在ejb 3.0 jboss 6环境中,我有一个名为DBInterface的bean,它被注入到许多dao类中以执行sql查询。DBInterface bean将数据源作为字段变量注入。DBInterface bean中的所有方法都从注入的数据源获取数据库连接,并在处理完db调用后关闭连接。在运行应用程序时,经过一段时间后,我得到sql异常,说不能创建db连接。我关闭了finally块中每个方法调用的连接。我在哪里出错了?我在jboss中使用ejb 3.0。问候V
public class DBInterface {
@Resource(mappedName = "java:ora.ds", type = DataSource.class)
private static DataSource dataSource;
protected Connection getConnection(){
try {
return dataSource.getConnection();
} catch (SQLException e) {
e.printstacktrace();
}
}
public void method1() {
Connection connection = null;
try {
connection = getConnection();
...............
db codes
.................
} catch (SQLException e) {
logger.error(e);
throw new DBException("sql exception ", e);
} finally {
try {
closeResources(rs, statement, connection);
} catch (SQLException e) {
logger.error(e);
throw new DBException("sql exception ", e);
}
}
}
public void closeResources(ResultSet rs, Statement st, Connection con)
throws SQLException {
if (rs != null) {
rs.close();
}
if (st != null) {
st.close();
}
if (con != null) {
con.close();
}
}
}
你应该使用try-catch块来关闭任何资源。
if (rs != null) {
rs.close();
}
if (st != null) {
st.close();
}
if (con != null) {
con.close();
}
应替换为:
if (rs != null) {
try {
rs.close();
} catch (Exception exception) {
logger.log("Failed to close ResultSet", exception);
}
}
if (st != null) {
try {
st.close();
} catch (Exception exception) {
logger.log("Failed to close Statement", exception);
}
}
if (con != null) {
try {
con.close();
} catch (Exception exception) {
logger.log("Failed to close Connection", exception);
}
}
可以使用AbstractDAO类将其重构为更容易阅读的内容:
public class DAOException extends RuntimeException {
public DAOException(Throwable cause) {
super(cause);
}
}
public abstract class AbstractDAO {
private static Logger logger = ...;
private DataSource dataSource;
protected void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
public Connection getConnection() {
try {
return dataSource.getConnection();
} catch (SQLException exception) {
// There's nothing we can do
throw new DAOException(exception);
}
}
public void close(Connection connection) {
try {
connection.close();
} catch (Exception exception) {
// Log the exception
logger.log("Failed to close Connection", exception);
}
}
public void close(Statement statement) {
try {
statement.close();
} catch (Exception exception) {
// Log the exception
logger.log("Failed to close Statement", exception);
}
}
public void close(ResultSet resultSet) {
try {
resultSet.close();
} catch (Exception exception) {
// Log the exception
logger.log("Failed to close ResultSet", exception);
}
}
}
public class MyDAO extends AbstractDAO {
@Override
@Resource("jdbc/myDS")
protected void setDataSource(DataSource dataSource) {
super.setDataSource(dataSource);
}
public void insert(MyObject myObject) {
Connection connection = getConnection();
try {
PreparedStatement query = connection.createPreparedStatement("INSERT INTO MYOBJECT (ID, VALUE) VALUES (?, ?)");
try {
query.setLong(1, myObject.getID());
query.setString(2, myObject.getValue());
if (query.executeUpdate() != 1) {
throw new DAOException("ExecuteUpdate did not return expected result");
}
} finally {
close(query);
}
} catch (SQLException exception) {
// There's nothing we can do
throw new DAOException(exception);
} finally {
close(connection);
}
}
}
我想知道的是,为什么你不使用JPA?我会考虑只将JDBC用于不能从缓存中获益的性能关键型应用程序。