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Java/Servlet error with calculation class [duplicate]

There is a VERY similar question to mine but in my case I don't have any duplicate jars in my build path, so the solution does not work for me. I've searched google for a couple of hours now, but none of the solutions I've found there actually resolve my issue. I'm creating a web site with some database connectivity for a homework. I'm using a MySQL database, developing in Eclipse and running on Windows.
I keep getting java.lang.ClassNotFoundException: com.mysql.jdbc.Driver with the following code:
import java.sql.*;
//...
public void someMethodInMyServlet(PrintWriter out)
{
Connection connection = null;
PreparedStatement query = null;
try {
out.println("Create the driver instance.<br>");
Class.forName("com.mysql.jdbc.Driver").newInstance();
out.println("Get the connection.<br>");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "secret");
query = connection.prepareStatement( "SELECT * FROM customers");
//...
} catch (Exception e)
{
out.println(e.toString()+"<br>");
}
}
//...
When I run the above code I get the following output:
Create the driver instance.
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
It doesn't get past the Class.forName... line and I can't figure out why! Here is what I did:
Download mysql-connector.
Put it in my MySQL folder C:\Program Files\MySQL\mysql-connector-java-5.1.12\mysql-connector-java-5.1.12-bin.jar.
Opened the project properties in Eclipse.
Add External Jar to my Build Path and I selected mysql-connector-java-5.1.12-bin.jar.
Every time I attempt to use the servlet I get the same error regardless if I have the jar in there or if I don't. Could you help me figure this out?

As for every "3rd-party" library in flavor of a JAR file which is to be used by the webapp, just copy/drop the physical JAR file in webapp's /WEB-INF/lib. It will then be available in webapp's default classpath. Also, Eclipse is smart enough to notice that. No need to hassle with buildpath. However, make sure to remove all unnecessary references you added before, else it might collide.
An alternative is to install it in the server itself by dropping the physical JAR file in server's own /lib folder. This is required when you're using server-provided JDBC connection pool data source which in turn needs the MySQL JDBC driver.
See also:
How to add JAR libraries to WAR project without facing java.lang.ClassNotFoundException? Classpath vs Build Path vs /WEB-INF/lib
How should I connect to JDBC database / datasource in a servlet based application?
Where do I have to place the JDBC driver for Tomcat's connection pool?
JDBC CLASSPATH Not Working

Since you are running it in servlet, you need to have the jar accessible by the servlet container. You either include the connector as part of your application war or put it as part of the servlet container's extended library and datasource management stuff, if it has one. The second part is totally depend on the container that you have.

The others are right about making the driver JAR available to your servlet container. My comment was meant to suggest that you verify from the command line whether the driver itself is intact.
Rather than an empty main(), try something like this, adapted from the included documentation:
public class LoadDriver {
public static void main(String[] args) throws Exception {
Class.forName("com.mysql.jdbc.Driver");
}
}
On my platform, I'd do this:
$ ls mysql-connector-java-5.1.12-bin.jar
mysql-connector-java-5.1.12-bin.jar
$ javac LoadDriver.java
$ java -cp mysql-connector-java-5.1.12-bin.jar:. LoadDriver
On your platform, you need to use ; as the path separator, as discussed here and here.

Place mysql-connector-java-5.1.6-bin.jar to the \Apache Tomcat 6.0.18\lib folder. Your problem will be solved.

What you should not do do (especially when working on a shared project)
Ok, after had the same issue and after reading some answers here and other places. it seems that putting external lib into WEB-INF/lib is not that good idea as it pollute webapp/JRE libs with server-specific libraries - for more information check this answer"
Another solution that i do NOT recommend is: to copy it into tomcat/lib folder. although this may work, it will be hard to manage dependency for a shared(git for example) project.
Good solution 1
Create vendor folder. put there all your external lib. then, map this folder as dependency to your project. in eclipse you need to
add your folder to the build path
Project Properties -> Java build path
Libraries -> add external lib or any other solution to add your files/folder
add your build path to deployment Assembly (reference)
Project Properties -> Deployment Assembly
Add -> Java Build Path Entries
You should now see the list of libraries on your build path that you can specify for inclusion into your finished WAR.
Select the ones you want and hit Finish.
Good solution 2
Use maven (or any alternative) to manage project dependency

Just follow these steps:
1) Install eclipse
2) Import Apache to eclipse
3) Install mysql
4) Download mysqlconnector/J
5) Unzip the zipped file navigate through it until you get the bin file in it. Then place all files that are present in the folder containing bin to C:\Program Files\mysql\mysql server5.1/
then give the same path as the address while defining the driver in eclipse.
That's all very easy guys.

