added reference serialization and deserialization in both json (text) and jbon (binary) format

2019-07-26 12:42:35 +01:00
parent 89fb8ac1b7
commit ff9b26ed93
14 changed files with 426 additions and 100 deletions
--- a/build.sbt
+++ b/build.sbt
@@ -26,10 +26,6 @@ libraryDependencies += "org.antlr" % "antlr4" % "4.7.1" % Test
 libraryDependencies += "org.antlr" % "antlr4-runtime" % "4.7.1" % Test
 libraryDependencies += "org.tukaani" % "xz" % "1.8" % Test

-artifactName := { (sv: ScalaVersion, module: ModuleID, artifact: Artifact) =>
-  artifact.name + "-" + module.revision + "." + artifact.extension
-}
-
 enablePlugins(Antlr4Plugin)
 antlr4Version in Antlr4 := "4.7.1"
 antlr4PackageName in Antlr4 := Some("net.woggioni.worth.antlr")
--- a/src/main/java/net/woggioni/worth/serialization/ValueDumper.java
+++ b/src/main/java/net/woggioni/worth/serialization/ValueDumper.java
@@ -2,8 +2,11 @@ package net.woggioni.worth.serialization;

 import lombok.RequiredArgsConstructor;
 import net.woggioni.worth.exception.NotImplementedException;
-import net.woggioni.worth.value.ArrayValue;
-import net.woggioni.worth.value.ObjectValue;
+import net.woggioni.worth.traversal.TraversalContext;
+import net.woggioni.worth.traversal.ValueIdentity;
+import net.woggioni.worth.traversal.ValueVisitor;
+import net.woggioni.worth.traversal.ValueWalker;
+import net.woggioni.worth.value.*;
 import net.woggioni.worth.xface.Dumper;
 import net.woggioni.worth.xface.Value;

@@ -11,9 +14,9 @@ import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.io.Writer;
 import java.nio.charset.Charset;
-import java.util.ArrayDeque;
-import java.util.Iterator;
-import java.util.Map;
+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;

 public abstract class ValueDumper implements Dumper {

@@ -25,6 +28,47 @@ public abstract class ValueDumper implements Dumper {
        public final Value value;
    }

+    protected Map<ValueIdentity, Integer> getIdMap(Value root) {
+        Map<ValueIdentity, Integer> occurrencies = new HashMap<>();
+        ValueVisitor visitor = new ValueVisitor(){
+
+            private void visit(Value v) {
+                ValueIdentity identity = new ValueIdentity(v);
+                Integer i = occurrencies.getOrDefault(identity, 0);
+                occurrencies.put(identity, ++i);
+            }
+
+            @Override
+            public boolean filter(Value value, TraversalContext ctx) {
+                if(value.type() == Value.Type.ARRAY || value.type() == Value.Type.OBJECT) {
+                    ValueIdentity identity = new ValueIdentity(value);
+                    Integer i = occurrencies.getOrDefault(identity, 0);
+                    occurrencies.put(identity, ++i);
+                    return i == 1;
+                } else {
+                    return true;
+                }
+            }
+
+            @Override
+            public void visit(ObjectValue value, TraversalContext ctx) {
+                visit(value);
+            }
+
+            @Override
+            public void visit(ArrayValue value, TraversalContext ctx) {
+                visit(value);
+            }
+        };
+        ValueWalker.walk(root, visitor);
+        Map<ValueIdentity, Integer> result = new HashMap<>();
+        int i = 0;
+        for(ValueIdentity identity : occurrencies.keySet()) {
+            result.put(identity, i++);
+        }
+        return result;
+    }
+
    protected static class ArrayStackLevel extends StackLevel implements Iterator<Value> {
        private final Iterator<Value> iterator = ((ArrayValue) value).iterator();

