Question

我遇到了一个空结果集的问题，这会导致一些错误。但只要它不是空的，它就能正常工作。

String sql = "SELECT M2.fromProfileId, profiles.profileMiniature, profiles.firstName, profiles.lastName, profiles.timeFormat, lastMessages.message, lastMessages.timeStamp " +
                "FROM   (" +
                "       SELECT M1.fromProfileId, " +
                "           max(M1.timeStamp) AS lastMessageTime " +
                "       FROM messages AS M1 " +
                "       WHERE M1.toProfileId = ? " +
                "       GROUP BY M1.fromProfileId " +
                "       ORDER BY max(M1.timeStamp) DESC " +
                "       LIMIT 10 " +//line 60
                "       ) AS M2 " +
                "INNER JOIN messages AS lastMessages " +
                "ON     (" +
                "       lastMessages.timeStamp = M2.lastMessageTime " +
                "AND    lastMessages.fromProfileId = M2.fromProfileId" +
                "       )" +
                "INNER JOIN profiles " +
                "ON M2.fromProfileId = profiles.profileId ";

PreparedStatement statement = con.prepareStatement(sql);

statement.setString(1, profileId);
ResultSet result = statement.executeQuery();

JSONArray messages = new JSONArray();
while(result.next()){
    JSONObject message = new JSONObject();

    message.put("fromProfileId", result.getString("fromProfileId"));
    message.put("profileMiniature", result.getString("profileMiniature"));
    message.put("firstName", result.getString("firstName"));
    message.put("lastName", result.getString("lastName"));
    message.put("lastMessage", result.getString("message"));
    message.put("lastMessageTime", result.getString("timeStamp"));
    message.put("timeFormat", result.getString("timeFormat"));
    messages.put(message);
}

，错误为Illegal operation on empty result set。我该如何解决这个问题？

堆栈跟踪：

空结果集上的非法操作。在 com.mysql.jdbc.SQLError.createSQLException（SQLError.java:1073）在 com.mysql.jdbc.SQLError.createSQLException（SQLError.java:987）在 com.mysql.jdbc.SQLError.createSQLException（SQLError.java:982）在 com.mysql.jdbc.SQLError.createSQLException（SQLError.java:927）在 com.mysql.jdbc.ResultSetImpl.checkRowPos（ResultSetImpl.java:841）在 com.mysql.jdbc.ResultSetImpl.getStringInternal（ResultSetImpl.java:5656）在 com.mysql.jdbc.ResultSetImpl.getString（ResultSetImpl.java:5576）在 com.mysql.jdbc.ResultSetImpl.getString（ResultSetImpl.java:5616）在 messages.GetMessages.doGet（GetMessages.java:60）在 javax.servlet.http.HttpServlet.service（HttpServlet.java:707）在 javax.servlet.http.HttpServlet.service（HttpServlet.java:820）在 org.eclipse.jetty.servlet.ServletHolder.handle（ServletHolder.java:534）等。

Answer 1

我在MySQL JDBC驱动程序中发现了many个错误，这似乎导致了这个异常。

java中的错误SQL：空结果集上的非法操作

1 个答案: