From 4c0a16df6f97bc8351451bb4e0ac47c8a30c2cd8 Mon Sep 17 00:00:00 2001
From: bergtwvd <tom.vandenberg@tno.nl>
Date: Fri, 14 Jan 2022 02:03:34 +0100
Subject: [PATCH] Additions to parse and generate a stream of JSON values.

---
 joy-classic-tests/pom.xml                     |   4 -
 .../org/leadpony/joy/api/JsonGenerator.java   |  18 +-
 .../java/org/leadpony/joy/api/JsonParser.java |  38 ++++
 .../joy/core/AbstractJsonParserFactory.java   |  10 +-
 .../joy/core/AbstractJsonProvider.java        |  14 +-
 .../leadpony/joy/core/BasicJsonParser.java    | 140 +++++++-------
 .../joy/core/CompactJsonGenerator.java        |   4 +-
 .../joy/core/JsonGeneratorFactoryImpl.java    |   9 +-
 .../joy/core/JsonParserFactoryImpl.java       |   6 +-
 .../joy/core/PrettyJsonGenerator.java         |   5 +-
 .../joy/core/SimpleJsonGenerator.java         | 174 +++++++++++++-----
 joy-yaml-tests/pom.xml                        |   9 +-
 12 files changed, 284 insertions(+), 147 deletions(-)
 create mode 100644 joy-core/src/main/java/org/leadpony/joy/api/JsonParser.java

diff --git a/joy-classic-tests/pom.xml b/joy-classic-tests/pom.xml
index 20af9fb..fa72ea4 100644
--- a/joy-classic-tests/pom.xml
+++ b/joy-classic-tests/pom.xml
@@ -15,10 +15,6 @@
     <packaging>jar</packaging>
     <name>org.leadpony.joy.classic.tests</name>
 
-    <properties>
-        <maven.compiler.release>14</maven.compiler.release>
-    </properties>
-
     <dependencies>
         <dependency>
             <groupId>org.junit.jupiter</groupId>
diff --git a/joy-core/src/main/java/org/leadpony/joy/api/JsonGenerator.java b/joy-core/src/main/java/org/leadpony/joy/api/JsonGenerator.java
index a479e0d..dc9167f 100644
--- a/joy-core/src/main/java/org/leadpony/joy/api/JsonGenerator.java
+++ b/joy-core/src/main/java/org/leadpony/joy/api/JsonGenerator.java
@@ -40,8 +40,8 @@ public interface JsonGenerator extends jakarta.json.stream.JsonGenerator {
     String INDENTATION_SIZE = "org.leadpony.joy.api.JsonGenerator.indentationSize";
 
