JDBC的ORM，全拼是Object Relationship Database Mapping 对象关系映射

对象关系映射虽然比较简单基础，不过却是后边持久层框架的根基，所以还是需要记录一下的

insert的时候出现乱码问题，以前没有遇到过，这次也顺手写一下总结，暂时不放在这里了，怕篇幅太长

将一个对象插入数据库中

package ORM;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;


/**
 * 
 * 将一个对象插入数据库中
 * @author zhuang
 *
 */
public class TestJdbcInsert {
	
	static void add(User user) {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		//使用预编译sql
		String sql = "insert into user values(?,?,?)";
		
		try (
			Connection c = DriverManager.getConnection(
					"jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=UTF-8",
					"root",
					"123");
			PreparedStatement ps = c.prepareStatement(sql);
			)
		{
			ps.setInt(1, user.id);
			ps.setString(2, user.name);
			ps.setInt(3, user.age);
			//此处使用execute或者executeUpdate都行
			ps.executeUpdate();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public static void main(String[] args) {
		User user = new User(3, "DZ", 23);
		add(user);
	}
}

把这个User对象对应的数据删除掉

package ORM;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

/**
 * 把这个User对象对应的数据删除掉
 * 
 * @author zhuang
 *
 */
public class TestJdbcDelete {
	
	static void delete(User user) {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		//使用预编译sql
		String sql = "delete from user where id=?";
		
		try (
			Connection c = DriverManager.getConnection(
					"jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=UTF-8",
					"root",
					"123");
			PreparedStatement ps = c.prepareStatement(sql);
			)
		{
			ps.setInt(1, user.id);
			
			//此处使用execute或者executeUpdate都行
			ps.execute();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public static void main(String[] args) {
		User user = new User(2, "凌志玲", 33);
		delete(user);
	}
}

更新这条User对象

package ORM;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

/**
 * 更新这条User对象
 * 
 * @author zhuang
 *
 */
public class TestJdbcUpdate {
	static void update(User user) {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		//使用预编译sql
		String sql = "update user set name=?,age=? where id=?";
		
		try (
			Connection c = DriverManager.getConnection(
					"jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=UTF-8",
					"root",
					"123");
			PreparedStatement ps = c.prepareStatement(sql);
			)
		{
			ps.setString(1, user.name);
			ps.setInt(2, user.age);
			ps.setInt(3, user.id);
			
			//此处使用execute或者executeUpdate都行
			ps.execute();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public static void main(String[] args) {
		User user = new User(1, "陈冠希", 37);
		update(user);
	}
}

//根据id值得到一个user对象

package ORM;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * //根据id值得到一个user对象
 * 
 * @author zhuang
 *
 */
public class TestJdbcGetById {

	static User user;

	/**
	 * 得到user对象的方法
	 * 
	 * @param id
	 * @return
	 */
	static User getUser(int id) {
		try {
			// 打开驱动
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		try (
				// 通过驱动获得连接
				Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/jdbc", "root", "123");
				Statement s = c.createStatement();) {
			String sql = "select * from user where id=" + id;
			ResultSet rs = s.executeQuery(sql);
			if (rs.next()) {
				String name = rs.getString("name");
				int age = rs.getInt("age");
				user = new User(id, name, age);

			}

		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		return user;
	}

	public static void main(String[] args) {

		User u = getUser(1);

		System.out.println(u.name);
	}
}

把所有的User数据查询出来，转换为User对象后，放在一个集合中返回

package ORM;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

/**
 * 把所有的User数据查询出来，转换为User对象后，放在一个集合中返回
 * @author zhuang
 *
 */
public class TestJdbcList {
	
	static List<User> getList(User user) {
		//准备一个集合
		List<User> userList = new ArrayList<>();
		
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		//使用预编译sql
		String sql = "select * from user";
		
		try (
			Connection c = DriverManager.getConnection(
					"jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=UTF-8",
					"root",
					"123");
			PreparedStatement ps = c.prepareStatement(sql);
			)
		{	
			ps.execute();
			ResultSet rs = ps.getResultSet();
			
			//获得集合
			while(rs.next()) {
				//把字段装进User对象
				user = new User(rs.getInt("id"), rs.getString("name"), rs.getInt("age"));
				//把user对象装进list
				userList.add(user);
			}
			
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return userList;
	}
	
	public static void main(String[] args) {
		User user = new User(1, "", 1);
		
		List<User> listUser = getList(user);
		
		System.out.println(listUser);
	}
}