用gson反序列化泛型

Question

我正在使用GSON 1.4并使用两个泛型序列化一个对象,arraylist<myObject>如下所示 String data = Gson.toJson(object, object.class).当我想要它时,我做到了gson.fromJson(json, type);

可悲的是,我明白了

java.lang.IllegalArgumentException:无法将java.util.ArrayList字段...设置为java.util.LinkedList

这是为什么 ？GSON doc指出,如果我使用object.class参数序列化它支持泛型.任何的想法？谢谢.

我的班级是:

public class IndicesAndWeightsParams {

    public List<IndexParams> indicesParams;
    public List<WeightParams> weightsParams;

    public IndicesAndWeightsParams() {
        indicesParams = new ArrayList<IndexParams>();
        weightsParams = new ArrayList<WeightParams>();
    }
    public IndicesAndWeightsParams(ArrayList<IndexParams> indicesParams, ArrayList<WeightParams> weightsParams) {
        this.indicesParams = indicesParams;
        this.weightsParams = weightsParams;
    }
}    
public class IndexParams {

    public IndexParams() {
    }
    public IndexParams(String key, float value, String name) {
      this.key = key;
      this.value = value;
      this.name = name;
    }
    public String key;
    public float value;
    public String name;
}

Answer 1

由于Java的类型擦除,Gson在集合方面有一些限制.你可以在这里阅读更多相关信息.

根据你的问题,我看到你正在使用ArrayList和LinkedList.你确定你不打算只使用List界面吗？

此代码有效:

List<String> listOfStrings = new ArrayList<String>();

listOfStrings.add("one");
listOfStrings.add("two");

Gson gson = new Gson();
String json = gson.toJson(listOfStrings);

System.out.println(json);

Type type = new TypeToken<Collection<String>>(){}.getType();

List<String> fromJson = gson.fromJson(json, type);

System.out.println(fromJson);

更新:我把你的课改成了这个,所以我不必乱用其他课:

class IndicesAndWeightsParams {

    public List<Integer> indicesParams;
    public List<String> weightsParams;

    public IndicesAndWeightsParams() {
        indicesParams = new ArrayList<Integer>();
        weightsParams = new ArrayList<String>();
    }
    public IndicesAndWeightsParams(ArrayList<Integer> indicesParams, ArrayList<String> weightsParams) {
        this.indicesParams = indicesParams;
        this.weightsParams = weightsParams;
    }
}

使用此代码,一切都适合我:

ArrayList<Integer> indices = new ArrayList<Integer>();
ArrayList<String> weights = new ArrayList<String>();

indices.add(2);
indices.add(5);

weights.add("fifty");
weights.add("twenty");

IndicesAndWeightsParams iaw = new IndicesAndWeightsParams(indices, weights);

Gson gson = new Gson();
String string = gson.toJson(iaw);

System.out.println(string);

IndicesAndWeightsParams fromJson = gson.fromJson(string, IndicesAndWeightsParams.class);

System.out.println(fromJson.indicesParams);
System.out.println(fromJson.weightsParams);