     /**
-     * Configuration property to use a tab for indentation instead of spaces. The
-     * value of the property could be anything.
+     * Configuration property to use a tab for indentation instead of spaces.
+     * The value of the property could be anything.
      * <pre>
      * <code>
      * Map&lt;String, Object&gt; config = new HashMap&lt;&gt;();
@@ -53,4 +53,18 @@ public interface JsonGenerator extends jakarta.json.stream.JsonGenerator {
      * @since 1.1
      */
     String TAB_INDENTATION = "org.leadpony.joy.api.JsonGenerator.tabIndentation";
+
+    /**
+     * Configuration property to indicate that the output of the generator is a
+     * sequence of JSON values. The value of the property could be anything.
+     * <pre>
+     * <code>
+     * Map&lt;String, Object&gt; config = new HashMap&lt;&gt;();
+     * config.put(JsonGenerator.VALUE_STREAM, Boolean.TRUE);
+     * </code>
+     * </pre>
+     *
+     * @since 1.2
+     */
+    String VALUE_STREAM = "org.leadpony.joy.api.JsonGenerator.valueStream";
 }
diff --git a/joy-core/src/main/java/org/leadpony/joy/api/JsonParser.java b/joy-core/src/main/java/org/leadpony/joy/api/JsonParser.java
new file mode 100644
index 0000000..4fb8f64
--- /dev/null
+++ b/joy-core/src/main/java/org/leadpony/joy/api/JsonParser.java
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2019-2020 the Joy Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.leadpony.joy.api;
+
+/**
+ * An extended {@link JsonParser}.
+ *
+ * @author leadpony
+ */
+public interface JsonParser {
+
+    /**
+     * Configuration property to indicate that the input of the parser is a
+     * sequence of JSON values. The value of the property could be anything.
+     * <pre>
+     * <code>
+     * Map&lt;String, Object&gt; config = new HashMap&lt;&gt;();
+     * config.put(JsonParser.VALUE_STREAM, Boolean.TRUE);
+     * </code>
+     * </pre>
+     *
+     * @since 1.2
+     */
+    String VALUE_STREAM = "org.leadpony.joy.api.JsonParser.valueStream";
+}
diff --git a/joy-core/src/main/java/org/leadpony/joy/core/AbstractJsonParserFactory.java b/joy-core/src/main/java/org/leadpony/joy/core/AbstractJsonParserFactory.java
index e443020..4b66fe8 100644
--- a/joy-core/src/main/java/org/leadpony/joy/core/AbstractJsonParserFactory.java
+++ b/joy-core/src/main/java/org/leadpony/joy/core/AbstractJsonParserFactory.java
@@ -13,7 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.leadpony.joy.core;
 
 import static org.leadpony.joy.core.Preconditions.requireNonNull;
@@ -34,12 +33,19 @@
  */
 public abstract class AbstractJsonParserFactory extends ConfigurableFactory implements JsonParserFactory {
 
+    private static final String[] SUPPORTED_PROPERTIES = {
+        org.leadpony.joy.api.JsonParser.VALUE_STREAM
+    };
+
+    final boolean valueStream;
+
     protected AbstractJsonParserFactory(Map<String, ?> properties) {
-        this(properties, NO_SUPPORTED_PROPERTIES);
+        this(properties, SUPPORTED_PROPERTIES);
     }
 
     protected AbstractJsonParserFactory(Map<String, ?> properties, String[] supported) {
         super(properties, supported);
+        this.valueStream = containsProperty(org.leadpony.joy.api.JsonParser.VALUE_STREAM);
     }
 
     @Override
diff --git a/joy-core/src/main/java/org/leadpony/joy/core/AbstractJsonProvider.java b/joy-core/src/main/java/org/leadpony/joy/core/AbstractJsonProvider.java
index 4c04f89..e69b154 100644
--- a/joy-core/src/main/java/org/leadpony/joy/core/AbstractJsonProvider.java
+++ b/joy-core/src/main/java/org/leadpony/joy/core/AbstractJsonProvider.java
@@ -70,14 +70,14 @@ protected AbstractJsonProvider() {
     @Override
     public JsonParser createParser(Reader reader) {
         requireNonNull(reader, "reader");
-        return new BasicJsonParser(reader, bufferFactory);
+        return new BasicJsonParser(reader, bufferFactory, false);
     }
 
     @Override
     public JsonParser createParser(InputStream in) {
         requireNonNull(in, "in");
         Reader reader = createStreamReader(in);
-        return new BasicJsonParser(reader, bufferFactory);
+        return new BasicJsonParser(reader, bufferFactory, false);
     }
 
     @Override
@@ -88,14 +88,14 @@ public JsonParserFactory createParserFactory(Map<String, ?> config) {
     @Override
     public JsonGenerator createGenerator(Writer writer) {
         requireNonNull(writer, "writer");
-        return new CompactJsonGenerator(writer, bufferFactory);
+        return new CompactJsonGenerator(writer, bufferFactory, false);
     }
 
     @Override
     public JsonGenerator createGenerator(OutputStream out) {
         requireNonNull(out, "out");
         Writer writer = new OutputStreamWriter(out, StandardCharsets.UTF_8);
-        return new CompactJsonGenerator(writer, bufferFactory);
+        return new CompactJsonGenerator(writer, bufferFactory, false);
     }
 
