Question

I have added my mysql-connector-java-5.1.18-bin.jar to jre and jdk libs. And Here it is:

C:\Windows\system32>javap java.io.Bits
    Compiled from "Bits.java"
    class java.io.Bits extends java.lang.Object{
        java.io.Bits();
        static boolean getBoolean(byte[], int);
        static char getChar(byte[], int);
        static short getShort(byte[], int);
        static int getInt(byte[], int);
        static float getFloat(byte[], int);
        static long getLong(byte[], int);
        static double getDouble(byte[], int);
        static void putBoolean(byte[], int, boolean);
        static void putChar(byte[], int, char);
        static void putShort(byte[], int, short);
        static void putInt(byte[], int, int);
        static void putFloat(byte[], int, float);
        static void putLong(byte[], int, long);
        static void putDouble(byte[], int, double);
    }


    C:\Windows\system32>javap com.mysql.jdbc.Driver
    ERROR:Could not find com.mysql.jdbc.Driver

But when I show a direct classpath to the same file, it is ok.

C:\Windows\system32>javap -classpath "B:\Java\Tools\mysql-connector-java-5.1.18\
mysql-connector-java-5.1.18\mysql-connector-java-5.1.18-bin.jar" com.mysql.jdbc.
Driver
Compiled from "Driver.java"
public class com.mysql.jdbc.Driver extends com.mysql.jdbc.NonRegisteringDriver i
mplements java.sql.Driver{
    public com.mysql.jdbc.Driver()       throws java.sql.SQLException;
    static {};
}

The problem started when I was using Thilo’s answer to load driver dynamically. There is no IOException. But on the string Class.forName(driver).newInstance() I have ClassNotFoundException exception. After adding jar to jre, nothing has changed. What is wrong with that?

Answer 1

What exactly do you mean by After adding jar to jre? I fear mysql-connector-java-5.1.18-bin.jar is not properly added to classpath. The ClassNotFoundException is only thrown when that class is not present in the searchable classpath. All the jars that come with JDK are bootstrap classes and are available for java to load them. All third party classes however need to be set in a searchable system or application level classpath so that java can load the specified class argument.

Try following commands at your command prompt and execute your java class.

set mysqljar="absolute-path-to\mysql-connector-java-5.1.18-bin.jar"  
set classpath=%classpath%;.;%mysqljar%

So long as this jar is available in searchable classpath, all class loaders can find and load class from the jar. Try this change and run Thilo’s example and it should be working.

Also read more on class paths, for command line, here.