我的程序是为了获得考试成绩，并将其转换为excel。它包含了很多人参加考试。我的问题是，当我的数据太大时，我无法将其转换为excel，如果我的数据低于70，则工作正常70以上，它只是在网页上打印出来，而不是转换为excel。我得到的错误就像“太多连接”。怎么解决这个？提前致谢。下面是我的代码：
String sql = "SELECT * FROM surveydata WHERE survey_wfverid=? LIMIT 100";// AND ID='c6500937-3a9e-42f2-b01a-c9174f9e2304'";
try{
pstatement = db.getDBConnection().prepareStatement(sql);
pstatement.setString(1, project_id);
rs = pstatement.executeQuery();
int proj_id = Integer.parseInt(project_id);
int wfstnodeid = 0;
if (proj_id==10869){
System.out.println("project_id 2 : " +proj_id);
strRecord = "\"ID\",\"Start\",\"End\",\"Department\",\"Topic\",\"Division\",\"Name\",\"StaffCode\",\"Designation\",\"TotalScore\",\"Answer\",,,,,,,,,,,,,,,,,,,,\n";
}
else if (proj_id==10293){
System.out.println("project_id 3 : " +proj_id);
strRecord = "\"ID\",\"Start\",\"End\",\"Department\",\"Topic\",\"Name\",\"StaffCode\",\"Designation\",\"TrainerName\",\"TotalScore\",\"Answer\",,,,,,,,,,,,,,,,,,,,\n";
}
pstatement2 = db.getDBConnection().prepareStatement("SELECT wfstnodeid FROM wfstation WHERE wfstdesc=? AND wfverid=?");
pstatement2.setString(1, "Start");
pstatement2.setString(2, project_id);
rs2 = pstatement2.executeQuery();
wfstnodeid = 0;
while(rs2.next()){
wfstnodeid = rs2.getInt("wfstnodeid");
System.out.println("wfstnodeid "+wfstnodeid);
}
rs2.close();
pstatement2.close();
while(rs.next()){
String department = null;
String topic = null;
String division = null;
int wflinktoid = 0;
int wfformid = 0;
int score = 0;
ByteArrayInputStream localByteArrayInputStream = new ByteArrayInputStream(rs.getBytes("DATA"));
ObjectInputStream localObjectInputStream = new ObjectInputStream(localByteArrayInputStream);
Map<String, String[]> map = (Map<String, String[]>)localObjectInputStream.readObject();
strRecord += "\"" + rs.getString("ID") + "\",";
strRecord += "\"" + rs.getTimestamp("START").toString() + "\",";
strRecord += "\"" + rs.getTimestamp("END").toString() + "\",";
department = map.get("department")[0];
topic = map.get("topic")[0];
strRecord += "\"" + department + "\",";
strRecord += "\"" + topic + "\",";
if(proj_id==10869){
if (map.get("division")==null){
division = "old samples";
}
else{
division = map.get("division")[0];
}
strRecord += "\"" + division + "\",";
strRecord += "\"" + map.get("11163")[0] + "\","; //name
strRecord += "\"" + map.get("11163")[1] + "\","; //staff code
strRecord += "\"" + map.get("11163")[2] + "\","; //designation
division = null;
}
else if(proj_id==10293){
strRecord += "\"" + map.get("10322")[0] + "\","; //name
strRecord += "\"" + map.get("10322")[1] + "\",";
strRecord += "\"" + map.get("10322")[2] + "\",";
strRecord += "\"" + map.get("10322")[3] + "\",";
}
//get routing topic -- start from here get topic id from wflinktoid
pstatement2 = db.getDBConnection().prepareStatement("SELECT wflinktoid FROM WFLINK WHERE WFLINKFROMID=? AND wfrule=?");
pstatement2.setInt(1, wfstnodeid);//station id
pstatement2.setString(2, "department == '" + department + "' && topic == '" + topic + "'");
rs2 = pstatement2.executeQuery();
wflinktoid = 0;
while(rs2.next()){
wflinktoid = rs2.getInt("wflinktoid");
}
rs2.close();
pstatement2.close();
db.closeDBConnection();
