我创建了一个带有数据的mongodb，但是在检索特定集合中的所有文档时，我的程序会给出一个空指针异常。
这是我的代码，userrepository.java

package com.weatherdata.api.dbconnector;

import com.weatherdata.api.users.User;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface UserRepository extends MongoRepository<User,String> {

}

用户种子.java

package com.weatherdata.api.users;

import com.weatherdata.api.dbconnector.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.List;

public class UserSeeder {
    @Autowired
    UserRepository userRepository;

    public List<User> getAllUsers(){
        List <User> allUsers = this.userRepository.findAll();
        return allUsers;
    }
}

用户.java

package com.weatherdata.api.users;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.DBRef;
import org.springframework.data.mongodb.core.mapping.Document;

import java.util.HashSet;
import java.util.Set;
@Document(collection = "users")
public class User {
    @Id
    private String id;
    private String username;
    private String email;
    private String mobile;
    private String method;
    private String password;

    @DBRef
    private Set<Role> roles = new HashSet<>();

    public User() {
    }

    public User(String username, String email,String mobile,String method, String password) {
        this.username = username;
        this.email = email;
        this.mobile = mobile;
        this.method = method;
        this.password = password;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getMobile() {
        return mobile;
    }

    public void setMobile(String mobile) {
        this.mobile = mobile;
    }

    public String getMethod() {
        return method;
    }

    public void setMethod(String method) {
        this.method = method;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Set<Role> getRoles() {
        return roles;
    }

    public void setRoles(Set<Role> roles) {
        this.roles = roles;
    }
}

错误是，
java.lang.nullpointerexception:无法调用“com.weatherdata.api.dbconnector.userrepository.findall（）”，因为com.weatherdata.api.users.userseeder.getallusers（userseeder）处的“this.userrepository”为null。java:13)~[classes/：na]位于com.weatherdata.api.filter.alert.isexceeded（警报。java:20)~[classes/：na]在com.weatherdata.api.controller.sensorcontroller.insert（传感器控制器。java:56)~[classes/：na]位于java.base/jdk.internal.reflect.nativemethodaccessorimpl.invoke0（本机方法）~[na:na]位于java.base/jdk.internal.reflect.nativemethodaccessorimpl.invoke（nativemethodaccessorimpl.invoke）。java:64)~[na:na]在java.base/jdk.internal.reflect.delegatingmethodaccessorimpl.invoke（delegatingmethodaccessorimpl。java:43)~[na:na]位于java.base/java.lang.reflect.method.invoke（method。java:564)~[na:na]位于org.springframework.web.method.support.invocablehandlermethod.doinvoke（invocablehandlermethod。java:197)~[spring-web-5.3.2。jar:5.3.2]在org.springframework.web.method.support.invocablehandlermethod.invokeforrequest（invocablehandlermethod。java:141)~[spring-web-5.3.2。jar:5.3.2]位于org.springframework.web.servlet.mvc.method.annotation.servletinvaccablehandlermethod.invokeandhandle（servletinvaccablehandlermethod）。java:106)~[spring-webmvc-5.3.2。jar:5.3.2]在org.springframework.web.servlet.mvc.method.annotation.requestmappinghandleradapter.invokehandlermethod（requestmappinghandleradapter。java:894)~[spring-webmvc-5.3.2。jar:5.3.2]位于org.springframework.web.servlet.mvc.method.annotation.requestmappinghandleradapter.handleinternal（requestmappinghandleradapter。java:808)~[spring-webmvc-5.3.2。jar:5.3.2] 位于org.springframework.web.servlet.mvc.method.abstracthandlermethodadapter.handle（abstracthandlermethodadapter）。java:87)~[spring-webmvc-5.3.2。jar:5.3.2]在org.springframework.web.servlet.dispatcherservlet.dodispatch（dispatcherservlet。java:1061)~[spring-webmvc-5.3.2。jar:5.3.2]在org.springframework.web.servlet.dispatcherservlet.doservice（dispatcherservlet。java:961)~[spring-webmvc-5.3.2。jar:5.3.2]位于org.springframework.web.servlet.frameworkservlet.processrequest（frameworkservlet。java:1006)~[spring-webmvc-5.3.2。jar:5.3.2]在org.springframework.web.servlet.frameworkservlet.dopost（frameworkservlet。java:909) ~[spring-webmvc-5.3.2。jar:5.3.2]
但restapi中的thig函数运行良好。
这是我在alert.java中使用usersedder的方法

package com.weatherdata.api.filter;

import com.weatherdata.api.users.User;
import com.weatherdata.api.users.UserSeeder;

import java.util.List;

public abstract class Alert implements AlertType {
    private double thresholdValue;
    private List<User> userList;

    @Override
    public double getThreshold() {
        return this.thresholdValue;
    }

    @Override
    public boolean isExceeded(double dataValue) {
        if(thresholdValue < dataValue){
            userList = new UserSeeder().getAllUsers();
            System.out.println(userList.stream().count());
            return true;
        }
        else{
            return false;
        }
    }

    public double getThresholdValue() {
        return thresholdValue;
    }

    public void setThresholdValue(double thresholdValue) {
        this.thresholdValue = thresholdValue;
    }
}