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();
            }
        }

    }

}

 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();
                }

            }