复现代码如下:

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.PropertyNamingStrategy;
import com.alibaba.fastjson.annotation.JSONType;
import com.alibaba.fastjson.serializer.SerializeConfig;
import lombok.AllArgsConstructor;
import lombok.Data;
import org.junit.Test;
public class Issue3652 {
    @Test
    public void test_SerializeConfig_different_Class_Annotation() {
        Object[] models = new Object[]{
                new Model1("hello,world"),
                new Model2("hello,world"),
                new Model3("hello,world"),
                new Model4("hello,world"),
        };
        for (int i = 0; i < 4; i++) {
            System.out.printf("---------- begin circle %d%n", i);
            for (int j = 0; j < 4; j++) {
                SerializeConfig config = new SerializeConfig();
                config.propertyNamingStrategy = PropertyNamingStrategy.values()[j];
                System.out.println(JSON.toJSONString(models[i], config));
            }
            System.out.printf("---------- end circle %d%n", i);
        }
    }
    @JSONType(naming = PropertyNamingStrategy.CamelCase)
    @Data
    @AllArgsConstructor
    public class Model1 {
        private String goodBoy;
    }
    @JSONType(naming = PropertyNamingStrategy.PascalCase)
    @Data
    @AllArgsConstructor
    public class Model2 {
        private String goodBoy;
    }
    @JSONType(naming = PropertyNamingStrategy.SnakeCase)
    @Data
    @AllArgsConstructor
    public class Model3 {
        private String goodBoy;
    }
    @JSONType(naming = PropertyNamingStrategy.KebabCase)
    @Data
    @AllArgsConstructor
    public class Model4 {
        private String goodBoy;
    }
}

输出为

---------- begin circle 0
{"goodBoy":"hello,world"}
{"GoodBoy":"hello,world"}
{"good_boy":"hello,world"}
{"good-boy":"hello,world"}
---------- end circle 0
---------- begin circle 1
{"GoodBoy":"hello,world"}
{"GoodBoy":"hello,world"}
{"GoodBoy":"hello,world"}
{"GoodBoy":"hello,world"}
---------- end circle 1
---------- begin circle 2
{"good_boy":"hello,world"}
{"good_boy":"hello,world"}
{"good_boy":"hello,world"}
{"good_boy":"hello,world"}
---------- end circle 2
---------- begin circle 3
{"good-boy":"hello,world"}
{"good-boy":"hello,world"}
{"good-boy":"hello,world"}
{"good-boy":"hello,world"}
---------- end circle 3

当类注解为 PropertyNamingStrategy.CamelCase 时,注解是无效的,会按照config输出.
原因就是上图红框框出来的那个判断.

如图,JSONType的默认naming为 PropertyNamingStrategy.CamelCase , 所以才需要框内的判断去避免"没有声明naming却使用了CamelCase"的情况.