在我的应用程序中，我需要将纯JDBC与Guice一起使用。但是，Guice没有提供任何内置的支持来管理交易。 guice-persist只提供基于JPA的支持，我不能使用它。
所以我尝试实现一个简单的解决方案来管理Guice和JDBC的事务。这是第一个版本：
使用TransactionHolder存储每个线程的事务。
公共类JdbcTransactionHolder {
private static ThreadLocal<JdbcTransaction> currentTransaction = new ThreadLocal<JdbcTransaction>();
public static void setCurrentTransaction(JdbcTransaction transaction) {
currentTransaction.set(transaction);
}
public static JdbcTransaction getCurrentTransaction() {
return currentTransaction.get();
}
public static void removeCurrentTransaction() {
currentTransaction.remove();
}
}
实现JDBC的事务管理器，现在只有begin（），getTransaction（），commit（）和rollback（）方法：
公共类JdbcTransactionManager实现TransactionManager {
@Inject
private DataSource dataSource;
@Override
public void begin() throws NotSupportedException, SystemException {
logger.debug("Start the transaction");
try {
JdbcTransaction tran = JdbcTransactionHolder.getCurrentTransaction();
Connection conn = null;
if(tran == null) {
conn = dataSource.getConnection();
}
else {
conn = tran.getConnection();
}
// We have to put the connection in the holder so that we can get later
// from the holder and use it in the same thread
logger.debug("Save the transaction for thread: {}.", Thread.currentThread());
JdbcTransactionHolder.setCurrentTransaction(new JdbcTransaction(conn));
} catch (Exception e) {
throw new RuntimeException(e);
}
}
@Override
public void commit() throws RollbackException, HeuristicMixedException,
HeuristicRollbackException, SecurityException,
IllegalStateException, SystemException {
logger.debug("Commit the transaction");
try {
logger.debug("Get the connection for thread: {}.", Thread.currentThread());
Transaction transaction = JdbcTransactionHolder.getCurrentTransaction();
transaction.commit();
}
catch(Exception e) {
throw new RuntimeException(e);
}
finally {
JdbcTransactionHolder.removeCurrentTransaction();
}
}
@Override
public Transaction getTransaction() throws SystemException {
logger.debug("Get transaction.");
final JdbcTransaction tran = JdbcTransactionHolder.getCurrentTransaction();
if(tran == null) {
throw new DBException("No transaction is availble. TransactionManager.begin() is probably not yet called.");
}
return tran;
}
@Override
public void rollback() throws IllegalStateException, SecurityException,
SystemException {
logger.debug("Rollback the transaction");
try {
logger.debug("Get the transaction for thread: {}.", Thread.currentThread());
Transaction conn = JdbcTransactionHolder.getCurrentTransaction();
conn.commit();
}
catch(Exception e) {
throw new RuntimeException(e);
}
finally {
JdbcTransactionHolder.removeCurrentTransaction();
}
}
}
实现DataSource的包装器，如果已启动事务，它可以从事务持有者获取当前连接：
公共类JdbcDataSource实现DataSource {
private final static org.slf4j.Logger logger = LoggerFactory.getLogger(JdbcDataSource.class);
private DataSource dataSource;
public JdbcDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
@Override
public PrintWriter getLogWriter() throws SQLException {
return dataSource.getLogWriter();
}
@Override
public int getLoginTimeout() throws SQLException {
return dataSource.getLoginTimeout();
}
@Override
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
return dataSource.getParentLogger();
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
this.dataSource.setLogWriter(out);
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
this.dataSource.setLoginTimeout(seconds);
}
@Override
public boolean isWrapperFor(Class<?> arg0) throws SQLException {
return this.isWrapperFor(arg0);
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return this.unwrap(iface);
}
@Override
public Connection getConnection() throws SQLException {
JdbcTransaction transaction = JdbcTransactionHolder.getCurrentTransaction();
if(transaction != null) {
// we get the connection from the transaction
logger.debug("Transaction exists for the thread: {}.", Thread.currentThread());
return transaction.getConnection();
}
Connection conn = this.dataSource.getConnection();
conn.setAutoCommit(false);
return conn;
}
@Override
