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镇江网站开发公司建立一个网站需要多少钱?

news 2025/7/14 4:24:06
镇江网站开发公司,建立一个网站需要多少钱?,广东佛山现在疫情严重吗,网站服务器建设新建库 新建表 插入点数据 先不用MVC模式写功能,来看下缺点是什么 新建一个空项目 选项项目使用的JDK 自己的IDEA总是要重启下 新建模块 因maven还没教 添加框架支持 添加后项目多了这些 添加些必要依赖 这里注意下,如果导入jar包不对可以重新导入下或者是jar包本身出了问…

新建库

新建表

插入点数据

先不用MVC模式写功能,来看下缺点是什么

新建一个空项目

选项项目使用的JDK

自己的IDEA总是要重启下

新建模块

因maven还没教

添加框架支持

添加后项目多了这些

添加些必要依赖  这里注意下,如果导入jar包不对可以重新导入下或者是jar包本身出了问题

添加页面

配置Tomcat

启动

请求地址  因现在没有后端

现在写后端 并测试

解决控制台输出乱码问题

System.out输出乱码

需要用到JDBC连接Mysql数据库

导入Mysql驱动jar包

java web项目  一般会在WEB-INF下有个lib用来放Tomcat内没有,外部引入的依赖

可以创建个lib目录  然后将jar包复制进来

具体代码

package com.bank.web;import com.bank.exception.AppException;
import com.bank.exception.MoneyNotEnoughException;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.sql.*;
import java.util.Locale;/*** 在不使用MVC架构模式的前提下,完成银行账户转账* 分析这个程序存在哪些问题?* @author hrui* @date 2023/8/31 23:06*/
@WebServlet("/transfer")
public class AccountTransferServlet extends HttpServlet {@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//获取响应流对象resp.setContentType("text/html;charset=UTF-8");PrintWriter writer = resp.getWriter();//获取前端传来的参数String fromActno = req.getParameter("fromActno");String toActno = req.getParameter("toActno");double money = Double.parseDouble(req.getParameter("money"));
//        System.out.println("转出账户:"+fromActno);
//        System.out.println("转入账户:"+fromActno);
//        System.out.println("转账金额:"+fromActno);//编写转账的业务逻辑代码,连接数据库,进行转账操作//1.转账之前要判断转出账户的余额是否充足Connection conn=null;PreparedStatement ps=null;//PreparedStatement ps2=null;ResultSet rs=null;try {//注册驱动Class.forName("com.mysql.cj.jdbc.Driver");//获取连接conn = DriverManager.getConnection("xxx", "xxx", "xxx");conn.setAutoCommit(false);//获取执行对象String sql="select balance from t_act where actno=?";ps = conn.prepareStatement(sql);ps.setString(1, fromActno);//执行sql,返回结果集rs = ps.executeQuery();//获取结果集if(rs.next()){double balance = rs.getDouble("balance");if(balance<money){//余额不足(使用异常处理机制)throw new MoneyNotEnoughException("余额不足");}//程序能到这里,说明余额重组  不需要else//开始转账sql="update t_act set balance=balance-? where actno=?";ps = conn.prepareStatement(sql);ps.setDouble(1, money);ps.setString(2, fromActno);int count = ps.executeUpdate();//模拟异常String str=null;str.toString();sql="update t_act set balance=balance+? where actno=?";ps=conn.prepareStatement(sql);ps.setDouble(1, money);ps.setString(2, toActno);//累计count += ps.executeUpdate();if(count!=2){throw new AppException("app异常,请联系管理员");}}conn.commit();writer.print("转账成功");} catch (ClassNotFoundException | SQLException | MoneyNotEnoughException | AppException e) {try {if(conn!=null) {conn.rollback();}} catch (SQLException e1) {e1.printStackTrace();}e.printStackTrace();writer.print(e.getMessage());}finally {//释放资源,根据JDBC规范 从小到大if(rs!=null){try {rs.close();} catch (SQLException e) {e.printStackTrace();}}if(ps!=null){try {ps.close();} catch (SQLException e) {e.printStackTrace();}}if(conn!=null){try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}}
}

1>负责了数据接收

2>负责了核心业务处理

3>负责了数据库表中的CRUD操作(Create(增) Retrieve(查) Update(改) Delete(删))

4>负责了数据的页面展示

引起的缺点:

代码复用性差  比如查余额,可以抽取出来,单独放到一个方法

代码复用性差的原因,没有职能分工,独立组件的概念,代码之间耦合度高,扩展力差

操作数据库代码和业务逻辑混杂在一起,容易出错,无法专注于业务逻辑书写

下面以MVC的模式对上面代码改进

1.系统为什么要分层?