     @Override
@@ -118,7 +118,7 @@ public JsonReader createReader(InputStream in) {
     @Override
     public JsonWriter createWriter(Writer writer) {
         requireNonNull(writer, "writer");
-        JsonGenerator generator = new CompactJsonGenerator(writer, bufferFactory);
+        JsonGenerator generator = new CompactJsonGenerator(writer, bufferFactory, false);
         return new JsonWriterImpl(generator);
     }
 
@@ -126,7 +126,7 @@ public JsonWriter createWriter(Writer writer) {
     public JsonWriter createWriter(OutputStream out) {
         requireNonNull(out, "out");
         Writer writer = new OutputStreamWriter(out, StandardCharsets.UTF_8);
-        JsonGenerator generator = new CompactJsonGenerator(writer, bufferFactory);
+        JsonGenerator generator = new CompactJsonGenerator(writer, bufferFactory, false);
         return new JsonWriterImpl(generator);
     }
 
@@ -202,7 +202,7 @@ public JsonPatch createPatch(JsonArray array) {
      * {@inheritDoc}
      *
      * @throws IllegalArgumentException if the type of {@code target} is not the
-     *                                  same as {@code source}.
+     * same as {@code source}.
      */
     @Override
     public JsonPatch createDiff(JsonStructure source, JsonStructure target) {
diff --git a/joy-core/src/main/java/org/leadpony/joy/core/BasicJsonParser.java b/joy-core/src/main/java/org/leadpony/joy/core/BasicJsonParser.java
index fac11d9..57bb6fa 100644
--- a/joy-core/src/main/java/org/leadpony/joy/core/BasicJsonParser.java
+++ b/joy-core/src/main/java/org/leadpony/joy/core/BasicJsonParser.java
@@ -36,6 +36,8 @@
  */
 class BasicJsonParser extends AbstractJsonParser {
 
+    private final boolean valueStream;
+
     private final Reader reader;
     private boolean alreadyClosed;
 
@@ -76,9 +78,10 @@ class BasicJsonParser extends AbstractJsonParser {
 
     private JsonLocation location = BasicJsonLocation.INITIAL;
 
-    BasicJsonParser(Reader reader, CharBufferFactory bufferFactory) {
+    BasicJsonParser(Reader reader, CharBufferFactory bufferFactory, boolean valueStream) {
         this.reader = reader;
         this.bufferFactory = bufferFactory;
+        this.valueStream = valueStream;
 
         this.lineNumber = 1;
         this.readBuffer = bufferFactory.createBuffer();
@@ -87,7 +90,6 @@ class BasicJsonParser extends AbstractJsonParser {
     }
 
     /* As a JsonParser */
-
     @Override
     public boolean hasNext() {
         if (readyToNext) {
@@ -188,7 +190,6 @@ public void close() {
     }
 
     /* As a DefaultJsonParser */
-
     @Override
     public final Event getCurrentEvent() {
         return currentEvent;
@@ -224,7 +225,6 @@ public boolean isInObject() {
     }
 
     /* As a BasicJsonParser */
-
     Event processKey() {
         consumeChar();
         return processKey(peekNonSpaceChar());
@@ -246,43 +246,43 @@ Event processValue() {
 
