[QUESTION] fastjson升级到2后，方法签名变化问题

[FutureZM]

JSON.toJSONString方法签名变化问题

在fastjson1.x中可以通过 SerializeConfig，NameFilter，SerializerFeature 实现对序列化后的数据进行定制，如下列通过SerializeConfig配置驼峰体转下划线， 然后通过NameFilter对 序列化后的key进行修改，通过SerializerFeature指定某些缺省值的处理方式，请问在fastjson2中该如何处理呢？

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    class Student{
        private String nameV1;
        private Integer ageB1;
        private String emptyC1;
    }
    
    // 样例代码
    Student test = new Student("z", 12, null);
    SerializeConfig config = new SerializeConfig();
    config.propertyNamingStrategy = PropertyNamingStrategy.SnakeCase;
    final NameFilter nameFilter = (o12, s, o1) -> {
        String res = s.substring(0, 1).toUpperCase();
        if (s.length() > 1) {
            res += s.substring(1);
        }
        return res;
    };
    String res = JSON.toJSONString(test, config, nameFilter, SerializerFeature.WriteNullStringAsEmpty);
    System.out.println(res);

[wenshao]

你是希望单个类这样的NamingPolicy，还是所有的类输出都是这样NamingPolicy？

[wenshao]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson/2.0.7-SNAPSHOT/
2.0.7-SNAPSHOT版本中，支持如下的使用方式，能满足你的需求么？

    public void test() {
        Student test = new Student("z", 12, null);
        NameFilter nameFilter = NameFilter.of(PropertyNamingStrategy.UpperCamelCaseWithUnderScores);
        String res = JSON.toJSONString(test, nameFilter, JSONWriter.Feature.WriteNullStringAsEmpty);
        assertEquals("{\"Age_B1\":12,\"Name_V1\":\"z\"}", res);
    }

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    static class Student{
        private String nameV1;
        private Integer ageB1;
        private String emptyC1;
    }

[FutureZM]

你是希望单个类这样的NamingPolicy，还是所有的类输出都是这样NamingPolicy？

是希望针对所有的类都输出这样的NamingPolicy的。如果只是针对单个类的话，可以使用您文档中的mix_in相关的操作处理别名。
在fastjson1.x 版本中，是tostring时通过传递config和nameFilter达成目的

[FutureZM]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson/2.0.7-SNAPSHOT/ 2.0.7-SNAPSHOT版本中，支持如下的使用方式，能满足你的需求么？

    public void test() {
        Student test = new Student("z", 12, null);
        NameFilter nameFilter = NameFilter.of(PropertyNamingStrategy.UpperCamelCaseWithUnderScores);
        String res = JSON.toJSONString(test, nameFilter, JSONWriter.Feature.WriteNullStringAsEmpty);
        assertEquals("{\"Age_B1\":12,\"Name_V1\":\"z\"}", res);
    }

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    static class Student{
        private String nameV1;
        private Integer ageB1;
        private String emptyC1;
    }

此种方式是可以实现上述例子中的这个需求。此外仍有一个疑问，就是是否可以实现1.x中的通过NameFilter进行某些定制化的需求，毕竟转成下划线+每一段首字母大写这个需求可能只是个例。

[wenshao]

NameFilter是可以，但配置全局的PropertyNamingPolicy还没实现，我还没想好怎么实现

[wenshao]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson/2.0.7-SNAPSHOT/

更新快照2.0.7-SNAPSHOT版本，已经兼容你原来的写法，不用改代码，如下：

  @Test
    public void test5() {
        Student test = new Student("z", 12, null);
        SerializeConfig config = new SerializeConfig();
        config.propertyNamingStrategy = PropertyNamingStrategy.SnakeCase;
        final NameFilter nameFilter = (o12, s, o1) -> {
            String res = s.substring(0, 1).toUpperCase();
            if (s.length() > 1) {
                res += s.substring(1);
            }
            return res;
        };
        String res = JSON.toJSONString(test, config, nameFilter, SerializerFeature.WriteNullStringAsEmpty);
        assertEquals("{\"Age_b1\":12,\"Name_v1\":\"z\"}", res);
    }

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    static class Student{
        private String nameV1;
        private Integer ageB1;
        private String emptyC1;
    }

[FutureZM]

https://oss.sonatype.org/content/repositories/snapshots/com/alibaba/fastjson/2.0.7-SNAPSHOT/

更新快照2.0.7-SNAPSHOT版本，已经兼容你原来的写法，不用改代码，如下：

  @Test
    public void test5() {
        Student test = new Student("z", 12, null);
        SerializeConfig config = new SerializeConfig();
        config.propertyNamingStrategy = PropertyNamingStrategy.SnakeCase;
        final NameFilter nameFilter = (o12, s, o1) -> {
            String res = s.substring(0, 1).toUpperCase();
            if (s.length() > 1) {
                res += s.substring(1);
            }
            return res;
        };
        String res = JSON.toJSONString(test, config, nameFilter, SerializerFeature.WriteNullStringAsEmpty);
        assertEquals("{\"Age_b1\":12,\"Name_v1\":\"z\"}", res);
    }

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    static class Student{
        private String nameV1;
        private Integer ageB1;
        private String emptyC1;
    }

收到，辛苦辛苦

[wenshao]

https://github.com/alibaba/fastjson2/releases/tag/2.0.7
问题已经修复，请用新版本