support export path, improved fastjson 1.x compatible, for issue #2590

core/src/main/java/com/alibaba/fastjson2/JSONWriter.java

@@ -51,6 +51,7 @@ public abstract class JSONWriter
     protected String lastReference;
     protected boolean pretty;
     protected int indent;
+    protected Object attachment;
 
     protected JSONWriter(
             Context context,
@@ -251,6 +252,22 @@ public final boolean containsReference(Object value) {
         return refs != null && refs.containsKey(value);
     }
 
+    public final String getPath(Object value) {
+        Path path;
+        return refs == null || (path = refs.get(value)) == null
+                ? "$"
+                : path.toString();
+    }
+
+    /**
+     * If ReferenceDetection has been set, returns the path of the current object, otherwise returns null
+     * @since 2.0.51
+     * @return the path of the current object
+     */
+    public String getPath() {
+        return path == null ? null : path.toString();
+    }
+
     public final boolean removeReference(Object value) {
         return this.refs != null && this.refs.remove(value) != null;
     }
@@ -2505,4 +2522,12 @@ public final void writeReference(Object object) {
             writeReference(path.toString());
         }
     }
+
+    public Object getAttachment() {
+        return attachment;
+    }
+
+    public void setAttachment(Object attachment) {
+        this.attachment = attachment;
+    }
 }

core/src/test/java/com/alibaba/fastjson2/issues_2500/Issue2590.java

@@ -0,0 +1,77 @@
+package com.alibaba.fastjson2.issues_2500;
+
+import com.alibaba.fastjson.serializer.JSONSerializer;
+import com.alibaba.fastjson.serializer.SerialContext;
+import com.alibaba.fastjson2.JSON;
+import com.alibaba.fastjson2.JSONWriter;
+import com.alibaba.fastjson2.filter.PropertyPreFilter;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class Issue2590 {
+    @Test
+    public void test() {
+        Bean bean = new Bean();
+        bean.item0 = new Item(101);
+        bean.item1 = new Item(102);
+        bean.item2 = new Item(103);
+
+        FilterDemo filter = new FilterDemo();
+        String json = JSON.toJSONString(bean, filter, JSONWriter.Feature.ReferenceDetection);
+        assertEquals("{\"item0\":{\"id\":101},\"item1\":{\"id\":102},\"item2\":{}}", json);
+    }
+
+    public static class FilterDemo
+            implements PropertyPreFilter {
+        @Override
+        public boolean process(JSONWriter writer, Object source, String name) {
+            String parentPath = writer.getPath();
+            if (parentPath.startsWith("$.item2")) {
+                return false;
+            }
+            return true;
+        }
+    }
+
+    @Test
+    public void test1() {
+        Bean bean = new Bean();
+        bean.item0 = new Item(101);
+        bean.item1 = new Item(102);
+        bean.item2 = new Item(103);
+
+        FilterDemo1 filter = new FilterDemo1();
+        String json = com.alibaba.fastjson.JSON.toJSONString(bean, filter);
+        assertEquals("{\"item0\":{\"id\":101},\"item1\":{\"id\":102},\"item2\":{}}", json);
+    }
+
+    public static class FilterDemo1
+            implements com.alibaba.fastjson.serializer.PropertyPreFilter {
+        @Override
+        public boolean apply(JSONSerializer serializer, Object object, String name) {
+            SerialContext context = serializer.getContext();
+            if (context.toString().startsWith("$.item2")) {
+                return false;
+            }
+            return true;
+        }
+    }
+
+    public static class Bean {
+        public Item item0;
+        public Item item1;
+        public Item item2;
+    }
+
+    public static class Item {
+        public int id;
+
+        public Item() {
+        }
+
+        public Item(int id) {
+            this.id = id;
+        }
+    }
+}

fastjson1-compatible/src/main/java/com/alibaba/fastjson/serializer/JSONSerializer.java

@@ -34,6 +34,20 @@ public JSONSerializer(SerializeWriter out, SerializeConfig config) {
         this.raw = out.raw;
     }
 
