Java操作MongoDB

這段時間一直在研究mongoDB，由於資料很少，網上的又都是互相抄襲，真正學到的不多。官方文檔對我來說又很難看懂，總之我是看的都想放棄了的。
但還好堅持了下來，現在把學習的心得記錄一下。

程序員特點，沒有廢話，直接上代碼：

publicclass Test2 {

@Test
publicvoid setDBData(){
// 連接本地數據庫
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//創建名爲test_db的數據庫
            DB db = m.getDB("test_db");
//獲取test_table中的集合（類似於獲取關係數據庫中的表）
            Set<String> cols = db.getCollectionNames();
//創建一個叫做"test_table"的集合
            DBCollection collection = db.getCollection("test_table");
for(int i=0;i<100;i++){
//基本DB對象，最終插入數據庫的就是這個DB對象
                BasicDBObject obj = new BasicDBObject();
                obj.put("id", i);
                obj.put("fid", i%30);
                obj.put("uid", "name"+i%60);
                obj.put("groupid", i%40);
                obj.put("ip", "192.168.0."+(i+1)%40);
                obj.put("regTime", new Date());
                collection.insert(obj);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

@Test
publicvoid getDBData(){
// 連接本地數據庫
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//創建名爲test_db的數據庫
            DB db = m.getDB("test_db");
//創建一個叫做"test_table"的集合
            DBCollection collection = db.getCollection("test_table");
//排序 1爲升序  -1爲降序
            DBCursor cursor=collection.find().sort(new BasicDBObject("id",-1));   //排序 1爲升序  -1爲降序
//DBCursor cursor=collection.find().limit(10);   //只取前十個
//DBCursor cursor=collection.find().skip(10); //取前十個記錄之後的
//collection.find().count()  ;  //總記錄數
//select * from test_table where id>=10 and id<30  注：$gt=(>)  $gte=(>=)  $lt=(<) $lte=(<=)  $ne=(!=)
//DBCursor cursor = collection.find(new BasicDBObject("id",new BasicDBObject("$lt", 30).append("$gte", 10)));
/**
            //select * form table where id in (1,12,23)
            int [] strs = new int[3];  //其實也可以放在List裏面
            strs[0] = 1;
            strs[1] = 12;
            strs[2] = 23;
            DBCursor cursor=collection.find(new BasicDBObject("id",new BasicDBObject("$in",strs)));
            */

/**查詢特定字段
            DBObject query = new BasicDBObject();//要查的條件
            query.put("uid", "name10");
            DBObject field = new BasicDBObject();//要查的哪些字段
            field.put("id", true);
            field.put("fid", true);
            field.put("ip", true);
            DBCursor cursor=collection.find(query,field);
            */


while(cursor.hasNext()){
                System.out.println(cursor.next());
            }
/** select distinct("uid") from table
             * 注意：distinct("uid")這個字段是什麼類型，list.get(i)就是什麼類型
            List list=(List) collection.distinct("uid");
            for(int i=0;i<list.size();i++){
                System.out.println(list.get(i));
            }
            */

/**按照groupid分組，並且分組後計算fid的sum
            //select groupid ,sum(fid) fidCount form  table group by groupid
            //key是group by 的字段
            BasicDBObject key = new BasicDBObject();
            key.put("groupid", true);

            //cond是where的條件 可以爲空
            BasicDBObject cond = new BasicDBObject();

            //initial是字段sum的初始值
            BasicDBObject initial = new BasicDBObject();
            initial.put("fidCount", 0);

            //reduce是分解歸納求和 fid的sum
            String reduce = "function(obj,prev) { prev.fidCount +=obj.fid; }";

            DBObject obj = collection.group(key, cond, initial, reduce);
            Set set = obj.keySet();
            Iterator it = set.iterator();
            int i=0;
            while(it.hasNext()){
                String str_key = (String) it.next();
                System.out.println(obj.get(str_key));
                i++;
            }
            */



        } catch (Exception e) {
            e.printStackTrace();
        }
    }

@Test
publicvoid deleteTable(){
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//創建名爲test_db的數據庫
            DB db = m.getDB("test_db");
//db.dropDatabase();  //刪除數據庫
            DBCollection collection = db.getCollection("test_table");
//collection.drop();  //刪除表
            collection.remove(new BasicDBObject()); //清空表數據
        } catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

@Test
publicvoid findDataByParams(){
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//創建名爲test_db的數據庫
            DB db = m.getDB("test_db");
            DBCollection collection = db.getCollection("test_table");
            DBObject obj = new BasicDBObject();
//select ip,groupid form table where uid=name1
            obj.put("uid", "name1");
            DBCursor cursor=collection.find(obj,new BasicDBObject("ip",1).append("groupid", 1));
while(cursor.hasNext()){
                System.out.println(cursor.next());
            }
        } catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

@Test
publicvoid updateData(){
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//創建名爲test_db的數據庫
            DB db = m.getDB("test_db");
            DBCollection collection = db.getCollection("test_table");
/**  以下是用findAndModify方法更改數據
            DBObject obj = new BasicDBObject();
            obj.put("uid", "name59");
            DBObject obj2 = new BasicDBObject();
            obj2.put("ip", "111.111.111.333");
            //UPDATE test_table  SET ip = 111.111.111.333 WHERE uid=name59;
            DBObject objOld = collection.findAndModify(obj, new BasicDBObject("$set",obj2));
            System.out.println("objOld==="+objOld);
            //這裏，findAndModify方法執行後，返回的DBObject內容還是舊的內容，但是數據庫裏的記錄已經改爲了新的記錄
            //如下：
            DBCursor cursor= collection.find(obj);
            while(cursor.hasNext()){
                System.out.println("objNew=="+cursor.next());
            }
            */

// 以下是用update方法更改數據  注：findOne是返回滿足條件的第一個記錄
// UPDATE test_table  SET ip = 100.100.100.333 WHERE uid=name59;
            DBObject obj = new BasicDBObject();
            obj.put("uid", "name59");
            DBObject obj2 = collection.findOne(obj);
            obj2.put("ip", "100.100.100.333");
            collection.update(obj, obj2);
            System.out.println("==="+collection.findOne(obj));


        } catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

@Test
publicvoid deleteData(){
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//創建名爲test_db的數據庫
            DB db = m.getDB("test_db");
            DBCollection collection = db.getCollection("test_table");
            DBObject obj = new BasicDBObject();
            obj.put("uid", "name59");
//刪除數據
            collection.remove(obj);
            getDBData();
        } catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

以上對mongodb的基本操作應該夠用，現在還有弄不明白的就是它的模糊查詢和MapReduce的用法，模糊查詢只知道是用正則來實現。
以後有空再細細摸索一下吧

Ref: http://jzkangta.iteye.com/blog/1018685