@@ -110,4 +154,8 @@ public abstract class ValueDumper implements Dumper {
    protected abstract void booleanValue(boolean value);

    protected abstract void nullValue();
+
+    protected abstract void valueId(int id);
+
+    protected abstract void valueReference(int id);
 }
--- a/src/main/java/net/woggioni/worth/serialization/ValueParser.java
+++ b/src/main/java/net/woggioni/worth/serialization/ValueParser.java
@@ -3,6 +3,7 @@ package net.woggioni.worth.serialization;
 import lombok.RequiredArgsConstructor;
 import net.woggioni.worth.exception.MaxDepthExceededException;
 import net.woggioni.worth.exception.NotImplementedException;
+import net.woggioni.worth.exception.ParseException;
 import net.woggioni.worth.utils.WorthUtils;
 import net.woggioni.worth.value.*;
 import net.woggioni.worth.xface.Parser;
@@ -11,8 +12,12 @@ import net.woggioni.worth.xface.Value;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.Reader;
+import java.lang.reflect.Array;
 import java.nio.charset.Charset;
 import java.util.ArrayDeque;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;

 import static net.woggioni.worth.utils.WorthUtils.newThrowable;

@@ -27,9 +32,6 @@ public class ValueParser implements Parser {
    }

    protected static class ArrayStackLevel extends StackLevel {
-        public ArrayStackLevel() {
-            super(new ArrayValue(), -1);
-        }
        public ArrayStackLevel(long expectedSize) {
            super(new ArrayValue(), expectedSize);
        }
@@ -38,16 +40,13 @@ public class ValueParser implements Parser {
    protected static class ObjectStackLevel extends StackLevel {
        public String currentKey;

-        public ObjectStackLevel(Value.Configuration cfg) {
-            super(ObjectValue.newInstance(cfg), -1);
-        }
-
        public ObjectStackLevel(Value.Configuration cfg, long expectedSize) {
            super(ObjectValue.newInstance(cfg), expectedSize);
        }
    }

    protected ArrayDeque<StackLevel> stack;
+    protected Map<Integer, Value> idMap;

    private void add2Last(Value value) {
        StackLevel last = stack.getFirst();
@@ -67,17 +66,20 @@ public class ValueParser implements Parser {

    protected ValueParser(Value.Configuration cfg) {
        this.cfg = cfg;
+        if (cfg.serializeReferences) {
+            idMap = new HashMap<>();
+        }
        stack = new ArrayDeque<>() {
            @Override
            public void push(StackLevel stackLevel) {
-                if(size() == cfg.maxDepth) {
+                if (size() == cfg.maxDepth) {
                    throw newThrowable(MaxDepthExceededException.class,
-                        "Objects is too deep, max allowed depth is %d", cfg.maxDepth);
+                            "Objects is too deep, max allowed depth is %d", cfg.maxDepth);
                }
                super.push(stackLevel);
            }
        };
-        stack.push(new ArrayStackLevel());
+        stack.push(new ArrayStackLevel(-1));
    }

    @Override
@@ -95,29 +97,40 @@ public class ValueParser implements Parser {
        return parse(new InputStreamReader(stream, encoding));
    }

-    protected void beginObject() {
-        stack.push(new ObjectStackLevel(cfg));
+    protected Value beginObject() {
+        return beginObject(-1);
    }

-    protected void beginObject(long size) {
-        stack.push(new ObjectStackLevel(cfg, size));
+    protected Value beginObject(long size) {
+        ObjectStackLevel osl = new ObjectStackLevel(cfg, size);
+        stack.push(osl);
+        return osl.value;
    }

-
    protected void endObject() {
-        add2Last(stack.pop().value);
+        ValueParser.StackLevel sl = stack.pop();
+        if(!(sl instanceof ValueParser.ObjectStackLevel)) {
+            error(ParseException::new, "Unexpected object terminator");
+        }
+        add2Last(sl.value);
    }

-    protected void beginArray() {
-        stack.push(new ArrayStackLevel());
+    protected Value beginArray() {
+        return beginArray(-1);
    }

-    protected void beginArray(long size) {
-        stack.push(new ArrayStackLevel(size));
+    protected Value beginArray(long size) {
+        ArrayStackLevel ale = new ArrayStackLevel(size);
+        stack.push(ale);
+        return ale.value;
    }

    protected void endArray() {
-        add2Last(stack.pop().value);
+        ValueParser.StackLevel sl = stack.pop();
+        if(!(sl instanceof ValueParser.ArrayStackLevel)) {
+            error(ParseException::new, "Unexpected array terminator");
+        }
+        add2Last(sl.value);
    }

