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Jsf java.lang.NullPointerException selectOneMenu转换器

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Jsf java.lang.NullPointerException selectOneMenu转换器,jsf,Jsf,我有一门专业课 public class Specialization implements Serializable { private static final long serialVersionUID = 1L; @Id @Basic(optional = false) @NotNull @Column(name = "id") private Integer id; @Basic(optional = false) @No

我有一门专业课

public class Specialization implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @Column(name = "id")
    private Integer id;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 45)
    @Column(name = "name")
    private String name;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "specialization")
    private Collection<Doctor> doctorCollection;
但是当我进入下一页时，我的selectOneMenu出现了一个错误

java.lang.NullPointerException
    at pl.ePrzychodnia.dao.GenericDao.find(GenericDao.java:40)
    at pl.ePrzychodnia.converter.SpecializationConverter.getAsObject(SpecializationConverter.java:24)
    at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getConvertedValue(HtmlBasicInputRenderer.java:171)
    at com.sun.faces.renderkit.html_basic.MenuRenderer.convertSelectOneValue(MenuRenderer.java:202)
    at com.sun.faces.renderkit.html_basic.MenuRenderer.getConvertedValue(MenuRenderer.java:319)
    at javax.faces.component.UIInput.getConvertedValue(UIInput.java:1030)
    at javax.faces.component.UIInput.validate(UIInput.java:960)
    at javax.faces.component.UIInput.executeValidate(UIInput.java:1233)
    at javax.faces.component.UIInput.processValidators(UIInput.java:698)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIForm.processValidators(UIForm.java:253)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1172)
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:722)
我现在不知道为什么。有人能帮忙吗？

private static SpecializationDao sdao=new SpecializationDao（）

假设此DAO是您的
GenericDAO
的子类，您能告诉我何时注入
EntityManager
吗？让容器创建您的DAO！您的
EntityManager
没有被注入，因此您得到了
NPE

我将创建一个无状态会话bean（如果您使用EJB），然后将其注入转换器


@Stateless
public class SpecializationService extends GenericCRUDService {...}

public class SpecializationConverter implements Converter{

    @Inject
    private SpecializationService specializationService;
...



我还认为术语和模式DAO有点过时。例如，请阅读。
在
pl.ePrzychodnia.dao.GenericDao.find（GenericDao.java:40）
上发布这行代码。使用
Integer.parseInt（）
而不是分配
新整数
，您不一定要创建新实例。我在Post中添加了find方法。Integer.parseInt（）没有帮助。请确保您的EntityManager被正确注入。我知道它在这种情况下没有帮助，但最好是这样使用。2013年5月，通过引用2009年1月的一篇文章声称某些东西过时了，至少很有趣：）@skuntsel:我很高兴随时能让您微笑。：）但你不认为，如果2009年某些人认为它过时了，那么几年后就更是如此了吗？@BalázsMáriaNémeth，亚当在那里得出了一些牵强的结论。“对象有状态和行为，道没有”。一把刀怎么没有状态或行为？这件事没有什么变化吗？我想这是一个观点问题。@kolossus:我找不到你引用的句子。他说：“DAO是无状态的，只包含数据操作。”。但是，尽管如此，我认为讨论的最佳场所应该是他的博客，而不是这里：）

public class SpecializationConverter implements Converter{

    private static SpecializationDao sdao = new SpecializationDao();

    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        return sdao.find(new Integer(value));
    }

    @Override
    public String getAsString(FacesContext context, UIComponent component, Object value) {
        //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        return ((Specialization) value).getId().toString();
    }

}



java.lang.NullPointerException
    at pl.ePrzychodnia.dao.GenericDao.find(GenericDao.java:40)
    at pl.ePrzychodnia.converter.SpecializationConverter.getAsObject(SpecializationConverter.java:24)
    at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getConvertedValue(HtmlBasicInputRenderer.java:171)
    at com.sun.faces.renderkit.html_basic.MenuRenderer.convertSelectOneValue(MenuRenderer.java:202)
    at com.sun.faces.renderkit.html_basic.MenuRenderer.getConvertedValue(MenuRenderer.java:319)
    at javax.faces.component.UIInput.getConvertedValue(UIInput.java:1030)
    at javax.faces.component.UIInput.validate(UIInput.java:960)
    at javax.faces.component.UIInput.executeValidate(UIInput.java:1233)
    at javax.faces.component.UIInput.processValidators(UIInput.java:698)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIForm.processValidators(UIForm.java:253)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1172)
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:722)



@Stateless
public class SpecializationService extends GenericCRUDService {...}

public class SpecializationConverter implements Converter{

    @Inject
    private SpecializationService specializationService;
...