使用JDBC来实现一个简单的增删改查

使用jdbc来实现一个简单的增删改查

package com.database;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import com.entity.Admin;


public class AdminDBHelp {
	
	 // 根据id来修改数据
	public void modify(Admin a) throws SQLException {

		Connection coon = null;
		PreparedStatement preparedStatement = null;

		try {
			coon = DBOpenClose.openConnection();

			String sql = "UPDATE admin SET username ='" + a.getUsername()
			        + "',password='" + a.getPassword()
					+ "'WHERE id = " + a.getId();

			preparedStatement = coon.prepareStatement(sql);

			preparedStatement.executeUpdate();

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBOpenClose.release(null, coon, preparedStatement);

		}
	}
	
    //插入数据
	public void update(Admin admin) throws SQLException {

		Connection coon = null;
		PreparedStatement preparedStatement = null;

		try {
			coon = DBOpenClose.openConnection();

			String sql = "INSERT INTO admin(username,password)" + "VALUES(?,?)";

			preparedStatement = coon.prepareStatement(sql);

			preparedStatement.setString(1, admin.getUsername());
			preparedStatement.setString(2, admin.getPassword());

			preparedStatement.executeUpdate();

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBOpenClose.release(null, coon, preparedStatement);

		}
	}
	
	// 根据id来删除数据
	public void delete(int id) throws SQLException {

		Connection coon = null;
		PreparedStatement preparedStatement = null;

		try {
			coon = DBOpenClose.openConnection();

			String sql = "DELETE FROM admin WHERE id =" + id;

			preparedStatement = coon.prepareStatement(sql);

			preparedStatement.executeUpdate();

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBOpenClose.release(null, coon, preparedStatement);

		}
	}

    
	//查询数据
	public ArrayList<Admin> query() {

		Connection coon = null;
		Statement statement = null;
		ResultSet rs = null;
		ArrayList<Admin>  list = new ArrayList<Admin>();

		try {
			coon = DBOpenClose.openConnection();

			statement = coon.createStatement();

			String sql = " SELECT id,username,password " + "FROM admin";

			rs = statement.executeQuery(sql);

			while (rs.next()) {

				Admin admin = new Admin();
				
				admin.setId(rs.getInt(1));
				admin.setUsername(rs.getString(2));
				admin.setPassword(rs.getString(3));

				list.add(admin);
			}

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBOpenClose.release(rs, coon, statement);
		}

		return list;
	}

}