This question already has answers here:
What causes and what are the differences between NoClassDefFoundError and ClassNotFoundException?
(15 answers)
Closed 6 years ago.
Got error while I'm tried to connect SQL database
using cmd. Here is my program.I use jdk 6 version to compile and run
Thanks in Advance.
import java.io.*;
import java.sql.*;
class Dbs
{
public static void main(String args[]) throws Exception
{
try
{
Connection con = null;
Statement s = null;
ResultSet rs = null;
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String bala = "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb)};DBQ=c:\\ss.mdb";
con = DriverManager.getConnection(bala,"","");
s = con.createStatement();
rs =s.executeQuery("select * from Table1");
while(rs.next())
{
System.out.println("Name"+rs.getString("name"));
System.out.println("No"+rs.getString("num"));
}
}
catch(Exception e)
{
System.out.print(e);
}
}
}
Error:
Are you in the correct directory ? It seems you are in your jdk directory, where you should be in your program's directory (where your Dbs.class resides).
Also, you missed the public keyword. Here, your Dbs is package local, so it won't be visible outside the package. Depending on where you use it, it may trigger the error.
Try:
public class Dbs {
// code
}
Also,
If you don’t explicitly specify a package, your classes and interfaces end up in an unnamed packaged, also known as the default package. Best practice is not to use the default package for any production code.
more here.
the error says the class you are trying to get is not where it must, check the the jdbc driver is in the correct place ,check if you have your JAVA_PATH set and put a try catch to see if there is another error who is causing that
Related
This question already has answers here:
Connect Java to a MySQL database
(14 answers)
What is a classpath and how do I set it?
(10 answers)
Closed last month.
I get the following error when trying to execute a Java program with SQL code:
java.sql.SQLException: No suitable driver found for
jdbc:mysql://localhost/opiejbc1
I have installed the driver mysql-connector-j-8.0.31.jar in /usr/share/java
I have called the class with java -cp ./:/usr/share/java TestApplication
and with CLASSPATH=./:/usr/share/java set.
My Java code is as follows:
import java.sql.*;
public class TestApplication {
static final String DB_URL = "jdbc:mysql://localhost/opiejbc1";
static final String USER = "opiejbc1";
static final String QUERY = "SELECT * FROM Test1";
public static void main(String[] args) {
// Open a connection
try(Connection conn = DriverManager.getConnection(DB_URL, USER, "");
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(QUERY);) {
// Extract data from result set
while (rs.next()) {
// Retrieve by column name
System.out.print("Name: " + rs.getInt("Name"));
System.out.print(", Phone: " + rs.getInt("Phone"));
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
I have tried inserting Class.forName("com.mysql.cj.jdbc.Driver"); immediately after the try statement, but then I get the following error:
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Syntax error on token(s), misplaced construct(s)
at TestApplication.main(TestApplication.java:10)
What am I doing wrong?
I have tried all the recommended solutions as far as I know, but I still get those errors.
As noted by #g00se, the real problem is that the JAR file for the Connector/J driver is not on your runtime classpath. So the java runtime cannot find it.
Solution: put the JAR file on the classpath.
Notes:
If you use a -cp option, the CLASSPATH environment variable is ignored.
If you put a directory on the classpath, you are NOT telling the java to put JAR files (in that directory) on the classpath.
If you wanted to put all JAR files in (say) "/usr/share/java" on the classpath, you could use a wildcard entry; e.g. -cp .:/usr/share/java/*.jar. Note that the *.jar is not shell globbing. It needs to be processed by the java command. (In some cases you may need to escape it to prevent globbing.)
You should (IMO) take the time to read the Oracle documentation on how the classpath works.
Adding a Class.forName call is NOT recommended (except by people who don't understand the problem). If the drivers are on the classpath then DriverManager will find them. And if they are not on the classpath, then using Class.forName is going to fail.
But the reason that you got a compilation error was that you were inserting it at the wrong place:
try ( // HERE is the wrong place
Connection conn = DriverManager.getConnection(DB_URL, USER, "");
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(QUERY);) {
The try with resources syntax only allows variable declarations with initializers in that context. A Class.forName call is not such a thing.
I haven't checked, but I think that inserting
Class dummy = Class.forName("com.mysql.cj.jdbc.Driver");
at // HERE in the above would make the compiler happier. But DON'T. It is unnecessary. It won't help. See above for the correct solution.
This question already has answers here:
Connect Java to a MySQL database
(14 answers)
Closed 1 year ago.