    protected void objectKey(String key) {
@@ -144,4 +157,20 @@ public class ValueParser implements Parser {
    protected void nullValue() {
        add2Last(Value.Null);
    }
+
+    protected void valueId(int id, Value value) {
+        idMap.put(id, value);
+    }
+
+    protected void valueReference(int id) {
+        Value referencedValue = idMap.get(id);
+        if (referencedValue == null) {
+            error(ParseException::new, "got invalid id '%d'", id);
+        }
+        add2Last(referencedValue);
+    }
+
+    protected <T extends RuntimeException> T error(Function<String, T> constructor, String fmt, Object... args) {
+        throw new NotImplementedException("Method not implemented");
+    }
 }
--- a/src/main/java/net/woggioni/worth/serialization/binary/JBONDumper.java
+++ b/src/main/java/net/woggioni/worth/serialization/binary/JBONDumper.java
@@ -4,6 +4,7 @@ import lombok.SneakyThrows;
 import net.woggioni.worth.exception.NotImplementedException;
 import net.woggioni.worth.serialization.ValueDumper;
 import net.woggioni.worth.serialization.json.JSONDumper;
+import net.woggioni.worth.traversal.ValueIdentity;
 import net.woggioni.worth.utils.Leb128;
 import net.woggioni.worth.utils.WorthUtils;
 import net.woggioni.worth.value.ArrayValue;
@@ -13,7 +14,9 @@ import net.woggioni.worth.xface.Value;

 import java.io.OutputStream;
 import java.io.Writer;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 import java.util.function.Consumer;

 public class JBONDumper extends ValueDumper {
@@ -44,8 +47,18 @@ public class JBONDumper extends ValueDumper {
    @Override
    @SneakyThrows
    public void dump(Value value, OutputStream outputStream) {
+        Map<ValueIdentity, Integer> ids;
+        Set<Integer> dumpedId;
+        if(cfg.serializeReferences) {
+            ids = getIdMap(value);
+            dumpedId = new HashSet<>();
+        } else {
+            ids = null;
+            dumpedId = null;
+        }
        this.os = outputStream;
        final Consumer<Value> handle_value = (v) -> {
+            Integer id;
            switch (v.type()) {
                case NULL:
                    nullValue();
@@ -64,13 +77,33 @@ public class JBONDumper extends ValueDumper {
                    break;
                case ARRAY:
                    ArrayValue arrayValue = WorthUtils.dynamicCast(v, ArrayValue.class);
-                    stack.push(new ArrayStackLevel(arrayValue));
-                    beginArray(arrayValue.size());
+                    if(ids != null && (id = ids.get(new ValueIdentity(arrayValue))) != null) {
+                        if(dumpedId.add(id)) {
+                            stack.push(new ArrayStackLevel(arrayValue));
+                            valueId(id);
+                            beginArray(arrayValue.size());
+                        } else {
+                            valueReference(id);
+                        }
+                    } else {
+                        stack.push(new ArrayStackLevel(arrayValue));
+                        beginArray(arrayValue.size());
+                    }
                    break;
                case OBJECT:
                    ObjectValue objectValue = WorthUtils.dynamicCast(v, ObjectValue.class);
-                    stack.push(new ObjectStackLevel(objectValue));
-                    beginObject(objectValue.size());
+                    if(ids != null && (id = ids.get(new ValueIdentity(objectValue))) != null) {
+                        if(dumpedId.add(id)) {
+                                stack.push(new ObjectStackLevel(WorthUtils.dynamicCast(v, ObjectValue.class)));
+                                valueId(id);
+                                beginObject(objectValue.size());
+                            } else {
+                                valueReference(id);
+                            }
+                    } else {
+                        stack.push(new ObjectStackLevel(WorthUtils.dynamicCast(v, ObjectValue.class)));
+                        beginObject(objectValue.size());
+                    }
                    break;
            }
        };
@@ -191,4 +224,18 @@ public class JBONDumper extends ValueDumper {
    protected void nullValue() {
        os.write(BinaryMarker.Null.value);
    }
+
+    @Override
+    @SneakyThrows
+    protected void valueReference(int id) {
+        os.write(BinaryMarker.Reference.value);
+        Leb128.encode(os, id);
+    }
+
+    @Override
+    @SneakyThrows
+    protected void valueId(int id) {
+        os.write(BinaryMarker.Id.value);
+        Leb128.encode(os, id);
+    }
 }
--- a/src/main/java/net/woggioni/worth/serialization/binary/JBONParser.java
+++ b/src/main/java/net/woggioni/worth/serialization/binary/JBONParser.java
@@ -18,7 +18,8 @@ public class JBONParser extends ValueParser {
    private int cursor = 0;


