自定义事务管理器TransactionManager对象

以aop思想，实现事务管理切面

1. DataSource注册容器

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd"><!--开启包扫描注解--><context:component-scan base-package="com.hang"/><!--导入jdbc.properties文件--><context:property-placeholder location="classpath:jdbc.properties"/><!--配置druid数据库连接池--><bean class="com.alibaba.druid.pool.DruidDataSource" id="dataSource"><property name="url" value="${jdbc.url}"/><property name="driverClassName" value="${jdbc.driver}"/><property name="username" value="${jdbc.username}"/><property name="password" value="${jdbc.password}"/><property name="initialSize" value="${jdbc.initialSize}"/></bean><!--开启aop注解--><aop:aspectj-autoproxy/>
</beans>

2. 定义事务管理器MyTransactionManager对象

定义事务管理器MyTransactionManager对象，注册进spring容器。(依赖Druid连接池，获取连接，开始事务，提交事务，回滚事务，关闭连接)

@Component
public class MyTransactionManager {@Autowiredprivate DataSource dataSource;// 获取连接public Connection getConnection(){Connection conn = null;try {conn = dataSource.getConnection();ConnUtil.setConn(conn);} catch (SQLException e) {e.printStackTrace();}return conn;}// 开始事务public void openTransaction(){try {ConnUtil.getConn().setAutoCommit(false);} catch (SQLException e) {e.printStackTrace();}}// 提交事务public void openCommit(){try {ConnUtil.getConn().commit();} catch (SQLException e) {e.printStackTrace();}}// 回滚事务public void openRollback(){try {ConnUtil.getConn().rollback();} catch (SQLException e) {e.printStackTrace();}}// 关闭连接public void closeConnection(){Connection conn = ConnUtil.getConn();try {if (conn!=null){conn.close();}} catch (SQLException e) {e.printStackTrace();}}public DataSource getDataSource() {return dataSource;}public void setDataSource(DataSource dataSource) {this.dataSource = dataSource;}
}

3. 定义dao接口

定义dao接口，使用jdbc定义dao实现，不要使用mybatis，把dao实现注册spring容器(curd)

public interface SysUserDao {SysUser queryById(Integer id) throws Exception;Integer insert(SysUser sysUser) throws Exception;int update(SysUser sysUser);int deleteById(Long id);
}

@Repository
public class SysUserDaoImpl implements SysUserDao {private Connection conn = null;private ResultSet rs = null;private PreparedStatement ps = null;@Overridepublic SysUser queryById(Integer id) throws Exception {SysUser sysUser = null;conn = ConnUtil.getConn();ps = conn.prepareStatement("select * from db_stage_three.sys_user where  id = ?");ps.setInt(1, id);rs = ps.executeQuery();if (rs.next()) {sysUser = new SysUser();sysUser.setUname("hello");}return sysUser;}@Overridepublic Integer insert(SysUser sysUser) throws Exception {Integer result = null;conn = ConnUtil.getConn();ps = conn.prepareStatement("insert into db_stage_three.sys_user ( uname, uphone, upwd, uwechat, uemail, role_id, dept_id) values (?,?,?,?,?,?,?)");ps.setString(1, sysUser.getUname());ps.setString(2, sysUser.getUphone());ps.setString(3, sysUser.getUpwd());ps.setString(4, sysUser.getUwechat());ps.setString(5, sysUser.getUemail());ps.setInt(6, sysUser.getRoleId());ps.setInt(7, sysUser.getDeptId());result = ps.executeUpdate();return result;}@Overridepublic int update(SysUser sysUser) {return 0;}@Overridepublic int deleteById(Long id) {return 0;}}

4. 定义service接口

定义service接口，定义service实现，注册容器(curd)。

public interface SysUserService {SysUser queryById(Integer id);SysUser insert(SysUser sysUser);
}

@Service()
public class SysUserServiceImpl implements SysUserService {@Resourceprivate SysUserDao sysUserDao;@Overridepublic SysUser queryById(Integer id) {Connection conn = null;// 织入获取连接，开始事务,提交事务,回滚事务,关闭连接SysUser sysUser = null;try {sysUser = this.sysUserDao.queryById(id);} catch (Exception e) {e.printStackTrace();}return sysUser;}@Transaction // 使用基于自定义注解方式定义切入点表达式@Overridepublic SysUser insert(SysUser sysUser) {try {this.sysUserDao.insert(sysUser);} catch (Exception e) {e.printStackTrace();}int i = 1/0;return sysUser;}}

自定义注解代码如下：

@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Transaction {}

5. 定义事务切面(依赖MyTransactionManag)

定义事务切面(依赖MyTransactionManag)，定义环绕通知，织入到service层的数据库操作方法，执行方法之前打开事务，异常回滚，方法返回提交事务，最终关闭连接。定义 ServiceTransAspect 类作为切面

@Component
@Aspect
public class ServiceTransAspect {@Autowiredprivate MyTransactionManager transactionManager;// 基于 AspectJ 的切入点表达式@Pointcut("execution(* com.hang.service.impl.SysUserServiceImpl.*(..))")public void servicePointCut() {}// 后置通知关闭数据库连接对象@After("servicePointCut()")public void closeConnection(){Connection conn = ConnUtil.getConn();if (conn!=null){try {conn.close();ConnUtil.clear();conn = null;} catch (SQLException e) {e.printStackTrace();}}}// 基于自定义注解形式@Pointcut("@annotation(com.hang.aspect.Transaction)")public void annotationPointCut() {}// 环绕通知 实现事务的开启、回滚、提交和连接对象的关闭@Around(value = "annotationPointCut()")public Object serviceManage(ProceedingJoinPoint pjp) {Object result = null;try {transactionManager.getConnection();transactionManager.openTransaction();result = pjp.proceed();transactionManager.openCommit();} catch (Throwable throwable) {transactionManager.openRollback();throwable.printStackTrace();} finally {transactionManager.closeConnection();}return result;}}

6. 自定义工具类

在并发环境下，如果没使用ThreadLocal类维护线程内部的局部变量Connection（单Connection对象），两个线程共同访问一个公共变量。例如A用户获取数据库连接对象，并将Connection对象占为己有，对数据进行操作时，B用户也获取到数据库连接对象，获取Connection对象，此时A不具有Connection对象，B用户完成事务提交关闭连接，此时Connection对象为null，A用户数据则会提交失败。

ThreadLocal类用来提供线程内部的局部变量。这种变量在多线程环境下访问（通过get和set方法访问）时能保证各个线程的变量相对独立于其他线程内的变量。

对ThreadLocal作用的总结：

线程并发: 在多线程并发的场景下
传递数据: 我们可以通过ThreadLocal在同一线程，不同组件中传递公共变量
线程隔离: 每个线程的变量都是独立的，不会互相影响

@Component
public class ConnUtil {private static ThreadLocal<Connection> threadLocalConn  = new ThreadLocal<>();@Resourceprivate MyTransactionManager tm;private static MyTransactionManager manager;public static void clear() {threadLocalConn.remove();}@PostConstructpublic void setTransactionManager(){manager = tm;}public static Connection getConn() {Connection connection = threadLocalConn.get();if (connection!=null){return  connection;}else {return manager.getConnection();}}public static void setConn(Connection conn) {threadLocalConn.set(conn);}
}