MYSQL JDBC NoClassDefFoundError: org/aspectj/lang/Signature

Question

i am trying to connect to a database via java using JDBC i have installed:
jdk1.5.0_01
mysql-connector-java-3.1.8-bin-g.jar
MySQL Server 4.1
Java works fine, MYSQL works fine from the command prompt but when it comes to testing using this simple java program
public class JdbcExample1 {
public static void main(String args[]) {
Connection con = null;
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
con = DriverManager.getConnection("localhost", "username", "password");
if(!con.isClosed())
System.out.println("Successfully connected to MySQL server...");
} catch(Exception e) {
System.err.println("Exception: " + e.getMessage());
} finally {
try {
if(con != null)
con.close();
} catch(SQLException e) {}
this compiles fine but when run i get the following error message
Exception in thread "main" java.lang.NoClassDefFoundError: org/aspectj/lang/Signature
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:164)
at JdbcExample1.main(JdbcExample1.java:10)
class path is set as .;C:\Program Files\Java\jdk1.5.0_01\jre\lib\ext\mysql-connector-java-3.1.8-bin.java
any help or input on this error would be appreciated
thanks in advanced Neil

Answer 1

Hi, All:
I just read this thread of discussion and got valueable info to solve my problem in a similar fashion. I'd suggest the last poster, Anil, to re-read the whole thread to correct the possible problems stated.
I would just like to add my problem/solution scenario to this thread to share my experience. I assume that readers already went through the previous notes in this thread.
#1. Space in Path:
I installed
MySQL DB server in: "C:\Program Files\MySQL\MySQL Server 4.1"
MySQL JDBC Driver: D:\mysql\mysql-connector-java-3.1.8
It seems to me that the DB server installed directory is not affected by whether there is a space in path name. The JDBC Driver path, on the other hand, does have the side effect of the space in path name when accessing by the Java client.
#2. -g in JDBC Driver:
I have been using the driver mysql-connector-java-3.1.8-bin.jar. However, right before I needed to create my ant build.xml configuration file (more details later), I thought the instruction asked me to use the mysql-connector-java-3.1.8-bin-g.jar (the debug version as kpreiser indicated), and therefore I got the now-well-known "org/aspectj/lang/Signature" error. After I removed that "-g" from the JDBC driver extression in my build.xml file, it then works well. (Great tip, kpreiser.)
#3. Middlegen with Hibernate:
My situation is a bit more complicated, but the issue of "org/aspectj/lang/Signature" error was the same (finally resolved in #2). I was trying to use Middlegen to re-generate my Hibernate map files from the data schema. (Hibernate is an open source tool that lets you create JavaBean source file from a Hibernate map file to map to a database table (see http://www.hibernate.org/ for more details.) Since I re-factored my data schema in the database, I needed to re-generate the Hibernate map files (from data schema) so that I can in turn use the map files to re-generate the JavaBean code. I wanted to use the Middlegen tool (see http://www.hibernate.org/98.html for more details) to re-generate the map files from database schema. However, in order to use Middlegen properly, you need to create the ant build.xml file to do that job. So I had to resort to MiddlegenIDE (see http://ultimania.org/middlegenide/ for more details) to help generate that build.xml file. (This is where I had the -g specified for the JDBC driver in the build.xml file that caused the problem.) Once that build.xml file is generated, the use of ant (a Java make tool) with the build.xml file can generate the hibernate map files. From these map files, JavaBean source files can be generated using Hibernate CodeGenerator.hbm2java tool. (There are several other useful tools in Hibernate too to convert the database ddl schema and the JavaBean source file.)
Obviously, there are other approaches and tools that you can use (XDoclet for instance) for different situations, but I am only providing a high level overview on what you can do to be more productive if you are involved in a large and complicated project with Java/JDBC and ORM (Object/Relational Mapping).
Item #3 may sound complicated at first, but it's worth the time to learn the tools and concept. Once you are familiar with these tools (Eclipse, Hibernate, Middlegen, Ant, etc.), you will become more productive in responding to the dynamic nature of the high-tech world where changing requirements are the only constant. I hope that these separate tools will become more integrated and easier to use in the future, but for now they do the job well.
Thanks for the great tips and hope that this helps too.
- Shuh