目录
3.3 自定义事务注解 (通过反射解析方法上的注解,如果有这个注解就执行事务逻辑)
3.5 通过AOP封装事务工具类, 基于环绕通知和异常通知来触发事务
1、简介
Transactional是spring中定义的事务注解,在方法或类上加该注解开启事务。主要是通过反射获取bean的注解信息,利用AOP对编程式事务进行封装实现。(spring-5.1.8.RELEASE)
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface Transactional {
@AliasFor("transactionManager")
String value() default "";
@AliasFor("value")
String transactionManager() default "";
Propagation propagation() default Propagation.REQUIRED;
Isolation isolation() default Isolation.DEFAULT;
int timeout() default TransactionDefinition.TIMEOUT_DEFAULT;
boolean readOnly() default false;
Class<? extends Throwable>[] rollbackFor() default {};
String[] rollbackForClassName() default {};
Class<? extends Throwable>[] noRollbackFor() default {};
String[] noRollbackForClassName() default {};
}
2、自定义注解
2.1 定义
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface MyAnnotation {
//自定义注解的属性
int id() default 0;
String name() default "默认名称";
String[]arrays();
String title() default "默认标题";
}
2.2 测试
public class App {
@MyAnnotation(name = "Yongqian Wang", arrays = {"2", "3"})
public void aMethod() {}
public void bMethod() {}
public static void main(String[] args) throws ClassNotFoundException {
// 反射获取到类的信息
Class<?> clazz = Class.forName("com.wyq.App");
// 获取当前类(不包括继承)所有方法
Method[] methods = clazz.getDeclaredMethods();
// 遍历每个方法的信息
for (Method method : methods) {
System.out.println("方法名称:" + method.getName());
// 获取方法上面的注解
MyAnnotation annotation = method.getDeclaredAnnotation(MyAnnotation.class);
if (annotation == null) {
System.out.println("该方法上没有加注解...");
} else {
System.out.println("Id : " + annotation.id());
System.out.println("Name : " + annotation.name());
System.out.println("Title : " + annotation.title());
System.out.println("Arrays : " + annotation.arrays());
}
System.out.println("--------------------------");
}
}
}
控制台信息:
方法名称:main
该方法上没有加注解...
--------------------------
方法名称:aMethod
Id : 0
Name : Yongqian Wang
Title : 默认标题
Arrays : [Ljava.lang.String;@24d46ca6
--------------------------
方法名称:bMethod
该方法上没有加注解...
--------------------------
2.3 总结
通过上面这么一个小demo我们就能发现,反射获取到每一个方法的注解信息然后进行判断,如果这是@Transactional注解,spring就会开启事务。接下来我们可以按照这种思路自己实现一个事务注解。
3、手写事务注解
3.1 maven依赖
<dependencies>
<!-- 引入Spring-AOP等相关Jar -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-orm</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.9.4</version>
</dependency>
<dependency>
<groupId>aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.5.4</version>
</dependency>
<dependency>
<groupId>cglib</groupId>
<artifactId>cglib</artifactId>
<version>3.3.0</version>
</dependency>
<dependency>
<groupId>com.mchange</groupId>
<artifactId>c3p0</artifactId>
<version>0.9.5.2</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.37</version>
</dependency>
</dependencies>
3.2 配置spring.xml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"
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">
<!--扫描指定路径-->
<context:component-scan base-package="com.wyq" />
<!--开启切面代理-->
<aop:aspectj-autoproxy />
<!--数据源对象,C3P0 连接池-->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="com.mysql.jdbc.Driver"/>
<property name="jdbcUrl" value="jdbc:mysql://localhost:3306/test"/>
<property name="user" value="root"/>
<property name="password" value="123456"/>
</bean>
<!--JdbcTemplate 工具类实例-->
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="dataSource"/>
</bean>
<!--配置事务-->
<bean id="dataSoutceTransactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"></property>
</bean>
</beans>
3.3 自定义事务注解 (通过反射解析方法上的注解,如果有这个注解就执行事务逻辑)
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface MyAnnotation {
//自定义注解的属性
int id() default 0;
String name() default "默认名称";
String[] arrays() default {};
String title() default "默认标题";
}
3.4 封装编程式事务
@Component
@Scope("prototype")
public class TransactionUtil {
// 全局接受事务状态
private TransactionStatus transactionStatus;
// 获取事务原
@Autowired
private DataSourceTransactionManager dataSourceTransactionManager;
// 开启事务
public TransactionStatus begin() {
System.out.println("开启事务");
transactionStatus = dataSourceTransactionManager.getTransaction(new DefaultTransactionAttribute());
return transactionStatus;
}
// 提交事务
public void commit(TransactionStatus transaction) {
System.out.println("提交事务");
if (dataSourceTransactionManager != null) {
dataSourceTransactionManager.commit(transaction);
}
}
public void rollback(TransactionStatus transaction) {
System.out.println("回滚事务");
if (dataSourceTransactionManager != null) {
dataSourceTransactionManager.rollback(transaction);
}
}
}
3.5 通过AOP封装事务工具类, 基于环绕通知和异常通知来触发事务
@Component
@Aspect
public class AopTransaction {
@Autowired
private TransactionUtil transactionUtil;
private TransactionStatus transactionStatus;
/**
* 环绕通知,在方法 前---后 处理事情
*
* @param pjp 切入点
*/
@Around("execution(* com.wyq.service.*.*(..))")
