java.sql.Blob 转为 java.io.File

 

                InputStream ins = blob.getBinaryStream();
                // 输出到文件
                File file = new File("E://test/a.pdf");
                OutputStream fos = new FileOutputStream(file);
                // 下面将BLOB数据写入文件
                byte[] b = new byte[1024];
                int len = 0;
                while ((len = ins.read(b)) != -1) {
                    fos.write(b, 0, len);
                }
                fos.close();

 

int java.io.InputStream.read(byte[] b) throws IOException


Reads some number of bytes from the input stream and stores them into the buffer array b. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown. 

If the length of b is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at the end of the file, the value -1 is returned; otherwise, at least one byte is read and stored into b. 

The first byte read is stored into element b[0], the next one into b[1], and so on. The number of bytes read is, at most, equal to the length of b. Let k be the number of bytes actually read; these bytes will be stored in elements b[0] through b[k-1], leaving elements b[k] through b[b.length-1] unaffected. 

The read(b) method for class InputStream has the same effect as: 

 read(b, 0, b.length) 
Parameters:
b the buffer into which the data is read.
Returns:
the total number of bytes read into the buffer, or -1 is there is no more data because the end of the stream has been reached.
Throws:
IOException - If the first byte cannot be read for any reason other than the end of the file, if the input stream has been closed, or if some other I/O error occurs.
NullPointerException - if b is null.
See Also:
java.io.InputStream.read(byte [], int, int)

 

Reads some number of bytes from the input stream and stores them into the buffer array b.

The number of bytes actually read is returned as an integer.