Gson cheat sheet for Map, List and Array
Constantly confronted with parsing, Json is always peeping in old projects or on the encountered implementation of an object on stackoverflow.com .
I decided to collect three basic types in the Map, List, Array cheat sheet.
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Serialization / Deserialization class operations are considered:
Serialization / Deserialization is performed using the Gson library. The GoodsItem class is considered as the “test subject”.
Hashmap
Result Serialization:
Deserialization result:
ArrayList
Result Serialization:
Deserialization result:
Array
Result Serialization:
Deserialization result:
As you can see, ArrayList and a simple array of objects are converted to the same Json string.
Useful tools:
parcelabler.com makes it possible by class type to generate parcelable methods for Android. For example for the GoodsItem class:
jsonschema2pojo.org - Generate Plain Old Java Objects from JSON or JSON-Schema.
It would be interesting to know what you use in your projects.
I decided to collect three basic types in the Map, List, Array cheat sheet.
Type itemsMapType = new TypeToken<Map<Integer, GoodsItem>>() {}.getType(); Type itemsListType = new TypeToken<List<GoodsItem>>() {}.getType(); Type itemsArrType = new TypeToken<GoodsItem[]>() {}.getType(); ')
Serialization / Deserialization class operations are considered:
public class GoodsItem{ String name; float price; public GoodsItem(String name, float price) { this.name = name; this.price = price; public String toString(){ return name + " : " + price; } } Serialization / Deserialization is performed using the Gson library. The GoodsItem class is considered as the “test subject”.
Hashmap
Map<Integer, GoodsItem> mapItems = new HashMap<Integer, GoodsItem>(); mapItems.put(1, new GoodsItem("Samsung", 51200.6f)); mapItems.put(2, new GoodsItem("Lg", 5400.6f)); mapItems.put(3, new GoodsItem("Alcatel", 4500.6f)); String jsonStr = new Gson().toJson(mapItems); System.out.println(jsonStr); Result Serialization:
{ "1":{"name":"Samsung","price":51200.6}, "2":{"name":"Lg","price":5400.6}, "3":{"name":"Alcatel","price":4500.6} } Map<Integer, GoodsItem> mapItemsDes = new Gson().fromJson(jsonStr, itemsMapType); System.out.println(mapItemsDes.toString()); Deserialization result:
{1=Samsung : 51200.6, 2=Lg : 5400.6, 3=Alcatel : 4500.6} ArrayList
List<GoodsItem> listItems = new ArrayList<GoodsItem>(); listItems.add( new GoodsItem("Samsung" , 51200.6f)); listItems.add( new GoodsItem("Lg" , 5400.6f)); listItems.add( new GoodsItem("Alcatel" , 4500.6f)); String jsonStr = new Gson().toJson(listItems); System.out.println(jsonStr); Result Serialization:
[ {"name":"Samsung","price":51200.6}, {"name":"Lg","price":5400.6}, {"name":"Alcatel","price":4500.6} ] List<GoodsItem> listItemsDes = new Gson().fromJson(jsonStr,itemsListType); System.out.println(listItemsDes.toString()); Deserialization result:
[Samsung : 51200.6, Lg : 5400.6, Alcatel : 4500.6] Array
GoodsItem[] arrItems = new GoodsItem[3]; arrItems[0] = new GoodsItem("Samsung", 51200.6f); arrItems[1] = new GoodsItem("Lg", 5400.6f); arrItems[2] = new GoodsItem("Alcatel", 4500.6f); String jsonStr = new Gson().toJson(arrItems); System.out.println(jsonStr); Result Serialization:
[ {"name":"Samsung","price":51200.6}, {"name":"Lg","price":5400.6}, {"name":"Alcatel","price":4500.6} ] GoodsItem[] arrItemsDes = new Gson().fromJson(jsonStr, itemsArrType); System.out.println(Arrays.toString(arrItemsDes)); Deserialization result:
[Samsung : 51200.6, Lg : 5400.6, Alcatel : 4500.6] As you can see, ArrayList and a simple array of objects are converted to the same Json string.
Useful tools:
parcelabler.com makes it possible by class type to generate parcelable methods for Android. For example for the GoodsItem class:
public class GoodsItem implements Parcelable
public class GoodsItem implements Parcelable { String name; float price; public GoodsItem(String name, float price) { this.name = name; this.price = price; public String toString(){ return name + " : " + price; } protected GoodsItem(Parcel in) { name = in.readString(); price = in.readFloat(); } @Override public int describeContents() { return 0; } @Override public void writeToParcel(Parcel dest, int flags) { dest.writeString(name); dest.writeFloat(price); } @SuppressWarnings("unused") public static final Parcelable.Creator<GoodsItem> CREATOR = new Parcelable.Creator<GoodsItem>() { @Override public GoodsItem createFromParcel(Parcel in) { return new GoodsItem(in); } @Override public GoodsItem[] newArray(int size) { return new GoodsItem[size]; } }; } jsonschema2pojo.org - Generate Plain Old Java Objects from JSON or JSON-Schema.
It would be interesting to know what you use in your projects.
Source: https://habr.com/ru/post/253266/
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