public void around(ProceedingJoinPoint pjp) throws Throwable {
// 获取方法的注解
MyAnnotation annotation = this.getMethodMyAnnotation(pjp);
// 判断是否需要开启事务
transactionStatus = begin(annotation);
// 调用目标代理对象方法
pjp.proceed();
// 判断关闭事务
commit(transactionStatus);
}
/**
* 获取代理方法上的事务注解
*
* @param pjp
* @return
* @throws Exception
*/
private MyAnnotation getMethodMyAnnotation(ProceedingJoinPoint pjp) throws Exception {
// 获取代理对象的方法
String methodName = pjp.getSignature().getName();
// 获取目标对象
Class<?> classTarget = pjp.getTarget().getClass();
// 获取目标对象类型
Class<?>[] par = ((MethodSignature) pjp.getSignature()).getParameterTypes();
// 获取目标对象方法
Method objMethod = classTarget.getMethod(methodName, par);
// 获取该方法上的事务注解
MyAnnotation annotation = objMethod.getDeclaredAnnotation(MyAnnotation.class);
return annotation;
}
/**
* 开启事务
*
* @param annotation
* @return
*/
private TransactionStatus begin(MyAnnotation annotation) {
if (annotation == null) {
return null;
}
return transactionUtil.begin();
}
/**
* 提交事务
*
* @param transactionStatus
*/
private void commit(TransactionStatus transactionStatus) {
if (transactionStatus != null) {
transactionUtil.commit(transactionStatus);
}
}
/**
* 异常通知进行 回滚事务
*/
@AfterThrowing("execution(* com.wyq.service.*.*(..))")
public void afterThrowing() {
// 获取当前事务 直接回滚
if (transactionStatus != null) {
transactionUtil.rollback(transactionStatus);
}
}
}
3.6 dao 层
/*
CREATE TABLE `t_user0` (
`name` varchar(20) NOT NULL,
`age` int(5) DEFAULT NULL,
PRIMARY KEY (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
*/
@Repository
public class UserDao {
@Autowired
private JdbcTemplate jdbcTemplate;
public int add(String name, Integer age) {
String sql = "INSERT INTO t_user0(NAME, age) VALUES(?,?);";
int result = jdbcTemplate.update(sql, name, age);
System.out.println("插入成功");
return result;
}
}
3.7 service 层
@Service
public class UserService {
@Autowired
private UserDao userDao;
// 加上事务注解
@MyAnnotation
public void add() {
userDao.add("test001", 20);
int i = 1 / 0; //设置异常,检查事务的正确性
userDao.add("test002", 21);
// // 如果非要try,那么出现异常不会被aop的异常通知监测到,必须手动在catch里面回滚事务。
// try {
// userDao.add("test001", 20);
// int i = 1 / 0;
// userDao.add("test002", 21);
// } catch (Exception e) {
// // 回滚当前事务
// System.out.println("回滚");
// TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();
// }
}
public void del() {
System.out.println("del...");
}
}
3.8 测试
public class Test {
public static void main(String[] args) {
ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring.xml");
UserService userService = (UserService) applicationContext.getBean("userService");
// aop()对userService类进行了拦截,添加自定义事务注解的方法会触发事务逻辑
userService.add();
// del()方法没有加注解,则什么也不会触发。
//userService.del();
}
}