数据库JDBC 增删改查

package com.dao;


import java.util.ArrayList;


import com.db.Mjdbc;
import com.entity.Student;




public class StudentDAO extends SuperDAO {

//增加学生
public boolean addStudent(Student stu)
{
try
{
int Id = getId();
conn=Mjdbc.getConnection();
String sql="insert into student values(?,?,?,?)";
stmt=conn.prepareStatement(sql);
stmt.setInt(1, Id);
stmt.setString(2, stu.getName());
System.out.println("1111111111111");
stmt.setInt(3, stu.getAge());
stmt.setString(4, stu.getSex());
int result=stmt.executeUpdate();
System.out.println("222222222");
if(result>0)
{
return true;
}
}
catch(Exception e)
{
System.out.println("无法执行sql");
}
finally
{
destory();
}
return false;
}
//删除学生
public boolean deleteStudent(String name)
{
try
{
conn=Mjdbc.getConnection();
String sql="delete from student where name=?";
stmt=conn.prepareStatement(sql);
stmt.setString(1, name);
int result=stmt.executeUpdate();
if(result>0)
{
return true;
}
}
catch(Exception e)
{
System.out.println("无法执行sql");
}
finally
{
destory();
}
return false;
}

//查询某同学的所有信息
public Student selectStudent(String userName)
{
try
{
conn=Mjdbc.getConnection();
String sql="select*from student where name=?";
stmt=conn.prepareStatement(sql);
stmt.setString(1, userName);
rs=stmt.executeQuery();
if(rs.next())
{
Student stu=new Student();
stu.setId(rs.getInt(1));
stu.setName(rs.getString(2));
stu.setAge(rs.getInt(3));
stu.setSex(rs.getString(4));
return stu ;
}
}
catch(Exception e)
{
System.out.println("无法执行sql");
}
finally
{
destory();
}
return null;
}
//查询所有用户名
public ArrayList<Student> selectAllStudent()
{
try
{
conn=Mjdbc.getConnection();
String sql="select * from student";
stmt=conn.prepareStatement(sql);
rs=stmt.executeQuery();
ArrayList<Student> list=new ArrayList<Student>();
while(rs.next())
{
Student stu=new Student();
stu.setId(rs.getInt(1));
stu.setName(rs.getString(2));
stu.setAge(rs.getInt(3));
stu.setSex(rs.getString(4));
list.add(stu);
}
return list;
}
catch(Exception e)
{
System.out.println("list没有增加成功");
}
finally
{
destory();
}
return null;
}

public int getMaxId()
{
try
{
conn=Mjdbc.getConnection();
String sql="select max(id) from student";
stmt=conn.prepareStatement(sql);
rs=stmt.executeQuery();
if(rs.next())
{
return rs.getInt(1);
}
}
catch(Exception e)
{
System.out.println("无法执行sql");
}
finally
{
destory();
}
return 0;
}
public int getId()
{
int id=getMaxId();
return id=id+1;

}
//更新资料
public boolean updateStudent(Student stu,String upname)
{
try
{
conn=Mjdbc.getConnection();
String sql="update  student set name=? , age=? , sex=? where name=? ";
stmt=conn.prepareStatement(sql);
stmt.setString(1, stu.getName());
stmt.setInt(2, stu.getAge());
stmt.setString(3, stu.getSex());
stmt.setString(4,upname);
int result=stmt.executeUpdate();
if(result>0)
{
return true;
}
}
catch(Exception e)
{
System.out.println("无法执行sql");
}
finally
{
destory();
}
return false;
}
public static void main(String[] args)
{
Student stu=new Student();
StudentDAO sdao=new StudentDAO();
stu.setName("王娜");
stu.setAge(20);
stu.setSex("女");
sdao.addStudent(stu);
//System.out.println(sdao.updateStudent(stu, "王五"));
}
}