使用spring框架实现数据库事务处理方式

目录

• 使用spring框架实现数据库事务处理
• JDBC对数据库事务处理的支持
• JDBC定义了五种事务隔离级别来解决这些并发导致的问题
• 在spring框架中调用一个数据库事务处理分三步走：
• spring 事务实现方式有哪些
• 在代码中调用 commit()、rollback()等事务管理相关的方法
• TransactionProxyFactoryBean 的声明式事务管理
• 注解 @Transactional 的声明式事务管理
• Aspectj AOP 配置（注解）事务

使用spring框架实现数据库事务处理

事务对于数据库来说是，是对sql语句的一系列操作，这些操作被组织成为一个事务。事务具有原子性的，要么全部执行，要么不执行。若事务中sql语句发生错误，事务需要对已经执行的sql进行回滚操作，撤销先前对数据库的操作，防止数据库出现错误状态。

JDBC对数据库事务处理的支持

jdbc本身提供了对数据库处理的支持，使用java.sql.Connection对象完成事务的提交。使用Connection提交数据库事务处理如下：

发现里面有一个方法叫setAutoCommit()，设置为true时，就是自动提交sql，如果设置为false时，sql语句的提交由程序负责，应用程序必须调用Commit方法，同时在执行sql语句异常处理块中调用rollback方法，对异常发生前进行的数据库进行回滚。

在企业级中，事务一般都是并发执行的，当事务并发执行时，就会发生数据库同步的问题，具体问题可分为下面四种类型：

• 脏读：
• 不可重复读：
• 丢失更新：
• 幻读：

为了解决上面的四种问题，解决事务并发的问题

JDBC定义了五种事务隔离级别来解决这些并发导致的问题

• transaction_read_uncommitted:数据级别最低，俗称脏读，在没有提交数据时，就已经读取到已经更新的数据。
• transaction_read_committed:当一个事务进行查询时，允许读取提交前的数据，数据提交后，当前查询就可以读取到数据，update数据的时候并不锁住表。(最长使用)
• transaction_repeatable_read:当一个事务进行查询时，不允许读取其他事务更新的数据，可以读取其他事务新增的数据。
• transaction_serializable:当一个事务进行查询时，不允许任何对这个事务进行查询，就是把并行改成了串行。不提倡使用。

在spring框架中调用一个数据库事务处理分三步走：

• 第一步就是配置数据源就是配置数据库的名称和密码，地址等。
• 第二步就是声明事务管理TransactionManagerspring框架提供了PlatformTransactionManager作为事务管理类的顶层接口，声明了初始化事务，提交事务，回滚事务等接口。接口实现由具体的数据库驱动类实现。具体包括DataTransactionManager等实现类。但是主要还是使用的是DataTransactionManager类。

• 
• 定义可以执行事务的DAO类DAO提供了应用程序访问数据源必要的接口和方法。

spring 事务实现方式有哪些

编程式事务管理，

在代码中调用 commit()、rollback()等事务管理相关的方法

maven pom.xml文件

<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-beans</artifactId>
	<version>4.2.4.RELEASE</version>
</dependency>
 
<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-context</artifactId>
	<version>4.2.4.RELEASE</version>
</dependency>
 
<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-aop</artifactId>
	<version>4.2.4.RELEASE</version>
</dependency>
 
<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-tx</artifactId>
	<version>4.2.4.RELEASE</version>
</dependency>
 
<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-jdbc</artifactId>
	<version>4.2.4.RELEASE</version>
</dependency>
 
<!-- mysql驱动 -->
<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
	<version>5.1.18</version>
</dependency>

编程式事务管理，可以通过 java.sql.Connection 控制事务。spring 配置文件

<?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"
	xsi:schemaLocation="
		http://www.springframework.org/schema/beans 
		http://www.springframework.org/schema/beans/spring-beans.xsd
	    http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
        
	<bean id="driver" class="com.mysql.jdbc.Driver"></bean>
 
	<bean id="datasource" class="org.springframework.jdbc.datasource.SimpleDriverDataSource">
		<constructor-arg index="0" name="driver" ref="driver" />
		<constructor-arg index="1">
			<value>jdbc:mysql://localhost:3306/test</value>
		</constructor-arg>
		<constructor-arg index="2">
			<value>root</value>
		</constructor-arg>
		<constructor-arg index="3">
			<value>root</value>
		</constructor-arg>
	</bean>	
</beans>