EDIT (fixed):
I found out how to fix this issue, it apperently had something to do with the fact I used gradle to build my project (which is standard for modding with FabricMC). Because of that, I had to add the MySQL Connector/J to the dependencies in the build.gradle file. After that I built another project and the SQL connection worked!
I didn't need to add it as a library or dependency afterward. I also didn't have to load the driver using Class.forName();
dependencies {
// To change the versions see the gradle.properties file
minecraft "com.mojang:minecraft:${project.minecraft_version}"
mappings "net.fabricmc:yarn:${project.yarn_mappings}:v2"
modImplementation "net.fabricmc:fabric-loader:${project.loader_version}"
// Fabric API. This is technically optional, but you probably want it anyway.
modImplementation "net.fabricmc.fabric-api:fabric-api:${project.fabric_version}"
// https://mvnrepository.com/artifact/mysql/mysql-connector-java
implementation 'mysql:mysql-connector-java:8.0.27'
}
Im writing a Minecraft mod using the Fabric API in Intellij Idea and need to communicate with a database that's on another server (which is using DirectAdmin).
I've tried a lot of solutions suggested from different questions, like loading the driver first or installing the Database Manager plugin. Those sadly don't seem to solve the problem.
I have also quadruple-checked if I'm using the correct path to the database, which I seem to be doing.
(Im using Java 16, in case that helps)
I tried make the connection, but keep getting the same error:
java.sql.SQLException: No suitable driver found for jdbc
I have included the mysql-connector-java-8.0.27.jar library and am still getting the error.
After that I also added it as a dependency, but it still doesn't work.
Am I missing something here? I've been reading a lot of these posts but none of the solutions seem to work.
Something I'm suspecting is that I have to add some sort of library to the server the database is on as well, but I don't know how I would do that.
This is the code I use to make the connection. I call the connect() method from my Main class, which is in a try/catch
package nl.egelblad.tutorial.sql;
import java.sql.*;
public class MySQL {
private String host = "185.102.34.56";
private String port = "3306";
private String database = "my_db";
private String username = "db_username";
private String password = "db_password";
private Connection connection;
public boolean isConnected() {
return (connection == null ? false : true);
}
public void connect() throws ClassNotFoundException, SQLException {
if (!isConnected()) {
connection = DriverManager.getConnection("jdbc:mysql://" + host + ":" + port + "/" + database + "?useSSL=false&autoReconnect=true", username, password);
}
}
public void disconnect() {
if (isConnected()) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public Connection getConnection() {
return connection;
}
}
You have to load driver at the beginning (only one time) :
try {
Class.forName("com.mysql.cj.jdbc.Driver");
// Or "com.mysql.jdbc.Driver" for some old mysql driver
} catch(ClassNotFoundException e) {
getLogger().error("Failed to load driver");
e.printStackTrace();
}
Then, you should check that the given jar is exported with good dependencies. Depending or your minecraft version, maybe it's already include. But it's possible that it's not.
So, you have to change your export settings to include the jar mysql-connector-java-8.0.27.jar in your own.
This question already has an answer here:
Manipulating an Access database from Java without ODBC
(1 answer)
Closed 6 years ago.
I want to connect Java 8 with Access but the following error occurs and I don't know how to fix it. I always get this error:
java.sql.SQLException: No suitable driver found for jdbc:ucanaccess://C:/Users/Ghazi/workspace/java w access/login.accdb
I added 4 libraries:
hsqldb.jar
jackcess-2.0.7.jar
org.apache.commons.lang-2.6-source.jar
org.apache.commons.loggin-1.1.1-source.jar
This is my code
import java.sql.*;
public class DbConnection {
Connection con;
Statement st;
DbConnection(){
dbconnect();
}
//-----------------------
public void dbconnect(){
try
{
Connection conn=DriverManager.getConnection("jdbc:ucanaccess://C:/Users/Ghazi/workspace/java w access/login.accdb");
Statement stment = conn.createStatement();
}
catch(Exception err)
{
System.out.println(err);
}
}
//--------------------------
public static void main(String[]args){
DbConnection ob=new DbConnection();
}//end main
}
Try adding "Class.forName():
public void dbconnect(){
try {
Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
Connection conn=DriverManager.getConnection("jdbc:ucanaccess://C:/Users/Ghazi/workspace/java w access/login.accdb");
Statement stment = conn.createStatement();
}
catch(Exception err) {
System.out.println(err);
}
}
The basic problem is that earlier versions of Java/JDBC used ODBC to connect to MS-Access ... and the ODBC driver has been removed from Java 8.
