java-mysql(3) 读写image

在mysql里面用来存储图片有一个特殊的数据对象叫做 Blob(Binary Large Object).

数据库里面插入一张图片:

第一步:需要为图片创建一个文件对象

File img = new File(proppath);
FileInputStream fileInputStream = null;
try {
       fileInputStream = new FileInputStream(img);
  } catch (FileNotFoundException e1) {
        // TODO Auto-generated catch block
         e1.printStackTrace();
   }

第二部：创建二进制的数据流

preparedStatement.setBinaryStream(1, fileInputStream,
                    (int) img.length());
 preparedStatement.executeUpdate();

调用的是prepared statement的setBinaryStream对象:几个参数分别是需要绑定的参数索引位置，一个文件输入流，图片的字节数

 package core;

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

 public class MethodReferencesTest {

     public static void main(String[] args) throws CloneNotSupportedException {
         // TODO Auto-generated method stub

         Connection connection = null;
         Statement statement = null;
         ResultSet resultSet = null;
         PreparedStatement preparedStatement = null;
         String proppath = System.getProperty("user.dir")
                 + "/src/core/c9c15f0edd07ee240f3af06de6775888.jpg";

         //创建image object
         File img = new File(proppath);
         FileInputStream fileInputStream = null;
         try {
             fileInputStream = new FileInputStream(img);
         } catch (FileNotFoundException e1) {
             // TODO Auto-generated catch block
             e1.printStackTrace();
         }
         String sqlurl = "jdbc:mysql://172.20.23.75:3306/testdb";
         String sqluser = "root";
         String sqlpassword = "123456";
         String sql = "INSERT INTO Images(Data) VALUES(?)";

         try {
             connection = DriverManager.getConnection(sqlurl, sqluser,
                     sqlpassword);

             preparedStatement = connection.prepareStatement(sql);
             preparedStatement.setBinaryStream(1, fileInputStream,
                     (int) img.length());
             preparedStatement.executeUpdate();

         } catch (SQLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         } finally {
             try {
                 if (resultSet != null) {
                     resultSet.close();
                 }
                 if (statement != null) {
                     statement.close();
                 }
                 if (preparedStatement != null) {
                     preparedStatement.close();
                 }
                 if (connection != null) {
                     connection.close();
                 }
             } catch (SQLException e) {
                 e.printStackTrace();
             }
         }

     }

 }

点我看完整代码

从数据库里面读取图片

第一步:创建一个输出流对象

//创建image object
File img = new File(proppath);
FileOutputStream fileputStream = null;
try {
    fileputStream = new FileOutputStream(img);
} catch (FileNotFoundException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
}

第二步:调用getblob()获取图片数据

 connection = DriverManager.getConnection(sqlurl, sqluser,
                     sqlpassword);

             preparedStatement = connection.prepareStatement(sql);
             resultSet = preparedStatement.executeQuery();
             if (resultSet.next()) {
                 // 获取图片数据
                 Blob blob = resultSet.getBlob("Data");
                 // 获取字节数
                 int len = (int) blob.length();
                 byte[] buf = blob.getBytes(1, len);
                 try {
                     fileputStream.write(buf, 0, len);
                 } catch (IOException e) {
                     // TODO Auto-generated catch block
                     e.printStackTrace();
                 }

             }