做一些处理
需要从一个表根据条件查出一个ID
然后通过这个ID去查另一个表里的一些值
private void updateSms() {
Log.getInstance().printInfo("", "正在更新");
Connection conn = null;
Statement stat = null;
ResultSet rsRecord = null;
//全部
ResultSet rsMoSmsAll = null;
int nArg = 0;
int nArg1 = 0;
int nArg2 = 0;
String ctrl=null;
try {
conn = DataBaseManage.getInstance().getConnection();
stat = conn.createStatement();
conn.setAutoCommit(false);
rsRecord = stat.executeQuery( "select SendID from table_a where Flag=1" );
while (rsRecord.next()) {
nArg = stat.executeUpdate( "update table_b set PushStatus = 5 " +"where SendID='"+rsRecord.getString(1)+"'" );
rsMoSmsAll=stat.executeQuery( "select Number from table_b " +"where SendID='"+rsRecord.getString(1)+"' and PushStatus=5" );
}
conn.commit();
} catch (Exception e) {
ExceptionHeading.getException(this.getClass().getName(), e);
}finally{
try {
rsRecord.close();
rsMoSmsAll.close();
stat.close();
conn.close();
} catch (SQLException e) {
ExceptionHeading.getException(this.getClass().getName(), e);
}
}
} 现在的问题是如果rsRecord没查到值的话,在finally时关闭rsMoSmsAll报空指针错误,因为rsMoSmsAll没进行初始化,怎么能初始化rsMoSmsAll呢?Javamysql 异常空指针
需要从一个表根据条件查出一个ID
然后通过这个ID去查另一个表里的一些值
private void updateSms() {
Log.getInstance().printInfo("", "正在更新");
Connection conn = null;
Statement stat = null;
ResultSet rsRecord = null;
//全部
ResultSet rsMoSmsAll = null;
int nArg = 0;
int nArg1 = 0;
int nArg2 = 0;
String ctrl=null;
try {
conn = DataBaseManage.getInstance().getConnection();
stat = conn.createStatement();
conn.setAutoCommit(false);
rsRecord = stat.executeQuery( "select SendID from table_a where Flag=1" );
while (rsRecord.next()) {
nArg = stat.executeUpdate( "update table_b set PushStatus = 5 " +"where SendID='"+rsRecord.getString(1)+"'" );
rsMoSmsAll=stat.executeQuery( "select Number from table_b " +"where SendID='"+rsRecord.getString(1)+"' and PushStatus=5" );
}
conn.commit();
} catch (Exception e) {
ExceptionHeading.getException(this.getClass().getName(), e);
}finally{
try {
rsRecord.close();
rsMoSmsAll.close();
stat.close();
conn.close();
} catch (SQLException e) {
ExceptionHeading.getException(this.getClass().getName(), e);
}
}
} 现在的问题是如果rsRecord没查到值的话,在finally时关闭rsMoSmsAll报空指针错误,因为rsMoSmsAll没进行初始化,怎么能初始化rsMoSmsAll呢?Javamysql 异常空指针
if (rsMoSmsAll != null) {
rsMoSmsAll.close();
}
rsMoSmsAll.close();
stat.close();
conn.close();
每个close必须先进行判断是否为null后,使用try..catch进行关闭
不能用一个try..catch来关闭所有,因为如果前面的哪一个项关闭失败,会导致后面的代码不执行的。