FastJsonConfig config = new FastJsonConfig();
    config.setWriterFeatures(
    JSONWriter.Feature.ReferenceDetection, // 处理循环引用和树形结构的处理
    JSONWriter.Feature.WriteEnumsUsingName, // 序列化enum使用name
    JSONWriter.Feature.BrowserCompatible, // 兼容IE6
    JSONWriter.Feature.BrowserSecure // 浏览器安全，将会’<’ ‘>’ ‘(’ ')'字符做转义输出
);

@Data
public class ClueListInfo implements Serializable {
    private static final long serialVersionUID = 8170584149020082450L;

    private Long clueId;

    private String name;

    private List<ContactInfo> contacts;
}

@Data
public class ContactInfo implements Serializable {
    private static final long serialVersionUID = -5313505758293424804L;
    
    private Long id;
    
    private String name;
}

public class Issue2687 {
    @Test
    void test(){
        ClueListInfo info1 = new ClueListInfo();
        info1.setClueId(1L);
        info1.setName("Clue 01");

        ClueListInfo info2 = new ClueListInfo();
        info2.setClueId(2L);
        info2.setName("Clue 02");

        ContactInfo contactInfo = new ContactInfo();
        contactInfo.setId(1L);
        contactInfo.setName("contact");
        ArrayList<ContactInfo> contacts = Lists.newArrayList(contactInfo);

        info1.setContacts(contacts);
        info2.setContacts(contacts);
        List infos = Lists.newArrayList(info1,info2);

        String jsonString = JSON.toJSONString(infos, JSONWriter.Feature.ReferenceDetection);
        System.out.println(jsonString);

    }
}