-    private <T extends RuntimeException> T error(Function<String, T> constructor, String fmt, Object... args) {
+    @Override
+    protected  <T extends RuntimeException> T error(Function<String, T> constructor, String fmt, Object... args) {
        return constructor.apply(
                String.format("Error at position %d: %s",
                        cursor, String.format(fmt, args)));
@@ -38,6 +39,7 @@ public class JBONParser extends ValueParser {
        stream.read();

        try {
+            Integer currentId = null;
            Leb128.Leb128Decoder decoder = new Leb128.Leb128Decoder(stream);
            ObjectStackLevel osl;
            while (true) {
@@ -52,7 +54,11 @@ public class JBONParser extends ValueParser {
                if(c == -1) {
                    break;
                }
-                if(c == BinaryMarker.Null.value) {
+                if(idMap != null && c == BinaryMarker.Id.value) {
+                    currentId = (int) decoder.decode();
+                } else if(idMap != null && c == BinaryMarker.Reference.value) {
+                    valueReference((int) decoder.decode());
+                } else if(c == BinaryMarker.Null.value) {
                    nullValue();
                } else if(c == BinaryMarker.True.value) {
                    booleanValue(true);
@@ -75,17 +81,26 @@ public class JBONParser extends ValueParser {
                    stream.read(buffer);
                    String text = new String(buffer);
                    stringValue(text);
-                } else if(c == BinaryMarker.EmptyArray.value) {
-                    beginArray(0);
-                } else if(c > BinaryMarker.EmptyArray.value && c < BinaryMarker.LargeArray.value) {
-                    beginArray(c - BinaryMarker.EmptyArray.value);
-                } else if(c == BinaryMarker.LargeArray.value) {
-                    long size = decoder.decode();
-                    beginArray(size);
-                } else if(c == BinaryMarker.EmptyObject.value) {
-                    beginObject(0);
-                } else if(c > BinaryMarker.EmptyObject.value && c < BinaryMarker.LargeObject.value) {
-                    beginObject(c - BinaryMarker.EmptyObject.value);
+                } else if(c >= BinaryMarker.EmptyArray.value && c <= BinaryMarker.LargeArray.value) {
+                    long size;
+                    if(c == BinaryMarker.LargeArray.value) {
+                        size = decoder.decode();
+                    } else {
+                        size = c - BinaryMarker.EmptyArray.value;
+                    }
+                    Value newArray = beginArray(size);
+                    if(currentId != null) valueId(currentId, newArray);
+                    currentId = null;
+                } else if(c >= BinaryMarker.EmptyObject.value && c <= BinaryMarker.LargeObject.value) {
+                    long size;
+                    if(c == BinaryMarker.LargeObject.value) {
+                        size = decoder.decode();
+                    } else {
+                        size = c - BinaryMarker.EmptyObject.value;
+                    }
+                    Value newObject = beginObject(size);
+                    if(currentId != null) valueId(currentId, newObject);
+                    currentId = null;
                } else if(c == BinaryMarker.LargeObject.value) {
                    long size = decoder.decode();
                    beginObject(size);
--- a/src/main/java/net/woggioni/worth/serialization/json/JSONDumper.java
+++ b/src/main/java/net/woggioni/worth/serialization/json/JSONDumper.java
@@ -2,17 +2,21 @@ package net.woggioni.worth.serialization.json;

 import lombok.SneakyThrows;
 import net.woggioni.worth.serialization.ValueDumper;
+import net.woggioni.worth.traversal.ValueIdentity;
 import net.woggioni.worth.utils.WorthUtils;
-import net.woggioni.worth.value.ArrayValue;
-import net.woggioni.worth.value.ObjectValue;
+import net.woggioni.worth.value.*;
 import net.woggioni.worth.xface.Dumper;
 import net.woggioni.worth.xface.Value;

