在SpringBoot应用程序中使用ManyToMany插入数据时出现NullPointerException [复制]

这个问题在这里已有答案：

• What is a NullPointerException, and how do I fix it? 12个答案

我已尽力而为但我不断收到NullPointerException错误 .

我有两个使用ManyToMany映射映射在一起的Spring引导实体 . 这些实体都很好，因为所有表都是创建的 .

但是，当我尝试插入数据时，我得到一个NullPointerException .

有人可以指点我做错了吗？

下面是我用来插入数据的代码：

import com.ait.aiadmin.model.Cluster;
import com.ait.aiadmin.model.Subscriber;
import com.ait.aiadmin.repository.ClusterRepository;
import com.ait.aiadmin.repository.SubscriberRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Component;

import javax.transaction.Transactional;

@SpringBootApplication
public class AiAdminApplication {
    public static void main(String[] args) {
        SpringApplication.run(AiAdminApplication.class, args);
        /*ApplicationContext ctx = SpringApplication.run(AiAdminApplication.class, args);

        String [] beanNames = ctx.getBeanDefinitionNames();
        Arrays.sort(beanNames);
        for (String name: beanNames){
            System.out.println(name);
        }*/
    }

    @Component
    public class DatabaseLoader implements CommandLineRunner {
        private final SubscriberRepository subscriberRepository;
        private final ClusterRepository clusterRepository;

        @Autowired
        public DatabaseLoader(SubscriberRepository subscriberRepository, ClusterRepository clusterRepository) {

            this.subscriberRepository = subscriberRepository;
            this.clusterRepository = clusterRepository;
        } 

        @Override
        @Transactional
        public void run (String...strings) throws Exception {

            Subscriber subscriber1 = new Subscriber("Olalekan Samuel", "Ogunleye", "olalekan@gmail.com");
            Cluster cluster1 = new Cluster("Aws-eu-west-1", "Ireland", "123.98.45", "Olalekan Samuel");
            subscriber1.clusters.add(cluster1);
            this.subscriberRepository.save(subscriber1);
            this.clusterRepository.save(cluster1);
    }
}

以下是我得到的错误

java.lang.IllegalStateException：无法在org.springframework.boot.SpringApplication.callRunner（SpringApplication.java:735）[spring-boot-1.5.8.RELEASE.jar：1.5.8.RELEASE]的org执行CommandLineRunner . springframework.boot.SpringApplication.callRunners（SpringApplication.java:716）[spring-boot-1.5.8.RELEASE.jar：1.5.8.RELEASE] org.springframework.boot.SpringApplication.afterRefresh（SpringApplication.java:703） [spring-boot-1.5.8.RELEASE.jar：1.5.8.RELEASE] org.springframework.boot.SpringApplication.run（SpringApplication.java:304）[spring-boot-1.5.8.RELEASE.jar：1.5 .8.RELEASE] org.springframework.boot.SpringApplication.run（SpringApplication.java:1118）[spring-boot-1.5.8.RELEASE.jar：1.5.8.RELEASE] org.springframework.boot.SpringApplication . 运行（SpringApplication.java:1107）[spring-boot-1.5.8.RELEASE.jar：1.5.8.RELEASE] at com.ait.aiadmin.AiAdminApplication.main（AiAdminApplication.java:19）[classes /：na] at sun.reflect.NativeMethodAccessorImpl.invoke0（Native Method）〜[na：1.8.0_ 152] at sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62）〜[na：1.8.0_152] at sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:43）〜[na：1.8.0_152] at java .lang.reflect.Method.invoke（Method.java:498）〜[na：1.8.0_152] at org.springframework.boot.devtools.restart.RestartLauncher.run（RestartLauncher.java:49）[spring-boot-devtools -1.5.8.RELEASE.jar：1.5.8.RELEASE]引起：java.lang.NullPointerException：null at com.ait.aiadmin.AiAdminApplication $ DatabaseLoader.run（AiAdminApplication.java:73）〜[classes /：na ] com.ait.aiadmin.AiAdminApplication $ DatabaseLoader $$ FastClassBySpringCGLIB $$ d20028d3.invoke（）〜[classes /：na] at org.springframework.cglib.proxy.MethodProxy.invoke（MethodProxy.java:204)~ [spring -core-4.3.12.RELEASE.jar：4.3.12.RELEASE] at org.springframework.aop.framework.CglibAopProxy $ CglibMethodInvocation.invokeJoinpoint（CglibAopProxy.java:738)~ [spring-aop-4.3.12.RELEASE . jar：4.3.12.RELEASE]在org.springframework.aop.framewor k.ReflectiveMethodInvocation.proceed（ReflectiveMethodInvocation.java:157）〜[spring-aop-4.3.12.RELEASE.jar：4.3.12.RELEASE] org.springframework.transaction.interceptor.TransactionInterceptor $ 1.proceedWithInvocation（TransactionInterceptor.java： 99）〜[spring-tx-4.3.12.RELEASE.jar：4.3.12.RELEASE] org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction（TransactionAspectSupport.java:282)~ [spring-tx-4.3.12 .RELEASE.jar：4.3.12.RELEASE] at org.springframework.transaction.interceptor.TransactionInterceptor.invoke（TransactionInterceptor.java:96）〜[spring-tx-4.3.12.RELEASE.jar：4.3.12.RELEASE] org.springframework.aop.framework.ReflectiveMethodInvocation.proceed（ReflectiveMethodInvocation.java:179）〜[spring-aop-4.3.12.RELEASE.jar：4.3.12.RELEASE] org.springframework.aop.framework.CglibAopProxy $ DynamicAdvisedInterceptor.intercept（CglibAopProxy.java:673）〜[spring-aop-4.3.12.RELEASE.jar：4.3.12.RELEASE] at com.ait.aiadmin.AiAdminApplication $ DatabaseLoader $$ E nhancerBySpringCGLIB $$ 6e72d57b.run（）〜[classes /：na] at org.springframework.boot.SpringApplication.callRunner（SpringApplication.java:732）[spring-boot-1.5.8.RELEASE.jar：1.5.8.RELEASE ] ...省略了11个常见帧