maven - INSERT 语句上的 Spring JDBC NullPointerException
问题描述
我正在处理一个 Maven、Spring-Boot、Vaadin 项目，当我尝试在我的大学表中创建一个新实体时，我无法解决 NullPointerException。
我创建了一个新视图并将所有内容绑定在一起，但如果我想使用示例值执行我的 saveUniversity() 函数，它总是会抛出 NullPointerException。希望这是所有相关的代码。
添加UniversityView.java
public class AddUniversityView extends VerticalLayout {
private TextField name = new TextField("Name");
private TextField city = new TextField("City");
private TextField country = new TextField("Country");
private Button save = new Button("Save", e -> saveUniversity()); // Line 23
Binder<University> binder = new Binder<>();
private University university = new University();
@Autowired
private UniversityService universityService;
public AddUniversityView() {
add(name, city, country, save);
/**
* Some values for example
*/
name.setValue("LMU");
city.setValue("Muenchen");
country.setValue("Deutschland");
binder.bind(name, University::getName, University::setName);
binder.bind(city, University::getCity, University::setCity);
binder.bind(country, University::getCountry, University::setCountry);
}
public void saveUniversity() {
binder.setBean(university);
System.out.println(binder.getBean().toString());
universityService.create(university); // Line 109
clearFields();
}
public void clearFields() {
binder.readBean(null);
}
大学服务
@Service
public class UniversityService {
@Autowired
private JdbcTemplate jdbcTemplate;
public void create(University university) {
jdbcTemplate.update("INSERT INTO university (name, city, country) VALUES (?, ?, ?)",
university.getName(), university.getCity(), university.getCountry());
}
}
应用程序属性
spring.datasource.url:jdbc:mysql://localhost/univers
spring.datasource.username=user
spring.datasource.password=password
spring.datasource.driverClassName=com.mysql.jdbc.Driver
大学数据库
+-------------------+
| Tables_in_univers |
+-------------------+
| student |
| university |
+-------------------+
大学专栏
+---------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(45) | NO | | NULL | |
| city | varchar(45) | NO | | NULL | |
| country | varchar(45) | NO | | NULL | |
+---------+-------------+------+-----+---------+----------------+
错误
java.lang.NullPointerException: null
at com.sandrofriedrich.ui.views.university.AddUniversityView.saveUniversity(AddUniversityView.java:109) ~[classes/:na]
at com.sandrofriedrich.ui.views.university.AddUniversityView.lambda$0(AddUniversityView.java:23) ~[classes/:na]
at com.vaadin.flow.component.ComponentEventBus.fireEvent(ComponentEventBus.java:133) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.component.ComponentEventBus.handleDomEvent(ComponentEventBus.java:327) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.component.ComponentEventBus.lambda$addDomTrigger$5ee67f2b$1(ComponentEventBus.java:191) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.internal.nodefeature.ElementListenerMap.lambda$fireEvent$2(ElementListenerMap.java:379) ~[flow-server-1.0.5.jar:na]
at java.util.ArrayList.forEach(ArrayList.java:1257) ~[na:1.8.0_181]
at com.vaadin.flow.internal.nodefeature.ElementListenerMap.fireEvent(ElementListenerMap.java:379) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.communication.rpc.EventRpcHandler.handleNode(EventRpcHandler.java:59) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.communication.rpc.AbstractRpcInvocationHandler.handle(AbstractRpcInvocationHandler.java:64) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.communication.ServerRpcHandler.handleInvocationData(ServerRpcHandler.java:377) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.communication.ServerRpcHandler.lambda$handleInvocations$0(ServerRpcHandler.java:367) ~[flow-server-1.0.5.jar:na]
at java.util.ArrayList.forEach(ArrayList.java:1257) ~[na:1.8.0_181]
at com.vaadin.flow.server.communication.ServerRpcHandler.handleInvocations(ServerRpcHandler.java:367) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:309) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:89) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:40) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.VaadinService.handleRequest(VaadinService.java:1486) ~[flow-server-1.0.5.jar:na]
at com.vaadin.flow.server.VaadinServlet.service(VaadinServlet.java:300) [flow-server-1.0.5.jar:na]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:728) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:470) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:356) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:316) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.servlet.mvc.ServletForwardingController.handleRequestInternal(ServletForwardingController.java:141) [spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:177) [spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:52) [spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) [spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) [spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) [spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:877) [spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) [spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) [spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) [spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) [spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498) [tomcat-embed-core-8.5.34.jar:8.5.34]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.34.jar:8.5.34]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_181]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_181]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.34.jar:8.5.34]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_181]
解决方案
你如何创建AddUniversityView?
如果它与@Route注释一起使用，或者它也在其他类中自动装配，它应该可以工作。
但是，如果您自己实例化它，如在 中new AddUniversityView()，自动装配将不起作用。
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