bug fix for multi ValueFilter, for issue #1078

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

@@ -1475,7 +1475,11 @@ protected void configFilter(Filter... filters) {
                 }
 
                 if (filter instanceof ValueFilter) {
-                    this.valueFilter = (ValueFilter) filter;
+                    if (this.valueFilter == null) {
+                        this.valueFilter = (ValueFilter) filter;
+                    } else {
+                        this.valueFilter = ValueFilter.compose(this.valueFilter, (ValueFilter) filter);
+                    }
                 }
 
                 if (filter instanceof PropertyFilter) {

core/src/test/java/com/alibaba/fastjson2/issues_1000/Issue1078.java

@@ -0,0 +1,51 @@
+package com.alibaba.fastjson2.issues_1000;
+
+import com.alibaba.fastjson2.JSON;
+import com.alibaba.fastjson2.JSONWriter;
+import com.alibaba.fastjson2.filter.ValueFilter;
+import org.junit.jupiter.api.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public class Issue1078 {
+    @Test
+    public void test() {
+        Map<String, String> map = new HashMap<>();
+        map.put("a", "b");
+
+        assertEquals(
+                "{\"a\":\"b12\"}",
+                JSON.toJSONString(
+                        map,
+                        new ValueFilter[]{new TestValueFilter1(), new TestValueFilter2()},
+                        JSONWriter.Feature.WriteMapNullValue
+                )
+        );
+
+        assertEquals(
+                "{\"a\":\"b21\"}",
+                JSON.toJSONString(
+                        map,
+                        new ValueFilter[]{new TestValueFilter2(), new TestValueFilter1()},
+                        JSONWriter.Feature.WriteMapNullValue
+                )
+        );
+    }
+
+    public static class TestValueFilter1 implements ValueFilter {
+        @Override
+        public Object apply(Object o, String s, Object o1) {
+            return o1.toString() + "1";
+        }
+    }
+
+    public static class TestValueFilter2 implements ValueFilter {
+        @Override
+        public Object apply(Object o, String s, Object o1) {
+            return o1.toString() + "2";
+        }
+    }
+}