Blob操作实例

 以Mysql数据库为例,  完成图片的简单存储, 查询操作来说明Blob的应用

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.sql.Blob;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.swing.ImageIcon;
import javax.swing.JApplet;
import javax.swing.JLabel;

public class BlobTest extends JApplet {

 public static final long serialVersionUID = 1l;

 /**
  * Mysql驱动类
  */
 private static final String CONN_DRIVER = "org.gjt.mm.mysql.Driver";

 /**
  * 数据库连接URL
  */
 private static final String CONN_URL = "jdbc:mysql://localhost:3306/dcc";

 /**
  * 数据库用户
  */
 private static final String CONN_USER = "root";

 /**
  * 图片存放位置
  */
 private static final String FILE_NAME = "C://Winter.jpg";

 /**
  * Bolb对象
  */
 static Blob blob = null;

 /**
  * 初始化
  */
 public void init() {
  insert();
  try {
   blob = query();
  } catch (Exception e) {
   e.printStackTrace();
  }
  ImageIcon icon = null;
  try {
   icon = new ImageIcon(blob.getBytes(1, (int) blob.length()));
  } catch (SQLException e) {
   e.printStackTrace();
  }
  JLabel lable = new JLabel(icon);
  getContentPane().add(lable);
  setVisible(true);
 }

 /**
  * 执行数据库insert操作
  *
  * @return boolean
  */
 private boolean insert() {

  boolean flag = false;
  PreparedStatement stmt = null;
  String sql = "insert into picture values(?,?)";

  File file = new File(FILE_NAME);
  FileInputStream in = null;
  Connection conn = null;
  try {
   conn = getConnection();
   in = new FileInputStream(file);
   stmt = conn.prepareStatement(sql);
   stmt.setString(1, "test");
   stmt.setBinaryStream(2, in, (int) file.length());
   if (stmt != null) {
    stmt.executeUpdate();
    flag = true;
   }
  } catch (FileNotFoundException e1) {
   e1.printStackTrace();
  } catch (SQLException e) {
   e.printStackTrace();
  } finally {
   try {
    if (stmt != null)
     stmt.close();
    if (conn != null)
     conn.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
  return flag;
 }

 /**
  * 查询图片对象
  *
  * @return
  * @throws Exception
  */
 private Blob query() throws Exception {

  PreparedStatement stmt = null;
  ResultSet rs = null;

  String quer_sql = "select pic from picture where id=?;";
  try {
   Connection conn = getConnection();
   stmt = conn.prepareStatement(quer_sql);
   stmt.setString(1, "test");
   if (stmt != null) {
    rs = stmt.executeQuery();
   }
  } catch (SQLException e) {
   e.printStackTrace();
  }

  rs.next();
  return rs.getBlob("pic");

 }

 /**
  * 获取数据库连接
  *
  * @return
  */
 private Connection getConnection() {

  Connection conn = null;
  try {
   Class.forName(CONN_DRIVER);
      conn = DriverManager.getConnection(CONN_URL, CONN_USER, "");
  } catch (ClassNotFoundException e) {
   e.printStackTrace();
  } catch (SQLException e) {
   System.out.println( "数据库出现异常" + e.getMessage() );
   e.printStackTrace();
  }
  return conn;
 }

}