Java 如何优化从resultset返回的大量数据

我的程序是获取考试结果，并将其转换为excel。它包含了很多参加考试的人。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，它工作正常。70以上，只需在网页中打印，不转换为excel。我遇到了“连接太多”这样的错误。如何解决这个问题？提前谢谢。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();

String sql=“从surveydata中选择*，其中survey\u wfverid=？限制100”//ID='c6500937-3a9e-42f2-b01a-c9174f9e2304'；
试一试{
pstatement=db.getDBConnection（）.prepareStatement（sql）；
pstatement.setString（1，项目id）；
rs=pstatement.executeQuery（）；
int proj_id=Integer.parseInt（项目id）；
int wfstnodeid=0；
如果（项目id==10869）{
System.out.println（“项目id 2:+项目id”）；
strRecord=“\'ID\”、\'Start\”、\'End\”、\'DEPARTY\、\'Topic\、\'DEVISITION\”、\'Name\、\'StaffCode\”、\'DESTATION\”、\'TOTALLSCORE\、\'ANSWERK\”、，，，，，，，，，，，，，，，，，，，，\n；
}
否则如果（项目id==10293）{
System.out.println（“项目id 3:+项目id”）；
strRecord=“\'ID\”、\'Start\”、\'End\”、\'Department\、\'Topic\、\'Name\、\'StaffCode\”、\'DESIGNTION\、\'TrainerName\、\'TOTALLSCORE\”、\'ANSWORT\，，，，，，，，，，，，，，，，，\n；
}
pstatement2=db.getDBConnection（）.prepareStatement（“从wfstation中选择wfstnodeid，其中wfstdesc=？和wfverid=？”；
pstatement2.设置字符串（1，“开始”）；
pstatement2.设置字符串（2，项目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（））{
字符串department=null；
字符串主题=null；
字符串除法=空；
int wflinktoid=0；
int wformid=0；
智力得分=0；
ByteArrayInputStream localByteArrayInputStream=新的ByteArrayInputStream（rs.getBytes（“数据”）；
ObjectInputStream localObjectInputStream=新ObjectInputStream（localByteArrayInputStream）；
Map Map=（Map）localObjectInputStream.readObject（）；
strRecord+=“\”+rs.getString（“ID”）+“\”，”；
strRecord+=“\”+rs.getTimestamp（“开始”）.toString（）+“\”，”；
strRecord+=“\”+rs.getTimestamp（“结束”）.toString（）+“\”，“；
department=map.get（“department”）[0]；
topic=map.get（“topic”）[0]；
STRECORD+=“\”+部门+“\”，“；
strRecord+=“\”+主题+“\”，“；
如果（项目id==10869）{
if（map.get（“division”）==null）{
分部=“旧样品”；
}
否则{
division=map.get（“division”）[0]；
}
strRecord+=“\”+除法+“\”，“；
strRecord+=“\”+map.get（“11163”）[0]+“\”，“；//name
strRecord+=“\”+map.get（“11163”）[1]+“\”，“；//员工代码
strRecord+=“\”“+map.get（“11163”）[2]+“\”，“；//名称
除法=空；
}
否则如果（项目id==10293）{
strRecord+=“\”+map.get（“10322”）[0]+“\”，“；//name
strRecord+=“\”+map.get（“10322”）[1]+“\”，”；
strRecord+=“\”+map.get（“10322”）[2]+“\”，”；
strRecord+=“\”+map.get（“10322”）[3]+“\”，”；
}
//获取路由主题--从这里开始从wflinktoid获取主题id
pstatement2=db.getDBConnection（）.prepareStatement（“从WFLINK中选择wflinktoid，其中WFLINKFROMID=？和wfrule=？”；
pstatement2.setInt（1，wfstnodeid）；//站点id
pstatement2.setString（2，“部门=='”+department+“'&&topic=='“+topic+””）；
rs2=pstatement2.executeQuery（）；
wflinktoid=0；
while（rs2.next（））{
wflinktoid=rs2.getInt（“wflinktoid”）；
}
rs2.close（）；
pstatement2.close（）；
db.closeDBConnection（）；
部门=空；
topic=null；
pstatement2=db.getDBConnection（）.prepareStatement（“从WFSubForm中选择wfformid，其中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（“从调查问题q中选择q.*，节点列表n，其中q.fieldid=n.nlnodeid和n.nlidatch=？和（q.exttype='checkbox'或q.exttype='radio'），q.answer按q.seq的顺序不是空的”）；
pstatement2.setInt（1，wformid）；
rs2=pstatement2.executeQuery（）；
得分=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”）；//获取分数
}   
}
否则{
字符串映射_answer=“”；
int y=0；
while（yConnection connection = db.getDBConnection();
pstatement = connection.prepareStatement(sql);
// ...
pstatement2 = connection.prepareStatement("SELECT ...");
// ...
// and at the end (in the finally block):
db.closeDBConnection();