java mongodb 基础系列—查询，排序，limit，$in,$or,输出为list,创建索引,$ne 非操作

官方api教程：http://docs.mongodb.org/ecosystem/tutorial/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 );//建立连接
        DB get_db_credit = mongoClient.getDB("credit_2");//数据库名
        DBCollection collection = get_db_credit.getCollection("report");//集合名，对应mysql中的表名
        BasicDBObject filter_dbobject = new BasicDBObject();        //建立查询条件,如果还有其他条件，类似的写即可
        // 如:version=3,filter_dbobject.put("version", 3),mongod区分String 和 Integer类型，所以要小心"3"!=3
        filter_dbobject.put("user_id", "10065716153075");        //下面执行查询，设置limit,只要10条数据,排序(类mysql orderby) 再建一个BasicDBObject即可，－1表示倒序
        DBCursor cursor = collection.find(filter_dbobject).limit(10).sort(new BasicDBObject("create_time",-1));       //把结果集输出成list类型
        List<DBObject> list = cursor.toArray();
        System.out.println(list.size());//list的长度
        System.err.println(cursor.count());//计算结果的数量，类似于(mysql count()函数),不受limit的影响        //遍历结果集
        while(cursor.hasNext()) {
            System.out.println(cursor.next());
        }
    }
}

补充:1.关于查询:如果想要查 “a=30或a=50″这样的条件怎么办?

可以使用$in进行查询:

    @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.关于查询:如果想要查 “a>30或a<１0″这样的条件怎么办?

可以使用$or进行查询:

@Test
    public void testOrSingleField(){
        DBObject queryCondition = new BasicDBObject();
        //查询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);    }

那么,如果想要查 “a>30或b<１0″这样的条件怎么办?

只需要将上面代码改为如下,即可:

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

3.如果是多值and查询只用new BasicDBobject(),然后再put即可,如下所示:

BasicDBObject basic=new BasicDBObject();
basic.put("name","amosli");
basic.put("hobby","code");
....
collection.find(basic).toArray();//将值转为list

4.创建索引

        // 创建索引
        BasicDBObject obj = new BasicDBObject();
        obj.put("create_time", -1);
        collection.ensureIndex(obj);
        // 查询索引,遍历索引
        List<DBObject> list = collection.getIndexInfo();
        for (DBObject o : list) {
            System.out.println("\t" + o);
        }

5.查询非操作

查询level为INFO,但status不为”已完成”的所结果数

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

另，可参见：

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/ 查询命令，$ne,$in