Fix #4863: add basic Stream methods in JsonNode (#4864)

release-notes/VERSION-2.x

@@ -34,6 +34,8 @@ Project: jackson-databind
  (requested by @nathanukey)
 #4849 Not able to deserialize Enum with default typing after upgrading 2.15.4 -> 2.17.1
  (reported by Kornel Zemla)
+#4863: Add basic Stream support in `JsonNode`: `valueStream()`, `entryStream()`,
+  `forEachEntry()`
 
 2.18.3 (not yet released)
 

src/main/java/com/fasterxml/jackson/databind/JsonNode.java

@@ -4,6 +4,8 @@
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.*;
+import java.util.function.BiConsumer;
+import java.util.stream.Stream;
 
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.databind.node.ArrayNode;
@@ -1039,6 +1041,44 @@ public Set<Map.Entry<String, JsonNode>> properties() {
         return Collections.emptySet();
     }
 
+    /**
+     * Returns a stream of all value nodes of this Node, iff
+     * this node is an {@code ArrayNode} or {@code ObjectNode}.
+     * In case of {@code Object} node, property names (keys) are not included, only values.
+     * For other types of nodes, returns empty stream.
+     *
+     * @since 2.19
+     */
+    public Stream<JsonNode> valueStream() {
+        return ClassUtil.emptyStream();
+    }
+
+    /**
+     * Returns a stream of all value nodes of this Node, iff
+     * this node is an an {@code ObjectNode}.
+     * For other types of nodes, returns empty stream.
+     *
+     * @since 2.19
+     */
+    public Stream<Map.Entry<String, JsonNode>> entryStream() {
+        return ClassUtil.emptyStream();
+    }
+
+    /**
+     * If this node is an {@code ObjectNode}, erforms the given action for each entry
+     * until all entries have been processed or the action throws an exception.
+     * Exceptions thrown by the action are relayed to the caller.     
+     * For other node types, no action is performed.
+     *<p>
+     * Actions are performed in the order of entries, same as order returned by
+     * method {@link #properties()}.
+     * 
+     * @param action Action to perform for each entry
+     */
+    public void forEachEntry(BiConsumer<? super String, ? super JsonNode> action) {
+        // No-op for all but ObjectNode
+    }
+
     /*
     /**********************************************************
     /* Public API, find methods

src/main/java/com/fasterxml/jackson/databind/node/ArrayNode.java

@@ -4,6 +4,7 @@
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.*;
+import java.util.stream.Stream;
 
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.core.type.WritableTypeId;
@@ -288,6 +289,11 @@ public JsonNode required(int index) {
                 index, _children.size());
     }
 
+    @Override // @since 2.19
+    public Stream<JsonNode> valueStream() {
+        return _children.stream();
+    }
+
     @Override
     public boolean equals(Comparator<JsonNode> comparator, JsonNode o)
     {

src/main/java/com/fasterxml/jackson/databind/node/ContainerNode.java

@@ -2,6 +2,7 @@
 
 import java.math.BigDecimal;
 import java.math.BigInteger;
+import java.util.stream.Stream;
 
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.databind.JsonNode;
@@ -54,6 +55,10 @@ protected ContainerNode(JsonNodeFactory nc) {
     @Override
     public abstract JsonNode get(String fieldName);
 
+    // Both ArrayNode and ObjectNode must re-implement
+    @Override // @since 2.19
+    public abstract Stream<JsonNode> valueStream();
+
     @Override
     protected abstract ObjectNode _withObject(JsonPointer origPtr,
             JsonPointer currentPtr,

src/main/java/com/fasterxml/jackson/databind/node/ObjectNode.java

@@ -4,6 +4,8 @@
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.*;
+import java.util.function.BiConsumer;
+import java.util.stream.Stream;
 
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.core.type.WritableTypeId;
@@ -329,7 +331,22 @@ public Iterator<Map.Entry<String, JsonNode>> fields() {
     public Set<Map.Entry<String, JsonNode>> properties() {
         return _children.entrySet();
     }
-
+
+    @Override // @since 2.19
+    public Stream<JsonNode> valueStream() {
+        return _children.values().stream();
+    }
+
+    @Override // @since 2.19
+    public Stream<Map.Entry<String, JsonNode>> entryStream() {
+        return _children.entrySet().stream();
+    }
+
+    @Override // @since 2.19
+    public void forEachEntry(BiConsumer<? super String, ? super JsonNode> action) {
+        _children.forEach(action);
+    }
+
     @Override
     public boolean equals(Comparator<JsonNode> comparator, JsonNode o)
     {

src/main/java/com/fasterxml/jackson/databind/util/ClassUtil.java

@@ -5,6 +5,7 @@
 import java.lang.annotation.Annotation;
 import java.lang.reflect.*;
 import java.util.*;
+import java.util.stream.Stream;
 
 import com.fasterxml.jackson.core.JacksonException;
 import com.fasterxml.jackson.core.JsonGenerator;
@@ -21,7 +22,7 @@ public final class ClassUtil
     private final static Annotation[] NO_ANNOTATIONS = new Annotation[0];
     private final static Ctor[] NO_CTORS = new Ctor[0];
 
