JDBC中级篇（MYSQL）——模拟从数据库中上传下载附件

注意：其中的JdbcUtil是我自定义的连接工具类：代码例子链接：

package b_blob_clob;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;

import util.JdbcUtil;

/**
 * 模拟一个从数据库中：
 * 			上传下载附件
 * 
 * @author mzy
 *
 */
public class Demo03 {
	public static void main(String[] args) {
		write();
		
		read();
	}

	private static void read() {
		/**
		 * 读出
		 */
		Connection conn = null;
		PreparedStatement stmt = null;
		ResultSet rs  = null;
		try{
			conn = JdbcUtil.getConnection();
			String sql = "select * from attachments where id=?";
			//预编译
			stmt = conn.prepareStatement(sql);
			//参数赋值
			stmt.setInt(1, 2);
			//执行查询
			rs = stmt.executeQuery();
			//遍历结果
			if(rs.next()){
				
				String name = rs.getString("name");
				InputStream in = rs.getBinaryStream("file"); //rs.getBlob("file").getBinaryStream();
				
				//取出附件
				//写出到硬盘
				BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream("e:/picture.png"));
				byte[] buf = new byte[1024];
				int len = 0;
				//边读边写
				while(  (len=in.read(buf))!=-1  ){
					out.write(buf, 0, len);
				}
				//关闭流
				out.close();
				in.close();
				
				Date date = rs.getDate("addtime");
				String author = rs.getString("author");
				
				System.out.println(name+"\t"+date+"\t"+author);
				
			}
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			JdbcUtil.close(stmt, conn);
		}
	}

	private static void write() {
		/**
		 * 写入
		 */
		Connection conn = null;
		PreparedStatement stmt = null;
		
		conn = JdbcUtil.getConnection();
		String sql = "insert into attachments(name,file,addtime,author) values(?,?,?,?)";
		
		try {
			// 预编译
			stmt = conn.prepareStatement(sql);
			// 读取图片
			File file = new File("./src/人和鸟.png");
			
			FileInputStream in = new FileInputStream(file);
			String fileName = file.getName();
			// 去掉后缀名
			fileName = fileName.substring(0, fileName.indexOf("."));
			stmt.setString(1, fileName);
			stmt.setBlob(2, in);
			// 第三个时间的插入，插入的话要遵照mysql的Date类型，所以要进行转换
			stmt.setDate(3, new java.sql.Date(new Date().getTime()));
			
			stmt.setString(4, "mzy");
			
			stmt.executeUpdate();
			in.close();
			System.out.println("添加成功！");
		} catch (SQLException | IOException e) {
			e.printStackTrace();
		} finally {
			JdbcUtil.close(stmt, conn);
		}
		
		
	}
}