     Event processValue(int c) {
         switch (c) {
-        case '[':
-            consumeChar();
-            pushState(State.ARRAY_FIRST_ITEM);
-            return Event.START_ARRAY;
-        case '{':
-            consumeChar();
-            pushState(State.OBJECT_FIRST_KEY);
-            return Event.START_OBJECT;
-        case 't':
-            parseTrue();
-            return Event.VALUE_TRUE;
-        case 'f':
-            parseFalse();
-            return Event.VALUE_FALSE;
-        case 'n':
-            parseNull();
-            return Event.VALUE_NULL;
-        case '"':
-            parseString();
-            return Event.VALUE_STRING;
-        case '-':
-        case '0':
-        case '1':
-        case '2':
-        case '3':
-        case '4':
-        case '5':
-        case '6':
-        case '7':
-        case '8':
-        case '9':
-            parseNumber(c);
-            return Event.VALUE_NUMBER;
-        case -1:
-            throw newUnexpectedEndException(ParserEventSet.VALUES);
-        default:
-            throw newUnexpectedCharException(c);
+            case '[':
+                consumeChar();
+                pushState(State.ARRAY_FIRST_ITEM);
+                return Event.START_ARRAY;
+            case '{':
+                consumeChar();
+                pushState(State.OBJECT_FIRST_KEY);
+                return Event.START_OBJECT;
+            case 't':
+                parseTrue();
+                return Event.VALUE_TRUE;
+            case 'f':
+                parseFalse();
+                return Event.VALUE_FALSE;
+            case 'n':
+                parseNull();
+                return Event.VALUE_NULL;
+            case '"':
+                parseString();
+                return Event.VALUE_STRING;
+            case '-':
+            case '0':
+            case '1':
+            case '2':
+            case '3':
+            case '4':
+            case '5':
+            case '6':
+            case '7':
+            case '8':
+            case '9':
+                parseNumber(c);
+                return Event.VALUE_NUMBER;
+            case -1:
+                throw newUnexpectedEndException(ParserEventSet.VALUES);
+            default:
+                throw newUnexpectedCharException(c);
         }
     }
 
@@ -519,30 +519,30 @@ private char unescape() {
         consumeChar();
         int c = peekValueChar();
         switch (c) {
-        case '"':
-        case '\\':
-        case '/':
-            consumeChar();
-            return (char) c;
-        case 'b':
-            consumeChar();
-            return '\b';
-        case 'f':
-            consumeChar();
-            return '\f';
-        case 'n':
-            consumeChar();
-            return '\n';
-        case 'r':
-            consumeChar();
-            return '\r';
-        case 't':
-            consumeChar();
-            return '\t';
-        case 'u':
-            return unescapeUnicode();
-        default:
-            throw newUnexpectedCharException(c);
+            case '"':
+            case '\\':
+            case '/':
+                consumeChar();
+                return (char) c;
+            case 'b':
+                consumeChar();
+                return '\b';
+            case 'f':
+                consumeChar();
+                return '\f';
+            case 'n':
+                consumeChar();
+                return '\n';
+            case 'r':
+                consumeChar();
+                return '\r';
+            case 't':
+                consumeChar();
+                return '\t';
+            case 'u':
+                return unescapeUnicode();
+            default:
+                throw newUnexpectedCharException(c);
         }
     }
 
@@ -808,11 +808,12 @@ boolean accepts(int c, BasicJsonParser parser) {
 
             @Override
             Event process(int c, BasicJsonParser parser) {
-                parser.setState(FINISHED);
+                if (!parser.valueStream) {
+                    parser.setState(FINISHED);
+                }
                 return parser.processValue(c);
             }
         },
-
         FINISHED() {
             @Override
             boolean accepts(int c, BasicJsonParser parser) {
@@ -828,7 +829,6 @@ Event process(int c, BasicJsonParser parser) {
                 throw parser.newUnexpectedCharException(c);
             }
         },
-
         ARRAY_FIRST_ITEM() {
             @Override
             Event process(int c, BasicJsonParser parser) {
@@ -845,7 +845,6 @@ boolean isInArray() {
                 return true;
             }
         },
-
         ARRAY_ITEM() {
             @Override
             Event process(int c, BasicJsonParser parser) {
@@ -865,7 +864,6 @@ boolean isInArray() {
                 return true;
             }
         },
-
         OBJECT_FIRST_KEY() {
             @Override
             Event process(int c, BasicJsonParser parser) {
@@ -882,7 +880,6 @@ boolean isInObject() {
                 return true;
             }
         },
-
         OBJECT_KEY() {
             @Override
             Event process(int c, BasicJsonParser parser) {
@@ -902,7 +899,6 @@ boolean isInObject() {
                 return true;
             }
         },
-
         OBJECT_VALUE() {
             @Override
             Event process(int c, BasicJsonParser parser) {
diff --git a/joy-core/src/main/java/org/leadpony/joy/core/CompactJsonGenerator.java b/joy-core/src/main/java/org/leadpony/joy/core/CompactJsonGenerator.java
index d63be44..16db1a2 100644
--- a/joy-core/src/main/java/org/leadpony/joy/core/CompactJsonGenerator.java
+++ b/joy-core/src/main/java/org/leadpony/joy/core/CompactJsonGenerator.java
@@ -29,8 +29,8 @@ class CompactJsonGenerator extends SimpleJsonGenerator {
     private final CharBufferFactory bufferFactory;
     private boolean alreadyClosed;
 
