title: Kotlin data class convert with gson...And the default value was convert by zero or null
body: <p>I use GSON to convert data class which the server comeback.
  and i define the data class like this... 
  And theres some field i don't want to convert with GSON..
  So i add the ExclusionStrategy with Annotation. 
  Through the test, i found that AnnotationExclusionStrategy operating normally,And skip the field i don't want to convert.
  I add annotation with the field like uiType and testData,But actually when I print the Object out. I found the field uiType and testData had convert to zero and null..</p>
  
  <p>Then i create a new data class. the uiType and testData had not erase to zero or null.Is go wrong when GSON convert??</p>
  
  <p>if there's any way to solve this problem?</p>
  
  <p>Here's the code.</p>
  
  <p><strong>Data class entity:</strong></p>
  
  <pre><code>data class Product(@SerializedName("num_iid") var productId: Long,
                 @SerializedName("title") var productName: String,
                 @SerializedName("item_url") var productUrl: String,
                 @SerializedName("pict_url") var productPic: String,
                 @SerializedName("small_images") var productPics: ProductImageList,
                 @SerializedName("zk_final_price") var productPrice: String,
                 @SerializedName("reserve_price") var originPrice: String,
                 @SerializedName("provcity") var place: String,
                 @SerializedName("volume") var sellCount: String,
                 @SerializedName("user_type") var sellerType: String,
                 @SerializedName("nick") var sellerName: String,
                 @SerializedName("seller_id") var sellerId: Long
  ) : MultiItemEntity {
  
  @Exclude
  @ShoppingCenterConstant.ProductListUiType
  var uiType = ShoppingCenterConstant.LIST_UI_TYPE_COMMON
  
  var testData = "TestData"
  
  override fun getItemType(): Int {
      return ShoppingCenterConstant.LIST_UI_TYPE_COMMON
  }
  
  override fun toString(): String {
      return "Product(productId=$productId, productName='$productName', productUrl='$productUrl', productPic='$productPic', productPics=$productPics, productPrice='$productPrice', originPrice='$originPrice', place='$place', sellCount='$sellCount', sellerType='$sellerType', sellerName='$sellerName', sellerId=$sellerId, uiType=$uiType, testData='$testData')"
  }
  }
  </code></pre>
  
  <p><strong>GSON AnnotationExclusion:</strong></p>
  
  <pre><code>public class AnnotationExclusion implements ExclusionStrategy {
  
  public static final String TAG = GsonUtil.TAG;
  
  @Override
  public boolean shouldSkipField(FieldAttributes f) {
      boolean isShouldSkip = f.getAnnotation(Exclude.class) != null;
      return isShouldSkip;
  }
  
  @Override
  public boolean shouldSkipClass(Class&lt;?&gt; clazz) {
      boolean isShouldSkip = clazz.getAnnotation(Exclude.class) != null;
      return isShouldSkip;
  }
  </code></pre>
  
  <p>}</p>
  
  <p><strong>The place i printout:</strong></p>
  
  <pre><code>override fun showData(data: BaseListBean&lt;Product&gt;) {
      var product = Product(0, "", "", ""
              , ProductImageList(List(0, { String() })), "", "", "", ""
              , "", "", 0)
      LogUtils.info("print out new product：" + product)
      mResultListener.onResponse(data)
  }
  </code></pre>
  
  <p><strong>Result with GSON Converter</strong>, <em>and you can see the field uiType and testData had convert to zero or null:</em></p>
  
  <pre><code>Product(productId=552634381786, productName='eoodoo新生儿礼盒婴儿衣服秋冬套装出生满月礼物初生母婴宝宝用品', productUrl='http://item.taobao.com/item.htm?id=552634381786', productPic='https://img.alicdn.com/tfscom/i4/2832303009/O1CN013tXM6L1Y6AFHSy7xN_!!0-item_pic.jpg', productPics=com.laka.ergou.mvp.shopping.center.model.bean.ProductImageList@1033f68, productPrice='259.72', originPrice='755.00', place='浙江 杭州', sellCount='1159', sellerType='1', sellerName='eoodoo旗舰店', sellerId=2832303009, uiType=0, testData='null')
  </code></pre>
  
  <p><strong>Result with create new Object</strong> , <em>this seem fine:</em> </p>
  
  <pre><code>Product(productId=0, productName='', productUrl='', productPic='', productPics=com.laka.ergou.mvp.shopping.center.model.bean.ProductImageList@1c228b, productPrice='', originPrice='', place='', sellCount='', sellerType='', sellerName='', sellerId=0, uiType=1, testData='testData')
  </code></pre>
  
  <p><strong>Here is the JSON i used</strong>
  .But the field like uiType and testData. just the field i define in the code and used in local, these are not the server comeback json field</p>
  
  <pre><code>{
  "tbk_item_get_response":{
      "results":{
          "n_tbk_item":[
              {
                  "item_url":"http://item.taobao.com/item.htm?id=582889134126",
                  "nick":"宝绒羊服饰旗舰店",
                  "num_iid":582889134126,
                  "pict_url":"https://img.alicdn.com/tfscom/i1/1720028843/O1CN01ERqlHz2FC8tL1m2tz_!!0-item_pic.jpg",
                  "provcity":"浙江 杭州",
                  "reserve_price":"1318.00",
                  "seller_id":1720028843,
                  "small_images":{
                      "string":[
                          "https://img.alicdn.com/tfscom/i4/1720028843/O1CN01xD9JyD2FC8tJMRuk2_!!1720028843.jpg",
                          "https://img.alicdn.com/tfscom/i4/1720028843/O1CN01twbf3O2FC8tLEHVJc_!!1720028843.jpg",
                          "https://img.alicdn.com/tfscom/i4/1720028843/O1CN01zM2clN2FC8tE0LO5q_!!1720028843.jpg",
                          "https://img.alicdn.com/tfscom/i3/1720028843/O1CN01WW6xzz2FC8tKjoitz_!!1720028843.jpg"
                      ]
                  },
                  "title":"羽绒服女2018新款女装冬季短款韩版时尚银色亮面滩羊毛领加厚外套",
                  "user_type":1,
                  "volume":2138,
                  "zk_final_price":"498.00"
              }
          ]
      },
      "total_results":19643,
      "request_id":"kvbqd1jrgqcg"
  }
  </code></pre>
  
  <p>}</p>