我应该如何在JDBC中使用try-with-resources？ [英] How should I use try-with-resources with JDBC?

问题描述

我有一种方法可以使用JDBC从数据库中获取用户：

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 试用资源 来改进此代码？

How should I use Java 7 try-with-resources to improve this code?

我尝试使用下面的代码，但它使用了许多尝试，并没有改善可读性许多。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, 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

我意识到这是很久以前的事了已回答但希望建议另一种方法，以避免嵌套的try-with-resources双重阻止。

I realize this was long ago answered but want to suggest an additional approach that avoids the nested try-with-resources double block.

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;
}

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