我应该如何使用jdbc来尝试使用资源呢？
我应该如何使用jdbc来尝试使用资源呢？
public List<User> getUser(int userId) {
String sql = "SELECT id, name FROM users WHERE id = ?";
List<User> users = new ArrayList<User>();
try {
Connection con = DriverManager.getConnection(myConnectionURL);
PreparedStatement ps = con.prepareStatement(sql);
ps.setInt(1, userId);
ResultSet rs = ps.executeQuery();
while(rs.next()) {
users.add(new User(rs.getInt("id"), rs.getString("name")));
}
rs.close();
ps.close();
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
return users;}trytry-with-resources
public List<User> getUser(int userId) {
String sql = "SELECT id, name FROM users WHERE id = ?";
List<User> users = new ArrayList<>();
try {
try (Connection con = DriverManager.getConnection(myConnectionURL);
PreparedStatement ps = con.prepareStatement(sql);) {
ps.setInt(1, userId);
try (ResultSet rs = ps.executeQuery();) {
while(rs.next()) {
users.add(new User(rs.getInt("id"), rs.getString("name")));
}
}
}
} catch (SQLException e) {
e.printStackTrace();
}
return users;}
动漫人物浏览 294回答 3
3回答
-
神不在的星期二
我意识到这很久以前就已经回答了，但我想提出一种额外的方法，以避免嵌套的使用资源的尝试双块。public List<User> getUser(int userId) { try (Connection con = DriverManager.getConnection(myConnectionURL); PreparedStatement ps = createPreparedStatement(con, userId); ResultSet rs = ps.executeQuery()) { // process the resultset here, all resources will be cleaned up } catch (SQLException e) { e.printStackTrace(); }}private PreparedStatement createPreparedStatement(Connection con, int userId) throws SQLException { String sql = "SELECT id, username FROM users WHERE id = ?"; PreparedStatement ps = con.prepareStatement(sql); ps.setInt(1, userId); return ps;} -
蝴蝶刀刀
在您的示例中不需要进行外部尝试，所以您至少可以从3下降到2，而且也不需要关闭;在资源列表的末尾。使用两个try块的优点是，您的所有代码都是预先出现的，因此您不必引用单独的方法：public List<User> getUser(int userId) { String sql = "SELECT id, username FROM users WHERE id = ?"; List<User> users = new ArrayList<>(); try (Connection con = DriverManager.getConnection(myConnectionURL); PreparedStatement ps = con.prepareStatement(sql)) { ps.setInt(1, userId); try (ResultSet rs = ps.executeQuery()) { while(rs.next()) { users.add(new User(rs.getInt("id"), rs.getString("name"))); } } } catch (SQLException e) { e.printStackTrace(); } return users;} -
杨__羊羊
下面是一种使用lambdas和JDK 8供应商来满足外部所有尝试的简洁方法： try (Connection con = DriverManager.getConnection(JDBC_URL, prop); PreparedStatement stmt = ((Supplier<PreparedStatement>)() -> { try { PreparedStatement s = con.prepareStatement( "SELECT userid, name, features FROM users WHERE userid = ?"); s.setInt(1, userid); return s; } catch (SQLException e) { throw new RuntimeException(e); } }).get(); ResultSet resultSet = stmt.executeQuery()) { }
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Java