MongoDB giving NullPointerException

Question

I have a problem in my code. I have a collection of objects in Mongo, all of which have a "name", "description", "imageURL", "code".

I want to do a search of my collection and return ArrayList of all the names, descriptions,codes and imageURLs

I tried it like this

else{
            DBCursor cursair = this.searchItem(code);
            while(cursair.hasNext()){
                this.searchNames = new ArrayList<String>();
                this.searchBarcodes = new ArrayList<String>();
                this.searchDescriptions = new ArrayList<String>();
                this.searchImageURLs = new ArrayList<String>();                 
                this.searchNames.add(cursair.curr().get(ITEMS_NAME).toString());
                this.searchDescriptions.add(cursair.curr().get(ITEMS_DESCRIPTION).toString());
                this.searchImageURLs.add(cursair.curr().get(ITEMS_IMAGEURL).toString());
                this.searchBarcodes.add(cursair.next().get(ITEMS_CODE).toString());
            }

I have a problem with it as it gives me a NullPointerException at this.searchNames.add(cursair.curr().get(ITEMS_NAME).toString()); . ITEMS_NAME is a String constant defined in the code.

the searchItem(code) method looks like this

public DBCursor searchItem(String searchQuery){

    BasicDBObject query = new BasicDBObject();
    query.put(ITEMS_NAME, java.util.regex.Pattern.compile(searchQuery));
    DBCursor cursor = itemsCollection.find(query);
    return cursor;
}

I also checked in my debugger, when I call cursor.toArray() it returns a List<DBObject> with a size of 5, so I am pretty confident about cursor having the right information in itself

Answer 1

您想调用cursair.next()作为while循环的第一步，并使用返回的DBObject来提取数据。