测试代码

package constxiong.interview.transaction; 
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement; 
import javax.sql.DataSource; 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext; 
public class TransactionTest {
 
	public static void main(String[] args) throws Exception {
		testManualTransaction();//测试函数式控制事务
	}
	
	private static void testManualTransaction() throws SQLException {
		ApplicationContext context = new ClassPathXmlApplicationContext("spring_transaction.xml");
		DataSource ds = (DataSource)context.getBean("datasource");
		Connection conn = ds.getConnection();
		try {
			initTable(conn);//初始化表
			conn.setAutoCommit(false);//设置不自动提交事务
			queryUsers(conn);//查询打印用户表
			deleteUser(conn);//删除 id=1 用户
			conn.rollback();//回滚
			queryUsers(conn);//查询打印用户表
		} finally {
			conn.close();
		}
	}
 
	private static void initTable(Connection conn) throws SQLException {
		conn.createStatement().execute("drop table if exists user");
		conn.createStatement().execute("create table user(id int, username varchar(60)) ENGINE=InnoDB DEFAULT CHARSET=utf8 ");//是否支持事务与数据库引擎有关，此处删除 ENGINE=InnoDB DEFAULT CHARSET=utf8 可能不支持事务
		conn.createStatement().execute("insert into user values(1, 'user1')");
		conn.createStatement().execute("insert into user values(2, 'user2')");
	}
 
	private static void deleteUser(Connection conn) throws SQLException {
		conn.createStatement().execute("delete from user where id = 1");
	}
 
	private static void queryUsers(Connection conn) throws SQLException {
		Statement st = conn.createStatement();
		st.execute("select * from user");
		ResultSet rs = st.getResultSet();
		while (rs.next()) {
			System.out.print(rs.getString("id"));
			System.out.print(" ");
			System.out.print(rs.getString("username"));
			System.out.println();
		}
	}	
}

删除用户语句回滚，打印出两个用户

1 user1

2 user2

1 user1

2 user2

TransactionProxyFactoryBean 的声明式事务管理

新增 UserDao 接口

package constxiong.interview.transaction; 
import java.util.List;
import java.util.Map; 
public interface UserDao { 
	/**
	 * 查询用户
	 * @return
	 */
	public List<Map<String, Object>> getUsers();
	
	/**
	 * 删除用户
	 * @param id
	 * @return
	 */
	public int deleteUser(int id);	
}

新增 UserDao 实现

package constxiong.interview.transaction; 
import java.util.List;
import java.util.Map; 
import org.springframework.jdbc.core.support.JdbcDaoSupport; 
public class UserDaoImpl extends JdbcDaoSupport implements UserDao {
	
	/**
	 * 查询用户
	 * @return
	 */
	public List<Map<String, Object>> getUsers() {
		String sql = "select * from user";
		return this.getJdbcTemplate().queryForList(sql);
	}
	
	/**
	 * 删除用户
	 * @param id
	 * @return
	 */
	public int deleteUser(int id){
		String sql = "delete from user where id = " + id;
		int result = this.getJdbcTemplate().update(sql);
		if (id == 1) {
			throw new RuntimeException();
		}
		return result;
	}
}

修改 spring 配置文件，添加事务管理器 DataSourceTransactionManager 和事务代理类 TransactionProxyFactoryBean

<?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"
	xsi:schemaLocation="
		http://www.springframework.org/schema/beans 
		http://www.springframework.org/schema/beans/spring-beans.xsd
	    http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
        
	<bean id="driver" class="com.mysql.jdbc.Driver"></bean>
	
	<bean id="datasource" class="org.springframework.jdbc.datasource.SimpleDriverDataSource">
		<constructor-arg index="0" name="driver" ref="driver" />
		<constructor-arg index="1">
			<value>jdbc:mysql://localhost:3306/test</value>
		</constructor-arg>
		<constructor-arg index="2">
			<value>root</value>
		</constructor-arg>
		<constructor-arg index="3">
			<value>root</value>
		</constructor-arg>
	</bean>
	
	<bean id="userDao" class="constxiong.interview.transaction.UserDaoImpl">
		<property name="dataSource" ref="datasource"></property>
	</bean>
	
	<!-- 事务管理器 -->
	<bean id="tracnsactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
		<property name="dataSource" ref="datasource"></property>
	</bean>
	
	<bean id="userProxy" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
		<property name="transactionManager" ref="tracnsactionManager"></property>
		<property name="target" ref="userDao"></property>
		<property name="transactionAttributes">
			<props>
				<!-- 主要 key 是方法   
					ISOLATION_DEFAULT  事务的隔离级别
					PROPAGATION_REQUIRED  传播行为
				-->
				<!-- -Exception 表示发生指定异常回滚，+Exception 表示发生指定异常提交 -->
				<prop key="deleteUser">-java.lang.RuntimeException</prop>
			</props>
		</property>
	</bean>
	
