Java运行时的ClassNotFoundException(Java runtime ClassN

刚刚有了一个关于我有一个奇怪的运行时错误的问题。我有当由外部源提示JSON对象响应一个JSON服务器的工作。截至目前，然而，我只是试图让JSON对象并发送出去之前运行。我的代码编译没有指定任何classpath中，但是当涉及到运行时，它抛出一个NoClassDefFoundError如下所示：

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/lang/exception/NestableRuntimeException
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at ExampleServer.sendData(ExampleServer.java:76)
at ExampleServer.runServer(ExampleServer.java:30)
at ExampleServer.main(ExampleServer.java:15)
   Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang.exception.NestableRuntimeException
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 15 more

我的代码如下位置：

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.lang.*;
import net.sf.json.*;

public class ExampleServer{

private DataOutputStream output;
private DataInputStream input;
private ServerSocket server;
private Socket connection;

public static void main(String[] args){
    new ExampleServer().runServer();
}

public void ExampleServer(){
    System.out.println("Server object created");
}

public void runServer(){
    try{
        server = new ServerSocket(12345,100);
        while(true){
            try{
                waitForConnection();
                getStreams();
                processConnection();
                sendData("Text");
            } catch(Exception e){
                System.out.println("Server Terminated Exception.");
            } finally {
                closeConnection();
            }
        }
    } catch(Exception e){
        e.printStackTrace();
    }
}

private void waitForConnection(){
    try{
        System.out.println("Waiting for connection.");
        connection = server.accept();
        System.out.println("Connection received from " + connection.getInetAddress().getHostName());
    } catch (IOException e){
        System.out.println(e);
    }
}

private void getStreams() throws IOException{
    output = new DataOutputStream(connection.getOutputStream());
    input = new DataInputStream(connection.getInputStream());
    System.out.println("Got streams");
}

private void processConnection() throws IOException{
    sendData("This is a test message");
}

private void closeConnection(){
    try{
        if(output != null && connection != null){
            sendData("SEVER>>> TERMINATE");
            output.close();
            connection.close();
        }
    } catch (IOException e){
        e.printStackTrace();
    }
}

private void sendData(String message){
    try{
        JSONObject g = new JSONObject();
        g.put("message", message);
        System.out.println(g.toString());
    } catch (Exception e){
        System.out.println("Error writing object");
    }
}

}

和JSON文件夹是在同一目录ExampleServer.java ，与JSON类居住在net/sf/json在我进口指定。为什么不工作，直到运行？是我的类路径不对因某种原因？什么是对包括必要的classpath适当的语法？

提前致谢

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