-    CompactJsonGenerator(Writer writer, CharBufferFactory bufferFactory) {
-        super(bufferFactory.createBuffer());
+    CompactJsonGenerator(Writer writer, CharBufferFactory bufferFactory, boolean valueStream) {
+        super(bufferFactory.createBuffer(), valueStream);
         this.writer = decorateWriter(writer);
         this.bufferFactory = bufferFactory;
     }
diff --git a/joy-core/src/main/java/org/leadpony/joy/core/JsonGeneratorFactoryImpl.java b/joy-core/src/main/java/org/leadpony/joy/core/JsonGeneratorFactoryImpl.java
index 80a93be..17c77c5 100644
--- a/joy-core/src/main/java/org/leadpony/joy/core/JsonGeneratorFactoryImpl.java
+++ b/joy-core/src/main/java/org/leadpony/joy/core/JsonGeneratorFactoryImpl.java
@@ -38,7 +38,8 @@ class JsonGeneratorFactoryImpl extends ConfigurableFactory implements JsonGenera
     private static final String[] SUPPORTED_PROPERTIES = {
         JsonGenerator.PRETTY_PRINTING,
         JsonGenerator.INDENTATION_SIZE,
-        JsonGenerator.TAB_INDENTATION
+        JsonGenerator.TAB_INDENTATION,
+        JsonGenerator.VALUE_STREAM
     };
 
     private static final int DEFAULT_INDENTATION_SIZE = 4;
@@ -46,6 +47,7 @@ class JsonGeneratorFactoryImpl extends ConfigurableFactory implements JsonGenera
     private final boolean prettyPrinting;
     private final char indentationChar;
     private final int indentationSize;
+    private final boolean valueStream;
     private final CharBufferFactory bufferFactory;
 
     JsonGeneratorFactoryImpl(Map<String, ?> config, CharBufferFactory bufferFactory) {
@@ -59,6 +61,7 @@ class JsonGeneratorFactoryImpl extends ConfigurableFactory implements JsonGenera
             this.indentationChar = ' ';
             this.indentationSize = getPropertyValue(JsonGenerator.INDENTATION_SIZE, DEFAULT_INDENTATION_SIZE);
         }
+        this.valueStream = containsProperty(JsonGenerator.VALUE_STREAM);
     }
 
     @Override
@@ -84,9 +87,9 @@ public JsonGenerator createGenerator(OutputStream out, Charset charset) {
 
     private JsonGenerator createConfiguredGenerator(Writer writer) {
         if (prettyPrinting) {
-            return new PrettyJsonGenerator(writer, bufferFactory, indentationChar, indentationSize);
+            return new PrettyJsonGenerator(writer, bufferFactory, indentationChar, indentationSize, valueStream);
         } else {
-            return new CompactJsonGenerator(writer, bufferFactory);
+            return new CompactJsonGenerator(writer, bufferFactory, valueStream);
         }
     }
 }
diff --git a/joy-core/src/main/java/org/leadpony/joy/core/JsonParserFactoryImpl.java b/joy-core/src/main/java/org/leadpony/joy/core/JsonParserFactoryImpl.java
index fee36d5..01c53d9 100644
--- a/joy-core/src/main/java/org/leadpony/joy/core/JsonParserFactoryImpl.java
+++ b/joy-core/src/main/java/org/leadpony/joy/core/JsonParserFactoryImpl.java
@@ -43,14 +43,14 @@ class JsonParserFactoryImpl extends AbstractJsonParserFactory {
     @Override
     public JsonParser createParser(Reader reader) {
         requireNonNull(reader, "reader");
-        return new BasicJsonParser(reader, bufferFactory);
+        return new BasicJsonParser(reader, bufferFactory, this.valueStream);
     }
 
     @Override
     public JsonParser createParser(InputStream in) {
         requireNonNull(in, "in");
         Reader reader = createStreamReader(in);
-        return new BasicJsonParser(reader, bufferFactory);
+        return new BasicJsonParser(reader, bufferFactory, this.valueStream);
     }
 
     @Override
@@ -58,6 +58,6 @@ public JsonParser createParser(InputStream in, Charset charset) {
         requireNonNull(in, "in");
         requireNonNull(charset, "charset");
         Reader reader = new InputStreamReader(in, charset);
-        return new BasicJsonParser(reader, bufferFactory);
+        return new BasicJsonParser(reader, bufferFactory, this.valueStream);
     }
 }
diff --git a/joy-core/src/main/java/org/leadpony/joy/core/PrettyJsonGenerator.java b/joy-core/src/main/java/org/leadpony/joy/core/PrettyJsonGenerator.java
index 6c6ac00..eee318f 100644
--- a/joy-core/src/main/java/org/leadpony/joy/core/PrettyJsonGenerator.java
+++ b/joy-core/src/main/java/org/leadpony/joy/core/PrettyJsonGenerator.java
@@ -26,8 +26,9 @@ final class PrettyJsonGenerator extends CompactJsonGenerator {
     private final int indentationSize;
     private int indentationTotal;
 
-    PrettyJsonGenerator(Writer writer, CharBufferFactory bufferFactory, char indentationChar, int indentationSize) {
-        super(writer, bufferFactory);
+    PrettyJsonGenerator(Writer writer, CharBufferFactory bufferFactory, char indentationChar, int indentationSize,
+            boolean valueStream) {
+        super(writer, bufferFactory, valueStream);
         this.indentationChar = indentationChar;
         this.indentationSize = indentationSize;
     }
diff --git a/joy-core/src/main/java/org/leadpony/joy/core/SimpleJsonGenerator.java b/joy-core/src/main/java/org/leadpony/joy/core/SimpleJsonGenerator.java
index 8362ec1..9e060b5 100644
--- a/joy-core/src/main/java/org/leadpony/joy/core/SimpleJsonGenerator.java
+++ b/joy-core/src/main/java/org/leadpony/joy/core/SimpleJsonGenerator.java
@@ -32,6 +32,7 @@
 import jakarta.json.JsonObject;
 import jakarta.json.JsonString;
 import jakarta.json.JsonValue;
+import jakarta.json.JsonValue.ValueType;
 import jakarta.json.stream.JsonGenerationException;
 
 import org.leadpony.joy.api.JsonGenerator;
@@ -43,14 +44,17 @@ class SimpleJsonGenerator extends JsonStringBuilder implements JsonGenerator {
 
     private final Deque<State> stateStack = new ArrayDeque<>();
     private State state;
+    private final boolean valueStream;
 
     SimpleJsonGenerator() {
         this.state = State.INITIAL;
+        this.valueStream = false;
     }
 
-    SimpleJsonGenerator(char[] buffer) {
+    SimpleJsonGenerator(char[] buffer, boolean valueStream) {
         super(buffer);
         this.state = State.INITIAL;
+        this.valueStream = valueStream;
     }
 