+    public static JSONSerializer getJSONSerializer(JSONWriter writer) {
+        JSONSerializer serializer = null;
+        Object attachment = writer.getAttachment();
+        if (attachment == null) {
+            attachment = serializer = new JSONSerializer(writer);
+            writer.setAttachment(attachment);
+        } else if (attachment instanceof JSONSerializer) {
+            serializer = (JSONSerializer) attachment;
+        } else {
+            serializer = new JSONSerializer(writer);
+        }
+        return serializer;
+    }
+
     public void config(SerializerFeature feature, boolean state) {
         if (!state) {
             throw new JSONException("not support");

fastjson1-compatible/src/main/java/com/alibaba/fastjson/serializer/PropertyPreFilter.java

@@ -1,5 +1,14 @@
 package com.alibaba.fastjson.serializer;
 
+import com.alibaba.fastjson2.JSONWriter;
+
 public interface PropertyPreFilter
-        extends SerializeFilter {
+        extends com.alibaba.fastjson2.filter.PropertyPreFilter, SerializeFilter {
+    default boolean process(JSONWriter writer, Object source, String name) {
+        JSONSerializer serializer = JSONSerializer.getJSONSerializer(writer);
+        serializer.setContext(new SerialContext(writer, serializer.context, source, name, 0, 0));
+        return apply(serializer, source, name);
+    }
+
+    boolean apply(JSONSerializer serializer, Object object, String name);
 }

fastjson1-compatible/src/main/java/com/alibaba/fastjson/serializer/SerialContext.java

@@ -1,15 +1,42 @@
 package com.alibaba.fastjson.serializer;
 
+import com.alibaba.fastjson2.JSONWriter;
+
 public class SerialContext {
     public final SerialContext parent;
     public final Object object;
     public final Object fieldName;
     public final int features;
+    JSONWriter jsonWriter;
+
+    SerialContext(JSONWriter jsonWriter, SerialContext parent, Object object, Object fieldName, int features, int fieldFeatures) {
+        this.parent = parent;
+        this.jsonWriter = jsonWriter;
+        this.object = object;
+        this.fieldName = fieldName;
+        this.features = features;
+    }
 
     public SerialContext(SerialContext parent, Object object, Object fieldName, int features, int fieldFeatures) {
         this.parent = parent;
         this.object = object;
         this.fieldName = fieldName;
         this.features = features;
     }
+
+    /**
+     * @deprecated
+     */
+    public String getPath() {
+        return toString();
+    }
+
+    public String toString() {
+        String path = null;
+        if (jsonWriter != null) {
+            path = jsonWriter.getPath();
+        }
+
+        return path;
+    }
 }

fastjson1-compatible/src/test/java/com/alibaba/fastjson/v2issues/Issue2590.java

@@ -0,0 +1,52 @@
+package com.alibaba.fastjson.v2issues;
+
+import com.alibaba.fastjson.JSON;
+import com.alibaba.fastjson.serializer.JSONSerializer;
+import com.alibaba.fastjson.serializer.PropertyPreFilter;
+import com.alibaba.fastjson.serializer.SerialContext;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class Issue2590 {
+    @Test
+    public void test() {
+        Bean bean = new Bean();
+        bean.item0 = new Item(101);
+        bean.item1 = new Item(102);
+        bean.item2 = new Item(103);
+
+        FilterDemo filter = new FilterDemo();
+        String json = JSON.toJSONString(bean, filter);
+        assertEquals("{\"item0\":{\"id\":101},\"item1\":{\"id\":102},\"item2\":{}}", json);
+    }
+
+    public static class FilterDemo
+            implements PropertyPreFilter {
+        @Override
+        public boolean apply(JSONSerializer serializer, Object object, String name) {
+            SerialContext context = serializer.getContext();
+            if (context.toString().startsWith("$.item2")) {
+                return false;
+            }
+            return true;
+        }
+    }
+
+    public static class Bean {
+        public Item item0;
+        public Item item1;
+        public Item item2;
+    }
+
+    public static class Item {
+        public int id;
+
+        public Item() {
+        }
+
+        public Item(int id) {
+            this.id = id;
+        }
+    }
+}