I was learning Spring Boot and i have run into this problem where AutoWired bean gives nullpointer exception.I have tried changing Annotations and checked all the usual suspects.
Here is the file structure File Structure
StsApplication.java
package com.Load.lsy;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class StsApplication {
public static void main(String[] args) {
SpringApplication.run(StsApplication.class, args);
}
}
loadService.java
package com.Load.lsy.service;
import java.util.List;
import com.Load.lsy.Entities.Load;
public interface LoadService {
public String getLoads();
}
STSController.java
package com.Load.lsy.Controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;
import com.Load.lsy.service.*;
@RestController
public class STSController {
@Autowired(required=false)
public LoadService service;
@PostMapping("/home")
public String getload() {
return service.getLoads();
}
}
LoadServiceImpl.java
package com.Load.lsy.service;
import java.util.List;
import java.util.*;
import com.Load.lsy.Entities.Load;
public class LoadServiceImpl implements LoadService {
List<Load> list;
public LoadServiceImpl() {
list = new ArrayList<>();
}
@Override
public String getLoads() {
//This is just a test
return "Load list" ;
}
}
stacktrace
java.lang.NullPointerException: Cannot invoke "com.Load.lsy.service.LoadService.getLoads()" because "this.service" is null
at com.Load.lsy.Controller.STSController.getload(STSController.java:18) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:567) ~[na:na]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-5.3.12.jar:5.3.12]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.12.jar:5.3.12]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.12.jar:5.3.12]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.12.jar:5.3.12]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.12.jar:5.3.12]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.12.jar:5.3.12]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067) ~[spring-webmvc-5.3.12.jar:5.3.12]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.12.jar:5.3.12]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.12.jar:5.3.12]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.12.jar:5.3.12]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:681) ~[tomcat-embed-core-9.0.54.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.12.jar:5.3.12]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.54.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.54.jar:9.0.54]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.12.jar:5.3.12]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.12.jar:5.3.12]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.12.jar:5.3.12]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.12.jar:5.3.12]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.12.jar:5.3.12]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.12.jar:5.3.12]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:895) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1722) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.54.jar:9.0.54]
at java.base/java.lang.Thread.run(Thread.java:831) ~[na:na]
[2m
CodePudding user response:
Make the dependency mandatory as follows:
@RestController
public class STSController {
@Autowired
public LoadService service;
@PostMapping("/home")
public String getload() {
return service.getLoads();
}
}
And add @Service
to LoadServiceImpl
so that a Spring-managed bean is created:
@Service
public class LoadServiceImpl implements LoadService {
List<Load> list;
public LoadServiceImpl() {
list = new ArrayList<>();
}
@Override
public String getLoads() {
//This is just a test
return "Load list" ;
}
}
CodePudding user response:
Let spring manage your service (before it can be injected anywhere)!
By:
-
@org.springframework.stereotype.Service public class LoadServiceImpl ...
plus adding it to component-scan.
or (without component scan):
@SpringBootApplication public class StsApplication { //... @Bean public LoadService myLoadService() { //... return new LoadService(); } } //in your app/config/main
CodePudding user response:
You forgot to write @Service annotation in your LoadServiceImpl class and remove that required = false in your @Autowired annotation in the controller class. And try to avoid using this Autowired, again and again, use constructor DI in your code, it make managing DI easy. DI----(Dependency Injection)....