我正在尝试使用Spring Boot Web应用程序实现Hibernate，但是在页面中始终会出现相同的错误：“ 发生意外错误（类型=内部服务器错误，状态= 500）。 “
这是我的Controller类：
public class MainController {
@Autowired
static SessionFactory factory;
@RequestMapping(value = "/")
String mainPage() {
return "mainPage";
}
@RequestMapping(value = "/addStudent")
String addStudent() {
return "addStudent";
}
@RequestMapping(value = "/allStudents")
String getStudents(Model model) {
ArrayList<Student> allStudents = getAllStudents();
model.addAttribute("allStudents", allStudents);
for(Student s : allStudents) {
System.out.println(s);
}
System.out.println("done");
return "StudentList";
}
@Autowired
static ArrayList<Student> getAllStudents(){
Session session = factory.openSession();
Transaction tx = null;
ArrayList<Student> allStudents = new ArrayList<Student>();
try {
allStudents = (ArrayList<Student>) session.createSQLQuery("SELECT * FROM students").list();
}catch(HibernateException e){
e.printStackTrace();
}finally {
return allStudents;
}
}
}
和我的学生班：
public class Student {
private String name;
private String surname;
private String id;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSurname() {
return surname;
}
public void setSurname(String surname) {
this.surname = surname;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
@Override
public String toString() {
return "Student [name=" + name + ", surname=" + surname + ", id=" + id + "]";
}
}
我总是收到此错误：
java.lang.NullPointerException: null
at com.example.demo.MainController.getAllStudents(MainController.java:45) ~[classes/:na]
at com.example.demo.MainController.getStudents(MainController.java:34) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_161]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_161]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_161]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_161]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1039) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.22.jar:9.0.22]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:853) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587) [tomcat-embed-core-9.0.22.jar:9.0.22]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.22.jar:9.0.22]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_161]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_161]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.22.jar:9.0.22]
at java.lang.Thread.run(Unknown Source) [na:1.8.0_161]
答案 0 :(得分：0)
从Spring Boot文档
https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#boot-features-sql
Spring框架为使用SQL提供了广泛的支持 数据库
您的application.properties文件应该已经配置了数据库 例如，您正在使用MySQL
spring.datasource.url = jdbc：mysql：// localhost / test
spring.datasource.username = dbuser
spring.datasource.password = dbpass
spring.datasource.driver-class-name = com.mysql.jdbc.Driver
然后注入
@PersistenceContext
private EntityManager entityManager;
public ArrayList<Student> getAllStudents(){
Session session = entityManager.unwrap(Session.class);
Transaction tx = null;
ArrayList<Student> allStudents = new ArrayList<Student>();
try {
allStudents = (ArrayList<Student>) session.createSQLQuery("SELECT * FROM students").list();
}catch(HibernateException e){
e.printStackTrace();
}finally {
return allStudents;
}
}