【发布时间】：2017-03-02 18:28:12
【问题描述】：
我正在尝试使用 JPa 连接到我的 mysql 数据库。
我已经生成了persistance.xml：
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0">
<persistence-unit name="NewPersistenceUnit">
<class>com.example.TorkoEntity</class>
<properties>
<property name="eclipselink.jdbc.url" value="jdbc:mysql://localhost:3306/tornoci"/>
<property name="eclipselink.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="eclipselink.jdbc.user" value="matej"/>
<property name="eclipselink.jdbc.password" value="123456"/>
<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/tornoci"/>
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
<property name="hibernate.connection.username"/>
<property name="hibernate.connection.password"/>
<property name="openjpa.ConnectionURL" value="jdbc:mysql://localhost:3306/tornoci"/>
<property name="openjpa.ConnectionDriverName" value="com.mysql.jdbc.Driver"/>
<property name="openjpa.ConnectionUserName"/>
<property name="openjpa.ConnectionPassword"/>
<property name="toplink.jdbc.url" value="jdbc:mysql://localhost:3306/tornoci"/>
<property name="toplink.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="toplink.jdbc.user"/>
<property name="toplink.jdbc.password"/>
</properties>
</persistence-unit>
</persistence>
并且还通过这样做 intelij 生成 POJO 类：
@Entity
@Table(name = "torko", schema = "tornoci", catalog = "")
public class TorkoEntity {
private int id;
private String meno;
TorkoEntity(){}
@Id
@Column(name = "Id", nullable = false)
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Basic
@Column(name = "meno", nullable = false, length = 250)
public String getMeno() {
return meno;
}
public void setMeno(String meno) {
this.meno = meno;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
TorkoEntity that = (TorkoEntity) o;
if (id != that.id) return false;
if (meno != null ? !meno.equals(that.meno) : that.meno != null) return false;
return true;
}
@Override
public int hashCode() {
int result = id;
result = 31 * result + (meno != null ? meno.hashCode() : 0);
return result;
}
}
我创建了实体管理器并希望从中获得结果：
public class manager {
@PersistenceContext
EntityManager em;
manager(){}
public List<TorkoEntity> getHim(){
Query q = em.createNativeQuery("SELECT * FROM TorkoEntity", TorkoEntity.class);
return q . getResultList();
}
}
和路线：
@RestController
public class test {
@RequestMapping( value = "hi" , method = RequestMethod.GET)
public String testt(){
manager m = new manager();
List<TorkoEntity> t = m.getHim();
return t.get(0).getMeno();
}
}
但是当我导航到 localhost:8080/hi
它抛出
Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Thu Mar 02 19:21:15 CET 2017
There was an unexpected error (type=Internal Server Error, status=500).
No message available
在浏览器中和
java.lang.NullPointerException: null
at com.example.manager.getHim(manager.java:17) ~[classes/:na]
at com.example.test.testt(test.java:19) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_65]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_65]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_65]
at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_65]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.6.RELEASE.jar:4.3.6.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:798) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1434) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.11.jar:8.5.11]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_65]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.11.jar:8.5.11]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_65]
在控制台中。 我不知道是什么导致了这个问题，非常感谢所有帮助
【问题讨论】：
标签： java mysql spring jpa intellij-idea