JDBC java null pointer exception on my resultset while loop -
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- what nullpointerexception, , how fix it? 12 answers
i getting java.lang.nullpointerexception on while loop on aftermigration method not working properly. , getting warnings on if statement preparedstatements.setstring(..) , setint(..). please appreciate responses.
in jdbc code connecting local db. first selecting records in 1 method updating on next aftermigration method.
public static void main (string[] args) throws exception { resultset rs = null; connection bidsconnection = null; mydatabasetest migration = new mydatabasetest(); try { bidsconnection = migration.getoracleconnection(); rs = migration.selectrecordsbids(bidsconnection); migration.aftermigration(bidsconnection, rs); } catch (exception e){ e.printstacktrace(); } { if (migration.scanner != null) { migration.scanner.close(); system.out.println("close scanner"); } if (rs != null) { rs.close(); system.out.println("close resultset"); } if (migration.preparedstatement != null) { migration.preparedstatement.close(); system.out.println("preparedstatement closed"); } if (bidsconnection != null) { bidsconnection.close(); system.out.println("bids connection closed"); } } } public resultset selectrecordsbids(connection dbconnection) throws sqlexception, classnotfoundexception { statement statement = null; string selecttablesql = "select traffic_profile_id traffic_profile_temp" + " traffic_profile_id >= ? , traffic_profile_id <= ? "; system.out.println("bids select statement: " + selecttablesql); preparedstatement = dbconnection.preparestatement(selecttablesql); preparedstatement.setint(1, 1); preparedstatement.setint(2, 1000); // execute select sql statement resultset res = preparedstatement.executequery(); //gets max profile_id record statement = dbconnection.createstatement(); resultset r = statement.executequery("select traffic_profile_id rowcount traffic_profile_temp pe_egress_flag null " +" , pe_ingress_flag null " +" , ce_ingress_flag null " +" , ce_egress_flag null " +" , cos_profile_type null " +" , traffic_profile_id >= 1 , traffic_profile_id <= 1000 "); r.next(); int nullvalues = r.getint("rowcount"); system.out.println("query null valies " + nullvalues); r.close(); statement.close(); system.out.println("traffic_profile_temp table has null traffic_profile_id of " + nullvalues ); return res; } public void aftermigration(connection dbconnection, resultset rs) throws exception { preparedstatement preparedstatement = null; string update1 = "update traffic_profile_temp set cos_profile_type = ?, pe_ingress_flag = ?, pe_egress_flag = ?, ce_ingress_flag = ?, ce_egress_flag = ?" + " traffic_profile_id >= ? , traffic_profile_id <= ?"; string update2 = "update traffic_profile_temp set cos_profile_type = ?, pe_ingress_flag = ?, pe_egress_flag = ?, ce_ingress_flag = ?, ce_egress_flag = ? " + " cosmodel = ? "; system.out.println("bids manual updating after migration statement: " + update1); system.out.println("updating bids database in process ..."); preparedstatement = dbconnection.preparestatement(update1); while (rs.next()) { string cosprofiletype = rs.getstring("cos_profile_type"); string peingressflag = rs.getstring("pe_ingress_flag"); string peegressflag = rs.getstring("pe_egress_flag"); string ceingressflag = rs.getstring("ce_ingress_flag"); string ceegressflag = rs.getstring("ce_egress_flag"); int trafficprofileid = rs.getint("traffic_profile_id"); string cosmodel = rs.getstring("cosmodel"); if ((trafficprofileid > 0 && trafficprofileid < 25 ) && cosprofiletype == null && cosprofiletype == "" && peingressflag == null && peegressflag == null && ceingressflag == null && ceegressflag == null) { system.out.println("first if statement"); preparedstatement.setstring(1, "legacy"); preparedstatement.setstring(2, "t"); preparedstatement.setstring(3, "t"); preparedstatement.setstring(4, "f"); preparedstatement.setstring(5, "f"); preparedstatement.setint (6, 1); preparedstatement.setint (7, 24); preparedstatement.addbatch(); } else if ((trafficprofileid > 126 && trafficprofileid < 138 ) && cosprofiletype == null && cosprofiletype == "" && peingressflag == null && peegressflag == null && ceingressflag == null && ceegressflag == null) { system.out.println("2 if statement"); preparedstatement.setstring(1, "standard"); preparedstatement.setstring(2, "t"); preparedstatement.setstring(3, "t"); preparedstatement.setstring(4, "f"); preparedstatement.setstring(5, "f"); preparedstatement.setint (6, 127); preparedstatement.setint (7, 137); preparedstatement.addbatch(); } else if ((trafficprofileid > 799 && trafficprofileid < 900 ) && cosprofiletype == null && cosprofiletype == "" && peingressflag == null && peegressflag == null && ceingressflag == null && ceegressflag == null ) { system.out.println("3 if statement"); preparedstatement.setstring(1, "standard"); preparedstatement.setstring(2, "t"); preparedstatement.setstring(3, "t"); preparedstatement.setstring(4, "f"); preparedstatement.setstring(5, "f"); preparedstatement.setint (6, 800); preparedstatement.setint (7, 899); preparedstatement.addbatch(); } system.out.println("bids manual update2 statement: " + update2); system.out.println("updating bids database in process ..."); preparedstatement = dbconnection.preparestatement(update2, resultset.type_scroll_insensitive, resultset.concur_updatable); if ((cosmodel == "optb" ) && cosprofiletype == null && cosprofiletype == "" && peingressflag == null && peegressflag == null && ceingressflag == null && ceegressflag == null ) { system.out.println("4 if statement"); preparedstatement.setstring(1, "optionb"); preparedstatement.setstring(2, "t"); preparedstatement.setstring(3, "t"); preparedstatement.setstring(4, "f"); preparedstatement.setstring(5, "f"); preparedstatement.setstring(6, "optb"); preparedstatement.addbatch(); } } int[] affectedrecords =preparedstatement.executebatch(); dbconnection.commit(); }
the java.lang.nullpointerexception , warnings getting due logic of if-statements.
for instance, take first if-statement:
if ((trafficprofileid > 0 && trafficprofileid < 25) && cosprofiletype == null && cosprofiletype == "" && peingressflag == null && peegressflag == null && ceingressflag == null && ceegressflag == null) { //dead code warning here } when cosprofiletype null, condition cosprofiletype == null true, code continues , hits cosprofiletype == "", triggers nullpointerexception.
this logic makes if-statement never true (an object null never empty). means code inside if-statements never executed, hence warnings.
edit:
as pointed out mark rotteveel, cosprofiletype == null not throw nullpointerexception.
i recommend reading on use of == compare strings:
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