动态代理加持事务的转账案例

Posted 2021-03-02 jianzha

此案例 使用动态代理 + 事务控制 完成转账

当有异常发生时，加在业务层中的事务会回滚，避免出现转出方钱已经转出，但接收放没有收到钱

pom依赖

<dependencies>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>5.2.4.RELEASE</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/commons-dbutils/commons-dbutils -->
    <dependency>
        <groupId>commons-dbutils</groupId>
        <artifactId>commons-dbutils</artifactId>
        <version>1.7</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.6</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/com.mchange/c3p0 -->
    <dependency>
        <groupId>com.mchange</groupId>
        <artifactId>c3p0</artifactId>
        <version>0.9.5.3</version>
    </dependency>

    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.13</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-test -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-test</artifactId>
        <version>5.2.4.RELEASE</version>
        <scope>test</scope>
    </dependency>
</dependencies>

POJO类

public class Account implements Serializable {

    private Integer id;
    private String name;
    private Float money;

    public Account() {
    }


    public Account(String name, Float money) {
        this.name = name;
        this.money = money;
    }

    public Account(Integer id, String name, Float money) {
        this.id = id;
        this.name = name;
        this.money = money;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Float getMoney() {
        return money;
    }

    public void setMoney(Float money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Account{" +
                "id=" + id +
                ", name=‘" + name + ‘‘‘ +
                ", money=" + money +
                ‘}‘;
    }
}

持久层接口

public interface AccountDao {

    /**
     * 查询所有
     * @return
     */
    List<Account> findAllAccount();

    /**
     * 查询一个
     */
    Account findAccountById(Integer accountId);

    /**
     * 保存
     */
    void saveAccount(Account account);

    /**
     * 更新
     */
    void updateAccount(Account account);

    /**
     * 删除
     */
    void deleteAccount(Integer accountId);

    /**
     * 根据名称查询账户
     * @param accountName
     * @return
     */
    Account findAccountByName(String accountName);
}

持久层接口的实现类

/**
 * 账户的持久层实现类
 */
public class AccountDaoImpl implements AccountDao {

    private QueryRunner runner;

    private ConnectionUtils connectionUtils;

    public void setConnectionUtils(ConnectionUtils connectionUtils) {
        this.connectionUtils = connectionUtils;
    }

    public void setRunner(QueryRunner runner) {
        this.runner = runner;
    }

    public List<Account> findAllAccount() {
        try {
            return runner.query(connectionUtils.getThreadConnection(),"select * from account", new BeanListHandler<Account>(Account.class));
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public Account findAccountById(Integer accountId) {
        try {
            return runner.query(connectionUtils.getThreadConnection(),"select * from account where id = ?", new BeanHandler<Account>(Account.class), accountId);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public void saveAccount(Account account) {
        try {
            runner.update(connectionUtils.getThreadConnection(),"insert into account(name, money) values(?, ?)", account.getName(), account.getMoney());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public void updateAccount(Account account) {
        try {
            runner.update(connectionUtils.getThreadConnection(),"update account set name=?, money =? where id = ?", account.getName(), account.getMoney(), account.getId());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public void deleteAccount(Integer accountId) {
        try {
            runner.update(connectionUtils.getThreadConnection(),"delete from account  where id = ?", accountId);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public Account findAccountByName(String accountName) {
        try {
            List<Account> accounts = runner.query(connectionUtils.getThreadConnection(),"select * from account where name = ?", new BeanListHandler<Account>(Account.class), accountName);
            if (accounts == null || accounts.size() == 0) {
                return null;
            }
            if(accounts.size() > 1){
                throw new RuntimeException("结果集不唯一，数据有问题");
            }
            return accounts.get(0);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

业务层接口

/**
 * 账户的业务层接口
 */
public interface AccountService {

    /**
     * 查询所有
     * @return
     */
    List<Account> findAllAccount();

    /**
     * 查询一个
     */
    Account findAccountById(Integer accountId);

    /**
     * 保存
     */
    void saveAccount(Account account);

    /**
     * 更新
     */
    void updateAccount(Account account);

    /**
     * 删除
     */
    void deleteAccount(Integer accountId);


    /**
     * 转账
     * @param sourceName 转出账户名称
     * @param targetName 转入账户名称
     * @param money      转账金额
     */
    void transfer(String sourceName, String targetName, Float money);
}

业务层接口的实现类

/**
 * 账户的业务层实现类
 */
public class AccountServiceImpl implements AccountService {

    private AccountDao accountDao;

    public void setAccountDao(AccountDao accountDao) {

        this.accountDao = accountDao;
    }

    public List<Account> findAllAccount() {

        return accountDao.findAllAccount();
    }

    public Account findAccountById(Integer accountId) {

        return findAccountById(accountId);
    }

    public void saveAccount(Account account) {

        accountDao.saveAccount(account);
    }

    public void updateAccount(Account account) {

        accountDao.updateAccount(account);
    }

    public void deleteAccount(Integer accountId) {

        accountDao.deleteAccount(accountId);
    }

    public void transfer(String sourceName, String targetName, Float money) {

        //执行操作
        //1.根据名称查询转出账户
        Account source = accountDao.findAccountByName(sourceName);
        //2.根据名称查询转入账户
        Account target = accountDao.findAccountByName(targetName);
        //3.转出账户减钱
        source.setMoney(source.getMoney() - money);
        //4.转入账户价钱
        target.setMoney(target.getMoney() + money);
        //5.更新转出账户
        accountDao.updateAccount(source);
        //6.更细转入账户
        int i = 1/0;