        希望专人干专事.各司其职.分工明确.这样可以降低耦合,扩展增强.复用增强

2.软件架构中,有一个非常著名的架构模式:MVC模式

M(Model:数据/业务)       V(View:视图/展示)       C(Controller:控制器/核心)

首先是对JDBC的封装

JDBC工具类

package com.bank.utils;import java.sql.*;
import java.util.ResourceBundle;/*** @author hrui* @date 2023/9/1 10:24*/
public class DBUtil {private static ResourceBundle bundle=ResourceBundle.getBundle("resources/jdbc");private static String driver=bundle.getString("driver");private static String url=bundle.getString("url");private static String username=bundle.getString("username");private static String password=bundle.getString("password");//不让创建对象,原因工具类方法一般都静态的,无需外部创建对象//为防止外部创建对象,构造私有化private DBUtil(){}//DBUtil类加载时注册驱动static{try {Class.forName(driver);} catch (ClassNotFoundException e) {e.printStackTrace();}}//没有使用连接池,直接创建的连接对象public static Connection getConnection() throws SQLException {Connection conn= DriverManager.getConnection(url,username,password);return conn;}public static void close(Connection conn, Statement statement, ResultSet rs){if(rs!=null){try {rs.close();} catch (SQLException e) {e.printStackTrace();}}if(statement!=null){try {statement.close();} catch (SQLException e) {e.printStackTrace();}}if(conn!=null){try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}
}

测试连接

封装实体类

package com.bank.mvc;import java.util.Objects;/*** 账户实体类,用于封装账户信息* POJO对象* 有的人也会把这种专门封装数据的对象,称为bean对象(javabean:咖啡豆)* 有的人也会把这种专门分装数据的对象,称为领域模型对象.domain对象.* pojo,bean,domain* @author hrui* @date 2023/9/1 15:34*/
public class Account {private Long id;private String actno;private Double balance;public Account() {}public Account(Long id, String actno, Double balance) {this.id = id;this.actno = actno;this.balance = balance;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getActno() {return actno;}public void setActno(String actno) {this.actno = actno;}public Double getBalance() {return balance;}public void setBalance(Double balance) {this.balance = balance;}@Overridepublic boolean equals(Object o) {if (this == o) return true;if (o == null || getClass() != o.getClass()) return false;Account acount = (Account) o;return id.equals(acount.id) && actno.equals(acount.actno) && balance.equals(acount.balance);}@Overridepublic int hashCode() {return Objects.hash(id, actno, balance);}@Overridepublic String toString() {return "Account{" +"id=" + id +", actno='" + actno + '\'' +", balance=" + balance +'}';}
}

编写DAO层

package com.bank.mvc;import com.bank.utils.DBUtil;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;/*** 负责Acount数据的增删改查* 1.什么是DAO*      Data Access Object(数据访问对象)* 2.DAO实际上是一种设计模式,属于JAVAEE的设计模式之一.(不是23种设计模式)* 3.DAO只负责数据库CRUD,没有任何业务逻辑* 4.没有任何业务逻辑,只负责表中数据增删改查,有一个特殊的称谓:DAO对象* @author hrui* @date 2023/9/1 12:39*/
public class AccountDao {public int insert(Account act){Connection conn=null;PreparedStatement ps=null;int count=0;try {conn= DBUtil.getConnection();String sql="insert into t_act(actno,balance) values (?,?)";ps=conn.prepareStatement(sql);ps.setString(1, act.getActno());ps.setDouble(2, act.getBalance());count=ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(conn,ps,null);}return count;}public int deleteByActno(Long id){Connection conn=null;PreparedStatement ps=null;int count=0;try {conn=DBUtil.getConnection();String sql="delete from t_act where id=?";ps=conn.prepareStatement(sql);ps.setLong(1, id);count = ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(conn,ps,null);}return count;}public int update(Account act){Connection conn=null;PreparedStatement ps=null;int count=0;try {conn=DBUtil.getConnection();String sql="update t_act set balance=? where id=?";ps=conn.prepareStatement(sql);ps.setDouble(1, act.getBalance());ps.setLong(2, act.getId());count = ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(conn,ps,null);}return count;}public Account selectBtActNo(String actno){Connection conn=null;PreparedStatement ps=null;ResultSet rs=null;Account account=new Account();try {conn=DBUtil.getConnection();String sql="select id,actno,balance from t_act where actno=?";ps=conn.prepareStatement(sql);ps.setString(1, actno);rs = ps.executeQuery();if(rs.next()){Long id=rs.getLong("id");String actno1=rs.getString("actno");Double balance=rs.getDouble("balance");account.setId(id);account.setActno(actno1);account.setBalance(balance);}} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(conn,ps,null);}return account;}public List<Account> selectAll(){Connection conn=null;PreparedStatement ps=null;ResultSet rs=null;List<Account> list=new ArrayList<>();try {conn=DBUtil.getConnection();String sql="select id,actno,balance from t_act ";ps=conn.prepareStatement(sql);rs = ps.executeQuery();while(rs.next()){Long id=rs.getLong("id");String actno=rs.getString("actno");Double balance=rs.getDouble("balance");Account account=new Account();account.setId(id);account.setActno(actno);account.setBalance(balance);list.add(account);}} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(conn,ps,null);}return list;}
}

