有人能告诉我是否第一个stmt.close();以下JDBC代码中是否需要针对两个不同的表执行两个不同的SQL查询？
public class MyService {
private Connection connection = null;
public void save(Book book) {
try {
Class.forName("com.MysqL.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:MysqL://localhost:3306/mydb","root","password");
PreparedStatement stmt = connection.prepareStatement("INSERT INTO PUBLISHER (CODE,PUBLISHER_NAME) VALUES (?,?)");
stmt.setString(1,book.getPublisher().getCode());
stmt.setString(2,book.getPublisher().getName());
stmt.executeUpdate();
stmt.close(); //1
stmt = connection.prepareStatement("INSERT INTO BOOK (ISBN,BOOK_NAME,PUBLISHER_CODE) VALUES (?,?,book.getIsbn());
stmt.setString(2,book.getName());
stmt.setString(3,book.getPublisher().getCode());
stmt.executeUpdate();
stmt.close(); //2
} catch (ClassNotFoundException e) { e.printStackTrace(); } catch (sqlException e) { e.printStackTrace(); }
finally { connection.close(); }
}
}
解决方法
在我的书中,我总是建议关闭已经打开的资源以避免可能的泄漏.
稍微更现代的方式是使用try-with-resources：
try (Connection connection = DriverManager.getConnection("jdbc:MysqL://localhost:3306/mydb","password")) {
try (PreparedStatement stmt = connection.prepareStatement("INSERT INTO PUBLISHER (CODE,?)")) {
stmt.setString(1,book.getPublisher().getCode());
stmt.setString(2,book.getPublisher().getName());
stmt.executeUpdate();
}
// stmt is auto closed here,even if sqlException is thrown
try (PreparedStatement stmt = connection.prepareStatement("INSERT INTO BOOK (ISBN,?)");
stmt.setString(1,book.getIsbn());
stmt.setString(2,book.getName());
stmt.setString(3,book.getPublisher().getCode());
stmt.executeUpdate();
}
// stmt is auto closed here,even if sqlException is thrown
}
// connection is auto closed here,even if sqlException is thrown
