add testcase for issue #2400

core/src/test/java/com/alibaba/fastjson2/issues_2400/Issue2400.java

@@ -0,0 +1,36 @@
+package com.alibaba.fastjson2.issues_2400;
+
+import com.alibaba.fastjson2.JSON;
+import com.alibaba.fastjson2.annotation.JSONField;
+import com.alibaba.fastjson2.filter.BeanContext;
+import com.alibaba.fastjson2.filter.ContextValueFilter;
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDate;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class Issue2400 {
+    @Test
+    public void test() {
+        final AtomicReference<String> formatRef = new AtomicReference<>();
+        ContextValueFilter contextValueFilter = new ContextValueFilter() {
+            @Override
+            public Object process(BeanContext context, Object object, String name, Object value) {
+                formatRef.set(context.getFormat());
+                return value;
+            }
+        };
+
+        Bean bean = new Bean();
+        bean.id = LocalDate.of(2012, 3, 4);
+        JSON.toJSONString(bean, contextValueFilter);
+        assertEquals("yyyyMMdd", formatRef.get());
+    }
+
+    public static class Bean {
+        @JSONField(format = "yyyyMMdd")
+        public LocalDate id;
+    }
+}