[英]Which of these two is the best way to handle try-catches for closing ResultSet, PreparedStatement, and Connection in a DAO class that uses JDBC?
我正在创建一个使用JDBC和MySQL的DAO类。 我没有收到任何有关如何关闭标题中列出的项目的指示,但我读到这样做是一种好习惯。 现在,我认为应该在每种CRUD方法中都执行此操作,但是处理异常似乎有些人为,而且我还不确定如何实现它。
第一个例子:
public boolean update2(Dto dto) {
assert dto != null;
if (readById(dto.getId()).getId() == 0) {
throw new RuntimeException("Row with this id doesn't exist");
}
boolean flag = false;
try {
Connection connection = DAOFactory.createConnection();
String sql = "SQL statement";
try {
PreparedStatement ps = connection.prepareStatement(sql);
try {
// Some stuff with preparedstatement
ps.executeUpdate();
flag = true;
} finally {
if (ps != null) ps.close();
}
} finally {
if (connection != null) connection.close();
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return flag;
}
第二个例子:
public boolean update(Dto dto) {
assert dto != null;
if (readById(dto.getId()).getId() == 0) {
throw new RuntimeException("Row with this id doesn't exist");
}
boolean flag = false;
PreparedStatement ps = null;
Connection connection = null;
try {
connection = DAOFactory.createConnection();
String sql = "SQL statement";
ps = connection.prepareStatement(sql);
// Some stuff with preparedstatement
ps.executeUpdate();
flag = true;
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (ps != null) {
try {
ps.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
return flag;
}
在第二个示例中,我需要重复的异常处理。 第一种解决方案对我来说似乎更聪明,但是我不确定它是否比第二种更具可读性。
设计中是否要采用不仅主观的惯例?
假设您使用的是Java 1.7及更高版本,则可以使用try with resources语句简化资源的关闭。 假设资源实现了AutoClosable
接口(在Connection
和PreparedStatement
就是这种情况),则可以按以下方式重写代码:
public boolean update2(String dto) {
assert dto != null;
if (readById(dto.getId()).getId() == 0) {
throw new RuntimeException("Row with this id doesn't exist");
}
boolean flag = false;
String sql = "SQL statement";
try (Connection connection = DAOFactory.createConnection();
PreparedStatement ps = connection.prepareStatement(sql)) {
ps.executeUpdate();
flag = true;
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return flag;
}
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