[英]Java Google App Engine Datastore put/get
The Put : 推杆:
DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
try{
Entity e = new Entity("Winners", "NFL" );
String winner_game = new String("winner_" + input_game );
e.setProperty(winner_game, input_win_value );
datastore.put(e);
.... ....
The Get : 获取:
DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
try{
Entity e = datastore.get(KeyFactory.createKey("Winners", "NFL" ));
String winner_game = new String("winner_" + i );
if( e.getProperty(winner_game) != null )
{
Integer property = new Integer(e.getProperty( winner_game ).toString());
return property;
}
else{
return 0;
}
... ...
The e.getProperty is returning null.....any ideas? e.getProperty返回null .....任何想法吗?
Do not create new String / Integer Objects. 不要创建新的字符串/整数对象。 If you need to append something to the property name just do it directly. 如果您需要在属性名称后添加一些内容,则只需直接进行操作即可。
Entity e = new Entity("Winners", "NFL" );
String winner_game = "winner_" + input_game; // Where input_game is "X"
e.setProperty(winner_game, input_win_value); // int input_win_value = 10;
datastore.put(e);
Same for retrieval: 检索相同:
Entity e = datastore.get(KeyFactory.createKey("Winners", "NFL" ));
String winner_game = "winner_" + i; // where i is also "X"
if( e.getProperty(winner_game) != null ) {
// Casting is ugly but does the trick
Integer property = (Integer) e.getProperty(winner_game);
return property;
} else{
return 0;
}
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