java - Autowiring 拒绝 Autowiring 的类的成员

Question

这个问题已经有答案了:

@Autowire failing with @Repository (3 个回答)

已关闭 4 年前。

我有一个类“ReportEverythingForm”，它拒绝通过自动连接注释实例化类“ReportQueryDetailsDAO”。如果我添加一个通过“new”实例化类“ReportQueryDetailsDAO”的黑客，那么类“reportQueryDetailsDAO”将反过来实例化其 Autowiring 字段，如实体管理器，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 Controller 类“MonitorReportController”实例化并调用。 Autowiring 似乎在这里起作用。

@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"

如何让 Autowiring 工作？它适用于代码的其他部分，因此我认为这不是一个普遍问题。

一些相关的导入如下:

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;

请求的“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>

Answer 1

尝试改变

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

至

@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)

同时从 ReportQueryDetailsDAO reportQueryDetailsDAO 字段中删除 @Autowired 注释

编辑

另一种解决方案是使用 @PostConstruct注释，并删除您的构造函数。这样，您就可以在 @PostConstruct 带注释的方法中设置初始状态