spring复习：（43）使用TransactionProxyFactoryBean来实现事务时，事务是怎么开启的？

一、配置文件：

    
        
        
        
            
                PROPAGATION_REQUIRED
            
        
    

二、代码块中使用TransactionProxyFactoryBean

package cn.edu.tju.study.service.transaction2;

public interface StudentService {
    public void addStudent(String name, int age);
}

package cn.edu.tju.study.service.transaction2;

import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;

@Service
public class StudentServiceImpl implements StudentService{
    private JdbcTemplate jdbcTemplate;

    public JdbcTemplate getJdbcTemplate() {
        return jdbcTemplate;
    }

    public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    @Override
    public void addStudent(String name,int age) {
        String sql = "insert into student values('";
        sql += name;
        sql +="'";
        sql += ",";
        sql += age;
        sql += ")";
        jdbcTemplate.execute(sql);
        jdbcTemplate.execute(sql);

    }
}

package cn.edu.tju.study.service.transaction2;

import cn.edu.tju.study.service.MyConfig3;
import cn.edu.tju.study.service.aspect.MyDemoService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TransactionTest {
    public static void main(String[] args) {

        ApplicationContext context = new ClassPathXmlApplicationContext("transaction.xml");

        StudentService studentService = context.getBean("myFactoryBean", StudentService.class);

        studentService.addStudent("paul",23);
    }
}

三、执行流程
当调用addStudent时，会直接跳转到JdkDynamicAopProxy的invoke方法（因为实现了接口，代理对象的实现为jdk 动态代理）

执行到invoke方法的
List chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);时，chain中包含一个对象：TransactionInterceptor.
执行到retVal = invocation.proceed();会进到ReflectiveMethodInvocation类：

该方法执行到return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);时，会进到TransactionInterceptor类：

其中调用的invokeWithinTransaction代码如下：

	protected Object invokeWithinTransaction(Method method, @Nullable Class targetClass,
			final InvocationCallback invocation) throws Throwable {

		// If the transaction attribute is null, the method is non-transactional.
		TransactionAttributeSource tas = getTransactionAttributeSource();
		final TransactionAttribute txAttr = (tas != null ? tas.getTransactionAttribute(method, targetClass) : null);
		final TransactionManager tm = determineTransactionManager(txAttr);

		if (this.reactiveAdapterRegistry != null && tm instanceof ReactiveTransactionManager) {
			ReactiveTransactionSupport txSupport = this.transactionSupportCache.computeIfAbsent(method, key -> {
				if (KotlinDetector.isKotlinType(method.getDeclaringClass()) && KotlinDelegate.isSuspend(method)) {
					throw new TransactionUsageException(
							"Unsupported annotated transaction on suspending function detected: " + method +
							". Use TransactionalOperator.transactional extensions instead.");
				}
				ReactiveAdapter adapter = this.reactiveAdapterRegistry.getAdapter(method.getReturnType());
				if (adapter == null) {
					throw new IllegalStateException("Cannot apply reactive transaction to non-reactive return type: " +
							method.getReturnType());
				}
				return new ReactiveTransactionSupport(adapter);
			});
			return txSupport.invokeWithinTransaction(
					method, targetClass, invocation, txAttr, (ReactiveTransactionManager) tm);
		}

		PlatformTransactionManager ptm = asPlatformTransactionManager(tm);
		final String joinpointIdentification = methodIdentification(method, targetClass, txAttr);

		if (txAttr == null || !(ptm instanceof CallbackPreferringPlatformTransactionManager)) {
			// Standard transaction demarcation with getTransaction and commit/rollback calls.
			TransactionInfo txInfo = createTransactionIfNecessary(ptm, txAttr, joinpointIdentification);

			Object retVal;
			try {
				// This is an around advice: Invoke the next interceptor in the chain.
				// This will normally result in a target object being invoked.
				retVal = invocation.proceedWithInvocation();
			}
			catch (Throwable ex) {
				// target invocation exception
				completeTransactionAfterThrowing(txInfo, ex);
				throw ex;
			}
			finally {
				cleanupTransactionInfo(txInfo);
			}

			if (vavrPresent && VavrDelegate.isVavrTry(retVal)) {
				// Set rollback-only in case of Vavr failure matching our rollback rules...
				TransactionStatus status = txInfo.getTransactionStatus();
				if (status != null && txAttr != null) {
					retVal = VavrDelegate.evaluateTryFailure(retVal, txAttr, status);
				}
			}

			commitTransactionAfterReturning(txInfo);
			return retVal;
		}

		else {
			final ThrowableHolder throwableHolder = new ThrowableHolder();