-    private final static Iterator<?> EMPTY_ITERATOR = Collections.emptyIterator();
+    private final static Iterator<Object> EMPTY_ITERATOR = Collections.emptyIterator();
 
     /*
     /**********************************************************
@@ -37,6 +38,16 @@ public static <T> Iterator<T> emptyIterator() {
         return (Iterator<T>) EMPTY_ITERATOR;
     }
 
+    /**
+     * @since 2.19
+     */
+    public static <T> Stream<T> emptyStream() {
+        // Looking at its implementation, seems there ought to be simpler/more
+        // efficient way to create and return a shared singleton but... no luck
+        // so far. So just use this for convenience for now:
+        return Stream.empty();
+    }
+
     /*
     /**********************************************************
     /* Methods that deal with inheritance

src/test/java/com/fasterxml/jackson/databind/node/ArrayNodeTest.java

@@ -1,8 +1,9 @@
 package com.fasterxml.jackson.databind.node;
 
-import java.io.*;
 import java.math.BigDecimal;
 import java.math.BigInteger;
+import java.util.Arrays;
+import java.util.stream.Collectors;
 import java.util.ArrayList;
 
 import org.junit.jupiter.api.Test;
@@ -13,8 +14,6 @@
 import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
 import com.fasterxml.jackson.databind.util.RawValue;
 
-import static java.util.Arrays.asList;
-
 import static org.junit.jupiter.api.Assertions.*;
 
 /**
@@ -24,7 +23,7 @@ public class ArrayNodeTest
     extends DatabindTestUtil
 {
     @Test
-    public void testDirectCreation() throws IOException
+    public void testDirectCreation() throws Exception
     {
         ArrayNode n = new ArrayNode(JsonNodeFactory.instance);
 
@@ -108,7 +107,7 @@ public void testDirectCreation() throws IOException
     }
 
     @Test
-    public void testDirectCreation2() throws IOException
+    public void testDirectCreation2() throws Exception
     {
         JsonNodeFactory f = objectMapper().getNodeFactory();
         ArrayList<JsonNode> list = new ArrayList<>();
@@ -139,7 +138,7 @@ public void testDirectCreation2() throws IOException
     }
 
     @Test
-    public void testArraySet() throws IOException {
+    public void testArraySet() throws Exception {
         final ArrayNode array = JsonNodeFactory.instance.arrayNode();
         for (int i = 0; i < 20; i++) {
             array.add("Original Data");
@@ -267,7 +266,7 @@ public void testAddAllWithNullInCollection()
         final ArrayNode array = JsonNodeFactory.instance.arrayNode();
 
         // test
-        array.addAll(asList(null, JsonNodeFactory.instance.objectNode()));
+        array.addAll(Arrays.asList(null, JsonNodeFactory.instance.objectNode()));
 
         // assertions
         assertEquals(2, array.size());
@@ -479,4 +478,28 @@ public void testSimpleMismatch() throws Exception
             verifyException(e, "from Integer value (token `JsonToken.VALUE_NUMBER_INT`)");
         }
     }
+
+    // [databind#4863]: valueStream(), entryStream(), forEachEntry()
+    @Test
+    public void testStreamMethods()
+    {
+        ObjectMapper mapper = objectMapper();
+        ArrayNode arr = mapper.createArrayNode();
+        arr.add(1).add("foo");
+        JsonNode n1 = arr.get(0);
+        JsonNode n2 = arr.get(1);
+
+        // First, valueStream() testing
+        assertEquals(2, arr.valueStream().count());
+        assertEquals(Arrays.asList(n1, n2),
+                arr.valueStream().collect(Collectors.toList()));
+
+        // And then entryStream() (empty)
+        assertEquals(0, arr.entryStream().count());
+        assertEquals(Arrays.asList(),
+                arr.entryStream().collect(Collectors.toList()));
+
+        // And then empty forEachEntry()
+        arr.forEachEntry((k, v) -> { throw new UnsupportedOperationException(); });
+    }
 }

src/test/java/com/fasterxml/jackson/databind/node/JsonNodeBasicTest.java

@@ -65,6 +65,8 @@ public void testBoolean() throws Exception
         // also, equality should work ok
         assertEquals(result, BooleanNode.valueOf(true));
         assertEquals(result, BooleanNode.getTrue());
+
+        assertNonContainerStreamMethods(f);
     }
 
