Transaction表示一个事务

Transaction表示一个事务,它是一个接口，定义了下面这样的常用的方法

/**
 * Wraps a database connection.
 * Handles the connection lifecycle that comprises: its creation, preparation, commit/rollback and close. 
 *
 */
public interface Transaction {

  /**
   * Retrieve inner database connection
   * @return DataBase connection
   * @throws SQLException
   */
  Connection getConnection() throws SQLException;

  /**
   * Commit inner database connection.
   * @throws SQLException
   */
  void commit() throws SQLException;

  /**
   * Rollback inner database connection.
   * @throws SQLException
   */
  void rollback() throws SQLException;

  /**
   * Close inner database connection.
   * @throws SQLException
   */
  void close() throws SQLException;

}

有JdbcTransaction实现,ManagedTransaction实现和SpringManagedTransaction实现

public class JdbcTransaction implements Transaction {
  protected Connection connection;
  protected DataSource dataSource;
  protected TransactionIsolationLevel level;
  protected boolean autoCommmit;

  public JdbcTransaction(DataSource ds, TransactionIsolationLevel desiredLevel, boolean desiredAutoCommit) {
    dataSource = ds;
    level = desiredLevel;
    autoCommmit = desiredAutoCommit;
  }

  public JdbcTransaction(Connection connection) {
    this.connection = connection;
  }

JdbcTransaction很简单，就是调用Connection的相应方法

public class ManagedTransaction implements Transaction {
  private DataSource dataSource;
  private TransactionIsolationLevel level;
  private Connection connection;
  private boolean closeConnection;

  public ManagedTransaction(Connection connection, boolean closeConnection) {
    this.connection = connection;
    this.closeConnection = closeConnection;
  }

  public ManagedTransaction(DataSource ds, TransactionIsolationLevel level, boolean closeConnection) {
    this.dataSource = ds;
    this.level = level;
    this.closeConnection = closeConnection;
  }

Managed Transaction更简单，和Jdbc一样，只是rollback和commit实现为空

public class SpringManagedTransaction implements Transaction {
  private final DataSource dataSource;

  private Connection connection;

  private boolean isConnectionTransactional;

  private boolean autoCommit;

  public SpringManagedTransaction(DataSource dataSource) {
    notNull(dataSource, "No DataSource specified");
    this.dataSource = dataSource;
  }

SpringManaged Transaction的实现也简单，就是调用Spring中的DataSourceUtils类来实现

类中使用了JDK5的语法，如下导入某些静态方法 。。。

import static org.springframework.jdbc.datasource.DataSourceUtils.isConnectionTransactional;
import static org.springframework.jdbc.datasource.DataSourceUtils.releaseConnection;
import static org.springframework.util.Assert.notNull;