I am working on Spring Boot version 2, using Java 8 and when I am trying to add a new List object to a pre-defined List object(i.e topicList) in the "createTopic" method I'm getting an error.
**
TopicService.java
**
public class TopicService {
private List<TopicObject> topicList = Arrays.asList(
new TopicObject("Java", "Java Course", "Spring boot in java"),
new TopicObject("Maths", "Mathematics class","12th maths")
);
public String createTopic(TopicObject topicObj){
topicList.add(new TopicObject("Java1", "Java Course1", "Spring boot in java1"));
return "Request successful" ;
}
}
**
TopicObject.java
**
package io.javabrains.springBootStarter.controller;
import com.fasterxml.jackson.annotation.JsonProperty;
public class TopicObject {
@JsonProperty("id")
private String id;
@JsonProperty("name")
private String name;
@JsonProperty("description")
private String description;
public TopicObject() {
}
public TopicObject(String id, String name, String description) {
this.id = id;
this.name = name;
this.description = description;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}
**
Error
**
2020-04-15 19:52:27.172 ERROR 15312 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.UnsupportedOperationException] with root cause
java.lang.UnsupportedOperationException: null at java.util.AbstractList.add(AbstractList.java:148) ~[na:1.8.0_221] at java.util.AbstractList.add(AbstractList.java:108) ~[na:1.8.0_221] at io.javabrains.springBootStarter.Service.TopicService.createTopic(TopicService.java:29) ~[classes/:na] at io.javabrains.springBootStarter.controller.TopicController.createTopic(TopicController.java:31) ~[classes/:na] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_221] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_221] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_221] at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_221] at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:981) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:884) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:858) ~[spring-webmvc-5.0.13.RELEASE.jar:5.0.13.RELEASE] at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.39.jar:8.5.39] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.13.RELEASE.jar:5.0.13.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) ~[tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:798) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498) [tomcat-embed-core-8.5.39.jar:8.5.39] at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.39.jar:8.5.39] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_221] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_221] at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.39.jar:8.5.39] at java.lang.Thread.run(Thread.java:748) [na:1.8.0_221]
>I don't know if a new object can be added to the "topicList" in this way. Can someone help?
Arrays.asLit retuns an unmodifiable List object. If you intend to add elements to it you need to use a modifiable List type, such as an ArrayList:
private List<TopicObject> topicList = new ArrayList<>(Arrays.asList(
new TopicObject("Java", "Java Course", "Spring boot in java"),
new TopicObject("Maths", "Mathematics class", "12th maths")
));