java.lang.NullPointerException bei dem Versuch, Einheit, die von id

Question

Ich bin mit Feder zu holen und überwintern.

Meine Einheit:

package com.igorgorbunov3333.core.entities.domain; 

import com.igorgorbunov3333.core.entities.enums.Proceeding; 

import javax.persistence.*; 
import java.util.Date; 

/** 
* Created by Игорь on 03.04.2016. 
*/ 

@Entity 
@Table(name = "cases") 
@NamedQueries({ 
    @NamedQuery(name = "getAllCases", query = "SELECT c FROM Case c JOIN FETCH c.client JOIN FETCH c.firstInstance " + 
      "JOIN FETCH c.secondInstance JOIN FETCH c.thirdInstance JOIN FETCH c.category") 
}) 
public class Case { 
    @Id 
    @GeneratedValue(strategy = GenerationType.IDENTITY) 
    private long id; 

    @Column(name = "case_number") 
    private String caseNumber; 

    @ManyToOne 
    @JoinColumn(name = "client_id") 
    private Client client; 

    @OneToOne 
    @JoinColumn(name = "first_instance_id") 
    private FirstInstance firstInstance; 

    @OneToOne 
    @JoinColumn(name = "second_instance_id") 
    private SecondInstance secondInstance; 

    @OneToOne 
    @JoinColumn(name = "third_instance_id") 
    private ThirdInstance thirdInstance; 

    @Enumerated(EnumType.ORDINAL) 
    private Proceeding proceeding; 

    @Temporal(TemporalType.DATE) 
    @Column(name = "closing_date") 
    private Date closingDate; 

    @ManyToOne 
    @JoinColumn(name = "category_id") 
    private Category category; 

    private float price; 

    public long getId() { 
     return id; 
    } 

    public String getCaseNumber() { 
     return caseNumber; 
    } 

    public Client getClient() { 
     return client; 
    } 

    public FirstInstance getFirstInstance() { 
     return firstInstance; 
    } 

    public SecondInstance getSecondInstance() { 
     return secondInstance; 
    } 

    public ThirdInstance getThirdInstance() { 
     return thirdInstance; 
    } 

    public Proceeding getProceeding() { 
     return proceeding; 
    } 

    public Date getClosingDate() { 
     return closingDate; 
    } 

    public Category getCategory() { 
     return category; 
    } 

    public float getPrice() { 
     return price; 
    } 

    public void setId(long id) { 
     this.id = id; 
    } 

    public void setCaseNumber(String caseNumber) { 
     this.caseNumber = caseNumber; 
    } 

    public void setClient(Client client) { 
     this.client = client; 
    } 

    public void setFirstInstance(FirstInstance firstInstance) { 
     this.firstInstance = firstInstance; 
    } 

    public void setSecondInstance(SecondInstance secondInstance) { 
     this.secondInstance = secondInstance; 
    } 

    public void setThirdInstance(ThirdInstance thirdInstance) { 
     this.thirdInstance = thirdInstance; 
    } 

    public void setProceeding(Proceeding proceeding) { 
     this.proceeding = proceeding; 
    } 

    public void setClosingDate(Date closingDate) { 
     this.closingDate = closingDate; 
    } 

    public void setCategory(Category category) { 
     this.category = category; 
    } 

    public void setPrice(float price) { 
     this.price = price; 
    } 
} 

feder config.xml

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
     xmlns:tx="http://www.springframework.org/schema/tx" 
     xmlns:context="http://www.springframework.org/schema/context" 
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd 
     http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd 
     http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd" > 

    <!--@Transaction annotation support --> 
    <tx:annotation-driven transaction-manager="transactionManager"/> 

    <!--Scanning components in base-package (look for annotations) --> 
    <context:component-scan base-package="com.igorgorbunov3333"/> 

    <!--Activates various annotations to be detected in bean classes: Spring's @Required and @Autowired and so on--> 
    <context:annotation-config/> 

    <!--Обеспечивает работу с транзакциями в Spring --> 
    <bean id="transactionManager" 
      class="org.springframework.orm.jpa.JpaTransactionManager"> 
     <property name="entityManagerFactory" ref="emf"/> 
    </bean> 

    <!-- Datasource. Источник данных - база MySQL --> 
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> 
     <property name="driverClassName" value="com.mysql.jdbc.Driver" /> 
     <property name="url" value="jdbc:mysql://localhost:3306/database" /> 
     <property name="username" value="root" /> 
     <property name="password" value="root" /> 
    </bean> 

    <!-- EntityManagerFactory --> 
    <bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> 
     <property name="dataSource" ref="dataSource" /> 
     <!--Поставщик данных - hibernate--> 
     <property name="jpaVendorAdapter"> 
      <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" /> 
     </property> 
     <!--поиск сущностей в этом пакете--> 
     <property name="packagesToScan" 
        value="com.igorgorbunov3333"/> 
     <!--детали конфигурации поставщика постоянства (hibernate) --> 
     <property name="jpaProperties"> 
      <props> 
       <prop key="hibernate.dialect"> 
        org.hibernate.dialect.MySQL5Dialect 
       </prop> 
       <prop key="hibernate.max_fetch_depth">3</prop> 
       <prop key="hibernate.jdbc.fetch_size">50</prop> 
       <prop key="hibernate.jdbc.batch_size">10</prop> 
       <prop key="hibernate.show_sql">true</prop> 
      </props> 
     </property> 
    </bean> 