 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.io.Writer;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.stream.Collectors;

 public class JSONDumper extends ValueDumper {

@@ -73,8 +77,18 @@ public class JSONDumper extends ValueDumper {
    @Override
    @SneakyThrows
    public void dump(Value value, Writer writer) {
+        Map<ValueIdentity, Integer> ids;
+        Set<Integer> dumpedId;
+        if(cfg.serializeReferences) {
+            ids = getIdMap(value);
+            dumpedId = new HashSet<>();
+        } else {
+            ids = null;
+            dumpedId = null;
+        }
        this.writer = writer;
        final Consumer<Value> handle_value = (v) -> {
+            Integer id;
            switch (v.type()) {
                case NULL:
                    nullValue();
@@ -93,13 +107,33 @@ public class JSONDumper extends ValueDumper {
                    break;
                case ARRAY:
                    ArrayValue arrayValue = WorthUtils.dynamicCast(v, ArrayValue.class);
-                    stack.push(new ArrayStackLevel(arrayValue));
-                    beginArray(arrayValue.size());
+                    if(ids != null && (id = ids.get(new ValueIdentity(arrayValue))) != null) {
+                        if(dumpedId.add(id)) {
+                            stack.push(new ArrayStackLevel(arrayValue));
+                            valueId(id);
+                            beginArray(arrayValue.size());
+                        } else {
+                            valueReference(id);
+                        }
+                    } else {
+                        stack.push(new ArrayStackLevel(arrayValue));
+                        beginArray(arrayValue.size());
+                    }
                    break;
                case OBJECT:
                    ObjectValue objectValue = WorthUtils.dynamicCast(v, ObjectValue.class);
-                    stack.push(new ObjectStackLevel(WorthUtils.dynamicCast(v, ObjectValue.class)));
-                    beginObject(objectValue.size());
+                    if(ids != null && (id = ids.get(new ValueIdentity(objectValue))) != null) {
+                        if(dumpedId.add(id)) {
+                            stack.push(new ObjectStackLevel(WorthUtils.dynamicCast(v, ObjectValue.class)));
+                            valueId(id);
+                            beginObject(objectValue.size());
+                        } else {
+                            valueReference(id);
+                        }
+                    } else {
+                        stack.push(new ObjectStackLevel(WorthUtils.dynamicCast(v, ObjectValue.class)));
+                        beginObject(objectValue.size());
+                    }
                    break;
            }
        };
@@ -197,4 +231,16 @@ public class JSONDumper extends ValueDumper {
    protected void nullValue() {
        this.writer.write("null");
    }
+
+    @Override
+    @SneakyThrows
+    protected void valueId(int id) {
+        this.writer.write("(" + id + ")");
+    }
+
+    @Override
+    @SneakyThrows
+    protected void valueReference(int id) {
+        this.writer.write("$" + id);
+    }
 }
--- a/src/main/java/net/woggioni/worth/serialization/json/JSONParser.java
+++ b/src/main/java/net/woggioni/worth/serialization/json/JSONParser.java
@@ -48,7 +48,7 @@ public class JSONParser extends ValueParser {
        return result;
    }

-    private final void parseNumber(LookAheadTextInputStream stream) {
+    private final String parseNumber(LookAheadTextInputStream stream) {
        StringBuilder sb = new StringBuilder();
        while (true) {
            int b = stream.getCurrentByte();
@@ -61,12 +61,31 @@ public class JSONParser extends ValueParser {
            }
            stream.read();
        }
-        String text = sb.toString();
-        if (text.indexOf('.') > 0) {
-            floatValue(Double.valueOf(text));
-        } else {
-            integerValue(Long.valueOf(text));
+        return sb.toString();
+    }
+
+    private final int parseId(LookAheadTextInputStream stream) {
+        StringBuilder sb = new StringBuilder();
+        boolean digitsStarted = false;
+        boolean digitsEnded = false;
+        while (true) {
+            int b = stream.getCurrentByte();
+            if(b == '(' ) {
+            } else if(Character.isWhitespace(b)) {
+                if(digitsStarted) digitsEnded = true;
+            } else if (b < 0 || b == ')') {
+                break;
+            } else if (isDecimal(b)) {
+                if(digitsEnded) {
+                    error(ParseException::new, "error parsing id");
+                } else {
+                    digitsStarted = true;
+                    sb.appendCodePoint(b);
+                }
+            }
+            stream.read();
        }
+        return Integer.valueOf(sb.toString());
    }

    private String readString(LookAheadTextInputStream stream) {
@@ -131,10 +150,10 @@ public class JSONParser extends ValueParser {
        }
    }

