FastJson字段解析问题

今天遇到一个问题，修改一个javaBean的字段后，fastJson转换成JsonString的时候字段却没有被修改，而Gson是正常的。

JavaBean如下：

public class DistrictInfo {
private String  province;
private String  city;
private String  dist;

public DistrictInfo() {
super();
}

public DistrictInfo(String province, String city, String district) {
super();
this.province = province;
this.city = city;
this.dist = district;
}

public String getProvince() {
return province;
}

public void setProvince(String province) {
this.province = province;
}

public String getCity() {
return city;
}

public void setCity(String city) {
this.city = city;
}

public String getDistrict() {
return dist;
}

public void setDistrict(String district) {
this.dist = district;
}

@Override
public String toString() {
return province + "," + city;
}

}

测试类如下：

public class testJson {

public static void main(String[] args) {

DistrictInfo district = new DistrictInfo("陕西省", "宝鸡市", "陈仓区");
System.out.println("FastJson: " + JSON.toJSONString(district, true));
System.out.println("Gson: " + new Gson().toJson(district));
}

}

运行结果如下：

FastJson: {
"city":"宝鸡市",
"district":"陈仓区",
"province":"陕西省"
}
Gson: {"province":"陕西省","city":"宝鸡市","dist":"陈仓区"}

可以看到对District字段，两者解析是不同的，FastJson是错的。其实，这是FastJson的反射机制有缺陷引起的，将修饰符改为Public之后就可以正常解析了。

public class DistrictInfo {
public String   province;
public String   city;
public String   dist;

public DistrictInfo() {
super();
}

public DistrictInfo(String province, String city, String district) {
super();
this.province = province;
this.city = city;
this.dist = district;
}

}
结果：
FastJson: {
"city":"宝鸡市",
"dist":"陈仓区",
"province":"陕西省"
}
Gson: {"province":"陕西省","city":"宝鸡市","dist":"陈仓区"}

如果修饰符为Protected/Private, fastJson走了一种曲线救国的方式，通过Public的getXXX()方法来获得该字段的名称和值。所以必须要保证getXXX()方法与字段XXX保持一致。如下：

public class DistrictInfo {
private String  province;
private String  city;
private String  dist;

public DistrictInfo() {
super();
}

public DistrictInfo(String province, String city, String district) {
super();
this.province = province;
this.city = city;
this.dist = district;
}

public String getProvince() {
return province;
}

public void setProvince(String province) {
this.province = province;
}

public String getCity() {
return city;
}

public void setCity(String city) {
this.city = city;
}

public String getDist() {
return dist;
}

public void setDist(String dist) {
this.dist = dist;
}

@Override
public String toString() {
return province + "," + city;
}

}

结果

FastJson: {
"city":"宝鸡市",
"dist":"陈仓区",
"province":"陕西省"
}
Gson: {"province":"陕西省","city":"宝鸡市","dist":"陈仓区"}

结论：

fastJson在将JsonString2Obj的速度和便捷性上优于Gson，但是在Obj2JsonString时需要注意如果字段不是public的，需要注意保证getXXX()方法与字段XXX保持一致。，