java是否在语句上尝试使用WithResources关闭连接？

Question

在这个代码中，连接会被关闭吗

Connection con = DriverManager.getConnection(dbUrl, user, pass);
try (Statement st = con.createStatement()) {
    ResultSet rs = st.executeQuery(query);
}

我的代码中有东西意外地关闭了连接，我想确定不是这样

Answer 1

不，调用closeon语句不会关闭连接。这将阻止我们在已经打开的连接上创建下一条语句，这意味着我们必须为每条语句创建新的连接（这可能是一个昂贵的操作）

你可以很容易地测试它。在上一条语句关闭后，尝试创建另一条语句

Connection con = DriverManager.getConnection(dbUrl,user,pass);
try (Statement st = con.createStatement()) {
    ResultSet rs = st.executeQuery(sqlQuery1);
    simplePrint(rs);
} catch (SQLException e) {
    e.printStackTrace();
}//here `st` will be closed automatically by try-with-resources

try (Statement st = con.createStatement()) {//lets try to create next statement
    ResultSet rs = st.executeQuery(sqlQuery2);
    simplePrint(rs);
} catch (SQLException e) {
    e.printStackTrace();
}

simplePrint方法可能如下所示：

public static void simplePrint(ResultSet rs) throws SQLException {
    ResultSetMetaData meta = rs.getMetaData();
    while (rs.next()) {
        for (int i = 1; i <= meta.getColumnCount(); i++) {
            System.out.print(rs.getObject(i)+"\t");
        }
        System.out.println();
    }
}