</beans>

测试代码

package constxiong.interview.transaction; 
import java.util.Map; 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext; 
public class TransactionTest { 
	static ApplicationContext context = new ClassPathXmlApplicationContext("spring_transaction.xml");	
	public static void main(String[] args) throws Exception {
		testUseTransactionProxy(); //测试使用 spring TransactionProxyFactoryBean
	}
	
	private static void testUseTransactionProxy() {
		final UserDao userDao = (UserDao)context.getBean("userProxy");
		printUsers(userDao);//打印用户
		userDao.deleteUser(1);//删除 id=1 用户
	}
 
	private static void printUsers(UserDao userDao) {
		for (Map<String, Object> user : userDao.getUsers()) {
			System.out.println(user);
		}
	} 
}

结果输出

{id=1, username=user1}
{id=2, username=user2}
Exception in thread "main" java.lang.RuntimeException
at constxiong.interview.transaction.UserDaoImpl.deleteUser(UserDaoImpl.java:28)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
at com.sun.proxy.$Proxy3.deleteUser(Unknown Source)
at constxiong.interview.transaction.TransactionTest.testUseTransactionProxy(TransactionTest.java:32)
at constxiong.interview.transaction.TransactionTest.main(TransactionTest.java:13)

注解 @Transactional 的声明式事务管理

UserDaoImpl 删除用户方法添加注解 @Transactional(rollbackFor=RuntimeException.class) 出现 RuntimeException 回滚

package constxiong.interview.transaction; 
import java.util.List;
import java.util.Map; 
import org.springframework.jdbc.core.support.JdbcDaoSupport;
import org.springframework.transaction.annotation.Transactional; 
public class UserDaoImpl extends JdbcDaoSupport implements UserDao {	
	/**
	 * 查询用户
	 * @return
	 */
	public List<Map<String, Object>> getUsers() {
		String sql = "select * from user";
		return this.getJdbcTemplate().queryForList(sql);
	}
	
	/**
	 * 删除用户
	 * @param id
	 * @return
	 */
	@Transactional(rollbackFor=RuntimeException.class)
	public int deleteUser(int id){
		String sql = "delete from user where id = " + id;
		int result = this.getJdbcTemplate().update(sql);
		if (id == 1) {
			throw new RuntimeException();
		}
		return result;
	}
}

修改 spring 配置文件，开启 spring 的事务注解能力

<?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:tx="http://www.springframework.org/schema/tx"
	xsi:schemaLocation="
		http://www.springframework.org/schema/beans 
		http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
	    http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
        
	<bean id="driver" class="com.mysql.jdbc.Driver"></bean>
	
	<bean id="datasource" class="org.springframework.jdbc.datasource.SimpleDriverDataSource">
		<constructor-arg index="0" name="driver" ref="driver" />
		<constructor-arg index="1">
			<value>jdbc:mysql://localhost:3306/test</value>
		</constructor-arg>
		<constructor-arg index="2">
			<value>root</value>
		</constructor-arg>
		<constructor-arg index="3">
			<value>root</value>
		</constructor-arg>
	</bean>
	
	<bean id="userDao" class="constxiong.interview.transaction.UserDaoImpl">
		<property name="dataSource" ref="datasource"></property>
	</bean>
	
	<!-- 事务管理器 -->
	<bean id="tracnsactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
		<property name="dataSource" ref="datasource"></property>
	</bean>
	
	<!-- 启用事务注解 -->
	<tx:annotation-driven transaction-manager="tracnsactionManager"/>	
</beans>

测试代码

package constxiong.interview.transaction; 
import java.util.Map; 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext; 
public class TransactionTest { 
	static ApplicationContext context = new ClassPathXmlApplicationContext("spring_transaction.xml");	
	public static void main(String[] args) throws Exception {
		testAnnotationTransaction();
	}	
	
	private static void testAnnotationTransaction() {
		UserDao userDao = (UserDao)context.getBean("userDao");
		printUsers(userDao);
		userDao.deleteUser(1);
	} 
 
	private static void printUsers(UserDao userDao) {
		for (Map<String, Object> user : userDao.getUsers()) {
			System.out.println(user);
		}
	} 
}

输出结果

{id=1, username=user1}
{id=2, username=user2}
Exception in thread "main" java.lang.RuntimeException
at constxiong.interview.transaction.UserDaoImpl.deleteUser(UserDaoImpl.java:30)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
at com.sun.proxy.$Proxy5.deleteUser(Unknown Source)
at constxiong.interview.transaction.TransactionTest.testAnnotationTransaction(TransactionTest.java:20)
at constxiong.interview.transaction.TransactionTest.main(TransactionTest.java:13)

Aspectj AOP 配置（注解）事务

maven pom.xml 添加 Aspectj 的支持

<dependency>
    <groupId>org.aspectj</groupId>
    <artifactId>aspectjweaver</artifactId>
    <version>1.8.13</version>
</dependency>

去除 UserDaoImpl 注解@Transactional(rollbackFor=RuntimeException.class)

package constxiong.interview.transaction; 
import java.util.List;
import java.util.Map; 
import org.springframework.jdbc.core.support.JdbcDaoSupport; 
public class UserDaoImpl extends JdbcDaoSupport implements UserDao {	
	/**
	 * 查询用户
	 * @return
	 */
	public List<Map<String, Object>> getUsers() {
		String sql = "select * from user";
		return this.getJdbcTemplate().queryForList(sql);
	}
	
	/**
	 * 删除用户
	 * @param id
	 * @return
	 */
	public int deleteUser(int id){
		String sql = "delete from user where id = " + id;
		int result = this.getJdbcTemplate().update(sql);
		if (id == 1) {
			throw new RuntimeException();
		}
		return result;
	}
}

修改 spring 配置文件，织入切面

<?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:tx="http://www.springframework.org/schema/tx"
	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/tx
        http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
	    http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
        
	<bean id="driver" class="com.mysql.jdbc.Driver"></bean>
	
	<bean id="datasource" class="org.springframework.jdbc.datasource.SimpleDriverDataSource">
		<constructor-arg index="0" name="driver" ref="driver" />
		<constructor-arg index="1">
			<value>jdbc:mysql://localhost:3306/test</value>
		</constructor-arg>
		<constructor-arg index="2">
			<value>root</value>
		</constructor-arg>
		<constructor-arg index="3">
			<value>root</value>
		</constructor-arg>
	</bean>
	
	<bean id="userDao" class="constxiong.interview.transaction.UserDaoImpl">
		<property name="dataSource" ref="datasource"></property>
	</bean>
	
	<!-- 事务管理器 -->
	<bean id="tracnsactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
		<property name="dataSource" ref="datasource"></property>
	</bean>
	
	<tx:advice id="txAdvice" transaction-manager="tracnsactionManager">
		<tx:attributes>
			<!-- 为连接点指定事务属性 -->
			<tx:method name="deleteUser" rollback-for="java.lang.RuntimeException"/>
		</tx:attributes>
	</tx:advice>
	
	<aop:config>
		<!-- 切入点配置 -->
		<aop:pointcut id="point" expression="execution(* *constxiong.interview.transaction.UserDao.deleteUser(..))" />
		<aop:advisor advice-ref="txAdvice" pointcut-ref="point"/>
	</aop:config>	
</beans>

测试代码

package constxiong.interview.transaction; 
import java.util.Map; 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext; 
public class TransactionTest { 
	static ApplicationContext context = new ClassPathXmlApplicationContext("spring_transaction.xml");	
	public static void main(String[] args) throws Exception {
		testAspectjTransaction();
	}	
	
	private static void testAspectjTransaction() {
		UserDao userDao = (UserDao)context.getBean("userDao");
		printUsers(userDao);
		userDao.deleteUser(1);
	} 
 
	private static void printUsers(UserDao userDao) {
		for (Map<String, Object> user : userDao.getUsers()) {
			System.out.println(user);
		}
	} 
}

输出结果

{id=1, username=user1}
{id=2, username=user2}
Exception in thread "main" java.lang.RuntimeException
at constxiong.interview.transaction.UserDaoImpl.deleteUser(UserDaoImpl.java:28)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
at com.sun.proxy.$Proxy2.deleteUser(Unknown Source)
at constxiong.interview.transaction.TransactionTest.testAnnotationTransaction(TransactionTest.java:20)
at constxiong.interview.transaction.TransactionTest.main(TransactionTest.java:13)

PS：

这篇仅用事务回滚为例，了解 spring 事务控制，还需要关注数据库的ACID四种特性、事务传播特性、事务的隔离级别（脏读、不可重复读、幻读）。

以上为个人经验，希望能给大家一个参考，也希望大家多多支持自由互联。