setObject将对象二进制数据存入数据库之后，读取时类型丢失

[冰蓝2099]

PreparedStatement setObject 之后将对象存入数据库，读取时无法强制转换回来

PreparedStatement stmt = connection.prepareStatement("UPDATE tb set aaa=? where id=1 ");
stmt.setObject(1, new myClass());
stmt.executeUpdate();

当我读取该对象时

PreparedStatement stmt = connection.prepareStatement("select aaa from tb where id=1");
ResultSet res = stmt.executeQuery();
			
res.next();
Object obj = res.getObject(1);
trace(obj);

竟然不是 myClass@xxxxxx
而是 [B@xxxxxx

这是怎么回事？

myClass my = (myClass)obj;

也会报错！ 说无法强制转换！
请高手指教

[龙四]

字段是什么类型

[不关橙猫猫事的哦]

表tb 的aaa是神马类型？

[冰蓝2099]

Blob 类型 存二进制数据

[游一游走一走]

[B@xxxxxx表示你读取的是字节数组
你还需要做进一步的处理,请参考下以下代码,是针对mysql的

public class Test {
	/**
	 * mysql> describe test;
	 * +-----------+------------+------+-----+---------+----------------+
	 * | Field     | Type       | Null | Key | Default | Extra          |
	 * +-----------+------------+------+-----+---------+----------------+
	 * | id        | bigint(20) | NO   | PRI | NULL    | auto_increment |
	 * | age       | int(11)    | YES  |     | NULL    |                |
	 * | firstname | blob       | YES  |     | NULL    |                |
	 * | LASTNAME  | blob       | YES  |     | NULL    |                |
	 * +-----------+------------+------+-----+---------+----------------+
	 */
	public static void main(String[] args) throws Exception {
		Class.forName(com.mysql.jdbc.Driver.class.getName());
		Connection conn=DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/zjjzyz", "root", "zhangyz");
		PreparedStatement ps=conn.prepareStatement("INSERT INTO test(AGE, FIRSTNAME, LASTNAME) VALUES(0, ?, ?)");
		ps.setObject(1, new Myclass("张", "zhang"));
		ps.setObject(2, new Myclass("三", "san"));
		ps.execute();
		ps.close();
		ps=conn.prepareStatement("SELECT id, AGE, FIRSTNAME, LASTNAME FROM test") ;
		ResultSet rs=ps.executeQuery();
		
		while(rs.next()){
			System.out.println(readObjectFromDataBase(rs.getBytes(3)));
			System.out.println(readObjectFromDataBase(rs.getBytes(4)));
		}
		rs.close();
		ps.close();
		conn.close();
	}
	static Object readObjectFromDataBase(byte[] bs) throws Exception{
		ObjectInputStream in=new ObjectInputStream(new ByteArrayInputStream(bs));
		return in.readObject();
	}
}

class Myclass implements Serializable {
	private static final long serialVersionUID = 1L;
	private String zhongWen;
	private String english;

	public Myclass(String zhongWen, String english) {
		super();
		this.zhongWen = zhongWen;
		this.english = english;
	}

	public String getZhongWen() {
		return zhongWen;
	}

	public void setZhongWen(String zhongWen) {
		this.zhongWen = zhongWen;
	}

	public String getEnglish() {
		return english;
	}

	public void setEnglish(String english) {
		this.english = english;
	}

	@Override
	public String toString() {
		return "Myclass [english=" + english + ", zhongWen=" + zhongWen + "]";
	}
}

[冰蓝2099]

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