添加 spring 启动验证依赖项后项目运行失败

Question

I'm working on a small project. Which uses mongoDB as DB. I want to add validation on my Player bean. But as soon as I add below dependency:

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

In my pom.xml file.

My project starts failing when I run as spring boot app.

Here is my 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 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.7.3</version> <relativePath/> <.-- lookup parent from repository --> </parent> <groupId>com.classhacker</groupId> <artifactId>tttapi</artifactId> <version>0.0.1-SNAPSHOT</version> <name>tttapi</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-mongodb</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-validation</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>

Here is my Player bean:

 package com.classhacker.tttapi.domain; import org.springframework.data.annotation.Id; import org.springframework.data.mongodb.core.mapping.Document; @Document public class Player { @Id int _id; String name; int gamesWon; public Player(int _id, String name, int gamesWon) { super(); this._id = _id; this.name = name; this.gamesWon = gamesWon; } public int get_id() { return _id; } public String getName() { return name; } public int getGamesWon() { return gamesWon; } @Override public String toString() { return String.format("Player[id=%d, name=%s, gamesWon=%d]", _id, name, gamesWon); } }

The error I'm getting after adding the validation dependency:

Error: Could not find or load main class com.classhacker.tttapi.DemoApplication
Caused by: java.lang.ClassNotFoundException: com.classhacker.tttapi.DemoApplication

But if I remove spring boot validation dependency my project doesn't give any error.

It will be really helpful if anybody can explain me what is going wrong here.

Answer 1

I understand that you have imported your project from spring initializr and your pom.xml looks same as this spring.io link:-

https://start.spring.io/#.type=maven-project&language=java&platformVersion=2.7.3&packaging=jar&jvmVersion=1.8&groupId=com.example&artifactId=demo&name=demo&description=Demo%20project%20for%20Spring%20Boot&packageName=com.example,demo&dependencies=data-mongodb,web,devtools,validation

Ideally you should not face ClassNotFoundException . Try:-

• reloading all maven dependencies
• clean install maven build
• restart your IDE
• delete local.m2 repository and rebuild

If that doesn't work, try adding following dependency and build project:-

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter</artifactId>
</dependency>

Answer 2

Have you tried to clean and build the application and then run it? If it did not work then have you tried to "run file" with your @SpringBootApplication annotation?