当我尝试对另一个服务进行休息调用时，它显示空指针异常，即使我在 Rating.class 中添加了一个空构造函数，尽管它说的是相同的
java.lang.NullPointerException：无法调用“java.util.List.stream()”，因为“com.microservice.model.UserRating.getUserRating()”的返回值为null
我按照下面的教程进行操作 [https://www.youtube.com/watch?v=Dmvhe2cw-_k&list=PLqq-6Pq4lTTZSKAFG6aCDVDP86Qx4lNas&index=15&ab_channel=JavaBrains]
请找到以下代码
package com.microservice;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@SpringBootApplication
public class MovieCatalogsServicesApplication {
@Bean
public RestTemplate getRestTemplate() {
return new RestTemplate();
}
public static void main(String[] args) {
SpringApplication.run(MovieCatalogsServicesApplication.class, args);
}
}
控制器类
package com.microservice.resources;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import com.microservice.model.CatalogItem;
import com.microservice.model.Movie;
import com.microservice.model.Rating;
import com.microservice.model.UserRating;
@RestController
@RequestMapping("/catalog")
public class MovieCatalogResource {
@Autowired
private RestTemplate restTemplate;
@RequestMapping("/{UserId}")
public List<CatalogItem> getCatalog(@PathVariable("UserId") String UserId) {
//RestTemplate restTemplate = new RestTemplate();
UserRating ratings = restTemplate.getForObject("http://localhost:1080/ratingdata/users" + UserId,
UserRating.class);
return ratings.getUserRating().stream().map(rating -> {
Movie movie = restTemplate.getForObject("http://localhost:9080/movies/" + rating.getMovieId(), Movie.class);
return new CatalogItem(movie.getName(), "Suspense", rating.getRating());
}).collect(Collectors.toList());
}
}
模特班
package com.microservice.model;
public class CatalogItem {
private String name;
private String desc;
private int rating;
public CatalogItem(String name, String desc, int rating) {
super();
this.name = name;
this.desc = desc;
this.rating = rating;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
public int getRating() {
return rating;
}
public void setRating(int rating) {
this.rating = rating;
}
}
package com.microservice.model;
public class Movie {
private String movieId;
private String name;
public Movie() {
super();
}
public Movie(String movieId, String name) {
super();
this.movieId = movieId;
this.name = name;
}
public String getMovieId() {
return movieId;
}
public void setMovieId(String movieId) {
this.movieId = movieId;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
package com.microservice.model;
public class Rating {
private String movieId;
private int rating;
public Rating() {
}
public Rating(String movieId, int rating) {
this.movieId = movieId;
this.rating = rating;
}
public String getMovieId() {
return movieId;
}
public void setMovieId(String movieId) {
this.movieId = movieId;
}
public int getRating() {
return rating;
}
public void setRating(int rating) {
this.rating = rating;
}
}
package com.microservice.model;
import java.util.List;
//mcs
public class UserRating {
private List<Rating> userRating;
public List<Rating> getUserRating() {
return userRating;
}
public void setUserRating(List<Rating> userRating) {
this.userRating = userRating;
}
}
我尝试点击 URL -> http://localhost:8080/catalog/foo ，预期结果是 [{"name":"Test","desc":"TestDesc"," rating":4},{ “名称”：“测试”，“描述”：“测试描述”，“评级”：3}] 但实际结果是
Whitelabel 错误页面 此应用程序没有 /error 的显式映射，因此您将其视为后备。
2022 年 12 月 12 日星期一 13:33:17 IST 出现意外错误（类型=内部服务器错误，状态=500）。
以下错误 `
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
[32m :: Spring Boot :: [39m [2m (v2.7.7-SNAPSHOT)[0;39m
[2m2022-12-12 13:33:08.931[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36mc.m.MovieCatalogsServicesApplication [0;39m [2m:[0;39m Starting MovieCatalogsServicesApplication using Java 16.0.2 on MKW58ZLPC0034 with PID 21932 (C:\Users\st57540\Documents\workspace-spring-tool-suite-4-4.12.0.RELEASE\microserviceworkspace\movie-catalogs-services\target\classes started by ST57540 in C:\Users\st57540\Documents\workspace-spring-tool-suite-4-4.12.0.RELEASE\microserviceworkspace\movie-catalogs-services)
[2m2022-12-12 13:33:08.934[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36mc.m.MovieCatalogsServicesApplication [0;39m [2m:[0;39m No active profile set, falling back to 1 default profile: "default"
[2m2022-12-12 13:33:09.827[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36mo.s.b.w.embedded.tomcat.TomcatWebServer [0;39m [2m:[0;39m Tomcat initialized with port(s): 8080 (http)
