javax.el.PropertyNotFoundException: Target Unreachable, 'null' trở null trên tài liệu tham khảo chính nước ngoài

Question

Tôi biết có cái gì đó sai với managedBean nhưng tôi không thể tìm ra những gì nó là

Khi tôi cố gắng departmentManagedBean.department.faculty.facultyName từ trang JSF nó mang lại cho một con trỏ null như thế này:

javax.el.PropertyNotFoundException: /administrator/department/DepartmentRegistration.xhtml @ giá trị 30.260 = "# {departmentRequestBean.department.faculty.facultyName}": Target Unreachable, 'null' đã trả về null

javax.el.PropertyNotFoundException: /administrator/department/DepartmentRegistration.xhtml @30,260 value="#{departmentRequestBean.department.faculty.facultyName}": Target Unreachable, 'null' returned null 
at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:100) 
at org.richfaces.component.util.InputUtils.findConverter(InputUtils.java:123) 
at org.richfaces.component.util.InputUtils$1.getConverterByProperty(InputUtils.java:56) 
at org.richfaces.component.util.InputUtils.getConvertedValue(InputUtils.java:148) 
at org.richfaces.component.util.InputUtils.getConvertedValue(InputUtils.java:137) 
at org.richfaces.renderkit.InputRendererBase.getConvertedValue(InputRendererBase.java:50) 
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.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:1542) 
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:849) 
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:746) 
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1045) 
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:228) 
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:636) 

---

public class Department implements Serializable { 
    private static final long serialVersionUID = 1L; 
    @Id 
    @Basic(optional = false) 
    @NotNull 
    @Column(name = "DepartmentID") 
    private Integer departmentID; 
    @Basic(optional = false) 
    @NotNull 
    @Size(min = 1, max = 255) 
    @Column(name = "DepartmentName") 
    private String departmentName; 
    @JoinColumn(name = "FacultyName", referencedColumnName = "FacultyName") 
    @ManyToOne(optional = false, fetch = FetchType.EAGER) 
    public Faculty faculty; 

    public Faculty getFaculty() { 
     return faculty; 
    } 

    public void setFaculty(Faculty faculty) { 
     this.faculty = faculty; 
    } 
    public Department() { 

    } 

    public Department(Integer departmentID) { 
     this.departmentID = departmentID; 
    } 

    public Department(Integer departmentID, String departmentName) { 
     this.departmentID = departmentID; 
     this.departmentName = departmentName; 
    } 

    public Integer getDepartmentID() { 
     return departmentID; 
    } 

    public void setDepartmentID(Integer departmentID) { 
     this.departmentID = departmentID; 
    } 

    public String getDepartmentName() { 
     return departmentName; 
    } 

    public void setDepartmentName(String departmentName) { 
     this.departmentName = departmentName; 
    } 
} 

---

public class DepartmentSessionBean { 
    @PersistenceContext(unitName = "ApplicationPU") 
    private EntityManager em; 

    public void persist(Department department) {  
     em.persist(department); 
    } 
} 

---

public class Faculty implements Serializable { 
    private static final long serialVersionUID = 1L; 
    @Id 
    @Basic(optional = false) 
    @NotNull 
    @Column(name = "FacultyID") 
    private Integer facultyID; 
    @Basic(optional = false) 
    @NotNull 
    @Size(min = 1, max = 255) 
    @Column(name = "FacultyName") 
    private String facultyName; 
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "faculty", fetch = FetchType.EAGER) 
    private List<Department> departmentList; 

    public Faculty() { 
    } 

    public Faculty(Integer facultyID) { 
     this.facultyID = facultyID; 
    } 

    public Faculty(Integer facultyID, String facultyName) { 
     this.facultyID = facultyID; 
     this.facultyName = facultyName; 
    } 

    public Integer getFacultyID() { 
     return facultyID; 
    } 

    public void setFacultyID(Integer facultyID) { 
     this.facultyID = facultyID; 
    } 

    public String getFacultyName() { 
     return facultyName; 
    } 

    public void setFacultyName(String facultyName) { 
     this.facultyName = facultyName; 
    } 

    public List<Department> getDepartmentList() { 
     return departmentList; 
    } 

    public void setDepartmentList(List<Department> departmentList) { 
     this.departmentList = departmentList; 
    } 
} 

Đây là ManagedBean rằng tôi cần một giải pháp với đề nghị:

@ViewScoped public class DepartmentRequestBean { 
@EJB 
private DepartmentSessionBean departmentSessionBean; 
private Department department = new Department(); 
public Department getDepartment() { 
    return department; 
} 

public void setDepartment(Department department) { 
    this.department = department; 
} 


public void save(){ 


     departmentSessionBean.persist(department); 

} 

public DepartmentRequestBean() { 
    this.faculty = new Faculty(); 
}} 

Answer 1

value = "# {departmentRequestBean.department.faculty.facultyName}": Target Unreachable, 'null' trở rỗng

này về cơ bản có nghĩa là một trong những giá trị sau

• #{departmentRequestBean.department}
• #{departmentRequestBean.department.faculty}

trả lại null trong khi xử lý gửi biểu mẫu. Vì bạn đã tự mình tạo chính mình Department, thì điều đó chỉ có thể có nghĩa là Faculty vẫn là null.

Để khắc phục nó đúng cách, thay thế trong DepartmentRequestBean

private Department department = new Department(); 

bởi

private Department department; 

@PostConstruct 
public void init() { 
    department = new Department(); 
    department.setFaculty(new Faculty()); 
} 

Answer 2

khởi tạo lớp bộ phận của bạn trong việc sao lưu đậu như cách này

public Department getDepartment() { 
if(department == null){ 
department = (Department)super.getInstance(Department.class); 
} 
return department; 
} 

này sẽ tạo ra một bộ phận mới đối tượng nếu đối tượng trở thành null