Java(TM) Boutique - Tutorial - Upload Files with Struts, Store Them with Hibernate

Tutorials : Upload Files with Struts, Store Them with Hibernate :

Preparing the Environment

If all the appropriate software is properly downloaded and installed on your PC, prepare the database and the user which will access it. Also, configure the Connection Pool and Datasource with the JNDI name MySqlDS. Please be sure that MySQL Connector/J is in your classpath! To check this, type:


echo %CLASSPATH%

mysql-connector-java-3.1.7-bin.jar (with full path) should be there.
This is required because WebLogic needs to find MySQL Connector/J to work with the driver.

Now that everything is set, it's time to create a table in the database, where you'll keep user entities. Log in to the database with any MySQL client and type:


drop table if exists TABLE_USER_FILE;
create table TABLE_USER_FILE
(
   USER_ID                       int auto_increment             not null,
   USER_USERNAME                 text,
   USER_FILENAME                 text,
   USER_FILETYPE                 text,
   USER_FILESIZE                 text,
   USER_FILEBIN                  longblob,
   primary key (USER_ID)
)
type = MyISAM;

As you can see, everything is very simple. The only unfamiliar thing here might be this longblob type. Binary Large Object (BLOB) columns are one of MySQL's secret weapons. These columns store binary data with processing that can be retrieved and manipulated like the other common datatypes. According to the MySQL guide, a BLOB is a binary large object that can hold a variable amount of data. As a matter a fact, MySQL has four BLOB types:

tinyblob: Only 255 characters
blob: This one is limited to 65 Kbytes
mediumblob: Limited to 16 MB
longblob: Up to 4GB.

As per MySQL's documentation (from MySQL 4.0), the maximum allowed length of a longblob column depends on the configured maximum packet size in the client/server protocol and available memory.

You may be wary of storing very large files in BLOBs, but there is such flexbility! The maximum packet size is easily configured by adding my.ini in the appropriate line. For examplee:


set-variable	=	max_allowed_packet=10M

You can specify almost any size you need. Its default is 1M.

There's only a few things left. At the moment, there is a problem between Hibernate and WebLogic. According to Hibernate's documentation, Hibernate 3.0 uses ANTLR for its new query parser. It's a pity, but BEA Weblogic includes a version of ANTLR in the system classpath which gets loaded before any application libraries and, because Weblog doesn't seem to support property class loader isolation, it won't see the Hibernate classes in the application's context. BEA seems to solve this issue by prefixing package names, but the distributed ANTLR doesn't have this prefix.
The workaround for this problem is to place all Hibernate and dependent libraries in your CLASSPATH. This is what it should look like:


C:\green\te3>echo %CLASSPATH%
.;C:\mysql-connector-java-3.1.7\mysql-connector-java-3.1.7-bin.jar;C:\hibernate-3.0\hibernate3.jar;
C:\hibernate-3.0\lib\ehcache-1.1.jar;C:\hibernate-3.0\lib\jta.jar;C:\hibernate-3.0\lib\xml-apis.jar;
C:\hibernate-3.0\lib\commons-logging-1.0.4.jar;C:\hibernate-3.0\lib\dom4j-1.5.2.jar;
C:\hibernate-3.0\lib\antlr-2.7.4.jar;C:\hibernate-3.0\lib\cglib-full-2.0.2.jar;
C:\hibernate-3.0\lib\jdbc2_0-stdext.jar;C:\hibernate-3.0\lib\xerces-2.6.2.jar;
C:\hibernate-3.0\lib\jaxen-1.1-beta-4.jar;C:\hibernate-3.0\lib\commons-collections-2.1.1.jar;
C:\hibernate-3.0\lib\log4j-1.2.9.jar;

Now, unzip the source code into any directory you want. Open the build.xml file with your favorite text editor, and check (and change, if necessary) the first few lines with paths to all your home directories, and the title of your domain. Save your changes and type:

ant

When the process of code building finishes, you will have TE3.EAR, a ready-to-deploy package (the name TE3 means absolutely nothing, it's just a freely choosen name). Deploy it with WebLogic's administration console, and when deployed, open it in your browser http://localhost:7001/te3/. There you will see two options: "upload file" and "list all files".

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