用jdbc访问二进制类型的数据

1、创建数据表（MYSQL数据库）

create table big_blob (
     id int(10), 
     blob_txt blob
);

 

2、JdbcUtils工具类

package com.sunrex;

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

/**
 * 东南西北风
 * @author Administrator
 *
 */
public final class JdbcUtils {
	
	private static Connection conn = null;
	/* 访问数据库的url*/
	private final static String DATABASE_URL = 
		"jdbc:mysql://localhost:3306/study?useUnicode=true&characterEncoding=UTF8";
	
	private final static String DATABASE_USERNAME = "root";
	
	private final static String DATABASE_PASSWORD = "root";

	static {
		try {
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(DATABASE_URL, DATABASE_USERNAME, DATABASE_PASSWORD);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	private JdbcUtils(){}
	
	public static Connection getConnection() {
		return conn;
	}
	
	public static void close(Connection conn, Statement stmt, ResultSet rs) {
		try {
			if(rs!=null) rs.close();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			try {
				if(stmt!=null)
					stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				try {
					if(conn!=null) 
						conn.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

 

3、二进制文件操作类

package com.sunrex.demo06;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Blob;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import com.sunrex.JdbcUtils;

/**
 * 用jdbc访问二进制类型的数据
 * 在数据库中，经常需要用到大字段类型，
 * 		如oracle中long/blob/clob,
 * 		sqlserver中text/image，
 * 		mysql中的text/longtext/clob/blob。 
 */
public class BlobTest {
	public static void main(String[] args) throws Exception {
//		insert();
		read(1);
	}
	
	/**
	 * 添加数据
	 * @throws Exception
	 */
	public static void insert() throws Exception {
		Connection conn = null;
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		try {
			conn = JdbcUtils.getConnection();
			//---注意：如果数据库中设置的是blob类型字段，二进制的最大容量不能超过64K
			String sql = "insert into big_blob (id, blob_txt) values (?, ?)";
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, 1);
			
			//使用字节流，读取文本信息
			File file = new File("blob.jpg");
			InputStream is = new BufferedInputStream(new FileInputStream(file));
			pstmt.setBinaryStream(2, is, (int)file.length());//填充二进制流
			
			is.close();
			pstmt.executeUpdate();
		} finally {
			JdbcUtils.close(conn, pstmt, rs);
		}
	}
	
	/**
	 * 读取数据
	 * @param id
	 */
	private static void read(int id) throws Exception {
		Connection conn = null;
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		try {
			conn = JdbcUtils.getConnection();
			//---注意：如果数据库中设置的是blob类型字段，二进制的最大容量不能超过64K
			String sql = "select blob_txt from big_blob where id=?";
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, id);
			rs =pstmt.executeQuery();
			
			while(rs.next()) {
//				//读取方法一：
//				Blob blob = rs.getBlob("blob_txt");
//				InputStream is = blob.getBinaryStream();//输入流
				//读取的方法二：
				InputStream is = rs.getBinaryStream("blob_txt");
				byte[] bytes = new byte[1024];
				
				//输出流
				File file = new File("blob_bak.jpg");
				OutputStream os = new BufferedOutputStream(new FileOutputStream(file));
				for(int i=0; (i=is.read(bytes))>0;) {
					os.write(bytes, 0, i);
				}
				
				os.close();
				is.close();
			}
		} finally {
			JdbcUtils.close(conn, pstmt, rs);
		}
	}
}