一：ORM框架Morphia的學習

Morphia 是一個針對Mongo和Java 對象轉換的映射的輕量級ORM類型安全類庫。

      1.簡單易用，輕量級，一旦每一種類型通過反射獲取將被緩存，性能比較好。

       2.Datastore和DAO<T,V>的抽象封裝。

      3.快速的查詢的支持，在類運行時進行校驗。

      4.Mapping是基於註解而不是基於xml。

      5.針對Validation和Log的擴展。

      6.生命週期的控制。

      7.可以和Spring，Guice等DI框架整合。

      8.支持各種功能的擴展。

在nosql的數據庫中，如果你用mongo api的驅動直接去開發，那個效率啊~~那個性能啊~~那個XX。。。

下面貼代碼，自己細細品味下，這樣寫好不好。當然，下面貼的代碼，是我網上找的。

Java代碼  

package com.easyway.mongodb.morphia;


import java.net.UnknownHostException;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.Mongo;
import com.mongodb.MongoException;

public class MongoApp {


        private Mongo m;
        private DB db;

        public void init() {

            try {
                //創建一個Mongo對象
                this.m = new Mongo("localhost");
                System.out.println(m.debugString());

                // // select a DB
                // // The database doesn't have to exist - if it doesn't, MongoDB
                // will create it for you.
                //創建一個Mongo的db對象
                this.db = m.getDB("test");
                System.out.println("DB [" + db.getName() + "] Connected");
            } catch (UnknownHostException e) {
                e.printStackTrace();
            } catch (MongoException e) {
                e.printStackTrace();
            }
        }
        /**
         * 查詢數據庫和表的信息
         */
        public void queryDatabaseInfo(){
            System.out.println("mongodb version  "+m.getVersion());
            List<String> dbNameList=this.m.getDatabaseNames();
            for (String dbName : dbNameList) {
                System.out.println(" "+dbName);
                DB db=m.getDB(dbName);
                Set<String> collectionList=db.getCollectionNames();
                for (String collName : collectionList) {
                    System.out.print(collName +"  ");
                }
            }
        }


        private void createIndex() {
            insertRecords();
            // MongoDB supports indexes, and they are very easy to add on a
            // collection. To create an index, you just specify the field that
            // should be indexed, and specify if you want the index to be ascending
            // (1) or descending (-1). The following creates an ascending index on
            // the "i" field :
            DBCollection dbconn = db.getCollection("things");
            dbconn.createIndex(new BasicDBObject("case", -1)); // create index on "i",
                                                            // ascending

            Iterator<DBObject> iter=dbconn.getIndexInfo().iterator();
            while (iter.hasNext()) {
                DBObject dbObject = (DBObject) iter.next();
                System.out.println("Index Info:"+dbObject);;
            }
            removeAll();
        }

        private void insertAndQuery() {
            insertRecords();
            query();
            removeAll();
        }

        private void query() {
            System.out.println("start  query");
            DBCollection dbconn = db.getCollection("things");
            // looks like find by example
            BasicDBObject queryDb = new BasicDBObject();
            queryDb.append("case", 5);
            DBCursor dbc = dbconn.find(queryDb);
            while (dbc.hasNext()) {
                DBObject dbObject = (DBObject) dbc.next();
                System.out.println("result case=5:" + dbObject);
            }
            System.out.println("end  query");
            // find in range
            BasicDBObject query = new BasicDBObject();
            query.put("case", new BasicDBObject("$gt", 5)); // e.g. find all where
                                                            // case > 5
            DBCursor cur = dbconn.find(query);
            while (cur.hasNext()) {
                System.out.println("case >5:" + cur.next());
            }
        }

        private void insertFindOneRemove() {
            insertRecords();
            testFindOneInCollections();
            removeAll();

        }

        private void testFindOneInCollections() {
            System.out.println("Collections Find one:");
            DBCollection dbconn = db.getCollection("things");
            // declare that just one object is needed,null if none
            System.out.println(dbconn.findOne());
            System.out.println("Collections Find one end");
        }

        private void insertFindAllRemove() {
            insertRecords();
            testFindAllInCollections();
            removeAll();

        }
       //刪除所有的對象
        private void removeAll() {
            System.out.println("start remove all");
            DBCollection dbconn = db.getCollection("things");
            DBCursor c = dbconn.find();
            while (c.hasNext()) {
                dbconn.remove(c.next());
            }
            System.out.println("done");
        }


        /**
         * 添加數據
         */
        public void insertRecords() {
            System.out.println("start insert :");
            DBCollection dbconn = db.getCollection("things");
            for (int i = 0; i < 10L; i++) {
                // BasicDBObject basic=new BasicDBObject();
                //
                // basic.append("time",System.currentTimeMillis());
                //
                // basic.append("obj",i);
                // dbconn.save(basic);
                BasicDBObject doc = new BasicDBObject();
                doc.put("case", i);
                doc.put("name", "MongoDB");
                doc.put("type", "database");
                doc.put("count", 1);
                BasicDBObject info = new BasicDBObject();
                info.put("x", 203);
                info.put("y", 102);
                doc.put("info", info);
                dbconn.insert(doc);
            }
            System.out.println("Insert End");
        }

        /**
         * 查詢所有
         */
        public void testFindAllInCollections() {
            System.out.println("Data in 'things':");
            DBCollection coll = db.getCollection("things");

            DBCursor c = coll.find();
            while (c.hasNext()) {
                System.out.println(c.next());

            }
        }


        public static void main(String[] args) {
            MongoApp test=new MongoApp();
            test.init();
            test.queryDatabaseInfo();


            test.insertFindAllRemove();
            test.insertFindOneRemove();
            test.insertAndQuery();
            test.createIndex();
        }
}