我想获取所有没有下载字段的文档
find{ "download" : {$exists: false}}
对于Java,我找到了一个示例:
BasicDBObject neQuery = new BasicDBObject();
neQuery.put("number", new BasicDBObject("$ne", 4));
DBCursor cursor = collection.find(neQuery);
while(cursor.hasNext()) {
System.out.println(cursor.next());
}
我的适应性是:
BasicDBObject field = new BasicDBObject();
field.put("entities.media", 1);
field.put("download", new BasicDBObject("$exists",false));
System.out.println("Start Find");
DBCursor cursor = collection.find(query,field);
System.out.println("End Find Start Loop ALL 100k");
int i = 1;
while(cursor.hasNext())
Exists命令行无法正常工作:
Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)
Caused by: com.mongodb.MongoException: Unsupported projection option: $exists
at com.mongodb.MongoException.parse(MongoException.java:82)
at com.mongodb.DBApiLayer$MyCollection.__find(DBApiLayer.java:314)
at com.mongodb.DBApiLayer$MyCollection.__find(DBApiLayer.java:295)
at com.mongodb.DBCursor._check(DBCursor.java:368)
at com.mongodb.DBCursor._hasNext(DBCursor.java:459)
at com.mongodb.DBCursor.hasNext(DBCursor.java:484)
at ImgToDisk.main(ImgToDisk.java:61)
... 5 more
目前我不知道正确的适应方式,因为在shell和UMongo中已经使我的查询工作正常,但是转移到Java中似乎并不那么容易。