在android開發以及javaEE的開發過程中，我們需要解析json，下面我為大家提供一個已經封裝好的工具類，在使用過程中，完全不需要再對gson作處理。一行程式碼即可以實現轉換

public final  class JsonUtil {
    private JsonUtil(){}

    /**
     * 物件轉換成json字串
     * @param obj
     * @return
     */
    public static String toJson(Object obj) {
        Gson gson = new GsonBuilder().registerTypeAdapter(Integer.class, new
 
 IntegerDefault0Adapter())
                .registerTypeAdapter(int.class, new IntegerDefault0Adapter())
                .registerTypeAdapter(Double.class, new DoubleDefault0Adapter())
                .registerTypeAdapter(double.class, new DoubleDefault0Adapter())
                .registerTypeAdapter(Long.class, new
 
 LongDefault0Adapter())
                .registerTypeAdapter(long.class, new LongDefault0Adapter())
                .create();
        return gson.toJson(obj);
    }

    /**
     * json字串轉成物件
     * @param str
     * @param type
     * @return
     */
    public static <T> T fromJson(String str, Type type) {
        Gson gson = new
 
 GsonBuilder().registerTypeAdapter(Integer.class, new IntegerDefault0Adapter())
                .registerTypeAdapter(int.class, new IntegerDefault0Adapter())
                .registerTypeAdapter(Double.class, new DoubleDefault0Adapter())
                .registerTypeAdapter(double.class, new DoubleDefault0Adapter())
                .registerTypeAdapter(Long.class, new LongDefault0Adapter())
                .registerTypeAdapter(long.class, new LongDefault0Adapter())
                .create();
        return gson.fromJson(str, type);
    }

    /**
     * json字串轉成物件
     * @param str
     * @param type
     * @return
     */
    public static <T> T fromJson(String str, Class<T> type) {
        Gson gson = new GsonBuilder().registerTypeAdapter(Integer.class, new IntegerDefault0Adapter())
                .registerTypeAdapter(int.class, new IntegerDefault0Adapter())
                .registerTypeAdapter(Double.class, new DoubleDefault0Adapter())
                .registerTypeAdapter(double.class, new DoubleDefault0Adapter())
                .registerTypeAdapter(Long.class, new LongDefault0Adapter())
                .registerTypeAdapter(long.class, new LongDefault0Adapter())
                .create();
        return gson.fromJson(str, type);
    }

}

在這裡，我們使用了IntegerDefault0Adapter，DoubleDefault0Adapter，LongDefault0Adapter自定義型別介面卡，用來解決解析過程中的型別轉換異常

IntegerDefault0Adapter.java

public class IntegerDefault0Adapter implements JsonSerializer<Integer>, JsonDeserializer<Integer> {
    @Override
    public Integer deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
        try {
            if (json.getAsString().equals("") || json.getAsString().equals("null")) {//定義為int型別,如果後臺返回""或者null,則返回0
                return 0;
            }
        } catch (Exception ignore) {
        }
        try {
            return json.getAsInt();
        } catch (NumberFormatException e) {
            throw new JsonSyntaxException(e);
        }
    }

    @Override
    public JsonElement serialize(Integer src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(src);
    }
}

DoubleDefault0Adapter.java

public class DoubleDefault0Adapter implements JsonSerializer<Double>, JsonDeserializer<Double> {
    @Override
    public Double deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        try {
            if (json.getAsString().equals("") || json.getAsString().equals("null")) {//定義為double型別,如果後臺返回""或者null,則返回0.00
                return 0.00;
            }
        } catch (Exception ignore) {
        }
        try {
            return json.getAsDouble();
        } catch (NumberFormatException e) {
            throw new JsonSyntaxException(e);
        }
    }

    @Override
    public JsonElement serialize(Double src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(src);
    }
}

LongDefault0Adapter.java

public class LongDefault0Adapter implements JsonSerializer<Long>, JsonDeserializer<Long> {
    @Override
    public Long deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
        try {
            if (json.getAsString().equals("") || json.getAsString().equals("null")) {//定義為long型別,如果後臺返回""或者null,則返回0
                return 0l;
            }
        } catch (Exception ignore) {
        }
        try {
            return json.getAsLong();
        } catch (NumberFormatException e) {
            throw new JsonSyntaxException(e);
        }
    }

    @Override
    public JsonElement serialize(Long src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(src);
    }
}