customize getFields() to return ordered Field Object

[pxb1988]

In some android devices (MI 4(c), android-4.4.4；Huawei P6, android-4.2.2).
the return array of Class.getFields() are dependent on the class name.
When a class and its parent class have same field name, (and the class is obfuscate to different names)
the result is unpredictable.
this patch force the fields in child-fields-first order when deserialize

[CLAassistant]

All committers have signed the CLA.

[wenshao]

bug fixed in 1.1.51.android & 1.2.11, please use the newst version.

[pxb1988]

The problem still occur in 1.2.11. I have tested this on MI 4c, android 4.4.4

I believe it is caused by the Class.getFields()

The elements in the array returned are not sorted and are not in any particular order.

When child and its parent class have a field with same name. the child's field may appear before parent's field on some devices/platforms; while on other devices/platforms, parent's field may appear before child's field.
But fastjson deserialize the value to the first appearance field, which cause an unpredictable situation.

here are steps to reproduce

• create a helloworld app in Android Studio
• add 1.2.11 as dependence in app/build.gradle

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.3.0'
    compile 'com.alibaba:fastjson:1.2.11'
}

• modify the Activity

package com.example.bob.fastjsontest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import com.alibaba.fastjson.JSON;

public class MainActivity extends AppCompatActivity {

    public static class A extends B {
        public String extra;
    }

    public static class B {
        public String extra;

        public String getB() {
            return extra;
        }
    }

    public static class C extends B {
        public String extra;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        String text = "{ extra:\"yes\" }";
        A a = JSON.parseObject(text, A.class);
        Log.d("T", "A: " + a.getB());
        C c = JSON.parseObject(text, C.class);
        Log.d("T", "C: " + c.getB());
    }
}

• run it !

D/T       (20692): A: null
D/T       (20692): C: yes

[wenshao]

please pull this merge request to android branch, not 1.2.4_android

[wenshao]

我合并了你的代码到1.2.4_android分支并且然后关闭了这个分支。你这个patch比较多系统方法调用，会降低首次反序列化的性能，我会参考你的代码改进重写，谢谢你的反馈。