-    private <T extends RuntimeException> T error(Function<String, T> constructor, String fmt, Object... args) {
-        return constructor.apply(
-                String.format("Error at line %d column %d: %s",
-                        currentLine, currentColumn, String.format(fmt, args)));
+    @Override
+    protected <T extends RuntimeException> T error(Function<String, T> constructor, String fmt, Object ...args) {
+        return constructor.apply(String.format("Error at line %d column %d: %s",
+            currentLine, currentColumn, String.format(fmt, args)));
    }

    public static Parser newInstance() {
@@ -175,22 +194,34 @@ public class JSONParser extends ValueParser {
        };

        try {
+            Integer currentId = null;
            while (true) {
                int c = stream.getCurrentByte();
                if (c == -1) {
                    break;
                } else if (c == ' ' || c == '\t' || c == '\n' || c == '\r') {
+                } else if (c == '(') {
+                    currentId = parseId(stream);
                } else if (c == '{') {
-                    beginObject();
+                    Value newObject = beginObject();
+                    if(currentId != null) valueId(currentId, newObject);
+                    currentId = null;
                } else if (c == '}') {
                    endObject();
                } else if (c == '[') {
-                    beginArray();
+                    Value newArray = beginArray();
+                    if(currentId != null) valueId(currentId, newArray);
+                    currentId = null;
                } else if (c == ']') {
                    endArray();
                } else if (isDecimal(c)) {
                    try {
-                        parseNumber(stream);
+                        String text = parseNumber(stream);
+                        if (text.indexOf('.') > 0) {
+                            floatValue(Double.valueOf(text));
+                        } else {
+                            integerValue(Long.valueOf(text));
+                        }
                        continue;
                    } catch (NumberFormatException nfe) {
                        throw error(ParseException::new, nfe.getMessage());
@@ -212,6 +243,11 @@ public class JSONParser extends ValueParser {
                } else if (c == 'n') {
                    consumeExpected(stream, "null", "Unrecognized null value");
                    nullValue();
+                } else if (idMap != null && c == '$') {
+                    stream.read();
+                    String text = parseNumber(stream);
+                    valueReference(Integer.valueOf(text));
+                    continue;
                }
                stream.read();
            }
--- a/src/main/java/net/woggioni/worth/traversal/ValueIdentity.java
+++ b/src/main/java/net/woggioni/worth/traversal/ValueIdentity.java
@@ -0,0 +1,26 @@
+package net.woggioni.worth.traversal;
+
+import lombok.RequiredArgsConstructor;
+import net.woggioni.worth.xface.Value;
+
+@RequiredArgsConstructor
+public class ValueIdentity {
+
+    private final Value value;
+
+    @Override
+    public int hashCode() {
+        return System.identityHashCode(value);
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if(other == null) {
+            return false;
+        } else if(!(other instanceof ValueIdentity)) {
+            return false;
+        } else {
+            return value == ((ValueIdentity) other).value;
+        }
+    }
+}
--- a/src/main/java/net/woggioni/worth/traversal/ValueVisitor.java
+++ b/src/main/java/net/woggioni/worth/traversal/ValueVisitor.java
@@ -1,14 +1,16 @@
 package net.woggioni.worth.traversal;

 import net.woggioni.worth.value.*;
+import net.woggioni.worth.xface.Value;

