Class loading error in Jdbc [duplicate] - java

This question already has answers here:
Why am I getting a NoClassDefFoundError in Java?
(31 answers)
JDBC -- java.lang.NoClassDefFoundError: Could not initialize class com.mysql.jdbc.Connection
(2 answers)
Closed 9 years ago.
I just created a Class Jdbc when i tried to run an error is shown.
Exception in thread "main" java.lang.NoClassDefFoundError: Jdbc
Here's the code
import java.sql.*;
public class Jdbc {
public static void main(String [] args)
{
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/ims","","");
Statement st=con.createStatement();
DatabaseMetaData meta=con.getMetaData();
ResultSet r=meta.getTables(null,null,"%",null);
String tableNames="";
while(r.next()){
tableNames=r.getString(3);
System.out.println(tableNames);
}
}catch (Exception e){}}}

The issue is not with mysql jar but your own class "Jdbc" is not on classpath, add it to classpath.
If you are running from console add .; to classpath.

Its most likely that your program is not able to find the class
Place the mysql jdbc driver mysql-connector-java-5.x.x.jar in classpath and then check.

The 2 quick fixes would be either
1) Pass the classspath to the execution java -classpath mysql.jar
See
JAVA classpath pass file as command line argument
2) Put the mysql jar in your JRE's extdirectory. Details.
You probably want to put your class in a package since you're using the default package. Also an IDE such as Eclipse could help you for convienience. You don't tell us your execution environment or build path and your result may depend on if you're running the program from the command line, from a runnable jar or from an IDE.
I use the Eclipse Juno IDE so I don't need to worry about setting my classpath. For Ubuntu and MS-Windows, Eclipse IDE is a development environment you might want to use.

!. Make sure that the jar is in your class path
2. If not then download it from here

Related

Jar not getting executed in other's pc [problem with JDBC external jar/maven dependency, connection not getting established] [duplicate]

This question already has answers here:
SQLException: this driver is not configured for integrated authentication tomcat
(3 answers)
Closed 2 years ago.
I have written a code to connect to a database using JDBC, I am using openJDK11.0.2, 64 bit, and external jar [mssql-jdbc-8.4.0.jre11] (which i added to libraries inside "properties" in eclipse)
I added a maven dependency as well
<dependency>
<groupId>com.microsoft.sqlserver</groupId>
<artifactId>mssql-jdbc</artifactId>
<version>8.4.0.jre11</version>
</dependency>
So in my code, I am using windows authentication and my code looks like this,
public static void main(String[] args) throws SQLException {
String connString = "jdbc:sqlserver://" + serverName + "\\MSSQLSERVER:1433;" + "databaseName = testUserDb; integratedSecurity = true;";
System.out.print("\nConnection String : " + connString + "\n");
conn = DriverManager.getConnection(connString);
System.out.println("\nConnection Established");
System.out.println("\nSuccess");
}
I exported my code as a runnable jar, and the code is running fine when I am executing my jar using java -jar demoJava.jar
But when I gave my jar to my partner, on his computer (using same version of java) on his I got error, connection is not getting established.
Exception in thread "main" com.microsoft.sqlserver.jdbc.SQLServerException: This driver is not configured for integrated authentication
It there a way I can make my code universal, and it will run anywhere (when I am exporting as a runnable jar, the external mssqljdbc jar is present in my JAR) but it is only getting executed in my system.
What am I missing? Something to do with driver dlls? Please suggest.
Just add "mssql-jdbc_auth-8.4.0.x64.dll" to other peoples jdk_version/bin and rerun the process, it will work, I faced same problem. That is how I resolved it.
Make sure to use correct version (64/86)
The very first Google result for this error message leads to documentation at Microsoft :
https://techcommunity.microsoft.com/t5/sql-server/com-microsoft-sqlserver-jdbc-sqlserverexception-this-driver-is/ba-p/383296
which says "This generally indicates that the driver can not find the appropriate sqljdbc_auth.dll in the JVM library path."
There's a fix recommend there for specifying the path to the DLL, assuming that you have it. Of course, that would only work on Windows.
A more universal approach would be to use a pure-java JDBC driver, like the jTDS JDBC Driver.

Error accessing PostgreSQL using Eclipse Windows 10 [duplicate]

This question already has answers here:
Postgres JDBC connection in Eclipse Help
(5 answers)
Closed 4 years ago.
I am in the process of learning Java and PostgreSQL. I am running Windows 10 with JRE 10, my IDE being Eclipse Oxygen 3a. I had written the following code:
import java.sql.Connection;
import java.sql.DriverManager;
public class PostgreSQLJDBC {
public static void main(String args[]) {
Connection c = null;
try {
Class.forName("org.postgresql.Driver");
c = DriverManager
.getConnection("jdbc:postgresql://localhost:5432/testdb",
"postgres", "123");
} catch (Exception e) {
e.printStackTrace();
System.err.println(e.getClass().getName()+": "+e.getMessage());
System.exit(0);
}
System.out.println("Opened database successfully");
}
}
It successfully compiles. However, it gives me the following error
java.lang.ClassNotFoundException: org.postgresql.Driver
In following the advice given in Stack Overflow, I have downloaded postgresql-42.2.2.jar and placed within C:\Program Files\Java\jre-10.0.1
I then edited my system variables and added "C:\Program Files\Java\jre-10.0.1" into it. However I still get the same error. Please help
Adding a .jar to your JRE is like forcing a DLL to load into every Windows application you run. There's almost never a good reason to do so.
Add the Postgres driver jar to the project's Java Build Path.
http://help.eclipse.org/oxygen/topic/org.eclipse.jdt.doc.user/reference/ref-properties-build-path.htm?cp=1_4_3_1
Maybe go through the tutorial and learn to use your tools. http://help.eclipse.org/oxygen/topic/org.eclipse.jdt.doc.user/gettingStarted/intro/overview.htm?cp=1_0

No suitable driver when trying to create SQL database [duplicate]

This question already has answers here:
SQLException: No suitable driver found for jdbc:derby://localhost:1527
(19 answers)
Closed 7 years ago.
I am trying to create a new SQL database with this Java program
import java.sql.*; //Needed for JDBC classes
public class BuildPhonebookDB {
public static void main(String[] args) throws Exception{
//Create a named constant for the URL
final String DB_URL = "jdbc:derby:Phonebook;create=true";
try {
//Create a connection to the database.
Connection conn = DriverManager.getConnection(DB_URL);
//Create a Statement object.
Statement stmt = conn.createStatement();
//Create the Entries table
stmt.execute("CREATE TABLE Entries (" +
"Name CHAR(20)"+
"Number INTEGER)"
);
System.out.println("Database Connected");
//Close the connection
conn.close();
}
catch(Exception ex) {
System.out.println(ex.getMessage());
}
}
}
When I try to run the program I get an error that:
No suitable driver found for jdbc:derby:Phonebook;create=true
I have looked at various other similar posts on Stack Overflow, such as this one, but none help. I have seen things about a driver jar, but I don't know what this is, if I need to edit this, could someone help me through it?
Thanks for any help
Did you see this guide and have you complited all step of this guide?
Apache Derby
Download Derby Download the binary Apache Derby distribution from the
Derby web site at http://db.apache.org/derby/derby_downloads.html.
These tutorial instructions use version 10.12.1.1 and assume you
downloaded one of the binary distribution files listed in the table
below:
Operating System Download File Windows db-derby-10.12.1.1-bin.zip
UNIX, Linux, and Mac db-derby-10.12.1.1-bin.tar.gz If a more recent
release is available, download that, then substitute that version
number for 10.12.1.1 in the following instructions.
Install Derby Choose the directory into which you want to install the
Derby software. You must have write permissions to this directory. The
sample instructions below use C:\Apache for Windows and /opt/Apache
for UNIX; be sure to use your actual location. Copy the software
distribution to the location you choose, then extract it as shown
below.
Windows (use your extraction tool e.g. WinZip -- these instructions
use mks unzip):
mkdir C:\Apache copy db-derby-10.12.1.1-bin.zip
> C:\Apache cd C:\Apache unzip db-derby-10.12.1.1-bin.zip
UNIX:
mkdir /opt/Apache cp db-derby-10.12.1.1-bin.tar.gz /opt/Apache
> cd /opt/Apache tar xzvf db-derby-10.12.1.1-bin.tar.gz
In both cases, the software will now be extracted into a subdirectory
named db-derby-10.12.1.1-bin.
Set DERBY_INSTALL Set the DERBY_INSTALL variable to the location where
you installed Derby. Examples are shown below, but be sure to use the
actual location on your system:
Windows: C:\> set DERBY_INSTALL=C:\Apache\db-derby-10.12.1.1-bin
UNIX Korn Shell:
$ export
> DERBY_INSTALL=/opt/Apache/db-derby-10.12.1.1-bin
Configure Embedded Derby To use Derby in its embedded mode set your
CLASSPATH to include the jar files listed below:
derby.jar: contains the Derby engine and the Derby Embedded JDBC
driver derbytools.jar: optional, provides the ij tool that is used by
a couple of sections in this tutorial You can set your CLASSPATH
explicitly with the command shown below:
Windows:
C:\> set
> CLASSPATH=%DERBY_INSTALL%\lib\derby.jar;%DERBY_INSTALL%\lib\derbytools.jar
;.
UNIX:
$ export
> CLASSPATH=$DERBY_INSTALL/lib/derby.jar:$DERBY_INSTALL/lib/derbytools.jar:.
...
Step 3: Embedded Derby
When an application accesses a Derby database using the Embedded Derby
JDBC driver, the Derby engine does not run in a separate process, and
there are no separate database processes to start up and shut down.
Instead, the Derby database engine runs inside the same Java Virtual
Machine (JVM) as the application. So, Derby becomes part of the
application just like any other jar file that the application uses.
Figure 1 depicts this embedded architecture.
Set the environment
To set up the environment, follow the "Configure Embedded Derby"
instructions.
Use this before you get the connection from the driver:
Class.forName("org.apache.derby.jdbc.ClientDriver").newInstance();

Java SQLite3 Connection Failing

I am having some trouble connecting my java script to my SQLite3 database.
I have my directory holding my script as followed
C:/PROG/JavaPROG/programs/java_database
Inside this directory I have 3 files
Query.java, Query.class and the database query.db
My java code looks as followed
import java.sql.*;
public class Query3 {
public static void main(String[] args) {
Connection conn = null;
try {
Class.forName("org.sqlite.JDBC");
conn = DriverManager.getConnection("jdbc:sqlite:C:/PROG/JavaPROG/programs/java_database/query.db");
System.out.println("Connection Success");
} catch(Exception log) {
System.out.println("Connection Failed: " + log);
}
}
}
my classpath does contain
C:\Program Files\Java\jdk1.8.0\bin
and inside that bin directory is the sqlite jdbc driver
sqlite-jdbc-3.7.2.jar
I can connect my script to PostgreSQL database but I can't see why it isn't connecting to the SQLite3, I am getting the following error message
java.lang.ClassNotFoundException: org.sqlite.JDBC
have I done something wrong?
You need to explicitly provide the sqlite-jdbc-3.7.2.jar file in your classpath while compiling and running your classes using the -cp option. The java and javac commands will only look for .class files in the classpath and not jars.
Try this :
javac -cp <path_to_jar/sqlite-jdbc-3.7.2.jar>;. <your_class_name>.java
And if you have more than one thirdparty library, you can use a wildcard :
javac -cp <path_to_jar/*>;. <your_class_name>.java
Note that ; is the separator used in Windows. If you are on unix based systems, you need to use : instead of ;. Java maybe platform independant but the java and javac commands are not.
Also note that the . tells the java and javac commands to look in the current directory for classes. Don't forget to provide the classpath to the jars when running your program using the java command.
I have found the answer to fix this.
compile the script as normal
javac Query.java
Then specify the driver when executing
java -classpath ".;sqlite-jdbc-3.7.2.jar" Query
And it will run fine

Java class will not run (command prompt) [duplicate]

This question already has answers here:
Exception in thread "main" java.lang.NoClassDefFoundError: wrong name
(3 answers)
Closed 9 years ago.
I have been fighting with this program for a little while now and cannot figure out what is wrong. Any help would be greatly appreciated.
So here's the issue. I have three classes one is for logging onto a mysql database, the other is to output data from the database, and the last one holds method main. I was having a huge issue with getting them to compile getting errors about not finding a symbol for a method in a different class. I finally got them to all compile by using command "javac -d bin/cdtPack src/CDT.java src/login.java src/ClientBase.java"
But, now when I try to run the class with method main I get error:
Exception in thread "main" java.lang.noClassDefFoundError: CDT (wrong
name: cdtPack/CDT)
then a list of at java....
Anyone have an idea what could be going wrong?
As the linked Q&A explains this happens when you try to run a Java application using the wrong class name.
Your class looks something like this:
package cdtPack;
public class CDT {
....
}
That means that its class name is "cdtpack.CDT".
But you are running it like this:
$ java CDT
The JVM is telling you this:
"You told me to run CDT, but when I looked at it, the class said its name is "cdtpack.CDT"!!"
You have to get your head around the way that the Java classpath works, and the way that javac and java and all of the other Java tools find classes.
Your "CDT.class" file should be in a directory called "cdtpack", and then "cdtpack"'s parent directory should be on the classpath; i.e.
Compile like this:
$ javac -d bin -classpath bin src/cdtpack/CDT.java
which should create "bin/cdtpack/CDT.class". Then run like this:
$ java -classpath bin cdtpack.CDT
It looks like CDT should either belong in the package cdtPack or you are running it from the wrong directory...
Try changing into the bin directory and run the class file again. Don't forget to include the package name before the class name. For example:
...\bin> java cdtPack.CDT
try this
you goto src directory and if class file available there, then type
java CDT
if the class is present in some other directory then type
java a/b/c/JavaClassName
if you want to add some runtime jar while running then
java -cp classpath=%classpath%;jarfilename.jar; a/b/c/JavaClassName

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