</beans> 

Hier erhalte ich Nullpointer:

public Case findById(long id) { 
    return entityManager.find(Case.class, id); 
} 

ich sicher Sie - id ist richtig, aber Entität kann nicht gefunden werden. Aber wenn ich alle Einheiten in Ordnung bekomme:

public List<Case> findAll() { 
    Query query = entityManager.createNamedQuery("getAllCases"); 
    return query.getResultList(); 
} 

Was ist der Grund?

Voll Spur von NPE:

09-Oct-2016 12:40:41.650 SEVERE [http-nio-8080-exec-7] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [ShowSingleCase] in context with path [] threw exception 
java.lang.NullPointerException 
    at com.igorgorbunov3333.core.entities.service.impl.CaseServiceImpl.findById(CaseServiceImpl.java:32) 
    at com.igorgorbunov3333.web.servlet.display.single.ShowSingleCase.doGet(ShowSingleCase.java:29) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) 
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) 
    at org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:522) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) 
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) 
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:1096) 
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) 
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:760) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1480) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 
    at java.lang.Thread.run(Thread.java:745) 

Mein CaseServiceImpl:

package com.igorgorbunov3333.core.entities.service.impl; 

import com.igorgorbunov3333.core.entities.domain.Case; 
import com.igorgorbunov3333.core.entities.enums.CaseStatus; 
import com.igorgorbunov3333.core.entities.service.api.CaseService; 
import com.igorgorbunov3333.core.util.DateUtil; 
import org.springframework.stereotype.Repository; 
import org.springframework.stereotype.Service; 

import javax.persistence.EntityManager; 
import javax.persistence.PersistenceContext; 
import javax.persistence.Query; 
import java.util.*; 

/** 
* Created by Игорь on 27.07.2016. 
*/ 

@Repository 
@Service("CaseService") 
public class CaseServiceImpl implements CaseService { 

    @PersistenceContext 
    private EntityManager entityManager; 

    public Case findById(long id) { 
     return entityManager.find(Case.class, id); 
    } 
} 

Servlets:

package com.igorgorbunov3333.web.servlet.display.single; 

import com.igorgorbunov3333.core.entities.domain.Case; 
import com.igorgorbunov3333.core.entities.service.api.CaseService; 
import com.igorgorbunov3333.core.entities.service.impl.CaseServiceImpl; 

import javax.servlet.ServletException; 
import javax.servlet.annotation.WebServlet; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import java.io.IOException; 

import static com.igorgorbunov3333.web.util.Views.SINGLE_CASE_PAGE; 

/** 
* Created by Игорь on 09.08.2016. 
*/ 
@WebServlet(name = "ShowSingleCase", urlPatterns = "/showSingleCase") 
public class ShowSingleCase extends HttpServlet { 
    private CaseService caseService = new CaseServiceImpl(); 

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     doGet(request, response); 
    } 

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     long id = Long.valueOf(request.getParameter("caseID")); 
     Case c = caseService.findById(id); 

     request.setAttribute("case", c); 

     request.getRequestDispatcher(SINGLE_CASE_PAGE).forward(request, response); 
    } 
} 

Answer 1

Ihr Problem ist in dieser Zeile:

private CaseService caseService = new CaseServiceImpl(); 

, das nicht ist, wie Dependency Injection funktioniert. Sie instanziieren Ihr CaseService-Objekt manuell. In diesem Fall werden durch das Framework keine Abhängigkeiten eingefügt, sodass das Feld private EntityManager entityManager;null ist. Stattdessen müssen Sie Ihr caseService Feld mit @Autowired Annotation kommentieren. Das wird Frühling sagt die Bohne von Kontext zu injizieren:

@Autowired 
private CaseService caseService; 

Answer 2

Die einzige Sache, die Null sein kann (ist nicht primitiv) auf der Linie Sie haben angegeben, dass das Problem EntityManager verursachen würde, also suchen Sie nach dem Grund dafür, den ich nicht sehe der Code, den du gepostet hast.

Answer 3

Wie Sie CaseServiceImpl Klassenobjekt selbst in Ihrer Servlet-Klasse erstellen, wird EntityManager Objekt autowire nicht automatisch durch die Feder und das ist der Grund, warum Sie bekommen Nullpointer. Entweder sollten Sie das Dienstklassenobjekt in die servlet-Klasse einfügen, damit spring die Entitymanager-Abhängigkeit selbst auflöst und Ihnen das vollständig konfigurierte Dienstobjekt bereitstellt, oder Sie sollten das Entitätsmanagerobjekt beim Erstellen des Objekts im Servlet in Ihre Dienstklasse setzen.