JDBC处理CLOB 和 BLOB大对象

在数据库中：
clob用于存储大量的文本数据
可以使用字符流操作

clob用于存储大量的二进制数据
可以使用字节流操作

以mysql为例 先准备一张表：

CREATE TABLE `t_user2` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(10) DEFAULT NULL,
  `myInfo` text,
  `headImage` blob,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

ClOB 操作：

public static void main(String[] args) {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		BufferedReader br = null;
		try {
			// 加载驱动类
			Class.forName("com.mysql.jdbc.Driver");
			// 建立连接
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/testjdbc?useSSL=false", "root", "123456");
			/*存入
			 * ps = conn.prepareStatement("insert into t_user2 (username, myInfo) values(?, ?)");
			ps.setString(1, "张三");
			//			ps.setClob(2, new FileReader(new File("f:/temp/最强兵王0--10.txt")));
			ps.setClob(2, new BufferedReader(
					new InputStreamReader(new ByteArrayInputStream("hello world!".getBytes()))));
			ps.executeUpdate();*/
			
			// 取出
			ps = conn.prepareStatement("select * from t_user2 where id = ?");
			ps.setInt(1, 2);
			
			rs = ps.executeQuery();
			while(rs.next()) {
				Clob clob = rs.getClob("myInfo");
				br = new BufferedReader(clob.getCharacterStream());
				String line;
				while((line  = br.readLine()) != null) {
					System.out.println(line);
				}
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			try {
				if(br != null) {
					br.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			try {
				if(rs != null) {
					rs.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			}
			try {
				if(ps != null) {
					ps.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			}
			try {
				if(conn != null) {
					conn.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

运行代码：

可以看到我把存入的小说又读出来了

blob操作

public static void main(String[] args) {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		BufferedReader br = null;
		ByteArrayInputStream bis = null;
		FileOutputStream fos = null;
		try {
			// 加载驱动类
			Class.forName("com.mysql.jdbc.Driver");
			// 建立连接
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/testjdbc?useSSL=false", "root", "123456");
			//存入
			/*ps = conn.prepareStatement("insert into t_user2 (username, headImage) values(?, ?)");
			ps.setString(1, "张飞");
			ps.setBlob(2, new BufferedInputStream(new FileInputStream("f:/aa/temp/张飞.jpg")));
			ps.executeUpdate();*/
			
			// 取出
			ps = conn.prepareStatement("select * from t_user2 where id = ?");
			ps.setInt(1, 3);
			
			rs = ps.executeQuery();
			while(rs.next()) {
				Blob blob = rs.getBlob("headImage");
				bis = (ByteArrayInputStream) blob.getBinaryStream();
				ByteArrayOutputStream bos = new ByteArrayOutputStream();
				byte[] flush = new byte[1024];
				int len;
				while((len = bis.read(flush)) != -1) {
					bos.write(flush, 0, len);
				}
				fos = new FileOutputStream("f:/aa/a.jpg");
				fos.write(bos.toByteArray());
				fos.flush();
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			try {
				if(fos != null) {
					fos.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			try {
				if(br != null) {
					br.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			try {
				if(rs != null) {
					rs.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			}
			try {
				if(ps != null) {
					ps.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			}
			try {
				if(conn != null) {
					conn.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

运行测试：

{{uploading-image-960855.png(uploading...)}}
存入的图片又回来了