java - 无法从 H2 数据库获得结果

Question

我试图从 h2 db 中获取值，但总是出现此错误

 org.h2.jdbc.JdbcSQLException: No data is available [2000-171]
    at org.h2.message.DbException.getJdbcSQLException(DbException.java:329)
    at org.h2.message.DbException.get(DbException.java:169)
    at org.h2.message.DbException.get(DbException.java:146)
    at org.h2.message.DbException.get(DbException.java:135)
    at org.h2.jdbc.JdbcResultSet.checkOnValidRow(JdbcResultSet.java:2956)
    at org.h2.jdbc.JdbcResultSet.get(JdbcResultSet.java:2962)
    at org.h2.jdbc.JdbcResultSet.getInt(JdbcResultSet.java:306)

我用谷歌搜索了一个答案

Make sure to call rs.next(); prior to using any of the getter methods.

但我调用 rs.next() ...

这是我的代码:

public User getUser(int userId) throws SQLException {
    User u = new User(userId);

    try {
        Statement st = conn.createStatement();
        ResultSet rs = st.executeQuery("SELECT * FROM invited_users WHERE user_id=" + userId);
        rs.next();

        u.setName(rs.getString("user_name"));

    } catch (SQLException except) {
        JOptionPane.showMessageDialog(null, "Unable to load user! " + except);
    }
    return u;
}

Answer 1

问题出在结果集中，它是空的。

只需替换这段代码

rs.next();

u.setName(rs.getString("user_name"));

与

if (rs.next()) {
    u.setName(rs.getString("user_name"));
}