关于数据序列化(5),定制FastJSON序列化（解决Java大Long类型js的Number接收丢失数据的问题，不序列化某些属性）

1. 指定某个类型序列化

问题描述：
JavaScript使用IEEE 754标准

1位用来表示符号位11位用来表示指数52位表示尾数

javaScript对于整形只能识别52位。遇到Long大整数可能会丢失数据
因为后台是Java写的难免有属性的类型是long。本来项目的做法是手动写每个类的toString();方法要拼接很多双引号。比较费劲也容易出错。
后来我使用了FastJson定制序列化遇到Long就写字符串来解决返回给客户端的JSON。
主要代码如下：

定制Long类型的序列化    public final static SerializeConfig resultJsonConfig = new SerializeConfig();    static{        resultJsonConfig.put(Long.class, new ObjectSerializer() {            @Override            public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType, int features)                    throws IOException {                SerializeWriter out = serializer.getWriter();                out.writeString(Objects.toString(object, null));            }        });    }使用：    protected <T> String getResult(T value) {        JSONObject json = new JSONObject();        json.put("state", state.getState());        json.put("desc", state.getDesc());        json.put("value", value);        return JSON.toJSONString(json, resultJsonConfig, SerializerFeature.DisableCircularReferenceDetect);    }

2.如果要让这个策略全局生效

SerializeConfig.getGlobalInstance().put(Long.class, new ObjectSerializer() {            @Override            public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType, int features)                    throws IOException {                SerializeWriter out = serializer.getWriter();                if (fieldType == long.class || fieldType == Long.class) {                    out.writeString(Objects.toString(object, null));                }                // if (numberValue == null) {                // if (out.isEnabled(SerializerFeature.WriteNullNumberAsZero)) {                // out.write('0');                // } else {                // out.writeNull();                // }                // return;                // }            }        });

2. 对某些属性不序列化

2.1 定义一个注解

@Retention(RetentionPolicy.RUNTIME)@Target({ElementType.FIELD})public @interface ResultNotSerialize {}

2.2 将注解加在属性上

public class MemberVO {    private String memberId;    private String memberName;    @ResultNotSerialize    private String password;

2.3 定义一个过滤器

    public static final PropertyFilter controllerResultJsonFilter = new PropertyFilter() {        @Override        public boolean apply(Object object, String key, Object value) {            try {                Field field = object.getClass().getDeclaredField(key);                if(null !=field && null != field.getAnnotation(ResultNotSerialize.class)){                    return false;                }                return true;            } catch (Exception e) {                return true;            }        }    };

2.4 如何使用

SON.toJSONString(obj, controllerResultJsonFilter);

3. Java长ID，js接收丢失数据问题最终的解决办法

@Retention(RetentionPolicy.RUNTIME)@Target({ElementType.FIELD})public @interface SerializeAsSting {}

public class MemberVO {    @SerializeAsSting    private Long id = 0L;//long type id

 public static final PropertyFilter resultJsonPropertyFilter = new PropertyFilter() {        @Override        public boolean apply(Object object, String key, Object value) {            try {                Field field = object.getClass().getDeclaredField(key);                if (null != field && null != field.getAnnotation(NotSerialize.class)) {                    return false;                }                return true;            } catch (Exception e) {                return true;            }        }    };    public static final ValueFilter resultValueFilter = new ValueFilter() {        @Override        public Object process(Object object, String name, Object value) {//          LogCore.BASE.info("object={}, name={},value={}", object, name, value);            if(value == null){                return value;            }            try {                Field field = object.getClass().getDeclaredField(name);                if (null != field && null != field.getAnnotation(SerializeAsSting.class)) {                    return value.toString();                }                return value;            } catch (Exception e) {                return value;            }        }    };    public final static SerializeFilter[] resultJsonFilters = new SerializeFilter[]{resultJsonPropertyFilter, resultValueFilter};

protected <T> String getResult(ErrorState state, T value) {        JSONObject json = new JSONObject();        json.put("state", state.getState());        json.put("desc", state.getDesc());        json.put("value", value);        return JSON.toJSONString(json, resultJsonConfig, resultJsonFilters,                SerializerFeature.WriteMapNullValue, SerializerFeature.DisableCircularReferenceDetect);    }

其他的序列化见这篇文章fastjson使用@JSONField、@JSONType、SerializeFilter定制序列化