6. MongoDB——Java操作（增删改查）

转自：https://blog.csdn.net/kai402458953/article/details/79626148

 import java.net.UnknownHostException;
     import java.util.Iterator;
     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 MongoMain {  

         static DB db = null;
         static DBCollection coll = null;  

         static {
              Mongo m = null;
             try {
                 //m = new Mongo();//默认本地
                 //m = new Mongo("127.0.0.1");//默认端口
                 m = new Mongo("127.0.0.1",27017);
             } catch (UnknownHostException e) {
                 e.printStackTrace();
             } catch (MongoException e) {
                 e.printStackTrace();
             }  

             //获取名为 test 的数据库，不存在的情况下创建
             db = m.getDB("test");  

             //登录数据库（用户名:test，密码:test）
             boolean auth = db.authenticate("test", "test".toCharArray());
             if(auth){
                 //只有admin中的用户才有此权限(show dbs)
                 //获取所有数据库，不显示无collection的db
                 //System.out.println("所有数据库名："+m.getDatabaseNames());  

                 //获取名为 user 的collection(相当于表)，不存在的情况下创建
                 coll = db.getCollection("user");
             }else{
                 System.out.println("登录失败!");
             }
         }  

         public static void main(String[] args) {
             MongoMain test = new MongoMain();
             if(coll!=null){
                 test.saveData();
                 test.searchData();
                 test.updateData();
                 test.deleteData();
             }
         }  

         /**
          * 保存数据
          */
         public void saveData(){
             //录入学生1的信息
             BasicDBObject stu1 = new BasicDBObject();
             stu1.put("name", "jack");
             stu1.put("age", "25");
             BasicDBObject sight1 = new BasicDBObject();
             sight1.put("left", 1.5);
             sight1.put("right", 1.2);
             stu1.put("sight", sight1);  

             //录入学生2的信息
             BasicDBObject stu2 = new BasicDBObject();
             stu2.put("name", "lucy");
             stu2.put("age", "22");
             BasicDBObject sight2 = new BasicDBObject();
             sight2.put("left", 1.0);
             sight2.put("right", 1.3);
             stu2.put("sight", sight2);  

             //注意：不能直接对sight赋值{left:1.0,right:1.3}  

             coll.insert(stu1);
             coll.insert(stu2);
         }  

         /**
          * 查询数据
          */
         public void searchData(){
             System.out.println("=======================");
             //show collections
             //获取数据库下所有的collection，不显示无数据的collection
             Set<String> colls = db.getCollectionNames();
             showData(colls);  

             System.out.println("=======================");  

             //查询coll中全部记录
             DBCursor ite = coll.find();
             showData(ite);  

             System.out.println("=======================");  

             //获取第一条记录
             DBObject o = coll.findOne();
             System.out.println(o);  

             System.out.println("=======================");  

             //统计colletion的数据条数
             System.out.println(coll.getCount());  

             System.out.println("=======================");  

             //查询 name为jack的对象
             BasicDBObject query = new BasicDBObject();
             query.put("name", "jack");
             DBCursor it = coll.find(query);
             showData(it);  

             System.out.println("=======================");  

             //查询age小于30，age不等于20的对象
             BasicDBObject query2 = new BasicDBObject();
             query2.put("age", new BasicDBObject("$lt", 30));
             query2.put("age", new BasicDBObject("$ne", 20));
             DBCursor it2 = coll.find(query2);
             showData(it2);
         }  

         /**
          * 修改数据
          */
         public void updateData(){
             BasicDBObject query = new BasicDBObject();
             query.put("name", "lucy");
             //这里的new_info对象一定要是find出的而不是new的，否则多字段的情况下就会丢失其它字段信息
             DBObject new_info = coll.findOne(query);  

             //方法一（缺点，必须把2个值都put进去）
             BasicDBObject sight = new BasicDBObject();
             sight.put("left", 1.3);
             sight.put("right", 1.3);
             new_info.put("sight", sight);  

             //方法二（优点，只需设置要修改的字段的值）
             DBObject obj = (DBObject)new_info.get("sight");
             obj.put("right", 1.5);  

             coll.update(query, new_info);
         }  

         /**
          * 删除数据
          */
         public void deleteData(){
             BasicDBObject data = new BasicDBObject();
             //删除名称为lucy的记录
             data.put("name", "lucy");
             //传入[空实例]删除所有
             coll.remove(data);
         }  

         /**
          * 遍历显示结果
          * @param result
          */
         @SuppressWarnings("rawtypes")
         public void showData(Iterable result){
             Iterator it = result.iterator();
             while(it.hasNext())
             {
                 System.out.println(it.next());
             }
         }
     }