[英]How to Parse a JAVA ArrayList from a JSON file
我已经编写了以下代码,将包含多个其他对象的复杂Java对象作为文件存储在磁盘上
public static void savePattern(ArrayList<Pattern> p,String filename){
String fn;
Gson gson = new Gson();
JsonElement element = gson.toJsonTree(p, new TypeToken<ArrayList<Pattern>>() {}.getType());
JsonArray jsonArray = element.getAsJsonArray();
String json = gson.toJson(jsonArray);
try {
//write converted json data to a file named "file.json"
if(filename != null){
fn = "JsonObjects/objects.json";
}
else{
fn = "JsonObjects/" + filename + ".json";
}
FileWriter writer = new FileWriter("fn");
writer.write(json);
writer.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
当我尝试编写将文件从磁盘加载到具有该类型的ArrayList的方法时,我完全陷入困境。
public static ArrayList<Pattern> loadPattern(){
ArrayList<Pattern> patterns = new ArrayList<>();
Gson gson = new Gson();
JsonParser jsonParser = new JsonParser();
try {
BufferedReader br = new BufferedReader(new FileReader("JsonObjects/objects.json"));
JsonObject jo = (JsonObject)jsonParser.parse(br);
} catch (IOException e) {
e.printStackTrace();
}
return patterns;
}
你有没有尝试过:
public static List<Pattern> loadPattern(){
ArrayList<Pattern> patterns = new ArrayList<>();
Gson gson = new Gson();
JsonParser jsonParser = new JsonParser();
try {
BufferedReader br = new BufferedReader(new FileReader("JsonObjects/objects.json"));
JsonElement jsonElement = jsonParser.parse(br);
//Create generic type
Type type = new TypeToken<List<Pattern>>() {}.getType();
return gson.fromJson(jsonElement, type);
} catch (IOException e) {
e.printStackTrace();
}
return patterns;
}
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