Reputation: 2834
I have a Movie
class and I have to store a database in the form of JSON File on directory Database\Movies.JSON
The movie class has a method for admin to add new movie list to the database.
The thing is, when the first movie is created, the JSON is not an array of movies
object. When I try to add subsequent movies I need to read from it and create it as an array of movie objects. Is there a neat way to do so on Jackson JSON API?
I am using the latest Jackson 2.6.3
public void createMovie() {
ObjectMapper objectMapper = new ObjectMapper();
File f = new File("./Database/Movies.json");
if (f.exists() && !f.isDirectory()) { // if existing data exist, read
// from it and append new movie
// data
} else {
try {
objectMapper.writeValue(new FileOutputStream(f), this);
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
I have since created it as an array of movie objects.
objectMapper.writeValue(new FileOutputStream(f), Collections.singleton(this));
But when I try to use the below for handling exisiting datas, it crashes on the first line
List<Movie> myMovies = objectMapper.readValue(f,objectMapper.getTypeFactory().constructCollectionType(List.class, Movie.class));
myMovies.add(this);
objectMapper.writeValue(new FileOutputStream(f), myMovies);
Error trace
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148)
at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:857)
at com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:62)
at com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:11)
at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:520)
at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:95)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:258)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:125)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:245)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:217)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:25)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3736)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2658)
at entity.Movie.createMovie(Movie.java:167)
Sample JSON Data
[
{
"movieID": 0,
"title": "213131 13213 axda",
"type": "DIGITAL",
"synopsis": null,
"director": null,
"casts": [],
"status": "COMING_SOON",
"showTimes": null,
"cinema": null,
"mRating": "G",
"rRating": "_0",
"reviews": [],
"totalSales": 0
}
]
Upvotes: 0
Views: 1038
Reputation: 11
To avoid dealing with this array/non array problem, you should always store a json array in your file. You can add your first movie as an array containing this single element. You can do it with :
objectMapper.writeValue(new FileOutputStream(f), Collections.singleton(this));
Upvotes: 1