employee
,它有EPMID,EMPNAME,EMPAGE,SALARY,ADDRESS,department_id(引用于department_id in部门表)和department
,其中有department_id和名称......这里是Department.java
public class Department {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "department_id")
private int depId;
@Column(name = "name")
private String depName;
@OneToMany(mappedBy="department",cascade = { CascadeType.ALL }, orphanRemoval=true)
private List<Employee> employees;}
Employee.java
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "EMPID")
private int empId;
@Column(name = "EMPNAME")
private String empName;
@Column(name = "ADDRESS")
private String empAddress;
@Column(name = "SALARY")
private String salary;
@Column(name = "EMPAGE")
private int empAge;
@ManyToOne(cascade={CascadeType.ALL})
@JoinColumn(name="department_id")
private Department department;}
以及在服务中添加员工的功能
public void addEmployee(String[] list, Employee employee) {
employee.getDepartment().setDepId(Integer.parseInt(list[3]));
employee.setEmpName(list[2]);
employee.setEmpAge(Integer.parseInt(list[4]));
employee.setEmpAddress(list[6]);
employee.setSalary(list[1]);
this.employeeDao.addOrEditEmployee(employee);
没有那行employee.getDepartment().setDepId(Integer.parseInt(list[3]));
,一切都很顺利,但我想在主要的一行上添加外键来引用..
这是例外
SEVERE: Servlet.service() for servlet [sdnext] in context with path [/Spring3HibernateApp1] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
at com.dineshonjava.service.EmployeeServiceImpl.addEmployee(EmployeeServiceImpl.java:27)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:266)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
at com.sun.proxy.$Proxy30.addEmployee(Unknown Source)
at com.dineshonjava.controller.EmployeeController.doPostSave(EmployeeController.java:65)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:781)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:721)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
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答案 0 :(得分:0)
不使用类似
之类的内容维护外键ambhas
取而代之的是
employee.getDepartment().setDepId(Integer.parseInt(list[3]));
Hibernate现在通过在employee表中插入department_id来创建部门和员工之间的数据库关系。
P.S。我假设一些类和方法名称,因为我没有你的所有代码。
关于NPE
我相信您收到了空指针异常,因为员工当时没有部门。
Department dept = departmentDao.findById(Integer.parseInt(list[3]));
employee.setDepartment(dept);