     @Test
@@ -92,6 +94,8 @@ public void testBinary() throws Exception
 
         assertEquals("AAMD", new BinaryNode(data).asText());
         assertNodeNumbersForNonNumeric(n);
+
+        assertNonContainerStreamMethods(n2);
     }
 
     @Test
@@ -110,6 +114,8 @@ public void testPOJO()
         assertNodeNumbersForNonNumeric(n);
         // but if wrapping actual number, use it
         assertNodeNumbers(new POJONode(Integer.valueOf(123)), 123, 123.0);
+
+        assertNonContainerStreamMethods(n);
     }
 
     // [databind#743]

src/test/java/com/fasterxml/jackson/databind/node/NodeTestBase.java

@@ -34,4 +34,16 @@ protected void assertNodeNumbers(JsonNode n, int expInt, double expDouble)
 
         assertTrue(n.isEmpty());
     }
+
+    // Testing for non-ContainerNode (ValueNode) stream method implementations
+    //
+    // @since 2.19
+    protected void assertNonContainerStreamMethods(ValueNode n)
+    {
+        assertEquals(0, n.valueStream().count());
+        assertEquals(0, n.entryStream().count());
+
+        // And then empty forEachEntry()
+        n.forEachEntry((k, v) -> { throw new UnsupportedOperationException(); });
+    }
 }

src/test/java/com/fasterxml/jackson/databind/node/NullNodeTest.java

@@ -69,6 +69,8 @@ public void testBasicsWithNullNode() throws Exception
         assertFalse(n.has(3));
 
         assertNodeNumbersForNonNumeric(n);
+
+        assertNonContainerStreamMethods(n);
     }
 
     @Test

src/test/java/com/fasterxml/jackson/databind/node/NumberNodesTest.java

@@ -43,6 +43,8 @@ public void testShort()
         assertTrue(ShortNode.valueOf((short) 0).canConvertToLong());
         assertTrue(ShortNode.valueOf(Short.MAX_VALUE).canConvertToLong());
         assertTrue(ShortNode.valueOf(Short.MIN_VALUE).canConvertToLong());
+
+        assertNonContainerStreamMethods(n);
     }
 
     @Test
@@ -101,6 +103,7 @@ public void testInt()
         assertTrue(IntNode.valueOf(Integer.MAX_VALUE).canConvertToLong());
         assertTrue(IntNode.valueOf(Integer.MIN_VALUE).canConvertToLong());
 
+        assertNonContainerStreamMethods(n);
     }
 
     @Test
@@ -130,6 +133,8 @@ public void testLong()
         assertTrue(LongNode.valueOf(0L).canConvertToLong());
         assertTrue(LongNode.valueOf(Long.MAX_VALUE).canConvertToLong());
         assertTrue(LongNode.valueOf(Long.MIN_VALUE).canConvertToLong());
+
+        assertNonContainerStreamMethods(n);
     }
 
     @Test
@@ -193,6 +198,8 @@ public void testDouble() throws Exception
         n = (DoubleNode) num;
         assertEquals(-0.0, n.doubleValue());
         assertEquals("-0.0", String.valueOf(n.doubleValue()));
+
+        assertNonContainerStreamMethods(n);
     }
 
     @Test
@@ -264,6 +271,8 @@ public void testFloat()
         assertTrue(FloatNode.valueOf(0L).canConvertToLong());
         assertTrue(FloatNode.valueOf(Integer.MAX_VALUE).canConvertToLong());
         assertTrue(FloatNode.valueOf(Integer.MIN_VALUE).canConvertToLong());
+
+        assertNonContainerStreamMethods(n);
     }
 
     @Test
@@ -322,6 +331,8 @@ public void testDecimalNode() throws Exception
 
         // also, equality should work ok
         assertEquals(result, DecimalNode.valueOf(value));
+
+        assertNonContainerStreamMethods(n);
     }
 
     @Test
@@ -391,6 +402,8 @@ public void testBigIntegerNode() throws Exception
         assertTrue(BigIntegerNode.valueOf(BigInteger.ZERO).canConvertToLong());
         assertTrue(BigIntegerNode.valueOf(BigInteger.valueOf(Long.MAX_VALUE)).canConvertToLong());
         assertTrue(BigIntegerNode.valueOf(BigInteger.valueOf(Long.MIN_VALUE)).canConvertToLong());
+
+        assertNonContainerStreamMethods(n);
     }
 
     @Test