException, DecodeException {
+  /**
+   * Parse a JSON value given the {@code parser}, consuming the current parser token and possibly more
+   * when parsing an object or an array.
+   *
+   * @param parser the parser
+   * @return the parsed value as an object
+   */
+  public static Object parseValue(JsonParser parser) throws IOException, DecodeException {
     switch (parser.currentTokenId()) {
       case JsonTokenId.ID_START_OBJECT:
-        return parseObject(parser);
+        return internalParseObject(parser);
       case JsonTokenId.ID_START_ARRAY:
-        return parseArray(parser);
+        return internalParseArray(parser);
       case JsonTokenId.ID_STRING:
         return parser.getText();
       case JsonTokenId.ID_NUMBER_FLOAT:
@@ -255,21 +262,34 @@ private static Object parseAny(JsonParser parser) throws IOException, DecodeExce
     }
   }
 
-  private static Map<String, Object> parseObject(JsonParser parser) throws IOException {
+  /**
+   * Parse a JSON object given the {@code parser}, the parser current token must be {@link JsonTokenId#ID_START_OBJECT}
+   *
+   * @param parser the parser
+   * @return the parsed object
+   */
+  public static Map<String, Object> parseObject(JsonParser parser) throws IOException {
+    if (parser.currentTokenId() != JsonTokenId.ID_START_OBJECT) {
+      throw new DecodeException("Expecting the current parser token to be the start of an object");
+    }
+    return internalParseObject(parser);
+  }
+
+  private static Map<String, Object> internalParseObject(JsonParser parser) throws IOException {
     String key1 = parser.nextFieldName();
     if (key1 == null) {
       return new LinkedHashMap<>(2);
     }
     parser.nextToken();
-    Object value1 = parseAny(parser);
+    Object value1 = parseValue(parser);
     String key2 = parser.nextFieldName();
     if (key2 == null) {
       LinkedHashMap<String, Object> obj = new LinkedHashMap<>(2);
       obj.put(key1, value1);
       return obj;
     }
     parser.nextToken();
-    Object value2 = parseAny(parser);
+    Object value2 = parseValue(parser);
     String key = parser.nextFieldName();
     if (key == null) {
       LinkedHashMap<String, Object> obj = new LinkedHashMap<>(2);
@@ -283,14 +303,27 @@ private static Map<String, Object> parseObject(JsonParser parser) throws IOExcep
     obj.put(key2, value2);
     do {
       parser.nextToken();
-      Object value = parseAny(parser);
+      Object value = parseValue(parser);
       obj.put(key, value);
       key = parser.nextFieldName();
     } while (key != null);
     return obj;
   }
 
-  private static List<Object> parseArray(JsonParser parser) throws IOException {
+  /**
+   * Parse a JSON array given the {@code parser}, the parser current token must be {@link JsonTokenId#ID_START_ARRAY}
+   *
+   * @param parser the parser
+   * @return the parsed array
+   */
+  public static List<Object> parseArray(JsonParser parser) throws IOException {
+    if (parser.currentTokenId() != JsonTokenId.ID_START_ARRAY) {
+      throw new DecodeException("Expecting the current parser token to be the start of an array");
+    }
+    return internalParseArray(parser);
+  }
+
+  private static List<Object> internalParseArray(JsonParser parser) throws IOException {
     List<Object> array = new ArrayList<>();
     while (true) {
       parser.nextToken();
@@ -300,7 +333,7 @@ private static List<Object> parseArray(JsonParser parser) throws IOException {
       } else if (tokenId == JsonTokenId.ID_END_ARRAY) {
         return array;
       }
-      Object value = parseAny(parser);
+      Object value = parseValue(parser);
       array.add(value);
     }
   }

vertx-core/src/test/java/io/vertx/tests/json/JacksonTest.java

@@ -11,6 +11,8 @@
 
 package io.vertx.tests.json;
 
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.JsonTokenId;
 import io.vertx.core.json.DecodeException;
 import io.vertx.core.json.EncodeException;
 import io.vertx.core.json.JsonArray;
@@ -20,6 +22,9 @@
 import org.junit.Assert;
 import org.junit.Test;
 
+import java.util.Arrays;
+import java.util.Map;
+
 import static com.fasterxml.jackson.core.StreamReadConstraints.*;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
@@ -134,4 +139,43 @@ private static JsonObject testMaxNameLength(int len) {
     String json = "{\"" + "a".repeat(len) + "\":3}";
     return new JsonObject(json);
   }
+
+  @Test
+  public void testParseMap() throws Exception {
+    JsonParser parser = JacksonCodec.createParser("{\"nested\":{\"key\":\"value\"},\"another\":4}");
+    assertEquals(JsonTokenId.ID_START_OBJECT, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_FIELD_NAME, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_START_OBJECT, parser.nextToken().id());
+    Map<String, Object> nested = JacksonCodec.parseObject(parser);
+    assertEquals(Map.of("key", "value"), nested);
+    assertEquals(JsonTokenId.ID_FIELD_NAME, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_NUMBER_INT, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_END_OBJECT, parser.nextToken().id());
+  }
+
+  @Test
+  public void testParseAny() throws Exception {
+    JsonParser parser = JacksonCodec.createParser("{\"nested\":{\"key\":\"value\"},\"another\":4}");
+    assertEquals(JsonTokenId.ID_START_OBJECT, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_FIELD_NAME, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_START_OBJECT, parser.nextToken().id());
+    Object nested = JacksonCodec.parseValue(parser);
+    assertEquals(Map.of("key", "value"), nested);
+    assertEquals(JsonTokenId.ID_FIELD_NAME, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_NUMBER_INT, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_END_OBJECT, parser.nextToken().id());
+  }
+
+  @Test
+  public void testParseArray() throws Exception {
+    JsonParser parser = JacksonCodec.createParser("{\"nested\":[0,1,2],\"another\":4}");
+    assertEquals(JsonTokenId.ID_START_OBJECT, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_FIELD_NAME, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_START_ARRAY, parser.nextToken().id());
+    Object nested = JacksonCodec.parseArray(parser);
+    assertEquals(Arrays.asList(0, 1, 2), nested);
+    assertEquals(JsonTokenId.ID_FIELD_NAME, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_NUMBER_INT, parser.nextToken().id());
+    assertEquals(JsonTokenId.ID_END_OBJECT, parser.nextToken().id());
+  }
 }