fastjson序列化对象后属性变更问题

使用fastjson进行JSON序列化存储到数据库后，发现JSON字符串“莫名其妙地”多了一些属性。

public class MyClass {// boolean 类型的属性private boolean isActive;private boolean valid;// int 类型的属性private int id;// 默认构造器public MyClass() {}// 带有所有属性的构造器public MyClass(boolean isActive, boolean valid, int id) {this.isActive = isActive;this.valid = valid;this.id = id;}// isActive 的 getter 和 setter 方法public boolean isActive() {return isActive;}public void setActive(boolean isActive) {this.isActive = isActive;}// valid 的 getter 和 setter 方法public boolean getValid() {return valid;}public void setValid(boolean valid) {this.valid = valid;}// id 的 getter 和 setter 方法public int getId() {return id;}public void setId(int id) {this.id = id;}
}

测试 

import com.alibaba.fastjson.JSON;public class MyClassMain {public static void main(String[] args) {// 创建 MyClass 对象MyClass myClass = new MyClass(true, false, 123);// 使用 fastjson 序列化对象String jsonString = JSON.toJSONString(myClass);// 打印 JSON 字符串System.out.println(jsonString);}
}

结果 

{“active”:true,“id”:123,“valid”:false}

多了一个 active 属性，少了一个isActive属性。

问题出在这个函数

com.alibaba.fastjson.serializer.SerializeConfig

public final ObjectSerializer createJavaBeanSerializer(Class<?> clazz) {String className = clazz.getName();long hashCode64 = TypeUtils.fnv1a_64(className);if (Arrays.binarySearch(denyClasses, hashCode64) >= 0) {throw new JSONException("not support class : " + className);}// 关键SerializeBeanInfo beanInfo = TypeUtils.buildBeanInfo(clazz, null, propertyNamingStrategy, fieldBased);if (beanInfo.fields.length == 0 && Iterable.class.isAssignableFrom(clazz)) {return MiscCodec.instance;}return createJavaBeanSerializer(beanInfo);
}

om.alibaba.fastjson.util.TypeUtils#computeGetters

public static List<FieldInfo> computeGetters(Class<?> clazz, //JSONType jsonType, //Map<String,String> aliasMap, //Map<String,Field> fieldCacheMap, //boolean sorted, //PropertyNamingStrategy propertyNamingStrategy //
){// 省略部分代码if(methodName.startsWith("is")){if(methodName.length() < 3){continue;}if(returnType != Boolean.TYPE&& returnType != Boolean.class){continue;}char c2 = methodName.charAt(2);String propertyName;Field field = null;if(Character.isUpperCase(c2)){if(compatibleWithJavaBean){propertyName = decapitalize(methodName.substring(2));} else{propertyName = Character.toLowerCase(methodName.charAt(2)) + methodName.substring(3);}// 这里 isActive 的属性名被计算出 activepropertyName = getPropertyNameByCompatibleFieldName(fieldCacheMap, methodName, propertyName, 2);}// 省略其他JSONField fieldAnnotation = null;if(field != null){fieldAnnotation = TypeUtils.getAnnotation(field, JSONField.class);if(fieldAnnotation != null){if(!fieldAnnotation.serialize()){continue;}ordinal = fieldAnnotation.ordinal();serialzeFeatures = SerializerFeature.of(fieldAnnotation.serialzeFeatures());parserFeatures = Feature.of(fieldAnnotation.parseFeatures());if(fieldAnnotation.name().length() != 0){//关键： 使用 JSONField 注解设置的 name 替代属性名propertyName = fieldAnnotation.name();if(aliasMap != null){propertyName = aliasMap.get(propertyName);if(propertyName == null){continue;}}}if(fieldAnnotation.label().length() != 0){label = fieldAnnotation.label();}}}// 省略部分代码FieldInfo fieldInfo = new FieldInfo(propertyName, method, field, clazz, null, ordinal, serialzeFeatures, parserFeatures,annotation, fieldAnnotation, label);fieldInfoMap.put(propertyName, fieldInfo);}}Field[] fields = clazz.getFields();computeFields(clazz, aliasMap, propertyNamingStrategy, fieldInfoMap, fields);return getFieldInfos(clazz, sorted, fieldInfoMap);
}

fastjson通过反射虽然有能力识别真实的属性名，但是实际操作时会根据 getter 方法反推出属性名，造成转为JSON字符串时和实际属性名存在偏差。

解决办法

布尔类型的变量不要加is前缀或者使用fastjson自带的@JSONField注解，不过这种方式fastjson的侵入性太强。

public class MyClass {@JSONField( name="isActive")// boolean 类型的属性private boolean isActive;private boolean valid;// 省略其他}

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