add testcase for issue alibaba#3157

fastjson1-compatible/src/test/java/com/alibaba/fastjson/v2issues/Issue3157.java

@@ -0,0 +1,48 @@
+package com.alibaba.fastjson.v2issues;
+
+import com.alibaba.fastjson.JSON;
+import com.alibaba.fastjson.serializer.SerializeConfig;
+import com.alibaba.fastjson.serializer.ToStringSerializer;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class Issue3157 {
+    public static class People {
+        private Integer age;
+
+        private Long hairNums;
+
+        private String name;
+
+        public People(Integer age, String name, Long hairNums) {
+            this.age = age;
+            this.name = name;
+            this.hairNums = hairNums;
+        }
+
+        public Integer getAge() {
+            return age;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public Long getHairNums() {
+            return hairNums;
+        }
+    }
+
+    @Test
+    public void test() {
+        SerializeConfig stringSerializeConfig = new SerializeConfig();
+        stringSerializeConfig.put(Integer.class, ToStringSerializer.instance);
+        stringSerializeConfig.put(Long.class, ToStringSerializer.instance);
+
+        People one = new People(10, "aaa", 10000000L);
+        assertEquals(
+                "{\"age\":\"10\",\"hairNums\":\"10000000\",\"name\":\"aaa\"}",
+                JSON.toJSONString(one, stringSerializeConfig));
+    }
+}