我在实体包中又添加了一个类 UserDetails.java。我已将所有必要的 Controller 和 DAO 类添加到相应的包中。但我对这两个实体使用单个服务类。现在,当我为早期实体类运行服务时,它工作正常。但是当我为稍后添加的实体类运行服务时,我给出了错误消息。
2020 年 5 月 20 日上午 12:20:26 org.apache.catalina.core.StandardWrapperValve 调用
严重:路径 [/TwoFactor] 上下文中 servlet [dispatcher] 的 Servlet.service() 引发异常 [请求处理失败;嵌套异常是 java.lang.NullPointerException] 其根本原因
java.lang.NullPointerException
位于 com.firstapp129.twofactor.service.DistScannerServiceImpl.getUsers(DistScannerServiceImpl.java:39)
我正在使用以下服务类代码:
package com.firstapp129.twofactor.service;
import java.util.List;
import javax.transaction.Transactional;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.firstapp129.twofactor.dao.DistScannerDAO;
import com.firstapp129.twofactor.dao.UserDetailsDAO;
import com.firstapp129.twofactor.entity.DistScanner;
import com.firstapp129.twofactor.entity.UserDetails;
@Service
public class DistScannerServiceImpl implements DistScannerService {
@Autowired
private DistScannerDAO distScannerDAO;
private UserDetailsDAO userDetailsDAO;
@Override
@Transactional
public List<DistScanner> getCustomers() {
// TODO Auto-generated method stub
return distScannerDAO.getCustomers();
}
@Override
@Transactional
public void saveDistScanner(DistScanner theDistScanner) {
distScannerDAO.saveDistScanner(theDistScanner);
// TODO Auto-generated method stub
}
@Override
@Transactional
public List<UserDetails> getUsers() {
// TODO Auto-generated method stub
return userDetailsDAO.getUsers();
}
@Override
@Transactional
public void saveUserDetails(UserDetails theUserDetails) {
userDetailsDAO.saveUserDetails(theUserDetails);
// TODO Auto-generated method stub
}
}
最佳答案
UserDetailsDAO 未 Autowiring ,因此会引发空指针异常。\ 在其上添加@Autowired注释。
关于java - [请求处理失败;嵌套异常是 java.lang.NullPointerException],我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/61927188/