我应该如何将 try-with-resources 与 JDBC 一起使用? [英] How should I use try-with-resources with JDBC?
问题描述
我有一种使用 JDBC 从数据库中获取用户的方法:
I have a method for getting users from a database with JDBC:
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;
}
我应该如何使用 Java 7 try-with-resources 改进此代码?
How should I use Java 7 try-with-resources to improve this code?
我已经尝试过下面的代码,但它使用了许多 try
块,并没有大大提高可读性.我应该以另一种方式使用 try-with-resources
吗?
I have tried with the code below, but it uses many try
blocks, and doesn't improve the readability much. Should I use try-with-resources
in another way?
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;
}
推荐答案
在你的例子中不需要外部 try,所以你至少可以从 3 降到 2,而且你不需要关闭 ;
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预先存在,因此您不必引用单独的方法:
There's no need for the outer try in your example, so you can at least go down from 3 to 2, and also you don't need closing ;
at the end of the resource list. The advantage of using two try blocks is that all of your code is present up front so you don't have to refer to a separate method:
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;
}
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