通过JDBC将MATLAB连接到Apache Derby数据库

Question

I've been asked to connect an Apache Derby database to our existing MATLAB data-mining tools. I am running MATLAB R2014a (no Database toolbox)

After some research and trial and error, here's what I did:

went to http://www.java2s.com/Code/Jar/d/Downloadderbyclientjar.htm and downloaded derbyclient.jar and saved it, and unzipped it to a shared folder.

edited the text file C:\\Users\\tyler.davis\\AppData\\Roaming\\MathWorks\\MATLAB\\R2014a\\javaclasspath.txt and added full path to derbyclient.jar, saved it, restarted MATLAB.

At MATLAB command line

javaclasspath

shows "S:\\SHARED...\\derbyclientjar\\derbyclient.jar\\derbyclient.jar" at the end of the static path list. So far so good.

Next, try

driverClassName = 'org.apache.derby.jdbc.ClientDriver';
java.lang.Class.forName(driverClassName);

reports error:

Java exception occurred:
java.lang.ClassNotFoundException: org/apache/derby/jdbc/ClientDriver

at java.lang.Class.forName0(Native Method)

at java.lang.Class.forName(Unknown Source)

Tried an alternative:

classLoader = com.mathworks.jmi.ClassLoaderManager.getClassLoaderManager;
driverClass = classLoader.loadClass(driverClassName);

That seemed to work, created objects "driverClass, type 1x1 java.lang.Class" and "classLoader, value 1x1 com.mathworks.jmi.ClassLoaderManager"

Then I tried

DriverManager.registerDriver(driverClass.newInstance);

which reports error

Undefined variable "DriverManager" or class "DriverManager.registerDriver".

and if I try to create a sample database using

cxnStr = 'jdbc:derby:sampleDB:create=true';
cxn = java.sql.DriverManager.getConnection(cxnStr);

I get

Java exception occurred:
java.sql.SQLException: No suitable driver found for jdbc:derby:sampleDB:create=true

at java.sql.DriverManager.getConnection(Unknown Source)

at java.sql.DriverManager.getConnection(Unknown Source)

I really don't know what I'm doing here; just copying other's code from around the web. Any suggestions on what to try next?

Answer 1

Since you're just getting started with Derby, can I recommend that you take an hour or two and run through the Derby tutorial: http://db.apache.org/derby/docs/10.11/getstart/cgstutorialintro.html

Also, can I recommend that you get in the habit of downloading Derby from the Apache website rather than other Internet sites? The copies of Derby on other sites are probably fine, but it seems most reliable and safest to get Derby from the Apache website: http://db.apache.org/derby/derby_downloads.html

Most of what you did in your description seems OK to me; I suspect the place where you went astray is when you unzipped derbyclient.jar itself.

Although a '*.jar' file is in fact a valid ZIP archive, you are not expected to unzip those packaged jar files. Instead, you should leave the jar as 'derbyclient.jar' and then set your CLASSPATH to include 'derbyclient.jar' as one of the entries in the CLASSPATH list.

Lastly, note that the JDBC Connection URL

jdbc:derby:sampleDB:create=true

is a correct JDBC Connection URL for the embedded configuration of Derby, not for the client-server configuration of Derby.

So even if you get a good copy of derbyclient.jar into your CLASSPATH correctly, you won't be able to use

jdbc:derby:sampleDB:create=true

Instead, you'll either have to use a client-server style JDBC Connection URL, such as:

jdbc:derby://my.server.name:1527/sampleDB

(and learn how to operate a Derby Network Server), or you'll need to switch to using the Embedded Driver (org.apache.derby.jdbc.EmbeddedDriver).

For more information about this notion of configurations, see: http://db.apache.org/derby/docs/10.11/getstart/cgsquck70629.html

And for more information on the JDBC Connection URL and the two JDBC driver classes, see: http://db.apache.org/derby/docs/10.11/getstart/cgsquck19524.html

Once you've had a chance to work through the Derby Getting Started guide, I recommend asking some follow-on questions based on what you learn during that experience.