Question

我尝试读取blob，将其转换为JPG然后写回blob（它通过引用传入，但是当尝试在TOAD中编译时，我在ImageIO.write上出错

CREATE OR REPLACE AND RESOLVE JAVA SOURCE NAMED BANNADMIN.IMAGE_CONVERTER
   AS package uk.co.ImageUtil;

import javax.imageio.ImageIO;
import java.io.File;
import java.io.IOException;
import java.awt.image.BufferedImage;
import oracle.sql.*;
import java.io.OutputStream;

public class ImageConverter {
    public static void convertImage(BLOB[] blob) {
       BufferedImage image = null;
       OutputStream outputStream = null;
        try {
            image = ImageIO.read(blob[0].getBinaryStream());

            outputStream = blob[0].setBinaryStream(0);

            ImageIO.write(image, "JPG", outputStream);

        } catch (IOException e) {
            e.printStackTrace();
        }
        catch (SQLException e) {
            e.printStackTrace();
        }
        catch(IllegalArgumentException e) {
            e.printStackTrace();
        }
        finally {
            try {
                if (outputStream !== null) {
                    outputStream.flush();
                    outputStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
/

如何将BufferedImage转换为RenderedImage，以便将JPG版本重新编写回Blob？

更新：错误消息是

[Error]  (1: 0): IMAGE_CONVERTER:28: cannot find symbol
[Error]  (1: 0): symbol  : method    write(java.awt.image.BufferedImage,java.lang.String,java.lang.Object)
[Error]  (1: 0): location: class javax.imageio.ImageIO
[Error]  (1: 0):             ImageIO.write(image, "jpg", outputStream);
[Error]  (1: 0):                    ^
[Error]  (1: 0): 1 error

Answer 1

原来这是一个简单的错误，ImageIO.write接受一个RenderedImage，这意味着我必须将BufferedImage强制转换为RenderedImage，我在!==而不是!=中写了finally {1}}阻止。请参阅下文，了解成功编译的内容

CREATE OR REPLACE AND RESOLVE JAVA SOURCE NAMED BANNADMIN.IMAGE_CONVERTER AS package uk.co.ImageUtil;

import javax.imageio.ImageIO;
import java.io.File;
import java.io.IOException;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import oracle.sql.*;
import java.io.OutputStream;
import java.sql.SQLException;

public class ImageConverter {
    /**
      * Take in a BLOB file (specified as an array parameter but we only ever use [0])
      * Read in the binary stream of the BLOB
      * Change the binary stream to jpg
      * Write the binary stream jpg to the BLOB
      * The BLOB parameter is passed in via out - so there is no need to return the BLOB, only edit it
      */
    public static void convertImage(BLOB[] blob) {
       BufferedImage bufferedImage = null;
       OutputStream outputStream = null;
        try {
            bufferedImage = ImageIO.read(blob[0].getBinaryStream());

            outputStream = blob[0].setBinaryStream(0);

            RenderedImage renderedImage = (RenderedImage)bufferedImage;

            ImageIO.write(renderedImage, "JPG", outputStream);

        } catch (IOException e) {
            e.printStackTrace();
        }
        catch (SQLException e) {
            e.printStackTrace();
        }
        catch(IllegalArgumentException e) {
            e.printStackTrace();
        }
        finally {
            try {
                if (outputStream != null) {
                    outputStream.flush();
                    outputStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
/

将Blob转换为JPG并更新blob

1 个答案: