spring - 使用 Hibernate 和 Spring MVC 的 JSP

Question

美好的一天!当我将 war 部署到 tomcat 时，它会给我这个异常:可能有人可以使用@Transactional 注释帮助解决该问题，但在 2 周内无法解决该问题:(

    n22-Feb-2018 14:52:54.125 SEVERE [http-nio-8080-exec-11] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [dispatcher] in context with path [/page] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
 java.lang.NullPointerException
    at com.mycompany.app.controller.TypeController.listAll(TypeController.java:24)
    at sun.reflect.GeneratedMethodAccessor55.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:871)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:777)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:870)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:855)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

web.xml

    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/mvc-dispatcher-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

mvc-dispatcher-servlet.xml

    <context:component-scan base-package="com.mycompany.app" />
    <context:component-scan base-package="com.mycompany.app.controller" />
    <context:component-scan base-package="com.mycompany.app.service" />

    <mvc:annotation-driven />

    <bean
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix">
            <value>/WEB-INF/views/</value>
        </property>
        <property name="suffix">
            <value>.jsp</value>
        </property>
    </bean>

TypeController.java

@Controller
public class TypeController {

    private TypeServiceImpl typeService;

    @RequestMapping(value = "/main")
    public String listAll(Map<String, Object> map) {
        map.put("type", new Type());
        map.put("typeList", typeService.listAll());
        return "index";
    }

    @RequestMapping("/")
    public String home() {
        return "redirect:/main";
    }

    @RequestMapping(value = "/add", method = RequestMethod.POST)
    public String add(@ModelAttribute("type") Type type, BindingResult bindingResult) {
        typeService.add(type);
        return "redirect:/main";
    }

    @RequestMapping(value = "/delete/{id}")
    public String deleteType(@PathVariable("id") Integer id) {
        typeService.delete(id);
        return "redirect:/main";
    }
}

TypeServiceImpl.java不要使用 DAO

@Service
public class TypeServiceImpl implements TypeService {

    private SessionFactory sessionFactory;

    @Override
    @Transactional
    public void add(Type type) {
        sessionFactory.getCurrentSession().save(type);
    }

    @Override
    @Transactional
    @SuppressWarnings("unchecked")
    public List<Type> listAll() {
        return sessionFactory.getCurrentSession().createQuery("from Type").list();
    }

    @Override
    @Transactional
    public void delete(Integer id) {
        Type type = sessionFactory.getCurrentSession().load(Type.class, id);
        if (type != null) {
            sessionFactory.getCurrentSession().delete(type);
        }
    }
}

Type.java

@Entity
@Table(name = "type")
public class Type {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id_type")
    private Integer id_type;

    @Column(name = "type_name")
    private String type_name;

    // Communication with Event
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "type")
    private List<Event> event;

    public Type() {
    }

    public Type(Integer id_type, String type_name) {
        this.id_type = id_type;
        this.type_name = type_name;
    }
//Default getters and setters
}

index.jsp

<%@taglib uri="http://www.springframework.org/tags" prefix="spring"%>
<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ page contentType="text/html;charset=UTF-8" language="java"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Hello World Page</title>
</head>
<body>
    <form:form method="post" action="add" modelAttribute="type">
        <table>
            <tr>
                <td><form:label path=id_type>Type's ID</form:label></td>
                <td><form:input path="id_type" /></td>
            </tr>
            <tr>
                <td><form:label path=type_name>Type name</form:label></td>
                <td><form:input path="type_name" /></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="Submit" /></td>
            </tr>
        </table>
    </form:form>
    <h3>Types</h3>
    <c:if test="${!empty typeList}">
        <table class="data">
            <tr>
                <th>Type ID</th>
                <th>Type Name</th>
                <th>&nbsp;</th>
            </tr>
            <c:forEach items="${typeList}" var="type">
                <tr>
                    <td>${type.id_type}}</td>
                    <td>${type.type_name}</td>
                    <td><a href="delete/${type.id}">Delete</a></td>
                </tr>
            </c:forEach>
        </table>
    </c:if>
</body>

感谢收看!!!

Answer 1

我认为您的服务可能缺少一个 @Autowired 注释。

@Autowired
private TypeService typeService;

目前我看不到你在哪里实例化服务类。