        accountDao.updateAccount(target);
    }
}

连接的工具类，用于从数据源中获取一个连接，并且实现和线程的绑定

/**
 * 连接的工具类，它用于从数据源中获取一个连接，并且实现和线程的绑定
 */
public class ConnectionUtils {

    private ThreadLocal<Connection> tl = new ThreadLocal<Connection>();

    private DataSource dataSource;

    public void setDataSource(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    /**
     * 获取当前线程上的连接
     */
    public Connection getThreadConnection(){
        try {
            //1.先从ThreadLocal上获取
            Connection conn = tl.get();
            //2.判断当前线程上是否有连接
            if(conn == null){
                //3.从数据源中获取一个连接，并且存入ThreadLocal中
                conn = dataSource.getConnection();
                tl.set(conn);
            }
            //4.返回当前线程上的连接
            return conn;
        } catch (SQLException e) {
           throw new RuntimeException(e);
        }
    }


    /**
     * 线程与连接解绑
     */
    public void removeConnection(){
        tl.remove();
    }
}

和事务管理相关的工具类，包含开启事务、提交事务、回滚事务和释放连接

/**
 * 和事务管理相关的工具类，包含开启事务、提交事务、回滚事务和释放连接
 */
public class TransactionManager {

    private ConnectionUtils connectionUtils;

    public void setConnectionUtils(ConnectionUtils connectionUtils) {

        this.connectionUtils = connectionUtils;
    }

    /**
     * 开启事务
     */
    public void beginTransaction(){
        try {
            connectionUtils.getThreadConnection().setAutoCommit(false);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 提交事务
     */
    public void commit(){
        try {
            connectionUtils.getThreadConnection().commit();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 回滚事务
     */
    public void rollback(){
        try {
            connectionUtils.getThreadConnection().rollback();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 关闭事务
     */
    public void release(){
        try {
            connectionUtils.getThreadConnection().close();
            connectionUtils.removeConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

}

用于创建Service的代理对象工厂

/**
 * 用于创建Service的代理对象工厂
 */
public class BeanFactory {

    private AccountService accountService;

    public final void setAccountService(AccountService accountService) {
        this.accountService = accountService;
    }

    private TransactionManager txManager;

    public void setTxManager(TransactionManager txManager) {
        this.txManager = txManager;
    }

    /**
     * 获取Service代理对象
     * @return
     */
    public AccountService getAccountService() {
        AccountService proxy = (AccountService) Proxy.newProxyInstance(accountService.getClass().getClassLoader(), accountService.getClass().getInterfaces(), new InvocationHandler() {

            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                Object rtValue = null;
                try {
                    //开启事务
                    txManager.beginTransaction();

                    rtValue = method.invoke(accountService, args);

                    //提交事务
                    txManager.commit();
                    //返回结果
                    return rtValue;
                } catch (Exception e) {
                    //回滚操作
                    txManager.rollback();
                    throw new RuntimeException(e);
                } finally {
                    //释放连接
                    txManager.release();
                }
            }
        });
        return proxy;
    }
}

bean.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <!--配置代理service-->
    <bean id="proxyAccountService" factory-bean="beanFactory" factory-method="getAccountService"></bean>

    <!--配置beanFactory-->
    <bean id="beanFactory" class="com.jz.factory.BeanFactory">
        <property name="accountService" ref="accountService"/>
        <property name="txManager" ref="txManager"/>
    </bean>

    <!--配置Service-->
    <bean id="accountService" class="com.jz.service.impl.AccountServiceImpl">
        <!--注入dao-->
        <property name="accountDao" ref="accountDao"/>
    </bean>

    <!--配置Dao-->
    <bean id="accountDao" class="com.jz.dao.impl.AccountDaoImpl">
        <!--注入QueryRunner-->
        <property name="runner" ref="runner"/>
        <!--注入ConnectionUtils-->
        <property name="connectionUtils" ref="connectionUtils"/>
    </bean>

    <!--配置QueryRunner-->
    <bean id="runner" class="org.apache.commons.dbutils.QueryRunner" scope="prototype"></bean>

    <!--配置数据源-->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <!--连接数据库的必备信息-->
        <property name="driverClass" value="com.mysql.jdbc.Driver"/>
        <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/spring_db"/>
        <property name="user" value="root"/>
        <property name="password" value="root"/>
    </bean>

    <!--配置Connection的工具类-->
    <bean id="connectionUtils" class="com.jz.utils.ConnectionUtils">
        <property name="dataSource" ref="dataSource"/>
    </bean>

    <!--配置事务管理-->
    <bean id="txManager" class="com.jz.utils.TransactionManager">
        <property name="connectionUtils" ref="connectionUtils"/>
    </bean>


</beans>

测试

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:bean.xml")
public class AccountServiceTest {

    @Autowired
    @Qualifier("proxyAccountService")
    private AccountService as;

    @Test
    public void testTransfer(){
        as.transfer("aaa", "bbb", 100f);
    }
}

架构