Java操作MongoDB

这段时间一直在研究mongoDB，由于资料很少，网上的又都是互相抄袭，真正学到的不多。官方文档对我来说又很难看懂，总之我是看的都想放弃了的。
但还好坚持了下来，现在把学习的心得记录一下。

程序员特点，没有废话，直接上代码：

publicclass Test2 {

@Test
publicvoid setDBData(){
// 连接本地数据库
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//创建名为test_db的数据库
            DB db = m.getDB("test_db");
//获取test_table中的集合（类似于获取关系数据库中的表）
            Set<String> cols = db.getCollectionNames();
//创建一个叫做"test_table"的集合
            DBCollection collection = db.getCollection("test_table");
for(int i=0;i<100;i++){
//基本DB对象，最终插入数据库的就是这个DB对象
                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(){
// 连接本地数据库
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//创建名为test_db的数据库
            DB db = m.getDB("test_db");
//创建一个叫做"test_table"的集合
            DBCollection collection = db.getCollection("test_table");
//排序 1为升序  -1为降序
            DBCursor cursor=collection.find().sort(new BasicDBObject("id",-1));   //排序 1为升序  -1为降序
//DBCursor cursor=collection.find().limit(10);   //只取前十个
//DBCursor cursor=collection.find().skip(10); //取前十个记录之后的
//collection.find().count()  ;  //总记录数
//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("$gte", 10)));
/**
            //select * form table where id in (1,12,23)
            int [] strs = new int[3];  //其实也可以放在List里面
            strs[0] = 1;
            strs[1] = 12;
            strs[2] = 23;
            DBCursor cursor=collection.find(new BasicDBObject("id",new BasicDBObject("$in",strs)));
            */

/**查询特定字段
            DBObject query = new BasicDBObject();//要查的条件
            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")这个字段是什么类型，list.get(i)就是什么类型
            List list=(List) collection.distinct("uid");
            for(int i=0;i<list.size();i++){
                System.out.println(list.get(i));
            }
            */

/**按照groupid分组，并且分组后计算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的条件 可以为空
            BasicDBObject cond = new BasicDBObject();

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

            //reduce是分解归纳求和 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 );
//创建名为test_db的数据库
            DB db = m.getDB("test_db");
//db.dropDatabase();  //删除数据库
            DBCollection collection = db.getCollection("test_table");
//collection.drop();  //删除表
            collection.remove(new BasicDBObject()); //清空表数据
        } catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

@Test
publicvoid findDataByParams(){
try {
            Mongo m = new Mongo( "localhost" , 27017 );
//创建名为test_db的数据库
            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 );
//创建名为test_db的数据库
            DB db = m.getDB("test_db");
            DBCollection collection = db.getCollection("test_table");
/**  以下是用findAndModify方法更改数据
            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);
            //这里，findAndModify方法执行后，返回的DBObject内容还是旧的内容，但是数据库里的记录已经改为了新的记录
            //如下：
            DBCursor cursor= collection.find(obj);
            while(cursor.hasNext()){
                System.out.println("objNew=="+cursor.next());
            }
            */

// 以下是用update方法更改数据  注：findOne是返回满足条件的第一个记录
// 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 );
//创建名为test_db的数据库
            DB db = m.getDB("test_db");
            DBCollection collection = db.getCollection("test_table");
            DBObject obj = new BasicDBObject();
            obj.put("uid", "name59");
//删除数据
            collection.remove(obj);
            getDBData();
        } catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

以上对mongodb的基本操作应该够用，现在还有弄不明白的就是它的模糊查询和MapReduce的用法，模糊查询只知道是用正则来实现。
以后有空再细细摸索一下吧

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