我正在尝试发送图片的增加计数变量（每当新会话点击图片时，通过增加+1来增加该变量）。我收到以下错误消息，但我正在检查空结果集。我的思维过程是，我可以尝试选择已调用的pictureNo，如果找不到该pictureNo，我们只需将第一个计数插入表中，如果可以找到，则更新该计数。
错误消息： “ SQLException：对空结果集进行非法操作。”
增加会话计数的代码
HttpSession session = request.getSession() ;
Integer counter = (Integer) session.getAttribute("counter");
String accCount = (String) session.getAttribute("attributeKey") ;
String url = "http://localhost:8080/techfore";
String encodedURL = url + ";jsessionid=" + request.getSession().getId();
if (accCount == null || encodedURL == null) { // New session?
response.sendRedirect("/techfore/WelcomePage");
}
else{
if(counter == 0) {
counter = new Integer(counter.intValue() + 1);
session.setAttribute("counter", counter);
}
}
Utilities.initalCount(out, pictureName, counter);
运行查询的代码
public static void initalCount(PrintWriter out, String pictureName, int accessCount) {
Connection con = null;
try { // Connect to the database
con = openConnection(out);
}
catch (Exception e) { // Failed to open the connection
out.println("<P>" + e.getMessage());
}
try {
Statement stmt = con.createStatement();
String query0;
ResultSet rs1;
query0="SELECT PictureNo FROM Statistics WHERE PictureNo = (SELECT PictureNo FROM Pictures WHERE ShortName = '"+pictureName+"')";
rs1 = stmt.executeQuery(query0);
if(rs1.next()){
//yes exist
String description = rs1.getString("Description");
int pictureNo = rs1.getInt("PictureNo");
IncreaseCount(out, pictureNo, accessCount);
}
else {
//if rs is null insert
int pictureNo = rs1.getInt("PictureNo");
AddCount(out, pictureNo, accessCount);
}
stmt.close() ;
}
catch(SQLException ex) {
out.println("<P>SQLException: " + ex.getMessage()) ;
}
}
public static void AddCount(PrintWriter out, int pictureNo, int accessCount) {
Connection con = null;
try { // Connect to the database
con = openConnection(out);
}
catch (Exception e) { // Failed to open the connection
out.println("<P>" + e.getMessage());
return;
}
try {
Statement stmt = con.createStatement();
String query;
ResultSet rs1;
query="INSERT INTO Statistics VALUES "+pictureNo+","+accessCount+" ";
stmt.executeUpdate(query);
stmt.close() ;
}
catch(SQLException ex) {
out.println("<P>SQLException: " + ex.getMessage()) ;
}
}
public static void IncreaseCount(PrintWriter out, int pictureNo, int accessCount) {
Connection con = null;
try { // Connect to the database
con = openConnection(out);
}
catch (Exception e) { // Failed to open the connection
out.println("<P>" + e.getMessage());
return;
}
try {
Statement stmt = con.createStatement();
String query;
ResultSet rs1;
query="UPDATE Statistics SET AccessCount = "+accessCount+" + 1 WHERE PictureNo = "+pictureNo+"";
stmt.executeUpdate(query);
stmt.close() ;
}
catch(SQLException ex) {
out.println("<P>SQLException: " + ex.getMessage()) ;
}
}
新插入
query="INSERT INTO Statistics VALUES (SELECT PictureNo FROM Pictures WHERE FileName = '"+pictureName+"'),"+accessCount+" ";