VS Code can not run non-Spring Maven project correctly

Question

I must apologize if it is a duplicate question, but I googled first without getting a useful answer.

Description

Today I'm trying to migrate from IDEA to VS Code, but when running a non-spring Maven project in VS Code, it won't run with dependencies in pom.xml, I can only get Exception in thread "main" java.lang.NoClassDefFoundError in console.

Here I'll provided a brief example:

The project shown below use fastjson to parse a Map to JSON string, the fastjson is a maven repository defined in pom.xml .

Project Structure

App.java

package com.example;

import java.util.HashMap;
import java.util.Map;

import com.alibaba.fastjson.JSON;

public class App {
    public static void main(String[] args) {
        Map<String, String> item = new HashMap<>();
        item.put("a", "1");
        item.put("b", "2");
        System.out.println(JSON.toJSONString(item));
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.example</groupId>
  <artifactId>demo</artifactId>
  <version>0.0.1</version>

  <name>demo</name>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.78</version>
    </dependency>
  </dependencies>
</project>

Maven Dependencies Shown in VS Code

Try to run the project with Run and Debug in VS Code

Result

Look, The VS Code did not run this Maven project correctly. it did not run with dependencies in pom.xml!

Trivia

1. I have installed Extension Pack for Java for VS Code
2. I even installed Spring Boot Extension Pack for VS Code
3. I have installed Maven and configured corresponding Environment Variable, mvn command is able to run in console
4. The project above is running correctly in IDEA
5. Spring project is able to run normally in VS Code, but the problem project is maven without Spring

Help

Did I miss some configurations for VS Code to run Maven project? What should I do to make it running correctly in VS Code?

Answer 1

Your code throws no errors in my project:

I think there's a cache messed it, you may

1. Turn to local dependency installation folder, delete \User folder\.m2\repository\com\alibaba\fastjson\1.2.78
2. Delete the dependency fastjson in pom.xml
3. Open Command Palette and choose Java: Clean Java Language Server Workspace
4. re-add the fastjson dependency and follow the notification to synchronize project configuration.

Answer 2

Okay, finally I resolved my problem with VS Code myself. I put my solution here in case someone or I met the same problem in the future.

To solve the issue:

1. I moved my maven dependencies path to else where: I created a folder G:\maven-repo , and modified global settings.xml of maven like below:

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
  <localRepository>G:/maven-repo</localRepository>
</settings>

2. In settings.json of VS Code, I added the line below, which refers to where the settings.xml in step 1 is:

"java.configuration.maven.globalSettings": "G:/ideaIU/plugins/maven/lib/maven3/conf/settings.xml"

3. Restart VS Code, execute Java: Clean Java Language Server Workspace as @Molly Wang-MSFT said.

4. After restarting VS Code again, pressing the F5 key, the project finally runs correctly.