如何将 java.io.InputStream 转换为 java.sql.Blob

Question

How do I convert a java.io.InputStream to a java.sql.Blob using pure Java?

In response to tbodt's suggestions, I ran the following through the eclipse debugger. The debugger shows that myinputstream has content, but that blob remains null at the end of the code. What do I need to do to fix this?

byte[] contents;
ByteArrayOutputStream output = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int count;
while ((count = myinputstream.read(buffer)) != -1){output.write(buffer, 0, count);}//debugger says myinputstream has blksize 16384, buffcount 12742, and max 127394 here
contents = output.toByteArray();
Blob blob = null;
try {blob = new SerialBlob(contents);} 
catch (SerialException e) {e.printStackTrace();}
catch (SQLException e) {e.printStackTrace();}

someObject.setSomeBlobProperty(blob);//debugger says blob is null here

I also ran the IOUtils approach through the debugger, but got the exact same results, with a null blob but a populated myinputstream . How can I fix this?

Blob blob = null;
try {
    blob = new SerialBlob(IOUtils.toByteArray(myinputstream));//debugger says myinputstream has contents here.
    someObject.setSomeBlobProperty(blob);//debugger says blob is null here
} 
catch (SerialException e) {e.printStackTrace();}
catch (SQLException e) {e.printStackTrace();}

In both cases, the debugger says myinputstream has blksize 16384, buffcount 12742, and max 127394 at the indicated locations, despite blob remaining null . I also checked the underlying MySQL database after running this code and confirmed that the blob field is empty.

I then ran the following through the Eclipse debugger, which showed that the byte[] called content remained empty after the attempts to populate it. So the resulting blob is empty, while the inputstream does indeed continue to have the same content values as shown above:

Blob blob = null;
byte[] content = IOUtils.toByteArray(myinputstream);
try {
    blob = new SerialBlob(content);//debugger says content is empty here
    someObject.setSomeBlobProperty(blob);//debugger says blob is empty here.
}//debugger says myinputstream has the same values as in edit#1
catch (SerialException e) {e.printStackTrace();}
catch (SQLException e) {e.printStackTrace();}

Answer 1

The easy way:

contents = IOUtils.toByteArray(in);

But for that, you need Apache Commons IO, which might be hard to add. If you don't want to use it, or can't, here's one way of doing it yourself;

ByteArrayOutputStream output = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int count;
while ((count = input.read(buffer)) != -1)
    output.write(buffer, 0, count);
contents = output.toByteArray();

Answer 2

You can use the same:

Blob xmlForSign=null;
xmlForSign.getBinaryStream();

this method getBinaryStream() return an Inputfilestream.