我是Springboot的新手，我试图跟进其中的教程，在此过程中，我接受用户输入并将其存储到db中，并在UI上返回msg，信息已成功存储。但是，但是我无法存储低于错误-
2019-03-16 17:11:38.829 ERROR 4276 --- [nio-8080-exec-5] o.a.c.c.C.[.[.[.[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [/locationweb] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException: null
at com.testname.location.controllers.LocationController.saveLocation(LocationController.java:24) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_171]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_171]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_171]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.16.jar:9.0.16]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.16.jar:9.0.16]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.16.jar:9.0.16]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_171]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_171]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.16.jar:9.0.16]
at java.lang.Thread.run(Unknown Source) [na:1.8.0_171]
LocationController
package com.testname.location.controllers;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import com.testname.location.entities.Location;
import com.testname.location.service.LocationService;
@Controller
public class LocationController {
@Autowired
LocationService service;
@RequestMapping("/showCreate")
public String showCreate() {
return "createLocation";
}
@RequestMapping("/saveLoc")
public String saveLocation(@ModelAttribute("location") Location location, ModelMap modelMap) {
Location locationSaved = service.saveLocation(location);
String msg = "Location Saved with id: " + locationSaved.getId();
modelMap.addAttribute("msg", msg);
return "createLocation";
}
}
位置
package com.testname.location.entities;
import javax.persistence.Entity;
import javax.persistence.Id;
@Entity
public class Location {
@Id
private int id;
private String code, name, type ;
@Override
public String toString() {
return "Location [id=" + id + ", code=" + code + ", name=" + name + ", type=" + type + "]";
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCode() {
return code;
}
public void setCode(String code) {
this.code = code;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
}
LocationRepository
package com.testname.location.repos;
import java.util.List;
import java.util.Optional;
import org.springframework.data.domain.Example;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import com.testname.location.entities.Location;
@Repository("Location")
public class LocationRepository implements JpaRepository<Location, Integer> {
@Override
public Page<Location> findAll(Pageable pageable) {
// TODO Auto-generated method stub
return null;
}
@Override
public <S extends Location> S save(S entity) {
// TODO Auto-generated method stub
return null;
}
@Override
public Optional<Location> findById(Integer id) {
// TODO Auto-generated method stub
return null;
}
@Override
public boolean existsById(Integer id) {
// TODO Auto-generated method stub
return false;
}
@Override
public long count() {
// TODO Auto-generated method stub
return 0;
}
@Override
public void deleteById(Integer id) {
// TODO Auto-generated method stub
}
@Override
public void delete(Location entity) {
// TODO Auto-generated method stub
}
@Override
public void deleteAll(Iterable<? extends Location> entities) {
// TODO Auto-generated method stub
}
@Override
public void deleteAll() {
// TODO Auto-generated method stub
}
@Override
public <S extends Location> Optional<S> findOne(Example<S> example) {
// TODO Auto-generated method stub
return null;
}
@Override
public <S extends Location> Page<S> findAll(Example<S> example, Pageable pageable) {
// TODO Auto-generated method stub
return null;
}
@Override
public <S extends Location> long count(Example<S> example) {
// TODO Auto-generated method stub
return 0;
}
@Override
public <S extends Location> boolean exists(Example<S> example) {
// TODO Auto-generated method stub
return false;
}
@Override
public List<Location> findAll() {
// TODO Auto-generated method stub
return null;
}
@Override
public List<Location> findAll(Sort sort) {
// TODO Auto-generated method stub
return null;
}
@Override
public List<Location> findAllById(Iterable<Integer> ids) {
// TODO Auto-generated method stub
return null;
}
@Override
public <S extends Location> List<S> saveAll(Iterable<S> entities) {
// TODO Auto-generated method stub
return null;
}
@Override
public void flush() {
// TODO Auto-generated method stub
}
@Override
public <S extends Location> S saveAndFlush(S entity) {
// TODO Auto-generated method stub
return null;
}
@Override
public void deleteInBatch(Iterable<Location> entities) {
// TODO Auto-generated method stub
}
@Override
public void deleteAllInBatch() {
// TODO Auto-generated method stub
}
@Override
public Location getOne(Integer id) {
// TODO Auto-generated method stub
return null;
}
@Override
public <S extends Location> List<S> findAll(Example<S> example) {
// TODO Auto-generated method stub
return null;
}
@Override
public <S extends Location> List<S> findAll(Example<S> example, Sort sort) {
// TODO Auto-generated method stub
return null;
}
}
LocationService
package com.testname.location.service;
import java.util.List;
import java.util.Optional;
import com.testname.location.entities.Location;
public interface LocationService {
Location saveLocation(Location loc);
Location updateLocation(Location loc);
void deleteLocation(Location loc);
Location getLocationById(int id);
List<Location> getAllLocation();
}
LocationServiceImpl
package com.testname.location.service;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.testname.location.entities.Location;
import com.testname.location.repos.LocationRepository;
@Service
public class LocationServiceImpl implements LocationService {
@Autowired
private LocationRepository repo;
public LocationRepository getRepo() {
return repo;
}
public void setRepo(LocationRepository repo) {
this.repo = repo;
}
@Override
public Location saveLocation(Location loc) {
return repo.save(loc);
}
@Override
public Location updateLocation(Location loc) {
return repo.save(loc);
}
@Override
public void deleteLocation(Location loc) {
repo.delete(loc);
}
@Override
public Location getLocationById(int id) {
return repo.findById(id).orElse(null);
}
@Override
public List<Location> getAllLocation() {
return repo.findAll();
}
}
LocationWebApplication
package com.testname.location;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class LocationwebApplication {
public static void main(String[] args) {
SpringApplication.run(LocationwebApplication.class, args);
}
}
application.properties
spring.datasource.url=jdbc:mysql://localhost:3306/projectdb
spring.datasource.username=***
spring.datasource.password=***
spring.jpa.show-sql=true
spring.mvc.view.prefix=/WEB-INF/jsps/
spring.mvc.view.suffix=.jsp
server.servlet.context-path=/locationweb
createLocation.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Create Location</title>
</head>
<body>
<form action="saveLoc" method="post">
<pre>
Id: <input type="text" name="id"/>
Code: <input type="text" name="code"/>
Name: <input type="text" name="name"/>
Type: Urban <input type="radio" name="type" value="URBAN" />
Rural <input type="radio" name="type" value="RURAL"/>
<input type="submit" value="save"/>
</pre>
</form>
${msg}
</body>
</html>