 public interface ValueVisitor {

-    void visit(ObjectValue value, TraversalContext ctx);
-    void visit(ArrayValue value, TraversalContext ctx);
-    void visit(BooleanValue value, TraversalContext ctx);
-    void visit(StringValue value, TraversalContext ctx);
-    void visit(IntegerValue value, TraversalContext ctx);
-    void visit(FloatValue value, TraversalContext ctx);
-    void visit(NullValue value, TraversalContext ctx);
+    default void visit(ObjectValue value, TraversalContext ctx) {}
+    default void visit(ArrayValue value, TraversalContext ctx) {}
+    default void visit(BooleanValue value, TraversalContext ctx) {}
+    default void visit(StringValue value, TraversalContext ctx) {}
+    default void visit(IntegerValue value, TraversalContext ctx) {}
+    default void visit(FloatValue value, TraversalContext ctx) {}
+    default void visit(NullValue value, TraversalContext ctx) {}
+    default boolean filter(Value value, TraversalContext ctx) { return true; }
 }
--- a/src/main/java/net/woggioni/worth/traversal/ValueWalker.java
+++ b/src/main/java/net/woggioni/worth/traversal/ValueWalker.java
@@ -108,28 +108,30 @@ public class ValueWalker {
        stack.add(ase);
        while(true) {
            Value currentValue = stack.get(stack.size() - 1).next();
-            if((av = dynamicCast(currentValue, ArrayValue.class)) != null) {
-                ase = new ArrayStackElement(av);
-                stack.add(ase);
-            } else if((ov = dynamicCast(currentValue, ObjectValue.class)) != null) {
-                ObjectStackElement ose = new ObjectStackElement(ov);
-                stack.add(ose);
-            } else {
-                IntegerValue iv;
-                BooleanValue bv;
-                NullValue nv;
-                FloatValue fv;
-                StringValue sv;
-                if((iv = dynamicCast(currentValue, IntegerValue.class)) != null) {
-                    visitor.visit(iv, ctx);
-                } else if((fv = dynamicCast(currentValue, FloatValue.class)) != null) {
-                    visitor.visit(fv, ctx);
-                } else if((bv = dynamicCast(currentValue, BooleanValue.class)) != null) {
-                    visitor.visit(bv, ctx);
-                } else if ((sv = dynamicCast(currentValue, StringValue.class)) != null) {
-                    visitor.visit(sv, ctx);
-                } else if ((nv = dynamicCast(currentValue, NullValue.class)) != null) {
-                    visitor.visit(nv, ctx);
+            if(visitor.filter(currentValue, ctx)) {
+                if ((av = dynamicCast(currentValue, ArrayValue.class)) != null) {
+                    ase = new ArrayStackElement(av);
+                    stack.add(ase);
+                } else if ((ov = dynamicCast(currentValue, ObjectValue.class)) != null) {
+                    ObjectStackElement ose = new ObjectStackElement(ov);
+                    stack.add(ose);
+                } else {
+                    IntegerValue iv;
+                    BooleanValue bv;
+                    NullValue nv;
+                    FloatValue fv;
+                    StringValue sv;
+                    if ((iv = dynamicCast(currentValue, IntegerValue.class)) != null) {
+                        visitor.visit(iv, ctx);
+                    } else if ((fv = dynamicCast(currentValue, FloatValue.class)) != null) {
+                        visitor.visit(fv, ctx);
+                    } else if ((bv = dynamicCast(currentValue, BooleanValue.class)) != null) {
+                        visitor.visit(bv, ctx);
+                    } else if ((sv = dynamicCast(currentValue, StringValue.class)) != null) {
+                        visitor.visit(sv, ctx);
+                    } else if ((nv = dynamicCast(currentValue, NullValue.class)) != null) {
+                        visitor.visit(nv, ctx);
+                    }
                }
            }
            while(true) {
--- a/src/main/java/net/woggioni/worth/utils/WorthUtils.java
+++ b/src/main/java/net/woggioni/worth/utils/WorthUtils.java
@@ -5,6 +5,8 @@ import net.woggioni.worth.xface.Value;

 import java.io.*;
 import java.lang.reflect.Constructor;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.Optional;
 import java.util.function.Function;
 import java.util.function.Predicate;
@@ -27,20 +29,27 @@ public class WorthUtils {
    }

    public static void writeObject2File(String fileName, Object o) {
-        writeObject2File(new File(fileName), o);
+        writeObject2File(Paths.get(fileName), o);
    }

    @SneakyThrows
-    public static void writeObject2File(File file, Object o) {
-        try (Writer writer = new OutputStreamWriter(new FileOutputStream(file.getPath()))) {
+    public static void writeObject2File(Path file, Object o) {
+        try (Writer writer = new OutputStreamWriter(new FileOutputStream(file.toString()))) {
            writer.write(o.toString());
        }
    }

