[Control] affairs

Example: Transfer Case

A programmatic transaction control

1, no code of transaction control

As follows AccountServiceImpl, query and update user accounts, each line of code is a separate thread, error (/ 0) code appears
before the code has been executed in error, the error code will not be executed, resulting in business logic error.

2, demo code

AccountServiceImpl.java

public class AccountServiceImpl implements AccountService {

    private AccountDao accountDao;
    
    public void setAccountDao(AccountDao accountDao) {
        this.accountDao = accountDao;
    }
    
    public void transfer(String sourceName, String targetName, Float money) {
		System.out.println("transfer....");
		//2.1根据名称查询转出账户
		Account source = accountDao.findAccountByName(sourceName);
		//2.2根据名称查询转入账户
		Account target = accountDao.findAccountByName(targetName);
		//2.3转出账户减钱
		source.setMoney(source.getMoney() - money);
		//2.4转入账户加钱
		target.setMoney(target.getMoney() + money);
		//2.5更新转出账户
		accountDao.updateAccount(source);
		
		int i = 1 / 0;
		
		//2.6更新转入账户
		accountDao.updateAccount(target);
    }
}

AccountDaoImpl.java

public class AccountDaoImpl implements AccountDao {

    private QueryRunner queryRunner;

    public void setQueryRunner(QueryRunner queryRunner) {
        this.queryRunner = queryRunner;
    }

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

    public Account findAccountByName(String accountName) {
        try {
            List<Account> accounts = queryRunner.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);
        }
    }
}

applicationContext.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
        http://www.springframework.org/schema/beans/spring-beans.xsd">

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

    <!--配置Dao对象-->
    <bean id="accountDao" class="com.donglei.dao.AccountDaoImpl">
        <!-- 注入QueryRunner -->
        <property name="queryRunner" ref="runner"></property>
    </bean>

    <!--配置QueryRunner-->
    <bean id="runner" class="org.apache.commons.dbutils.QueryRunner" scope="prototype">
        <constructor-arg name="ds" ref="dataSource"></constructor-arg>
    </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>
        <property name="jdbcUrl" value="jdbc:mysql:///donglei"></property>
        <property name="user" value="root"></property>
        <property name="password" value="root"></property>
    </bean>
</beans>

Test.java

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

    @Autowired
    private AccountService as;

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

3, analyze the reasons

Each operation data acquisition DBUtils is a connection connector of each transaction are independent, and the default is automatically submitted.

4. Solution

It requires the use of ThreadLocal objects Connection and the current thread binding, so that the object can only be connected to a transaction can control a thread.

5, the solution code

ConnectionUtils.java
tools connection, which is used to obtain a connection from the data source, and the binding threads and to achieve

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
     * @return
     */
    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 (Exception e){
            throw new RuntimeException(e);
        }
    }

    /**
     * 把连接和线程解绑（在当前线程结束的时候执行）
     */
    public void removeConnection(){
        tl.remove();
    }
}

TransactionManager.java
transaction management-related tools, including open transactions, commit the transaction, roll back the transaction and release connections

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 (Exception e){
            e.printStackTrace();
        }
    }

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

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


    /**
     * 释放连接
     */
    public  void release(){
        try {
            connectionUtils.getThreadConnection().close();//把连接还回连接池中
            connectionUtils.removeConnection();//线程和连接解绑
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

Modified AccountDaoImpl.java
queryRunner operation specified connection conn, obtaining a connection with the local thread

public class AccountDaoImpl implements AccountDao {

    private QueryRunner queryRunner;

    private ConnectionUtils connectionUtils;

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

    public void setQueryRunner(QueryRunner queryRunner) {
        this.queryRunner = queryRunner;
    }

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

AccountServiceImpl.java modify
transaction operation requires a certain Service layer control, control transactions through the transaction manager

public class AccountServiceImpl implements AccountService {

    private AccountDao accountDao;

    private TransactionManager txManager;

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

    public void setAccountDao(AccountDao accountDao) {
        this.accountDao = accountDao;
    }

    public void transfer(String sourceName, String targetName, Float money) {
        try {
            //1.开启事务
            txManager.beginTransaction();
            System.out.println("transfer....");
            //2.1根据名称查询转出账户
            Account source = accountDao.findAccountByName(sourceName);
            //2.2根据名称查询转入账户
            Account target = accountDao.findAccountByName(targetName);
            //2.3转出账户减钱
            source.setMoney(source.getMoney() - money);
            //2.4转入账户加钱
            target.setMoney(target.getMoney() + money);
            //2.5更新转出账户
            accountDao.updateAccount(source);

            int i = 1 / 0;

            //2.6更新转入账户
            accountDao.updateAccount(target);
            //3.提交事务
            txManager.commit();
        } catch (Exception e) {
            //4.回滚操作
            txManager.rollback();
            e.printStackTrace();
        } finally {
            //5.释放连接
            txManager.release();
        }
    }
}

Modify applicationContext.xml
DAO injected into the connection management tools, service inject the transaction manager, into the database connectivity tools instead of in queryRunner

<?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
        http://www.springframework.org/schema/beans/spring-beans.xsd">

    <!-- 配置Service -->
    <bean id="accountService" class="com.donglei.service.AccountServiceImpl">
        <!-- 注入dao -->
        <property name="accountDao" ref="accountDao"></property>
        <!--注入事务管理器-->
        <property name="txManager" ref="txManager"></property>
    </bean>

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

    <!--配置QueryRunner-->
    <bean id="runner" class="org.apache.commons.dbutils.QueryRunner" scope="prototype">
        <!--<constructor-arg name="ds" ref="dataSource"></constructor-arg>-->
    </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>
        <property name="jdbcUrl" value="jdbc:mysql:///donglei"></property>
        <property name="user" value="root"></property>
        <property name="password" value="root"></property>
    </bean>

    <!-- 配置Connection的工具类 ConnectionUtils -->
    <bean id="connectionUtils" class="com.donglei.util.ConnectionUtils">
        <!-- 注入数据源-->
        <property name="dataSource" ref="dataSource"></property>
    </bean>

    <!-- 配置事务管理器-->
    <bean id="txManager" class="com.donglei.util.TransactionManager">
        <!-- 注入ConnectionUtils -->
        <property name="connectionUtils" ref="connectionUtils"></property>
    </bean>
</beans>

6, the question is

Coupling the code, which is full of the business layer method a lot of code repetition.

Two, AOP JDK agent

7, proxy mode

public class BeanFactory {
    private AccountService accountService;
    private TransactionManager txManager;
    
    public void setTxManager(TransactionManager txManager) {
        this.txManager = txManager;
    }

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

    public AccountService getAccountService() {
        return (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 {
                            //1.开启事务
                            txManager.beginTransaction();
                            //2.执行操作
                            rtValue = method.invoke(accountService, args);
                            //3.提交事务
                            txManager.commit();
                            //4.返回结果
                            return rtValue;
                        } catch (Exception e) {
                            //5.回滚操作
                            txManager.rollback();
                            throw new RuntimeException(e);
                        } finally {
                            //6.释放连接
                            txManager.release();
                        }
                    }
                });
    }
}

At this point in serviceImpl would not inject Affairs controller, modify applicationContext.xml increase agent service

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

    <!--配置beanfactory-->
    <bean id="beanFactory" class="com.donglei.util.BeanFactory">
        <!-- 注入service -->
        <property name="accountService" ref="accountService"></property>
        <!-- 注入事务管理器 -->
        <property name="txManager" ref="txManager"></property>
    </bean>

Note that in the test method proxy service
because there have been two types of spring AccountService container, so use @Qualifier ( "proxyAccountService") specify the desired type

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