import java.sql.*;
import java.util.*;
import java.io.*;
public class Charu {
public String driver;
Connection conn;
public String pass;
public String user;
public String url;
Statement sta;
public void ininpram(String wenjian) throws IOException
{
Properties props=new Properties();
props.load(new FileInputStream(wenjian));
driver=props.getProperty("driver");
pass=props.getProperty("pass");
user=props.getProperty("user");
url=props.getProperty("url");
}
public ResultSet inser(String sql) throws Exception
{ try
{
// Class.forName(driver);
//conn=DriverManager.getConnection(url,user,pass);
Class.forName(driver);
conn=DriverManager.getConnection(url,user,pass);
sta=conn.createStatement();
ResultSet re=sta.executeQuery(sql);
return re;
}
finally{
if(sta!=null)
{
sta.close();
}
if(conn!=null)
{
conn.close();
}
}
}
public static void main(String[] args) throws Exception
{
Charu ed=new Charu();
ResultSet res=ed.inser("select * from student");
while (res.next())
{
System.out.println(res.getInt(1)+"\t"+
res.getInt(1)+"\t"+
res.getInt(1)+"\t"+
res.getInt(1)+"\t");
}
}
}
用eclipe提示Exception in thread "main" java.lang.NullPointerException
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at Charu.inser(Charu.java:32)
at Charu.main(Charu.java:54)
import java.util.*;
import java.io.*;
public class Charu {
public String driver;
Connection conn;
public String pass;
public String user;
public String url;
Statement sta;
public void ininpram(String wenjian) throws IOException
{
Properties props=new Properties();
props.load(new FileInputStream(wenjian));
driver=props.getProperty("driver");
pass=props.getProperty("pass");
user=props.getProperty("user");
url=props.getProperty("url");
}
public ResultSet inser(String sql) throws Exception
{ try
{
// Class.forName(driver);
//conn=DriverManager.getConnection(url,user,pass);
Class.forName(driver);
conn=DriverManager.getConnection(url,user,pass);
sta=conn.createStatement();
ResultSet re=sta.executeQuery(sql);
return re;
}
finally{
if(sta!=null)
{
sta.close();
}
if(conn!=null)
{
conn.close();
}
}
}
public static void main(String[] args) throws Exception
{
Charu ed=new Charu();
ResultSet res=ed.inser("select * from student");
while (res.next())
{
System.out.println(res.getInt(1)+"\t"+
res.getInt(1)+"\t"+
res.getInt(1)+"\t"+
res.getInt(1)+"\t");
}
}
}
用eclipe提示Exception in thread "main" java.lang.NullPointerException
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at Charu.inser(Charu.java:32)
at Charu.main(Charu.java:54)
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props.load(new FileInputStream(wenjian)); // 这里wenjian路径对了没?
driver=props.getProperty("driver");