原先在Servlet里

1>负责了数据接收

2>负责了狠心业务处理

3>负责了数据库表中数据CRUD操作

4>负责了页面数据展示

现在已经一层层分离了

两个异常类

用AccountSAervice来做业务处理

具体业务处理代码

package com.bank.mvc;import com.bank.exception.AppException;
import com.bank.exception.MoneyNotEnoughException;/*** Service:业务* 专门处理Account的业务处理类* 该类只专注业务处理* 主要专注于MVC模式,不需要专注于取什么名字  xxx都可以* @author hrui* @date 2023/9/2 0:49*/
public class AccountService {private AccountDao accountDao=new AccountDao();/*** 完成转账的业务逻辑* @param fromActno* @param toActno* @param money*/public void transfer(String fromActno,String toActno,double money) throws MoneyNotEnoughException, AppException {//查询余额是否充足Account fromAccount = accountDao.selectBtActNo(fromActno);if(fromAccount.getBalance()<money){throw new MoneyNotEnoughException("余额不足");}//程序到这里说明余额够Account toAct=accountDao.selectBtActNo(toActno);//修改余额fromAccount.setBalance(fromAccount.getBalance()-money);toAct.setBalance(toAct.getBalance()+money);//更新数据库int count=accountDao.update(fromAccount);count += accountDao.update(toAct);//count++;if(count!=2){throw new AppException("转账异常");}}}

servlet里做的就是调度

package com.bank.mvc;import com.bank.exception.AppException;
import com.bank.exception.MoneyNotEnoughException;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;/*** 让AcountServlet做为Controller  调度员* 负责调度其他组件* @author hrui* @date 2023/9/1 12:27*/
@WebServlet("/transfer")
public class AccountServlet extends HttpServlet {@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//获取前端传来的参数String fromActno = req.getParameter("fromActno");String toActno = req.getParameter("toActno");double money = Double.parseDouble(req.getParameter("money"));//调用业务方法处理业务(调度Model处理业务)AccountService accountService=new AccountService();try {accountService.transfer(fromActno,toActno,money);resp.sendRedirect(req.getContextPath()+"/success.jsp");} catch (MoneyNotEnoughException e) {e.printStackTrace();resp.sendRedirect(req.getContextPath()+"/moneynoenough.jsp");} catch (AppException e) {e.printStackTrace();resp.sendRedirect(req.getContextPath()+"/error.jsp");}}
}

三个页面显示

 

上面代码缺少事务控制,一般事务都在service进行控制

一般来说是在service层去开启事务  提交事务

这里事务管理,做的low的方式就是在业务层获取数据库连接对象,然后传进去,当然这样做的话,在DAO层就不要在finally中关闭事务了.传个null就行,在Service中开启事务,并在Service中提交事务,在Service中的finally中关闭连接

上代码

DAO

package com.bank.mvc;import com.bank.utils.DBUtil;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;/*** 负责Acount数据的增删改查* 1.什么是DAO*      Data Access Object(数据访问对象)* 2.DAO实际上是一种设计模式,属于JAVAEE的设计模式之一.(不是23种设计模式)* 3.DAO只负责数据库CRUD,没有任何业务逻辑* 4.没有任何业务逻辑,只负责表中数据增删改查,有一个特殊的称谓:DAO对象* @author hrui* @date 2023/9/1 12:39*/
public class AccountDao {public int insert(Account act,Connection conn){PreparedStatement ps=null;int count=0;try {String sql="insert into t_act(actno,balance) values (?,?)";ps=conn.prepareStatement(sql);ps.setString(1, act.getActno());ps.setDouble(2, act.getBalance());count=ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return count;}public int deleteByActno(Long id,Connection conn){PreparedStatement ps=null;int count=0;try {String sql="delete from t_act where id=?";ps=conn.prepareStatement(sql);ps.setLong(1, id);count = ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return count;}public int update(Account act,Connection conn){PreparedStatement ps=null;int count=0;try {String sql="update t_act set balance=? where id=?";ps=conn.prepareStatement(sql);ps.setDouble(1, act.getBalance());ps.setLong(2, act.getId());count = ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return count;}public Account selectBtActNo(String actno,Connection conn){PreparedStatement ps=null;ResultSet rs=null;Account account=new Account();try {String sql="select id,actno,balance from t_act where actno=?";ps=conn.prepareStatement(sql);ps.setString(1, actno);rs = ps.executeQuery();if(rs.next()){Long id=rs.getLong("id");String actno1=rs.getString("actno");Double balance=rs.getDouble("balance");account.setId(id);account.setActno(actno1);account.setBalance(balance);}} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return account;}public List<Account> selectAll(Connection conn){Connection conn=null;PreparedStatement ps=null;ResultSet rs=null;List<Account> list=new ArrayList<>();try {String sql="select id,actno,balance from t_act ";ps=conn.prepareStatement(sql);rs = ps.executeQuery();while(rs.next()){Long id=rs.getLong("id");String actno=rs.getString("actno");Double balance=rs.getDouble("balance");Account account=new Account();account.setId(id);account.setActno(actno);account.setBalance(balance);list.add(account);}} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return list;}
}

Service

package com.bank.mvc;import com.bank.exception.AppException;
import com.bank.exception.MoneyNotEnoughException;
import com.bank.utils.DBUtil;import java.sql.Connection;
import java.sql.SQLException;/*** Service:业务* 专门处理Account的业务处理类* 该类只专注业务处理* 主要专注于MVC模式,不需要专注于取什么名字  xxx都可以* @author hrui* @date 2023/9/2 0:49*/
public class AccountService {private AccountDao accountDao=new AccountDao();/*** 完成转账的业务逻辑* @param fromActno* @param toActno* @param money*/public void transfer(String fromActno,String toActno,double money) throws MoneyNotEnoughException, AppException {//Service层控制事务//开启事务(需要用到Connection对象)Connection conn=null;try {conn = DBUtil.getConnection();conn.setAutoCommit(false);//查询余额是否充足Account fromAccount = accountDao.selectBtActNo(fromActno,conn);if(fromAccount.getBalance()<money){throw new MoneyNotEnoughException("余额不足");}//程序到这里说明余额够Account toAct=accountDao.selectBtActNo(toActno,conn);//修改余额fromAccount.setBalance(fromAccount.getBalance()-money);toAct.setBalance(toAct.getBalance()+money);//更新数据库int count=accountDao.update(fromAccount,conn);count += accountDao.update(toAct,conn);
//        String str=null;
//        str.toString();//或者//count++;  会向用户提示转账失败  但是转账确已经完成   或者1账户减款而2账户没有加的情况if(count!=2){throw new AppException("转账异常");}conn.commit();} catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(conn,null,null);}}}

 

但上面代码有点low

如何解决Connection传参问题

用ThreadLocal

改造代码

DBUtil

package com.bank.utils;import java.sql.*;
import java.util.ResourceBundle;/*** @author hrui* @date 2023/9/1 10:24*/
public class DBUtil {private static ResourceBundle bundle=ResourceBundle.getBundle("resources/jdbc");private static String driver=bundle.getString("driver");private static String url=bundle.getString("url");private static String username=bundle.getString("username");private static String password=bundle.getString("password");//不让创建对象,原因工具类方法一般都静态的,无需外部创建对象//为防止外部创建对象,构造私有化private DBUtil(){}//DBUtil类加载时注册驱动static{try {Class.forName(driver);} catch (ClassNotFoundException e) {e.printStackTrace();}}private static ThreadLocal<Connection> local=new ThreadLocal<>();//没有使用连接池,直接创建的连接对象public static Connection getConnection() throws SQLException {Connection conn=local.get();if(conn==null) {conn = DriverManager.getConnection(url, username, password);local.set(conn);}return conn;}public static void close(Connection conn, Statement statement, ResultSet rs){if(rs!=null){try {rs.close();} catch (SQLException e) {e.printStackTrace();}}if(statement!=null){try {statement.close();} catch (SQLException e) {e.printStackTrace();}}if(conn!=null){try {conn.close();//注意:关闭连接时候移除  Tomcat是支持线程池的,不从当前线程里移除 有可能下次别人拿到了,但是conn已经关闭local.remove();} catch (SQLException e) {e.printStackTrace();}}}
}