    @SneakyThrows
-    public static String readFile2String(File file) {
+    public static void writeBytes2File(Path file, byte[] bytes) {
+        try (OutputStream os = new FileOutputStream(file.toString())) {
+            os.write(bytes);
+        }
+    }
+
+    @SneakyThrows
+    public static String readFile2String(Path file) {
        StringBuilder builder = new StringBuilder();
-        try (Reader reader = new InputStreamReader(new BufferedInputStream(new FileInputStream(file.getPath())))) {
+        try (Reader reader = new InputStreamReader(new BufferedInputStream(new FileInputStream(file.toString())))) {
            char[] buffer = new char[1024];
            while (true) {
                int read = reader.read(buffer);
--- a/src/main/java/net/woggioni/worth/xface/Value.java
+++ b/src/main/java/net/woggioni/worth/xface/Value.java
@@ -100,6 +100,11 @@ public interface Value {
        @Builder.Default
        public final int maxDepth =
            Integer.parseInt(System.getProperty(Value.class.getName() + ".maxDepth", "1048576"));
+
+        @Builder.Default
+        public final boolean serializeReferences =
+            Boolean.parseBoolean(System.getProperty(
+            Value.class.getName() + ".serializeReferences", "false"));
    }

    Configuration configuration = Configuration.builder().build();
--- a/src/test/java/net/woggioni/worth/serialization/ReferenceTest.java
+++ b/src/test/java/net/woggioni/worth/serialization/ReferenceTest.java
@@ -0,0 +1,62 @@
+package net.woggioni.worth.serialization;
+
+import lombok.SneakyThrows;
+import net.woggioni.worth.serialization.binary.JBONDumper;
+import net.woggioni.worth.serialization.binary.JBONParser;
+import net.woggioni.worth.serialization.json.JSONDumper;
+import net.woggioni.worth.serialization.json.JSONParser;
+import net.woggioni.worth.utils.WorthUtils;
+import net.woggioni.worth.value.IntegerValue;
+import net.woggioni.worth.value.ObjectValue;
+import net.woggioni.worth.xface.Dumper;
+import net.woggioni.worth.xface.Parser;
+import net.woggioni.worth.xface.Value;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.nio.file.Paths;
+import java.util.function.Function;
+
+public class ReferenceTest {
+
+    @SneakyThrows
+    private void common(Function<Value.Configuration, Dumper> dumperConstructor,
+                        Function<Value.Configuration, Parser> parserConstructor) {
+        Value.Configuration cfg = Value.Configuration.builder()
+                .serializeReferences(true)
+                .objectValueImplementation(ObjectValue.Implementation.HashMap)
+                .build();
+        Value value = ObjectValue.newInstance(cfg);
+        value.put("child", value);
+        value.put("id", new IntegerValue(25));
+
+        byte[] bytes;
+        try(ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+            Dumper dumper = dumperConstructor.apply(cfg);
+            dumper.dump(value, baos);
+            bytes = baos.toByteArray();
+        }
+        WorthUtils.writeBytes2File(Paths.get("/tmp/ciao.jbon"), bytes);
+        Value reparsedValue;
+        try(ByteArrayInputStream bais = new ByteArrayInputStream(bytes)) {
+            Parser parser = parserConstructor.apply(cfg);
+            reparsedValue = parser.parse(bais);
+        }
+        Assert.assertEquals(reparsedValue, reparsedValue.get("child"));
+        Assert.assertEquals(value.get("id"), reparsedValue.get("id"));
+    }
+
+    @Test
+    @SneakyThrows
+    public void json() {
+        common(JSONDumper::new, JSONParser::new);
+    }
+
+    @Test
+    @SneakyThrows
+    public void jbon() {
+        common(JBONDumper::new, JBONParser::new);
+    }
+}
--- a/src/test/java/net/woggioni/worth/serialization/json/JSONTest.java
+++ b/src/test/java/net/woggioni/worth/serialization/json/JSONTest.java
@@ -8,7 +8,9 @@ import net.woggioni.worth.buffer.LookAheadTextInputStream;
 import net.woggioni.worth.exception.NotImplementedException;
 import net.woggioni.worth.utils.WorthUtils;
 import net.woggioni.worth.value.ArrayValue;
+import net.woggioni.worth.value.IntegerValue;
 import net.woggioni.worth.value.ObjectValue;
+import net.woggioni.worth.xface.Dumper;
 import net.woggioni.worth.xface.Parser;
 import net.woggioni.worth.xface.Value;
 import org.junit.Assert;
@@ -20,6 +22,7 @@ import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.lang.reflect.Method;
 import java.util.Map;
+import java.util.Objects;

 public class JSONTest {