     @Override
@@ -221,8 +225,14 @@ public JsonGenerator writeNull() {
 
     @Override
     public void close() {
-        if (state != State.FINAL) {
-            throw newJsonGenerationException(Message.thatGeneratorIsNotCompleted());
+        if (valueStream) {
+            if (state != State.INITIAL && state != State.NEXT_VALUE) {
+                throw newJsonGenerationException(Message.thatGeneratorIsNotCompleted());
+            }
+        } else {
+            if (state != State.FINAL) {
+                throw newJsonGenerationException(Message.thatGeneratorIsNotCompleted());
+            }
         }
     }
 
@@ -247,29 +257,29 @@ final void appendKey(String name) {
 
     final void appendValue(JsonValue value) {
         switch (value.getValueType()) {
-        case ARRAY:
-            appendArray((JsonArray) value);
-            break;
-        case OBJECT:
-            appendObject((JsonObject) value);
-            break;
-        case STRING:
-            appendValue(((JsonString) value).getString());
-            break;
-        case NUMBER:
-            append(value.toString());
-            break;
-        case TRUE:
-            append("true");
-            break;
-        case FALSE:
-            append("false");
-            break;
-        case NULL:
-            appendNull();
-            break;
-        default:
-            break;
+            case ARRAY:
+                appendArray((JsonArray) value);
+                break;
+            case OBJECT:
+                appendObject((JsonObject) value);
+                break;
+            case STRING:
+                appendValue(((JsonString) value).getString());
+                break;
+            case NUMBER:
+                append(value.toString());
+                break;
+            case TRUE:
+                append("true");
+                break;
+            case FALSE:
+                append("false");
+                break;
+            case NULL:
+                appendNull();
+                break;
+            default:
+                break;
         }
     }
 
@@ -330,6 +340,10 @@ protected void appendColon() {
         append(':');
     }
 
+    protected void appendSpace() {
+        append(' ');
+    }
+
     static JsonException newJsonException(String message, IOException e) {
         return new JsonException(message, e);
     }
@@ -349,75 +363,155 @@ enum State {
             @Override
             State writeStartObject(SimpleJsonGenerator g) {
                 g.appendOpeningBracket('{');
-                g.pushState(FINAL);
+                g.pushState(g.valueStream ? NEXT_VALUE : FINAL);
                 return START_OBJECT;
             }
 
             @Override
             State writeStartArray(SimpleJsonGenerator g) {
                 g.appendOpeningBracket('[');
-                g.pushState(FINAL);
+                g.pushState(g.valueStream ? NEXT_VALUE : FINAL);
                 return START_ARRAY;
             }
 
             @Override
             State write(SimpleJsonGenerator g, JsonValue value) {
                 g.appendValue(value);
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
 
             @Override
             State write(SimpleJsonGenerator g, String value) {
                 g.appendValue(value);
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
 
             @Override
             State write(SimpleJsonGenerator g, BigDecimal value) {
                 g.append(value);
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
 
             @Override
             State write(SimpleJsonGenerator g, BigInteger value) {
                 g.append(value);
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
 
             @Override
             State write(SimpleJsonGenerator g, int value) {
                 g.append(value);
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
 
             @Override
             State write(SimpleJsonGenerator g, long value) {
                 g.append(value);
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
 
             @Override
             State write(SimpleJsonGenerator g, double value) {
                 g.append(value);
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
 
             @Override
             State write(SimpleJsonGenerator g, boolean value) {
                 g.append(value);
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
 
