我用下面的代码测试了这个。问题似乎是您没有保存appuser示例。
appuser类

package no.mycompany.myapp.misc;

import lombok.Data;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Data
@Entity
public class AppUser {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToMany
    @JoinTable(
            name = "app_user_job",
            joinColumns = @JoinColumn(name = "internal_user_id"),
            inverseJoinColumns = @JoinColumn(name = "job_id", referencedColumnName = "id")
    )
    private Set<Job> jobs = new HashSet<>();

    Job addJob(Job job) {
        job.getAppUsers().add(this);
        this.jobs.add(job);
        return job;
    }

    void removeJob(Job job) {
        this.jobs.remove(job);
    }
}

appuser回购

package no.mycompany.myapp.misc;

import org.springframework.data.jpa.repository.JpaRepository;

public interface AppUserRepo extends JpaRepository<AppUser, Long> {}

工作等级

package no.mycompany.myapp.misc;

import lombok.Getter;
import lombok.Setter;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Getter
@Setter
@Entity
public class Job {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToMany(mappedBy = "jobs")
    private Set<AppUser> appUsers = new HashSet<>();
}

工作回购

package no.mycompany.myapp.misc;

import org.springframework.data.jpa.repository.JpaRepository;

public interface JobRepo extends JpaRepository<Job, Long> {}

测验

package no.mycompany.myapp.misc;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
import org.springframework.test.context.ActiveProfiles;

import static org.assertj.core.api.AssertionsForClassTypes.assertThat;

@DataJpaTest
public class AppUserRepoTest {

    @Autowired
    TestEntityManager testEntityManager;

    @Autowired
    AppUserRepo appUserRepo;

    @Autowired
    JobRepo jobRepo;

    @Test
    public void test() {

        var appUser = testEntityManager.persist(createValidAppUser());

        var job1 = testEntityManager.persist(createValidJob());
        var job2 = testEntityManager.persist(createValidJob());
        var job3 = testEntityManager.persist(createValidJob());

        var appUserInDb = appUserRepo.getOne(appUser.getId());

        // add 3 jobs to AppUser instance
        var job1InDb = appUserInDb.addJob(jobRepo.getOne(job1.getId()));
        var job2InDb = appUserInDb.addJob(jobRepo.getOne(job2.getId()));
        appUserInDb.addJob(jobRepo.getOne(job3.getId()));
        appUserRepo.save(appUserInDb);

        // verify that AppUser instance has 3 jobs
        appUser = testEntityManager.find(AppUser.class, appUser.getId());
        assertThat(appUser.getJobs().size()).isEqualTo(3);

        // verify that job #1 instance has 1 AppUser instance
        job1 = testEntityManager.find(Job.class, job1.getId());
        assertThat(job1.getAppUsers().size()).isEqualTo(1);

        // remove 2 jobs from AppUser instance
        appUserInDb = appUserRepo.getOne(appUser.getId());
        appUserInDb.removeJob(job1InDb);
        jobRepo.delete(job1InDb);

        appUserInDb.removeJob(job2InDb);
        jobRepo.delete(job2InDb);

        appUserRepo.save(appUserInDb);

        // verify that AppUser instance has 1 job
        appUser = testEntityManager.find(AppUser.class, appUser.getId());
        assertThat(appUser.getJobs().size()).isEqualTo(1);

        // verify that job instances are deleted in db
        assertThat(testEntityManager.find(Job.class, job1.getId())).isNull();
        assertThat(testEntityManager.find(Job.class, job2.getId())).isNull();
    }

    private static AppUser createValidAppUser() {
        return new AppUser();
    }

    private static Job createValidJob() {
        return new Job();
    }
}