JDBC 笔记3 通过PreparedStatement 对数据库进行增删改查

1 插入数据


public boolean ChaRu3(User user){
boolean flag=true;
Connection conn=null;
PreparedStatement ps=null; //创建PreparedStatement 对象
String sql= "insert into user (name,pwd) values(?,?)"; //sql语句不再采用拼接方式，应用占位符问号的方式写sql语句。
conn=DBConnUtil.getConn();
try {
ps=conn.prepareStatement(sql);
ps.setString(1, user.getName()); //对占位符设置值，占位符顺序从1开始，第一个参数是占位符的位置，第二个参数是占位符的值。
ps.setString(2, user.getPwd());
int i=ps.executeUpdate();
if(i==0){
flag=false;
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
DBConnUtil.closeAll(null, ps, conn);
}
return flag;

}



2 修改数据




public boolean XiuGai3(User user){
boolean flag=true;
Connection conn=null;
PreparedStatement ps=null;
String sql="update user set pwd=? where name=?";
conn=DBConnUtil.getConn();
try {
ps=conn.prepareStatement(sql);
ps.setString(1, user.getPwd());
ps.setString(2, user.getName());
int i= ps.executeUpdate();
if(i==0){
flag=false;
}

} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
DBConnUtil.closeAll(null, ps, conn);
}
return flag;
}



3 删除数据


public boolean ShanChu3(int id){
boolean flag=true;
Connection conn=null;
PreparedStatement ps=null;
String sql="delete from user where id=?";
conn=DBConnUtil.getConn();
try {
ps=conn.prepareStatement(sql);
ps.setInt(1, id);
int i=ps.executeUpdate();
if(i==0){
flag=false;
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
DBConnUtil.closeAll(null, ps, conn);
}

return flag;
}



4 查看数据


public List<User> ChaKan3(){
List<User> list= new ArrayList<User>();
Connection conn=null;
PreparedStatement ps=null;
ResultSet rs=null;
String sql="select * from user";
conn=DBConnUtil.getConn();
try {
ps=conn.prepareStatement(sql);
rs=ps.executeQuery();
while(rs.next()){
User user= new User();
user.setName(rs.getString("name"));
list.add(user);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
DBConnUtil.closeAll(rs, ps, conn);
}

return list;
}