使用Java从MongoDB检索数据时如何跳过文档?
从MongoDB集合中检索记录时,可以使用skip()方法跳过结果中的记录。
句法
db.COLLECTION_NAME.find().limit(NUMBER).skip(NUMBER)
JavaMongoDB库提供了一个具有相同名称的方法,以跳过记录,并绕过表示要跳过的记录数的整数值来调用此方法(基于find()方法的结果)。
示例
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.bson.Document;
import com.mongodb.MongoClient;
public class SkipRecords {
public static void main( String args[] ) {
//创建一个MongoDB客户端
MongoClient mongo = new MongoClient( "localhost" , 27017 );
//连接到数据库
MongoDatabase database = mongo.getDatabase("myDatabase");
//创建一个集合对象
MongoCollection<Document>collection = database.getCollection("students");
Document document1 = new Document("name", "Ram").append("age", 26).append("city", "Hyderabad");
Document document2 = new Document("name", "Robert").append("age", 27).append("city", "Vishakhapatnam");
Document document3 = new Document("name", "Rhim").append("age", 30).append("city", "Delhi");
Document document4 = new Document("name", "Radha").append("age", 28).append("city", "Mumbai");
Document document5 = new Document("name", "Ramani").append("age", 45).append("city", "Pune");
//插入创建的文档
List<Document> list = new ArrayList<Document>();
list.add(document1);
list.add(document2);
list.add(document3);
list.add(document4);
list.add(document5);
collection.insertMany(list);
System.out.println("Documents Inserted");
//检索集合对象
collection = database.getCollection("students");
//检索具有限制的文档
FindIterable<Document> iterDoc = collection.find().skip(2);
Iterator it = iterDoc.iterator();
while (it.hasNext()) {
System.out.println(it.next());
}
}
}输出结果
Documents Inserted
Documents Inserted
Document{{_id=5e8886f97631225872d13217, name=Rhim, age=30, city=Delhi}}
Document{{_id=5e8886f97631225872d13218, name=Radha, age=28, city=Mumbai}}
Document{{_id=5e8886f97631225872d13219, name=Ramani, age=45, city=Pune}}