如何阅读并从MySQL

Question

保存图像

我所要做的就是将图片插入MySQL表，然后获取图像数据（保存为BLOB类型），并把它写在某个文件位置的文件。

到目前为止，我有下面的代码，从表中读取图像数据，并将其写为图像文件：

package imageReadWrite; 

import dbConnection.testConnection; 

import java.io.BufferedOutputStream; 
import java.io.File; 
import java.io.FileOutputStream; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.sql.*; 

public class BlobImageReadWeite { 
    testConnection db = new testConnection(); 

    public String GetImage() { 
     String result = ""; 
     try { 
      db.connect(); 
      System.out.println("this is for test connection"); 
      String Banner_chk = "Select * from banner_file where image_name is not null and status='Active' order by upload_dt DESC LIMIT 1"; 
      ResultSet rs_Banner_chk = db.execSQL(Banner_chk); 
      if (rs_Banner_chk.next()) { 
       System.out.println(rs_Banner_chk.getString("image_name")); 

       Blob blob = rs_Banner_chk.getBlob("image"); 
       File image = new File("test.png"); 
       FileOutputStream fos = new FileOutputStream(image); 

       byte[] buffer = new byte[1024]; 

       // Get the binary stream of our BLOB data 
       InputStream is = rs_Banner_chk.getBinaryStream("image"); 
       while (is.read(buffer) > 0) { 
        fos.write(buffer); 
       } 

       fos.close(); 
      } 

      db.close(); 
     } catch (Exception e) { 
      System.out.println(e); 
     } 

     return result; 
    } 

    public static void main(String[] args) { 
     BlobImageReadWeite obj1 = new BlobImageReadWeite(); 
     obj1.GetImage(); 
    } 
} 

的问题在于所生成的图像文件没有打开。

我插入图像到数据库使用下面的代码

package promocode; 
import java.awt.Toolkit; 
import java.io.*; 
import java.util.*; 
import java.util.Date; 
import java.text.*; 
import java.sql.*; 
import java.util.Vector; 
import javax.imageio.*; 
import javax.swing.ImageIcon; 
import java.awt.*; 


import db.connection; 



public class ImageReader { 
connection db=new connection(); 
public String fileupload(String flname,String user,String promo_rad)throws  IOException, SQLException,ParseException{ 

String line=null; 

String line1 = null; 
String fval = ""; 
String fval_temp = ""; 
String flog,fileflag; 
String sqlst1 = ""; 
String sqlst2 = ""; 
String res = "false"; 
int er_count=0; 
int cor_count=0; 
String error_message=""; 
String chk1=""; 
String chk2=""; 
String chk3=""; 
String chk4=""; 

System.out.println("the path is"+flname); 
System.out.println(promo_rad); 
String filename1=""; 
filename1=flname.substring(flname.lastIndexOf("\\")+1) ; 
System.out.println(filename1); 

try { 

Image img=Toolkit.getDefaultToolkit().getImage(flname); 
ImageIcon icon=new ImageIcon(img); 
int height=icon.getIconHeight(); 
int width=icon.getIconWidth(); 
System.out.println("the image height is "+height+" and the image width is "+width); 
File file = new File(flname); 
FileInputStream fs = new FileInputStream(file); 

db.connect(); 
if(width == 260 && height == 187){ 

sqlst2="insert into banner_file (image_name,image, FileType,Status, userid,image_flag,upload_dt,height,width) values ('"+filename1+"','"+fs+"','jpg','Active','"+user+"','"+promo_rad+"',now(),'"+height+"','"+width+"')"; 
System.out.println(sqlst2); 
db.updateSQL(sqlst2); 
res="true"; 
} 

    }catch(Exception e){ 
     System.out.println(e); 

    } 
finally{ 

db.close(); 
} 

return res; 


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

     ImageReader obj1=new ImageReader(); 
     String fn = "C:\\Program Files\\Apache Software Foundation\\Tomcat 7.0\\webapps\\aircel-billpay\\online_images\\Ganesha13.jpg"; 
     String result = obj1.fileupload(fn,"internalpromo","yes"); 
     System.out.println(result); 
} 

} 

Answer 1

试换

InputStream is = rs_Banner_chk.getBinaryStream("image"); 

与

InputStream is = blob.getBinaryStream("image"); 

Answer 2

从is.read(buffer)返回的值表示多少字节读取，这可能不是buffer的整个长度。您忽略了返回的值，并且在每个循环迭代中写出buffer的全部内容。如果您检查文件的大小，您可能会发现它大于数据库中二进制数据的大小。

不是文件和FileOutputStream中，考虑使用的java.nio.file包代替：

Path image = Paths.get("test.png"); 
Files.copy(rs_Banner_chk.getBinaryStream("image"), image);