[2m2022-12-12 13:33:09.837[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36mo.apache.catalina.core.StandardService [0;39m [2m:[0;39m Starting service [Tomcat]
[2m2022-12-12 13:33:09.837[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36morg.apache.catalina.core.StandardEngine [0;39m [2m:[0;39m Starting Servlet engine: [Apache Tomcat/9.0.69]
[2m2022-12-12 13:33:09.991[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36mo.a.c.c.C.[Tomcat].[localhost].[/] [0;39m [2m:[0;39m Initializing Spring embedded WebApplicationContext
[2m2022-12-12 13:33:09.991[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36mw.s.c.ServletWebServerApplicationContext[0;39m [2m:[0;39m Root WebApplicationContext: initialization completed in 1001 ms
[2m2022-12-12 13:33:10.373[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36mo.s.b.w.embedded.tomcat.TomcatWebServer [0;39m [2m:[0;39m Tomcat started on port(s): 8080 (http) with context path ''
[2m2022-12-12 13:33:10.384[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[ main][0;39m [36mc.m.MovieCatalogsServicesApplication [0;39m [2m:[0;39m Started MovieCatalogsServicesApplication in 1.845 seconds (JVM running for 2.967)
[2m2022-12-12 13:33:16.888[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mo.a.c.c.C.[Tomcat].[localhost].[/] [0;39m [2m:[0;39m Initializing Spring DispatcherServlet 'dispatcherServlet'
[2m2022-12-12 13:33:16.889[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mo.s.web.servlet.DispatcherServlet [0;39m [2m:[0;39m Initializing Servlet 'dispatcherServlet'
[2m2022-12-12 13:33:16.889[0;39m [32m INFO[0;39m [35m21932[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mo.s.web.servlet.DispatcherServlet [0;39m [2m:[0;39m Completed initialization in 0 ms
[2m2022-12-12 13:33:17.048[0;39m [31mERROR[0;39m [35m21932[0;39m [2m---[0;39m [2m[nio-8080-exec-1][0;39m [36mo.a.c.c.C.[.[.[/].[dispatcherServlet] [0;39m [2m:[0;39m Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException: Cannot invoke "java.util.List.stream()" because the return value of "com.microservice.model.UserRating.getUserRating()" is null] with root cause
java.lang.NullPointerException: Cannot invoke "java.util.List.stream()" because the return value of "com.microservice.model.UserRating.getUserRating()" is null
at com.microservice.resources.MovieCatalogResource.getCatalog(MovieCatalogResource.java:34) ~[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-5.3.24.jar:5.3.24]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.24.jar:5.3.24]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.24.jar:5.3.24]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.24.jar:5.3.24]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.24.jar:5.3.24]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.24.jar:5.3.24]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1071) ~[spring-webmvc-5.3.24.jar:5.3.24]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:964) ~[spring-webmvc-5.3.24.jar:5.3.24]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.24.jar:5.3.24]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.24.jar:5.3.24]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:670) ~[tomcat-embed-core-9.0.69.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.24.jar:5.3.24]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:779) ~[tomcat-embed-core-9.0.69.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.69.jar:9.0.69]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.24.jar:5.3.24]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.24.jar:5.3.24]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.24.jar:5.3.24]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.24.jar:5.3.24]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.24.jar:5.3.24]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.24.jar:5.3.24]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:177) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:360) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:891) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1784) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.69.jar:9.0.69]
at java.base/java.lang.Thread.run(Thread.java:831) ~[na:na]
`
尝试从 getforobject 中捕获 List obj 中的数据，然后根据需要处理数据。这可能有效。