public Connection getConnection(String username, String password)
throws SQLException {
JdbcTransaction transaction = JdbcTransactionHolder.getCurrentTransaction();
if(transaction != null) {
// we get the connection from the transaction
logger.debug("Transaction exists for the thread: {}.", Thread.currentThread());
return transaction.getConnection();
}
return this.dataSource.getConnection(username, password);
}
}
然后创建一个DataSourceProvider，以便我们可以使用guice将DataSource注入任何POJO：
公共类DataSourceProvider实现Provider {
private static final Logger logger = LoggerFactory.getLogger(DataSourceProvider.class);
private DataSource dataSource;
public DataSourceProvider() {
JdbcConfig config = getConfig();
ComboPooledDataSource pooledDataSource = new ComboPooledDataSource();
try {
pooledDataSource.setDriverClass(config.getDriver());
} catch (Exception e) {
throw new RuntimeException(e);
}
pooledDataSource.setJdbcUrl(config.getUrl());
pooledDataSource.setUser(config.getUsername());
pooledDataSource.setPassword(config.getPassword() );
pooledDataSource.setMinPoolSize(config.getMinPoolSize());
pooledDataSource.setAcquireIncrement(5);
pooledDataSource.setMaxPoolSize(config.getMaxPoolSize());
pooledDataSource.setMaxStatements(config.getMaxStatementSize());
pooledDataSource.setAutoCommitOnClose(false);
this.dataSource = new JdbcDataSource(pooledDataSource);
}
private JdbcConfig getConfig() {
JdbcConfig config = new JdbcConfig();
Properties prop = new Properties();
try {
//load a properties file from class path, inside static method
prop.load(JdbcConfig.class.getResourceAsStream("/database.properties"));
//get the property value and print it out
config.setDriver(prop.getProperty("driver"));
config.setUrl(prop.getProperty("url"));
config.setUsername(prop.getProperty("username"));
config.setPassword(prop.getProperty("password"));
String maxPoolSize = prop.getProperty("maxPoolSize");
if(maxPoolSize != null) {
config.setMaxPoolSize(Integer.parseInt(maxPoolSize));
}
String maxStatementSize = prop.getProperty("maxStatementSize");
if(maxStatementSize != null) {
config.setMaxStatementSize(Integer.parseInt(maxStatementSize));
}
String minPoolSize = prop.getProperty("minPoolSize");
if(minPoolSize != null) {
config.setMinPoolSize(Integer.parseInt(minPoolSize));
}
}
catch (Exception ex) {
logger.error("Failed to load the config file!", ex);
throw new DBException("Cannot read the config file: database.properties. Please make sure the file is present in classpath.", ex);
}
return config;
}
@Override
public DataSource get() {
return dataSource;
}
然后实现TransactionalMethodInterceptor以使用Transactional注释管理方法的事务：
公共类TransactionalMethodInterceptor实现MethodInterceptor {
private final static Logger logger = LoggerFactory.getLogger(TransactionalMethodInterceptor.class);
@Inject
private JdbcTransactionManager transactionManager;
@Override
public Object invoke(MethodInvocation method) throws Throwable {
try {
// Start the transaction
transactionManager.begin();
logger.debug("Start to invoke the method: " + method);
Object result = method.proceed();
logger.debug("Finish invoking the method: " + method);
transactionManager.commit();
return result;
} catch (Exception e) {
logger.error("Failed to commit transaction!", e);
try {
transactionManager.rollback();
}
catch(Exception ex) {
logger.warn("Cannot roll back transaction!", ex);
}
throw e;
}
}
}
最后，将所有内容放在一起以便Guice可以注入实例的代码：
bind(DataSource.class).toProvider(DataSourceProvider.class).in(Scopes.SINGLETON);
bind(TransactionManager.class).to(JdbcTransactionManager.class);
TransactionalMethodInterceptor transactionalMethodInterceptor = new TransactionalMethodInterceptor();
requestInjection(transactionalMethodInterceptor);
bindInterceptor(Matchers.any(), Matchers.annotatedWith(Transactional.class), transactionalMethodInterceptor);
bind(TestDao.class).to(JdbcTestDao.class);
bind(TestService.class).to(TestServiceImpl.class);
我使用c3p0作为数据源池。所以，它在我的测试中运行得很好。
我找到了另一个相关问题：Guice, JDBC and managing database connections
但到目前为止，除了SpringFramework中的内容之外，我还没有找到任何类似的方法。但即使是Spring中的实现也显得非常复杂。
我想问一下是否有人对此解决方案有任何建议。
感谢。