			// It's a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in.
			try {
				Object result = ((CallbackPreferringPlatformTransactionManager) ptm).execute(txAttr, status -> {
					TransactionInfo txInfo = prepareTransactionInfo(ptm, txAttr, joinpointIdentification, status);
					try {
						Object retVal = invocation.proceedWithInvocation();
						if (vavrPresent && VavrDelegate.isVavrTry(retVal)) {
							// Set rollback-only in case of Vavr failure matching our rollback rules...
							retVal = VavrDelegate.evaluateTryFailure(retVal, txAttr, status);
						}
						return retVal;
					}
					catch (Throwable ex) {
						if (txAttr.rollbackOn(ex)) {
							// A RuntimeException: will lead to a rollback.
							if (ex instanceof RuntimeException) {
								throw (RuntimeException) ex;
							}
							else {
								throw new ThrowableHolderException(ex);
							}
						}
						else {
							// A normal return value: will lead to a commit.
							throwableHolder.throwable = ex;
							return null;
						}
					}
					finally {
						cleanupTransactionInfo(txInfo);
					}
				});

				// Check result state: It might indicate a Throwable to rethrow.
				if (throwableHolder.throwable != null) {
					throw throwableHolder.throwable;
				}
				return result;
			}
			catch (ThrowableHolderException ex) {
				throw ex.getCause();
			}
			catch (TransactionSystemException ex2) {
				if (throwableHolder.throwable != null) {
					logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
					ex2.initApplicationException(throwableHolder.throwable);
				}
				throw ex2;
			}
			catch (Throwable ex2) {
				if (throwableHolder.throwable != null) {
					logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
				}
				throw ex2;
			}
		}
	}

其中调用了createTransactionIfNecessary

它的代码如下：

其中调用了getTransaction,它的代码如下：

	public final TransactionStatus getTransaction(@Nullable TransactionDefinition definition)
			throws TransactionException {

		// Use defaults if no transaction definition given.
		TransactionDefinition def = (definition != null ? definition : TransactionDefinition.withDefaults());

		Object transaction = doGetTransaction();
		boolean debugEnabled = logger.isDebugEnabled();

		if (isExistingTransaction(transaction)) {
			// Existing transaction found -> check propagation behavior to find out how to behave.
			return handleExistingTransaction(def, transaction, debugEnabled);
		}

		// Check definition settings for new transaction.
		if (def.getTimeout() < TransactionDefinition.TIMEOUT_DEFAULT) {
			throw new InvalidTimeoutException("Invalid transaction timeout", def.getTimeout());
		}

		// No existing transaction found -> check propagation behavior to find out how to proceed.
		if (def.getPropagationBehavior() == TransactionDefinition.PROPAGATION_MANDATORY) {
			throw new IllegalTransactionStateException(
					"No existing transaction found for transaction marked with propagation 'mandatory'");
		}
		else if (def.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRED ||
				def.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW ||
				def.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
			SuspendedResourcesHolder suspendedResources = suspend(null);
			if (debugEnabled) {
				logger.debug("Creating new transaction with name [" + def.getName() + "]: " + def);
			}
			try {
				return startTransaction(def, transaction, debugEnabled, suspendedResources);
			}
			catch (RuntimeException | Error ex) {
				resume(null, suspendedResources);
				throw ex;
			}
		}
		else {
			// Create "empty" transaction: no actual transaction, but potentially synchronization.
			if (def.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT && logger.isWarnEnabled()) {
				logger.warn("Custom isolation level specified but no actual transaction initiated; " +
						"isolation level will effectively be ignored: " + def);
			}
			boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
			return prepareTransactionStatus(def, null, true, newSynchronization, debugEnabled, null);
		}
	}

其中调用的startTransaction代码如下：

其中调用的doBegin代码如下：

	protected void doBegin(Object transaction, TransactionDefinition definition) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
		Connection con = null;

		try {
			if (!txObject.hasConnectionHolder() ||
					txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
				Connection newCon = obtainDataSource().getConnection();
				if (logger.isDebugEnabled()) {
					logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
				}
				txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
			}

			txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
			con = txObject.getConnectionHolder().getConnection();

			Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
			txObject.setPreviousIsolationLevel(previousIsolationLevel);
			txObject.setReadOnly(definition.isReadOnly());

			// Switch to manual commit if necessary. This is very expensive in some JDBC drivers,
			// so we don't want to do it unnecessarily (for example if we've explicitly
			// configured the connection pool to set it already).
			if (con.getAutoCommit()) {
				txObject.setMustRestoreAutoCommit(true);
				if (logger.isDebugEnabled()) {
					logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
				}
				con.setAutoCommit(false);
			}

			prepareTransactionalConnection(con, definition);
			txObject.getConnectionHolder().setTransactionActive(true);

			int timeout = determineTimeout(definition);
			if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
				txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
			}

			// Bind the connection holder to the thread.
			if (txObject.isNewConnectionHolder()) {
				TransactionSynchronizationManager.bindResource(obtainDataSource(), txObject.getConnectionHolder());
			}
		}

		catch (Throwable ex) {
			if (txObject.isNewConnectionHolder()) {
				DataSourceUtils.releaseConnection(con, obtainDataSource());
				txObject.setConnectionHolder(null, false);
			}
			throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
		}
	}

可以看到其中设置手动提交事务的代码