Java - Error: A JNI error has occurred, ... in thread "main" java.lang.UnsupportedClassVersionError:

Question

Currently I try to connect locally to my mysql Server. My code for it looks the following:

import java.sql.*; 

public class JdbcSelectTest {
    public static void main(String[] args) {
        try (
                Connection conn = DriverManager.getConnection(
                        "jdbc:mysql://localhost:3306/ebookshop?useSSL=false", "...", "...");

                Statement stmt = conn.createStatement();
        ) {
            String strSelect = "select title, price, qty from books";
            System.out.println("The SQL query is: " + strSelect);
            System.out.println();

            ResultSet rset = stmt.executeQuery(strSelect);

            System.out.println("The records selected are:");
            int rowCount = 0;
            while(rset.next()) {   // Move the cursor to the next row, return false if no more row
                String title = rset.getString("title");
                double price = rset.getDouble("price");
                int    qty   = rset.getInt("qty");
                System.out.println(title + ", " + price + ", " + qty);
                ++rowCount;
            }
            System.out.println("Total number of records = " + rowCount);

        } catch(SQLException ex) {
            ex.printStackTrace();
        }
    }
}

Now when I compile with: javac JdbcSelectTest.java everything works fine. But now when I try to run the Compilation with: java -cp .;C:\Users\Marco\IdeaProjects\mysql-connector-java-8.0.13\mysql-connector-java-8.0.13.jar JdbcSelectTest I get this following error:

Error: A JNI error has occurred, please check your installation and try again Exception in thread "main" java.lang.UnsupportedClassVersionError: JdbcSelectTest has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0...

My JAVA_HOME property points to my locally installed jdk version 11.0.1.
The mysql-connector-java version ist: 8.0.13.
Can anyone help me out - btw. Im pretty newbie on java -so any comment helps.

Gergely Bacso · Accepted Answer · 2019-01-14 22:30:11Z

4

Your issue is not related to the mysql lib.

The meaningful parts of the errormessage:

JdbcSelectTest has been **compiled by** [...] Java Runtime (class file version **55.0**)

vs

this [...] Java Runtime only **recognizes** class file versions up to **52.0**

This can be translated to something like:

JdbcSelectTest has been compiled by Java 11, but was attempted to run by Java 8.

If you want to verify this, just type the following these commands into your console:

:~ > java -version
:~ > javac -version

And you will seem them being different. You have already checked your JAVA_HOME variable, but you must also need take a look at your PATH variable to have this fixed. This link will help you with that.

answered Jan 14, 2019 at 22:30

Gergely Bacso

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Andronicus · Accepted Answer · 2019-01-14 16:26:54Z

2

There is a java version mismatch. You need to install proper version of java, i.e. java 8 and compile you code with it. Here you can find a table with versions required: vers.

answered Jan 14, 2019 at 16:26

Andronicus

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