Why is my `BufferedImage` null when converting a Blob from a database?

Convert BufferedInputStream into an Image

You encounter an issue converting a blob from a database, which you assume to be an image in JPEG format, into a BufferedImage for further processing. The conversion fails, and your Image variable remains null.

Possible Reasons for Conversion Failure

Upon examining your code, several potential problems can cause the conversion to fail:

1. Data Retrieval: The code retrieves the blob data using blob.getBytes(1, blobLength). However, blobLength is obtained as a long (64-bit integer), while getBytes expects an int (32-bit integer). This mismatch could result in data truncation and incorrect image retrieval.
2. Image Verification: Ensuring the uploadedInputStream stream contains a valid image would be a good starting point. You could temporarily write the image to a file using ImageIO.write and then read it back in to verify its integrity.
3. Blob Content Handling: According to the H2 database documentation, the Blob contents are not stored in memory. Therefore, instead of using blob.getBytes, you should use blob.getBinaryStream to retrieve a stream representation of the blob.

Solution

To resolve the issues, try modifying your code as follows:

public Response post(@PathParam("id") String id) throws IOException {
    Connection con = connection();
    Blob blob = getPhoto(con);
    BufferedImage image = null;
    InputStream blobStream = null;
    int blobLength = 0;
    try {
        blobLength = (int) blob.length();
        blobStream = blob.getBinaryStream(1, blobLength);
        image = ImageIO.read(blobStream);
    } catch (SQLException e2) {
        e2.printStackTrace();
    }  

    return Response.ok(image).build();
}

Additionally, you should verify the validity of the uploadedInputStream by writing it to a file and reading it back in to ensure it contains an image.

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