mongodb-api编程

一，mongodb-api 介绍

1， 连接类

DBClientConnection(bool _autoReconnect=false, DBClientReplicaSet* cp=0, double so_timeout=0)

参数：

1. _autoReconnect 自动重连
2. cp 副本集使用参数,可以不用关心
3. so_timeout 超时时间 单位 秒

2，连接函数

virtual bool connect(const char * hostname, string& errmsg)

参数：

1. hostname 主机名 ip:端口 默认端口 27017
2. errmsg 错误信息 传出

返回值：

false 代表失败
true 代表成功

DBClientConnection 继承与 DBClientBase ,该类内部包含增删改查四个接口

进行增删改查操作

通过api删除文档
删除文档
virtual void remove( const string &ns , Query q , bool justOne = 0 );
○ ns 集合名,填法 库名.集合名
○ q 删除条件 Query 是一个类
○ justOne 是否删除一条,默认false

class Query {
public:
BSONObj obj;
Query() : obj(BSONObj()) { }
Query(const BSONObj& b) : obj(b) { }
Query(const string &json);
Query(const char * json);

增加文档

virtual void insert( const string &ns , BSONObj obj , int flags=0);
○ ns 库名.集合名
○ obj 要插入的内容,核心对象,需要BSONObjBuilder构造, append函数 BSONObj obj()

#include "mongo/client/dbclient.h"#include "mongo/bson/bsonobj.h"#include "mongo/client/dbclientinterface.h"#include <set>#include <list>#include <string>#include <vector>#include "mongo/bson/bsonelement.h"#include "mongo/bson/stringdata.h"#include "mongo/bson/util/atomic_int.h"#include "mongo/bson/util/builder.h"#include <iostream>#include <string>//命令空间using namespace mongo;using namespace std;#define REMOVE 0#define INSERT 1int main(int argc, char *argv[]){    //创建连接类mongdb    DBClientConnection conn(false, 0, 3);    std::string errmsg;    //连接mongdb virtual bool connect(const char * hostname, string& errmsg)     if (!conn.connect("localhost:27017", errmsg))    {        cout << "connection error " << errmsg << endl;        return -1;    }#if  REMOVE    //删除数据    //virtual void remove( const string &ns , Query q , bool justOne = 0 );    Query q("{name:'王蓉'}");    //参数一：    conn.remove("songli.songli", q, false);#endif //  REMOVE#if INSERT    //插入数据    //virtual void insert( const string &ns , BSONObj obj , int flags=0);    BSONObjBuilder builder;    builder.append("id", 7);    builder.append("name", "杨艳2");    builder.append("age", 23);    conn.insert("songli.songli", builder.obj());    BSONObjBuilder b;    b << "id" << 6 << "name" << "王盼盼" << "age" << 23;    conn.insert("songli.songli", b.obj());    //virtual void insert( const string &ns , BSONObj obj , int flags=0);    conn.insert("songli.songli", BSON("id" << 9 << "name" << "巍盼盼" << "age" << "23"));    //     Query q("{id:10, name:'陈丽', age: 23}");    conn.insert( "songli.songli", q.obj);#endif // INSERT    ////查询语句    ////virtual BSONObj findOne(const string &ns, const Query& query, const BSONObj *fieldsToReturn = 0, int queryOptions = 0);    //Query find("db.songli.find({name:'陈丽'})");    //BSONObj obj = conn.findOne("songli.songli", find.obj);    //cout <<  obj.numStr(1) << endl;    printf("connection ok\n");    return 0;}

查询

修改文档
void update( const string &ns,
Query query,
BSONObj obj,
bool upsert = false, bool multi = false );
○ ns 库名.集合名
○ query 查询条件
○ obj 要修改的内容

实现查询文档
virtual auto_ptr query(const string &ns, Query query=Query(), int nToReturn = 0, int nToSkip = 0,
const BSONObj *fieldsToReturn = 0, int queryOptions = 0 , int batchSize = 0 )
○ ns 库名.集合名
○ query 查询条件
○ nToReturn 返回记录数
○ nToSkip 跳过记录数
○ fieldsToReturn 返回的字段
○ queryOptions 查询选项
○ batchSize 批量大小

auto_ptr auto_ptr是智能指针,自动释放DBClientCursor内存区域

关注
DBClientCursor 类
可以先调用more 判断是否有next ,得到BSONObj next(); 对象
问题的核心就是如何解析 BSONObj
解析 BSONObj的方式 getFiled 获得 BSONElement对象 ,这个对象各种转换函数得到具体的value
可以先用hasField判断一下字段是否存在

//g++ -o testmongo testmongo.cpp -lmongoclient -lboost_thread -lboost_filesystem -lboost_program_options -L/home/itcast/driver/boost/lib -L/home/itcast/driver/mongo/lib -I/home/itcast/driver/mongo/include -I/home/itcast/driver/boost/include#include <iostream>   #include "mongo/client/dbclient.h"   char dbhost[20]="localhost"; using namespace mongo;using namespace std;void printIfAge(DBClientConnection& c, int age) {  auto_ptr<DBClientCursor> cursor = c.query("tutorial.persons", QUERY( "age" << age ).sort("name") );      while( cursor->more() ) {          BSONObj p = cursor->next();          cout << p.getStringField("name") << endl;      }  }  void run() {      DBClientConnection c;      c.connect(dbhost);       cout << "connected ok" << endl;      BSONObj p = BSON( "name" << "Joe" << "age" << 33 );      c.insert("tutorial.persons", p); /**< 向person表中插入数据 */      p = BSON( "name" << "Jane" << "age" << 40 );      c.insert("tutorial.persons", p);      p = BSON( "name" << "Abe" << "age" << 33 );      c.insert("tutorial.persons", p);      p = BSON( "name" << "Samantha" << "age" << 21 << "city" << "Los Angeles" << "state" << "CA" );      c.insert("tutorial.persons", p);      c.ensureIndex("tutorial.persons", fromjson("{age:1}"));      cout << "count:" << c.count("tutorial.persons") << endl; /**< 显示person表中的数据数目 */      auto_ptr<DBClientCursor> cursor = c.query("tutorial.persons", BSONObj());      while( cursor->more() ) {          cout << cursor->next().toString() << endl;      }      cout << "\nprintifage:\n";      printIfAge(c, 33);  }  int main(int argc,char *argv[]) {      if(argc == 2)    {        memset(dbhost,0x00,sizeof(dbhost));        strcpy(dbhost,argv[1]);        printf("connect to dbhost:[%s]\n",dbhost);    }    else    {        printf("connect to dbhost:[%s]\n",dbhost);        printf("if you need to connet to remote service,please input ip!\n");    }    try {          run();      }      catch( DBException &e ) {          cout << "caught " << e.what() << endl;      }      return 0;  }