If the problem still persists,
Put the-
mysql-connector-java-5.0.8-bin jar in a place inside your Tomcat->lib->folder (No matter where you've installed your Tomcat). And change your environmental variable (Done by clicking Properties of Mycomputer -Advanced system settings- Environmental variables-And set a new variable name & variable values as the place where your lib file resides.Dont forget to enter a ; at the end of the path)
If still problem persists
Try downloading commons-collections-2.0.jar (http://www.docjar.com/jar_detail/commons-collections-2.0.jar.html) and paste the jar in the same place where your mysql jar resides (ie) inside Tomcat-lib.
Clean your project-Stop your server- Finally try to run.

Many times I have been facing this problem, I have experienced ClassNotFoundException.
if jar is not at physical location.
So make sure .jar file(mysql connector) in the physical location of WEB-INF lib folder. and
make sure restarting Tomcat by using shutdown command in cmd.
it should work.

The only solution worked for me is putting the .jar file under WEB-INF/lib . Hope this will help.

assuming your project is maven based, add it to your POM:
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.26</version>
</dependency>
Save > Build > and test connection again. It works! Your actual mysql java connector version may vary.

Put mysql-connector-java-5.1.38-bin.jar to the C:\Program Files\Apache Software Foundation\Tomcat 7.0\lib folder.by doing this program with execute

My issue was a little different. Instead of jdbc:oracle:thin:#server:port/service i had it as server:port/service.
Missing was jdbc:oracle:thin:# in url attribute in GlobalNamingResources.Resource. But I overlooked tomcat exception's
java.sql.SQLException: Cannot create JDBC driver of class 'oracle.jdbc.driver.OracleDriver' for connect URL 'server:port/service'

for this error:
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
you need to:
Import java.sql.*;
Import com.mysql.jdbc.Driver;
even if its not used till app running.

Why am I getting NoClassDefFoundError / ClassNotFoundException

I have been following this tutorial accordingly.
Up to running the FirstExample class in the command prompt is when it starts to freak out for some reason. After attempting to run the following command:
java FirstExample
I get the following exception:
Exception in thread "main" java.lang.NoClassDefFoundError: FirstExample
I understand that it can't find the FirstExample class due to the classpath (for some reason) so I executed the following command:
java -cp . FirstExample
And now it returns a new exception:
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
Now it can't find the JDBC Driver. This confuses me because for starters, I ran the exact same coding through Eclipse and it works as expected, and secondly, I went as far as to ensure that I execute the same class file that Eclipse is executing, and the command prompt still returns exceptions. I also went as far as to put the FirstExample file in a separate folder, just for the purpose of copying and pasting the MySQL Connector into the same folder, and I still get exceptions.
I just don't understand whats going on, can someone help me please?
Many thanks.
The file path to the connector is as followed:
C:\Program Files\MySQL\mysql-connector-java-3.1.14\mysql-connector-java-3.1.14-bin.jar
Hope this helps.
For testing purposes, I have placed the FirstExample class under the following path:
C:\java

This confuses me because for starters, I ran the exact same coding through Eclipse and it works as expected
This is because in Eclipse you add the libraries to the Build Path, and it will use all the libraries specified there in the classpath automatically when running your project. This can be noted here:
In order for you to execute your project using third party libraries from command line tools, you should specify the libraries manually in your classpath explicitly:
java -cp <path/to/mysql_jar/goes/here>:. FirstExample
By your comment:
the path to the MySQL file is: C:\Program Files\MySQL\mysql-connector-java-3.1.14\mysql-connector-java-3.1.14-bin.jar (...) I have placed the FirstExample class under C:\java
This should be the command line to use:
java -cp "C:\Program Files\MySQL\mysql-connector-java-3.1.14\mysql-connector-java-3.1.14-bin.jar; ." FirstExample
Note that it is better to store all the third party libraries in a single folder within your project, usually called lib, and put a reference to there. Assuming your current folder has a lib folder and all the third party libraries are copied there, the command line would be:
java -cp "lib\*; ." FirstExample

Use the next example to add your jars to the classpath:
java -cp "jdbc.jar;lib/*" my.package.FirstExample

You need to have the class com.mysql.jdbc.Driver (and all the imported classes) in the classpath too.
You should download the jar (http://dev.mysql.com/downloads/connector/j/5.0.html) and add it to the classpath.

The ClassNotFound Exception rises when there is an issue with the class name that you have written in Class.forName() or if the package is not set to the classpath variable. Make sure that you have added the jar file to the classpath ( C:............\jarfilename.jar;).
This is applicable for any JDBC Driver and jar files. The .jar files that are added to the classpath will not be visible to IDEs, in this case, you need to add the jar files to buildpath (in eclipse) or you can also copy the jar files to ext folder available in the Java installation folder.
Also note that the jar files of the DB Softwares may vary based on the DB software version that you are using for example if you are using the Oracle 11g, you need ojdbc6.jar file, in other versions of Oracle the number changes like ojdbc14.jar etc.

MySQL JDBC: no suitable driver found

I have developed a program that pulls the data from a remote sql server and pushes it to local mysql server .I have a jar file exported for this .
Now I am trying to run this jar file on different machine to do the same task .All the IP's and ports have been changed accordingly .There is no IDE on this machine .
When i am running this jar file , i get an error saying "No suitable driver found for jdbc:sqlserver:/ 172 .* "
I have installed the jdbc driver in program files .
So what do i have to do to run this jar file .

You need to add the library to the runtime classpath. A straightforward way would be to export it as a dependency in the jar (although there might be licencing issues with that).
How are you creating the jar?

Add the jdbc driver in your classpath, not in your "program files".... Check the documentation of the JVM http://docs.oracle.com/javase/7/docs/technotes/tools/windows/java.html

All you need to run a Java program is a Java executable and class files or zipped/jared class files and other files needed by class files. So 1st step is locate your java executable, maybe c:\java.exe or /home/yourhome/java, and 2nd step is gather all your classes or zip/jar archive and put them in a String split by ':' on Unix or Unix-like or ';' on windows. 3rd step is to identify your main class, which is the only entry of your program.
In the end, use YOUR_JAVA_EXECYTABLE -classpath YOUR_CLASS_PATH YOUR_MAIN_CLASS. works fine for most scenarios.
Forget anything about "installed" a program or driver, which is just put some some in system's classpath or path or anything like this.

How a java application should discover extensions in runtime?

I want to look for extension jars in a predefined directory and examine their manifest. Those which match should be loaded, those which do not - should be unloaded.
Now, I can do it a primitive way - mandate that each extension pass the name of its bootstrapper on the command line and then for each jar found in the directory try and load any of the given bootstrapper types. Something like this:
java -jar myapp.jar --pluginDir=c:/a/b/c --exts="classA;classB;classC"
Then myapp would iterate over all the files inside the pluginDir and try to load each of classA, classB or classC. Once a classX is successfully loaded, it is removed from the list. The search stops when either all the extensions are found and loaded or there are no more jars in the plugin dir.
A slightly more javaish approach seems to be writing something in the manifest of extension jars and check the manifest of each found jar.
Can anyone show a working code snippet of this approach or of anything better, if there is?
EDIT
A quote from the postgre JDBC driver README file (see https://stackoverflow.com/a/12480373/80002):
INSTALLING THE DRIVER
To install the driver, the postgresql.jar file has to be in the classpath.
ie: under LINUX/SOLARIS (the example here is my linux box):
export CLASSPATH=.:/usr/local/pgsql/share/java/postgresql.jar

There is ServideLoader class for this purpose. JDBC drivers are built on this principle. Hope, it helped.

Running Java Program linking to thirdpary library (java -jar) issue ( Multiple methods tried )

This issue is related to running a Java program (jar) dependent on thirdparty jar library even after setting classpath and trying so many other methods by reading articles in Internet.
I want to use a thirdparty Pack1.jar (it is not a part of jvm) as dependency of my programme.
I do not know where the Pack1.jar file could be in the deployment machine and I want the deployer to specify the path for the thirdparty libraries
I have tried the following alternatives in vain
Setting the java.class.path programatically
String class_path = args[0];
System.setProperty("java.class.path",class_path);
Here I am assuming that deployer would supply the classpath as first argument while running the program
Setting the CLASSPATH env_var to locate the thirdparty directory
While running, using the classpath option
java -classpath /path/to/Pack1.jar -jar Pack2.jar
I think this would not work because documentation says that classpath is ignored when program is run with "java -jar"
Setting the java.ext.dirs programatically.
Setting the java.library.path programatically.
I do not want to specify the Class-Path in manifest because that takes only relative path and I do not know where the thirdparty library would be kept in deployment machine
But I am unable to get the jar running.
How can I fix this problem any help please.

Go for option 3. Put both jars on the classpath like this:
java -classpath '/path/to/Pack1.jar:/path/to/Pack2.jar' com.packagename.yourclassname
Note, that this is for Linux. on Windows, you would separate classpath elements with semicolons:
java -classpath "/path/to/Pack1.jar;/path/to/Pack2.jar" com.packagename.yourclassname
http://en.wikipedia.org/wiki/Classpath_%28Java%29

You can use Pack2.jar without running it using -jar--put it on the classpath and call the entry point listed in its manifest file.
I usually wrap that up in a launcher script to avoid those kinds of problems, and allow jar paths to be set using an argument.

Name the secondary JAR(s) in the Class-path entry of the Manifest.MF of the main JAR file, and use java -jar.
Your objection to this technique doesn't make sense. If you supply and deploy the secondary JAR files, as you should, you have the same degree of control over their location as you do over that of the major JAR file. It doesn't matter where else the user may have copies of them.