将AccountDao恢复原状,还是从DBUtil里取Connection,但是不需要再传参数,注意finally里面Connection照样传null,原因:还是需要在Service层进行事务控制

package com.bank.mvc;import com.bank.utils.DBUtil;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;/*** 负责Acount数据的增删改查* 1.什么是DAO*      Data Access Object(数据访问对象)* 2.DAO实际上是一种设计模式,属于JAVAEE的设计模式之一.(不是23种设计模式)* 3.DAO只负责数据库CRUD,没有任何业务逻辑* 4.没有任何业务逻辑,只负责表中数据增删改查,有一个特殊的称谓:DAO对象* @author hrui* @date 2023/9/1 12:39*/
public class AccountDao {public int insert(Account act){PreparedStatement ps=null;int count=0;try {Connection  conn= DBUtil.getConnection();String sql="insert into t_act(actno,balance) values (?,?)";ps=conn.prepareStatement(sql);ps.setString(1, act.getActno());ps.setDouble(2, act.getBalance());count=ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return count;}public int deleteByActno(Long id){PreparedStatement ps=null;int count=0;try {Connection  conn= DBUtil.getConnection();String sql="delete from t_act where id=?";ps=conn.prepareStatement(sql);ps.setLong(1, id);count = ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return count;}public int update(Account act){PreparedStatement ps=null;int count=0;try {Connection conn=DBUtil.getConnection();String sql="update t_act set balance=? where id=?";ps=conn.prepareStatement(sql);ps.setDouble(1, act.getBalance());ps.setLong(2, act.getId());count = ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return count;}public Account selectBtActNo(String actno){PreparedStatement ps=null;ResultSet rs=null;Account account=new Account();try {Connection conn=DBUtil.getConnection();String sql="select id,actno,balance from t_act where actno=?";ps=conn.prepareStatement(sql);ps.setString(1, actno);rs = ps.executeQuery();if(rs.next()){Long id=rs.getLong("id");String actno1=rs.getString("actno");Double balance=rs.getDouble("balance");account.setId(id);account.setActno(actno1);account.setBalance(balance);}} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return account;}public List<Account> selectAll(){PreparedStatement ps=null;ResultSet rs=null;List<Account> list=new ArrayList<>();try {Connection conn=DBUtil.getConnection();String sql="select id,actno,balance from t_act ";ps=conn.prepareStatement(sql);rs = ps.executeQuery();while(rs.next()){Long id=rs.getLong("id");String actno=rs.getString("actno");Double balance=rs.getDouble("balance");Account account=new Account();account.setId(id);account.setActno(actno);account.setBalance(balance);list.add(account);}} catch (SQLException e) {e.printStackTrace();throw new RuntimeException(e);}finally {DBUtil.close(null,ps,null);}return list;}
}

业务层

package com.bank.mvc;import com.bank.exception.AppException;
import com.bank.exception.MoneyNotEnoughException;
import com.bank.utils.DBUtil;import java.sql.Connection;
import java.sql.SQLException;/*** Service:业务* 专门处理Account的业务处理类* 该类只专注业务处理* 主要专注于MVC模式,不需要专注于取什么名字  xxx都可以* @author hrui* @date 2023/9/2 0:49*/
public class AccountService {private AccountDao accountDao=new AccountDao();/*** 完成转账的业务逻辑* @param fromActno* @param toActno* @param money*/public void transfer(String fromActno,String toActno,double money) throws MoneyNotEnoughException, AppException {try(Connection conn= DBUtil.getConnection()){conn.setAutoCommit(false);//查询余额是否充足Account fromAccount = accountDao.selectBtActNo(fromActno);if(fromAccount.getBalance()<money){throw new MoneyNotEnoughException("余额不足");}//程序到这里说明余额够Account toAct=accountDao.selectBtActNo(toActno);//修改余额fromAccount.setBalance(fromAccount.getBalance()-money);toAct.setBalance(toAct.getBalance()+money);//更新数据库int count=accountDao.update(fromAccount);count += accountDao.update(toAct);
//        String str=null;
//        str.toString();//或者//count++;  会向用户提示转账失败  但是转账确已经完成   或者1账户减款而2账户没有加的情况if(count!=2){throw new AppException("转账异常");}conn.commit();} catch (SQLException e) {e.printStackTrace();throw new AppException("转账异常");}}}

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