department = null;
topic = null;
pstatement2 = db.getDBConnection().prepareStatement("SELECT wfformid FROM wfsubsform where wfstationid=?");
pstatement2.setInt(1, wflinktoid);
rs2 = pstatement2.executeQuery();
while(rs2.next()){
wfformid = rs2.getInt("wfformid");
}
rs2.close();
pstatement2.close();
db.closeDBConnection();
pstatement2 = db.getDBConnection().prepareStatement("select q.* from survey_questions q, nodelist n where q.fieldid = n.nlnodeid and n.nlidatch=? and (q.exttype='checkbox' or q.exttype='radio') and q.answer is not null order by q.seq");
pstatement2.setInt(1, wfformid);
rs2 = pstatement2.executeQuery();
score = 0;
while(rs2.next()){
if(map.get(rs2.getString("fieldid"))==null){
strRecord += "\"" + map.get(rs2.getString("fieldid")) + "\",";
if(rs2.getString("ANSWER").trim().equals(map.get(rs2.getString("fieldid")))){
score += Integer.parseInt(rs2.getString("SCORE"));//get score
}
}
else{
String map_answer = "";
int y = 0;
while (y < map.get(rs2.getString("fieldid")).length){
map_answer += map.get(rs2.getString("fieldid"))[y] + ",";
y++;
}
map_answer = map_answer.substring(0, map_answer.length() - 1);
//compare answer
if(rs2.getString("ANSWER").trim().equals(map_answer)){
score += Integer.parseInt(rs2.getString("SCORE"));//get score
}
}
}
rs2.close();
pstatement2.close();
db.closeDBConnection();
strRecord += "\"" + score + "\",";
pstatement2 = db.getDBConnection().prepareStatement("select q.* from survey_questions q, nodelist n where q.fieldid = n.nlnodeid and n.nlidatch=? and (q.exttype='checkbox' or q.exttype='radio') and q.answer is not null order by q.seq");
pstatement2.setInt(1, wfformid);
rs2 = pstatement2.executeQuery();
wfformid = 0;
score = 0;
while(rs2.next()){
if(map.get(rs2.getString("fieldid"))==null){
strRecord += "\"" + map.get(rs2.getString("fieldid")) + "\",";
if(rs2.getString("ANSWER").trim().equals(map.get(rs2.getString("fieldid")))){
score += Integer.parseInt(rs2.getString("SCORE"));//get score
}
}
else{
String map_answer = "";
int y = 0;
while (y < map.get(rs2.getString("fieldid")).length){
map_answer += map.get(rs2.getString("fieldid"))[y] + ",";
y++;
}
map_answer = map_answer.substring(0, map_answer.length() - 1);
strRecord += "\"" + map_answer + "\","; //print out user answer
}
}
strRecord = strRecord.substring(0, strRecord.length() - 1);
strRecord += "\n";
rs2.close();
pstatement2.close();
db.closeDBConnection();
}//rs
output = strRecord;
rs.close();
pstatement.close();
db.closeDBConnection();
答案 0 :(得分：2)
阅读代码时会想到两件事：
首先，它组织得不是很好。
例如，pstatement2在pstatement1之后执行，但在读取rs的数据之前会读取其数据。因此，第一步是为您的代码添加一些订单。 （这也使得更容易发现潜在问题）。
其次，db.getDBConnection().prepareStatement(sql); ... db.closeDBConnection();听起来很可疑。 DBConnection不是标准的JDBC类，所以我不知道它的作用。但你打电话
你的代码多次db.closeDBConnection();听起来很奇怪。通常，您应该只在开始时打开一个连接并在结束时关闭它。也许
Connection connection = db.getDBConnection();
pstatement = connection.prepareStatement(sql);
// ...
pstatement2 = connection.prepareStatement("SELECT ...");
// ...
// and at the end (in the finally block):
db.closeDBConnection();
已经对你的情况有所帮助。
最后一句话：即使你修复了你的连接问题（很可能是因为泄漏了连接问题），对于一个大型数据库，你最有可能最终会遇到性能不佳的问题，因为你自己选择了依赖数据。您应该考虑使用JOIN组合查询，因为在连接相关表时，数据库比客户端快得多。