Two alternatives are to use:
1) UCanAccess: http://ucanaccess.sourceforge.net/site.html
... or ...
2) Jackcess (Jackcess 2.0: New crunchy outside, same yummy filling!): http://jackcess.sourceforge.net/
If that doesn't work:
3) Please specify what what IDE you're using (Eclipse, etc - if applicable)
4) Make sure your jackcess-2.0.7.jar is explicitly included in the CLASSPATH (how to do this depends on your IDE)
5) Consider using a directory without spaces in the name
I added 4 libraries
You need five (5) libraries. You forgot to add the "ucanaccess-x.y.z.jar" file itself.
For detailed instructions, see
Manipulating an Access database from Java without ODBC
So I just started learning about databases this week and one of the things I need to be able to do is connect to my mySQL database that I created using Java. I have done some research and I have tried to find the correct way of doing this I just can't seem to figure out how. Here is my code:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class Menu
{
public void menu()
{
Connection conn;
String url = "jdbc:mysql://localhost:3306/";
String dbName = "gym";
String driver = "com.mysql.jdbc.Driver";
String userName = "root";
String password = "password";
try
{
Class.forName(driver).newInstance();
conn = DriverManager.getConnection(url+dbName,userName,password);
System.out.println("Connected to the database");
conn.close();
System.out.println("Disconnected from database");
}
catch (Exception e)
{
System.out.println("NO CONNECTION =(");
System.out.println(e.getMessage());
}
}
}
Now the problem is, is that every time I run this code, the "No Connection =( " appears and then it says the error is: "com.mysql.jdbc.Driver". Can somebody please help me and say what I am doing wrong? Thank you. Much appreciated.
Your error means that your library path doesn't contain the jar that contains the com.mysql.jdbc.Driver class.
You don't have to change anything in your code. If you are running it via Eclipse, you should add mysql-connector-java-x.x.x-bin.jar to your build path (where x.x.x is the version of the jar).
All JDBC connection classes need their respective drivers which are normally supplied as jar files from the database vendor, add the relevant database driver to your classpath.
The .jar file will be available from the vendors site, in this case : http://www.mysql.com/products/connector/ and then to add this to the classpath of your project in the ide of your choice. Here is a guide for eclipse : http://www.wikihow.com/Add-JARs-to-Project-Build-Paths-in-Eclipse-(Java)
Try and run again once you have this.
There are a lot of questions: "How to start working with MySQL as an embedded database?", "How to use Connector/MXJ", etc. But there is no any useful information (neither tutorials!). I mean there is no detailed instructions how to do such things. Of course, there is a MySQL website, where is an article about using MysqldResource. Actually, I don't understand what it is.
Let's finish this lack of any restraint! Please, if you are experienced in this topic, give as full instruction as you can! (what to download, how to add jars(say, to eclipse), some code will be great...)
For example, the following code doesn't work - ClassNotFoundException- though I have added mysql-connector-mxj-gpl-5-0-11.jar and mysql-connector-mxj-gpl-5-0-11-bd-files.jar to the project classpath.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DatabaseWorks {
public static void main(String[] args) {
try {
Class.forName("com.mysql.jdbc.Driver");
try {
Connection con = DriverManager.getConnection("jdbc:mysql://localhost", "root", "");
Statement st = con.createStatement();
String query = "SELECT VERSION();";
ResultSet rs = st.executeQuery(query);
rs.next();
System.out.println("success!!!! " + rs.getString(1));
} catch (SQLException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
For example, the following code doesn't work - ClassNotFoundException- though I have added mysql-connector-mxj-gpl-5-0-11.jar and mysql-connector-mxj-gpl-5-0-11-bd-files.jar to the project classpath.
This is a basic Java problem. Here's what I'd do to solve it:
Examine the stacktrace to find out which class is missing.
Use jar tvf ... to list the contents of JAR file(s) you think the missing class should be in. Is it there? Is the name / package correct?
If it is there, you've got the application's runtime classpath wrong.
If it is not there, you are missing a JAR file. Go back to the documentation and read it again.
(If you showed us the stacktrace, and told us how you are building and launching your code, perhaps we could be a bit more specific ...)
More informations here:
http://dev.mysql.com/doc/refman/5.1/en/connector-mxj.html
http://jroller.com/mmatthews/entry/yes_it_really_is_this