代码之家 › 专栏 › 技术社区 › Adder

自动关联拒绝自动关联[重复]的类的成员

autowired spring java

Adder · 技术社区 · 6 年前

如果我添加一个通过“new”实例化类“ReportQueryDetailsDAO”的hack,那么类“ReportQueryDetailsDAO”将不会像实体管理器那样实例化其自动连接字段,这将导致空异常。

@Component
public class ReportEverythingForm
{
    @Autowired
    ReportQueryDetailsDAO reportQueryDetailsDAO;

    public ReportEverythingForm() {
        //reportQueryDetailsDAO = new ReportQueryDetailsDAO();//HACK FIXME Autowired is null
    }

类“ReportEverythingForm”由控制器类“MonitorReportController”实例化和调用。自动布线似乎在这里工作。

@Controller
public class MonitorReportController
{
    @Autowired
    private ReportEverythingForm reportEverythingForm;

@Transactional
@RequestMapping(value = "/reportEverything", method = RequestMethod.POST)
public ModelAndView getReportEverything(HttpServletRequest request,
        HttpServletResponse response, HttpSession session, Locale locale)
{
    //code which calls methods of "reportEverythingForm"

我怎样才能让自动布线工作?它适用于代码的其他部分,所以我想这不是一个一般性的问题。

一些相关的进口产品包括:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

按要求提供“ReportQueryDetailsDao”的内容:

@Repository
public class ReportQueryDetailsDAO
{

    private static final Logger logger = LoggerFactory
            .getLogger(ReportQueryDetailsDAO.class);

    @PersistenceContext(unitName = "RATOR_MONITORING_CONFIGURATION", type = PersistenceContextType.TRANSACTION)
    private EntityManager entityManager;


    /**
     * @param sql
     * @return
     */
    @Transactional
    public ReportQueryDetail findbySQLId(Long sqlId)
    {
        try
        {
            //Query query = entityManager.createNativeQuery("select * from REPORT_QUERY_DETAILS where REPORT_QUERY_DETAILS_ID = :sqlId");
            logger.info("select rqd from ReportQueryDetail rqd where rqd.reportQueryDetailsId = " + sqlId);
            Query query = entityManager.createQuery("select rqd from ReportQueryDetail rqd where rqd.reportQueryDetailsId = :sqlId");
            query.setParameter("sqlId", sqlId);

            List<ReportQueryDetail> results = query.getResultList();
            ReportQueryDetail reportQueryDetail = (ReportQueryDetail) results.get(0);

            return reportQueryDetail;
        } catch (Exception e)
        {
            logger.debug("Exception:" + e.getMessage(), e);
            return null;
        }
    }

摘自pom.xml:

<java-version>1.6</java-version>
<org.springframework-version>3.1.1.RELEASE</org.springframework-version>
<org.aspectj-version>1.6.10</org.aspectj-version>
<org.slf4j-version>1.6.6</org.slf4j-version>

2 回复 | 直到 6 年前

aBnormaLz 6 年前

public ReportEverythingForm() {
    //reportQueryDetailsDAO = new ReportQueryDetailsDAO();//HACK FIXME Autowired is null
}

到

@Autowired
public ReportEverythingForm(ReportQueryDetailsDAO reportQueryDetailsDAO) {
    this.reportQueryDetailsDAO = reportQueryDetailsDAO;
}

(我认为您需要该构造函数在ReportEverythingForm中设置一些初始状态)

同时拆下 @Autowired 来自 ReportQueryDetailsDAO reportQueryDetailsDAO 领域

另一个解决方案是使用 @PostConstruct 注释,并删除构造函数。有了它,您就可以在应用程序中设置初始状态 @PostConstruct

Oleksandr Papchenko 6 年前

ReportEverythingForm 通过- new . 问题是你不能得到 null @Autowired 字段-若并没有要自动连接的bean,则在上下文初始化时会出现异常。签入你的代码 报告一切形式 ReportQueryDetailsDAO 是由spring实例化的。您可以定义 xml @ComponentScan 或使用 @Bean 注释。