使用OKHttp请求json数据一直显示null

问题描述

在使用Okhttp3+retrofit2+Rxjava请求json数据时，可以正常请求数据，但是在转换成实体类时，一直显示null，具体问题如下：

D/OkHttp: { "error_code" : 0 , "reason" : "Success!" , "result" : { "GetRankTypeRsp" : { "RankList" : { "Rank" : [ { "rankTypeID" : "1" , "rankName" : "点击排行"} , { "rankTypeID" : "2" , "rankName" : "搜索排行"} , { "rankTypeID" : "3" , "rankName" : "收藏排行"} , { "rankTypeID" : "4" , "rankName" : "人气排行"}]} , "RankTimeList" : { "RankTime" : [ { "rankTimeID" : "1" , "rankTimeName" : "日排行"} , { "rankTimeID" : "2" , "rankTimeName" : "周排行"} , { "rankTimeID" : "3" , "rankTimeName" : "月排行"} , { "rankTimeID" : "4" , "rankTimeName" : "总排行"}]} , "ContentTypeList" : { "ContentType" : [ { "contentTypeID" : "1" , "contentType" : "图书"} , { "contentTypeID" : "2" , "contentType" : "杂志"} , { "contentTypeID" : "3" , "contentType" : "漫画"}]}}}}D/OkHttp: <-- END HTTP (784-byte body)D/onNext: 0,Result{getRankTypeRsp=null}D/BasePresenter-->: requestSuccess()D/OneFragment: loadSuccess------------Result{getRankTypeRsp=null}D/BasePresenter-->: requestComplete()

问题分析

从上面null异常说明肯定是json格式转换实体类时出现了问题，于是去检查了下ApiMananger类，相关代码如下：

   /**     * 初始化Retrofit     */    public ApiManager() {        initOkhttpClient();        Retrofit retrofit = new Retrofit.Builder()                .baseUrl(BASE_URL)                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())              //gson和java类相互转化      .addConverterFactory(GsonConverterFactory.create())                .client(mOkHttpClient)                .build();        //实例化api接口        mApiService = retrofit.create(ApiService.class);    }

确定addConverterFactory（）无误后，猜想可能是实体类有问题。
先看下实体类的相互关系

最底部HttpResult是通用的http实体类

public class HttpResult<T> {    private int errorCode;    private String reason;    private T result;    public int getErrorCode() {        return errorCode;    }    public void setErrorCode(int errorCode) {        this.errorCode = errorCode;    }    public String getReason() {        return reason;    }    public void setReason(String reason) {        this.reason = reason;    }    public T getResult() {        return result;    }    public void setResult(T result) {        this.result = result;    }    @Override    public String toString() {        return "HttpResult{" +                "errorCode=" + errorCode +                ", reason='" + reason + '\'' +                ", result=" + result +                '}';    }}

HttpResult中的result对应着json数据源对象，也就是下面的Result类

public class Result extends BaseEntity.BaseBean {    private GetRankTypeRsp getRankTypeRsp;    @Override    public String toString() {        return "Result{" +                "getRankTypeRsp=" + getRankTypeRsp +                '}';    }    public GetRankTypeRsp getGetRankTypeRsp() {        return getRankTypeRsp;    }    public void setGetRankTypeRsp(GetRankTypeRsp getRankTypeRsp) {        this.getRankTypeRsp = getRankTypeRsp;    }}

Result类中的getRankTypeRsp包含另一个json数据源对象，该类如下：

public class GetRankTypeRsp extends BaseEntity.BaseBean {    private RankList RankList;    private RankTimeList rankTimeList;    private ContentTypeList contentTypeList;    public com.ninoyang.geek.model.rankType.RankList getRankList() {        return RankList;    }    public void setRankList(com.ninoyang.geek.model.rankType.RankList rankList) {        RankList = rankList;    }    public RankTimeList getRankTimeList() {        return rankTimeList;    }    public void setRankTimeList(RankTimeList rankTimeList) {        this.rankTimeList = rankTimeList;    }    public ContentTypeList getContentTypeList() {        return contentTypeList;    }    public void setContentTypeList(ContentTypeList contentTypeList) {        this.contentTypeList = contentTypeList;    }    @Override    public String toString() {        return "GetRankTypeRsp{" +                "RankList=" + RankList +                ", rankTimeList=" + rankTimeList +                ", contentTypeList=" + contentTypeList +                '}';    }}

然后再对比一下json数组中

{ "error_code" : 0 , "reason" : "Success!" , "result" : { "GetRankTypeRsp" : { "RankList....省略部分json}}

发现json数组中的GetRankTypeRsp和上面Result类中的getRankTypeRsp大小写不一样，又可能是getxxx和系统中的get方法冲突了，于是尝试把实体类中getRankTypeRsp换成GetRankTypeRsp，然后重新生成了gettter和setter方法，发现居然不报nulll了！！！！！

最终解决方法

使java类中的字段名和json数据中的字段名保持一致，包括大小写。