Java运行时ClassNotFoundException [英] Java runtime ClassNotFoundException

问题描述

只是有一个关于我遇到的奇怪的运行时错误的问题.我正在使用一个JSON服务器，当外部源提示时，该服务器使用JSON对象进行响应.但是，截至目前，我只是在尝试将JSON对象发送出去之前使其启动并运行.我的代码在编译时没有指定任何类路径，但是在运行时，它会抛出一个NoClassDefFoundError，如下所示:

Just had a question about an odd runtime error that I'm having. I'm working with a JSON server that responds with a JSON object when prompted by an outside source. As of right now, however, I'm simply trying to get the JSON object up and running before sending it out. My code compiles without specifying any classpath, but when it comes to runtime, it throws a NoClassDefFoundError as seen here:

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:

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文件夹与ExampleServer.java在同一目录中，并且JSON类位于我的导入中指定的net/sf/json中.为什么直到运行时它才起作用?我的classpath是否由于某些原因而不合适?包括必要的类路径的合适语法是什么?

and the JSON folder is in the same directory as ExampleServer.java, with the JSON classes residing in net/sf/json as specified in my imports. Why is it not working until runtime? Is my classpath not right for some reason? What would be the appropriate syntax for including a necessary classpath?

预先感谢

推荐答案

来自 json-lib主页 :

Json-lib需要(至少)以下依赖项 类路径:

Json-lib requires (at least) the following dependencies in your classpath:

1. jakarta commons-lang 2.5
2. jakarta commons-beanutils 1.8.0
3. 雅加达Commons-Collections 3.2.1
4. 雅加达公共记录1.1.1
5. ezmorph 1.0.6

1. jakarta commons-lang 2.5
2. jakarta commons-beanutils 1.8.0
3. jakarta commons-collections 3.2.1
4. jakarta commons-logging 1.1.1
5. ezmorph 1.0.6

您的实现进行编译仅表明编译器可以找到正确的类和方法.但是，这些类和方法的实现可能取决于其他库.

That your implementation compiles only shows that the compiler can find the right classes and methods. The implementation of those classes and methods may however depend on other libraries.

有关项目依赖项的更多信息，请参见此处.

More information on project dependencies can be found here.

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