             @Override
             State writeNull(SimpleJsonGenerator g) {
                 g.appendNull();
-                return FINAL;
+                return g.valueStream ? NEXT_VALUE : FINAL;
             }
         },
+        NEXT_VALUE(Message::thatIllegalGeneratorMethodWasCalledBeforeAll) {
+            @Override
+            State writeStartObject(SimpleJsonGenerator g) {
+                g.appendOpeningBracket('{');
+                g.pushState(NEXT_VALUE);
+                return START_OBJECT;
+            }
+
+            @Override
+            State writeStartArray(SimpleJsonGenerator g) {
+                g.appendOpeningBracket('[');
+                g.pushState(NEXT_VALUE);
+                return START_ARRAY;
+            }
+
+            @Override
+            State write(SimpleJsonGenerator g, JsonValue value) {
+                if (!value.getValueType().equals(ValueType.OBJECT)
+                        && !value.getValueType().equals(ValueType.ARRAY)) {
+                    g.appendSpace();
+                }
+
+                g.appendValue(value);
+                return NEXT_VALUE;
+            }
+
+            @Override
+            State write(SimpleJsonGenerator g, String value) {
+                g.appendSpace();
+                g.appendValue(value);
+                return NEXT_VALUE;
+            }
+
+            @Override
+            State write(SimpleJsonGenerator g, BigDecimal value) {
+                g.appendSpace();
+                g.append(value);
+                return NEXT_VALUE;
+            }
+
+            @Override
+            State write(SimpleJsonGenerator g, BigInteger value) {
+                g.appendSpace();
+                g.append(value);
+                return NEXT_VALUE;
+            }
 
+            @Override
+            State write(SimpleJsonGenerator g, int value) {
+                g.appendSpace();
+                g.append(value);
+                return NEXT_VALUE;
+            }
+
+            @Override
+            State write(SimpleJsonGenerator g, long value) {
+                g.appendSpace();
+                g.append(value);
+                return NEXT_VALUE;
+            }
+
+            @Override
+            State write(SimpleJsonGenerator g, double value) {
+                g.appendSpace();
+                g.append(value);
+                return NEXT_VALUE;
+            }
+
+            @Override
+            State write(SimpleJsonGenerator g, boolean value) {
+                g.appendSpace();
+                g.append(value);
+                return NEXT_VALUE;
+            }
+
+            @Override
+            State writeNull(SimpleJsonGenerator g) {
+                g.appendSpace();
+                g.appendNull();
+                return NEXT_VALUE;
+            }
+        },
         FINAL(Message::thatIllegalGeneratorMethodWasCalledAfterAll) {
         },
-
         START_ARRAY(Message::thatIllegalGeneratorMethodWasCalledAfterArrayStart) {
 
             @Override
@@ -505,7 +599,6 @@ State writeEnd(SimpleJsonGenerator g) {
                 return g.popState();
             }
         },
-
         ARRAY(Message::thatIllegalGeneratorMethodWasCalledAfterArrayItem) {
 
             @Override
@@ -593,7 +686,6 @@ State writeEnd(SimpleJsonGenerator g) {
                 return g.popState();
             }
         },
-
         START_OBJECT(Message::thatIllegalGeneratorMethodWasCalledAfterObjectStart) {
 
             @Override
@@ -699,7 +791,6 @@ State writeEnd(SimpleJsonGenerator g) {
                 return g.popState();
             }
         },
-
         KEY_NAME(Message::thatIllegalGeneratorMethodWasCalledAfterPropertyKey) {
 
             @Override
@@ -770,7 +861,6 @@ State writeNull(SimpleJsonGenerator g) {
                 return OBJECT;
             }
         },
-
         OBJECT(Message::thatIllegalGeneratorMethodWasCalledAfterPropertyValue) {
             @Override
             State writeStartObject(SimpleJsonGenerator g, String name) {
diff --git a/joy-yaml-tests/pom.xml b/joy-yaml-tests/pom.xml
index 3d93ad0..fff5425 100644
--- a/joy-yaml-tests/pom.xml
+++ b/joy-yaml-tests/pom.xml
@@ -16,7 +16,7 @@
     <name>org.leadpony.joy.yaml.tests</name>
 
     <properties>
-        <maven.compiler.release>14</maven.compiler.release>
+        <maven.compiler.release>17</maven.compiler.release>
     </properties>
 
     <dependencies>
@@ -54,13 +54,6 @@
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-checkstyle-plugin</artifactId>
             </plugin>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <configuration>
-                    <compilerArgs>--enable-preview</compilerArgs>
-                </configuration>
-            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>