java mongodb 基礎系列---查詢，排序，limit，$in,$or,輸出爲list,建立索引,$ne 非操做

 

 

官方api教程：http://docs.mongodb.org/ecosystem/tutorial/getting-started-with-java-driver/#getting-started-with-java-driver

package com.infomorrow.webroot;

import java.util.List;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;

public class test_mongodb {
    public static void  main(String args[]) throws Exception {
        MongoClient        mongoClient = new MongoClient( "127.0.0.1" , 27017 );//創建鏈接
        DB get_db_credit = mongoClient.getDB("credit_2");//數據庫名
        DBCollection collection = get_db_credit.getCollection("report");//集合名，對應mysql中的表名
        BasicDBObject filter_dbobject = new BasicDBObject();
        
        //創建查詢條件,若是還有其餘條件，相似的寫便可
        // 如:version=3,filter_dbobject.put("version", 3),mongod區分String 和 Integer類型，因此要當心"3"!=3
        filter_dbobject.put("user_id", "10065716153075");
       
        //下面執行查詢，設置limit,只要10條數據,排序(類mysql orderby) 再建一個BasicDBObject便可，－1表示倒序
        DBCursor cursor = collection.find(filter_dbobject).limit(10).sort(new BasicDBObject("create_time",-1)); //把結果集輸出成list類型
        List<DBObject> list = cursor.toArray();
        System.out.println(list.size());//list的長度
        System.err.println(cursor.count());//計算結果的數量，相似於(mysql count()函數),不受limit的影響
        
        
        //遍歷結果集
        while(cursor.hasNext()) {
            System.out.println(cursor.next());
        }
    }
}

 

 

補充:1.關於查詢:若是想要查 "a=30或a=50"這樣的條件怎麼辦?

       能夠使用$in進行查詢:      

    @Test
    public void testIn(){
        //a=30或者a=50
        DBObject queryCondition = new BasicDBObject();        
                       
       BasicDBList values = new BasicDBList(); values.add(30); values.add(50);
        queryCondition.put("a", new BasicDBObject("$in", values));
        
        DBCursor dbCursor = coll.find(queryCondition);
        
    }    

２.關於查詢:若是想要查 "a>30或a<１0"這樣的條件怎麼辦?

能夠使用$or進行查詢:      

@Test public void testOrSingleField(){ DBObject queryCondition = new BasicDBObject(); //查詢a<10 OR a>30
       BasicDBList values = new BasicDBList(); values.add(new BasicDBObject("a", new BasicDBObject("$gt", 30))); values.add(new BasicDBObject("a", new BasicDBObject("$lt", 10))); queryCondition.put("$or", values); DBCursor dbCursor = coll.find(queryCondition); }

那麼,若是想要查 "a>30或b<１0"這樣的條件怎麼辦?

只須要將上面代碼改成以下,便可:

 values.add(new BasicDBObject("b", new BasicDBObject("$lt", 10)));

3.若是是多值and查詢只用new BasicDBobject(),而後再put便可,以下所示:

 

BasicDBObject basic=new BasicDBObject();
basic.put("name","amosli");
basic.put("hobby","code");
....
collection.find(basic).toArray();//將值轉爲list

 

4.建立索引

        // 建立索引
        BasicDBObject obj = new BasicDBObject();
        obj.put("create_time", -1);
        collection.ensureIndex(obj);
        // 查詢索引,遍歷索引
        List<DBObject> list = collection.getIndexInfo();
        for (DBObject o : list) {
            System.out.println("\t" + o);
        }
        

5.查詢非操做

查詢level爲INFO,但status不爲"已完成"的所結果數

        //not equal 非操做
        BasicDBObject basicDBObject = new BasicDBObject("level","INFO");
        System.out.println(collection.count(basicDBObject.append("status", new BasicDBObject("$ne",  "已完成"))));
    

 

 

 

 

另，可參見：

1.http://blog.csdn.net/llhhyy1989/article/details/12571111

2.http://blog.csdn.net/mydeman/article/details/6652387

3.http://docs.mongodb.org/manual/reference/operator/query/  查詢命令，$ne,$in