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 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","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 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"}

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。，