A simple blob access example

 

Code:

1. Import java. Io .*;
2. Import java. SQL .*;
4. /**
5. * Test the BLOB data operation.
6. */
7. Public class blobtest {
8. Connection con = NULL;
9. Private Static string filepath = "D:/test/smile.jpg ";
10. Private Static string fileoutpath = "D:/test/smilecopy.jpg ";
11. /**
12. * Add BLOB data to the database
13. */
14. Public void addblob (){
15. Try {
17. // Create a preparedstatement instance
18. Preparedstatement pstmt = con
19. . Preparestatement ("insert into blobtest values (1 ,?) ");
20. File file = new file (filepath );
21. Fileinputstream FCM = new fileinputstream (File );
22. // Set the input stream as the object of the preprocessing statement.
23. Pstmt. setbinarystream (1, FS, (INT) file. Length ());
24. // Execute update
25. Pstmt.exe cuteupdate ();
26. Pstmt. Close ();
27. FCM. Close ();
29. } Catch (Exception e ){
30. E. printStackTrace ();
31. }
32. }
34. /**
35. * Create a table
36. */
37. Public void createTable (){
38. Try {
39. Con.createstatement(cmd.exe cute (
40. "Create table blobtest (ID int, PIC blob ,"
41. + "Constraint pk_blobtest primary key (ID ));");
42. } Catch (exception e ){
43. E. printstacktrace ();
44. }
45. }
47. /**
48. * Reading BLOB data from the database
49. */
50. Public void getblob (){
52. Try {
53. // Create a statement instance
54. Statement stmt = con. createstatement ();
55. Resultset rst = stmt
56. . Executequery ("select * From blobtest where id = 1 ");
57. RST. Next ();
58. // Obtain BLOB data and its input stream, and then write the data to the file through the input stream.
59. Blob blob = RST. getblob ("pic ");
60. Fileoutputstream out = new fileoutputstream (new file (
61. Fileoutpath ));
62. Inputstream in = blob. getbinarystream ();
63. Int I;
64. While (I = in. Read ())! =-1)
65. Out. Write (I );
66. // Close the input and output streams.
67. In. Close ();
68. Out. Close ();
70. } Catch (exception e ){
71. E. printstacktrace ();
73. }
74. }
76. Public static void main (string [] ARGs) throws exception {
77. Class. forname ("com. MySQL. JDBC. Driver"). newinstance ();
78. Blobtest test = new blobtest ();
79. Test. Con = java. SQL. drivermanager. getconnection (
80. "JDBC: mysql: // localhost: 3306/test", "root", "123456 ");
81. Test. createtable ();
82. Test. addblob ();
83. Test. getblob ();
84. }
85. }

MySQL has four blob types:

· Tinyblob: Only 255 characters long

· BLOB: up to KB

· Mediumblob: up to 16 MB bytes

· Longblob: up to 4 GB