BEAN:
package beans;
import java.sql.*;
public class connDB{
Connection conn=null;
Statement stmt=null;
ResultSet rs=null;
public connDB(){
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
}catch(java.lang.ClassNotFoundException e){
System.err.println(e.getMessage());
}
}
public ResultSet executeQuery(String sql){
try{
conn=DriverManager.getConnection("jdbc:odbc:ayu","sa","");
stmt=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs=stmt.executeQuery(sql);
}catch(SQLException ex){
System.err.println(ex.getMessage());
}
return rs;
}
public int executeUpdate(String sql){
int result=0;
try{
conn=DriverManager.getConnection("jdbc:odbc:ayu","sa","");
stmt=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
result=stmt.executeUpdate(sql);
}catch(SQLException ex){
result=0;
}
return result;
}
public void close(){
try {
if (rs != null) rs.close();
}
catch (Exception e) {
e.printStackTrace(System.err);
}
try {
if (stmt != null) stmt.close();
}
catch (Exception e) {
e.printStackTrace(System.err);
}
try {
if (conn != null) {
conn.close();
}
}
catch (Exception e) {
e.printStackTrace(System.err);
}
}
public String chStr_In(String str){
if(str==null){
str="";
}else{
try{
str=(new String(str.getBytes("iso-8859-1"),"GB2312")).trim();
str=str.replace('\'',(char)1);
}catch(Exception e){
e.printStackTrace(System.err);
}
}
return str;
}
public String chStr_Out(String str){
if(str==null){
str="";
}else{
try{
str=str.replace((char)1,'\'');
}catch(Exception e){
e.printStackTrace(System.err);
}
}
return str;
}
}
參考答案:public ResultSet executeQuery(String sql){
try{
conn=DriverManager.getConnection("jdbc:odbc:ayu","sa","");
stmt=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs=stmt.executeQuery(sql);
}catch(SQLException ex){
System.err.println(ex.getMessage());
}
return rs;
}
这里你的SQL写错了就有可能返回一个空的ResultSet，你去引用的时候就要发生空指针错误！从你给出来的就只能看出这些了