以前學ssh ssm都有事務管理service層通過applicationContext.xml配置，所有service方法都加上事務操作；

用來保證一致性，即service方法里的多個dao操作，要么同時成功，要么同時失敗；

springboot下的話 搞一個@Transactional即可；

我們這里搞一個實例，轉賬實例，A用戶轉賬給B用戶xx元

設計如下：

Account類

package com.java1234.entity;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
 
@Entity
@Table(name="t_account")
public class Account {
 
    @Id
    @GeneratedValue
    private Integer id;
     
    @Column(length=50)
    private String userName;
     
    private float balance;
 
    public Integer getId() {
        return id;
    }
 
    public void setId(Integer id) {
        this.id = id;
    }
 
    public String getUserName() {
        return userName;
    }
 
    public void setUserName(String userName) {
        this.userName = userName;
    }
 
    public float getBalance() {
        return balance;
    }
 
    public void setBalance(float balance) {
        this.balance = balance;
    }
     
     
}

id 編號 userName用戶名 balance余額

運行啟動類，數據庫里我們加兩個數據

新建AccountDao接口

package com.java1234.dao;
 
import org.springframework.data.jpa.repository.JpaRepository;
 
import com.java1234.entity.Account;
 
/**
 * 賬戶Dao接口
 * @author user
 *
 */
public interface AccountDao extends JpaRepository<Account, Integer>{
 
}

AccountService接口

package com.java1234.service;
 
/**
 * 帳號Service接口
 * @author user
 *
 */
public interface AccountService {
 
    public void transferAccounts(int fromUser,int toUser,float account);
 
}

AccountServiceImpl接口實現類

package com.java1234.service.impl;
 
import javax.annotation.Resource;
import javax.transaction.Transactional;
 
import org.springframework.stereotype.Service;
 
import com.java1234.dao.AccountDao;
import com.java1234.entity.Account;
import com.java1234.service.AccountService;
 
/**
 * 帳號Service實現類
 * @author user
 *
 */
@Service("accountService")
public class AccountServiceImpl implements AccountService{
 
    @Resource
    private AccountDao accountDao;
 
    public void transferAccounts(int fromUserId, int toUserId, float account) {
        Account fromUserAccount=accountDao.getOne(fromUserId);
        fromUserAccount.setBalance(fromUserAccount.getBalance()-account);
        accountDao.save(fromUserAccount); // fromUser扣錢
         
        Account toUserAccount=accountDao.getOne(toUserId);
        toUserAccount.setBalance(toUserAccount.getBalance()+account);
        accountDao.save(toUserAccount); // toUser加錢
    }
     
}

AccountController類

package com.java1234;
 
import javax.annotation.Resource;
 
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
 
import com.java1234.service.AccountService;
 
/**
 * 賬戶Controoler類
 * @author user
 *
 */
@RestController
@RequestMapping("/account")
public class AccountController {
 
    @Resource
    private AccountService accountService;
     
    @RequestMapping("/transfer")
    public String transferAccounts(){
        try{
            accountService.transferAccounts(1, 2, 200);
            return "ok";
        }catch(Exception e){
            return "no";
        }
    }
}

我們執行啟動類

瀏覽器輸入：http://localhost:8888/account/transfer

運行OK

OK 我們先把數據恢復到700  300

現在我們把service層方法改下 

這時候 扣錢dao能執行成功  加錢操作執行不了了 因為前面會報錯。

我們重啟啟動類

瀏覽器輸入：http://localhost:8888/account/transfer

運行NO