春ブーツRestfull APIが取得：ネスティングexcepion

Question

私は@RestControllerと@RequestMappingがrestfull APIサービスのプロジェクトを作る使用したいが、私はappDao.findAllを（使用する場合）のすべてのアプリを取得するには、ネスティングexcepionを取得し、ようなコード：

App.java

@Entity 
@Table(name = "apps") 
public class App { 

    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    private long id; 


    @NotNull 
    private String name; 

    public App() { } 

    public App(String name, User user) { 
     this.name = name; 
     this.user = user; 
    } 

    public long getId() { 
     return id; 
    } 

    public void setId(long id) { 
     this.id = id; 
    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    @ManyToOne(fetch=FetchType.LAZY) 
    @JoinColumn(name = "user_id") 
    private User user; 

    public User getUser(){ 
     return user; 
    } 

    public void setUser(User user) { 
     this.user = user; 
    } 

    @Override 
    public String toString(){ 

     return "AppName: " + name; 
    } 


} 

User.java

@Entity 
@Table(name = "users") 
public class User { 

    // ------------------------ 
    // PRIVATE FIELDS 
    // ------------------------ 

    // An autogenerated id (unique for each user in the db) 
    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    private long id; 


    // The user's email 
    @NotNull 
    private String email; 

    // The user's name 
    @NotNull 
    private String name; 

    @NotNull 
    private Integer age; 

    // ------------------------ 
    // PUBLIC METHODS 
    // ------------------------ 

    public User() { } 

    public User(long id) { 
     this.id = id; 
    } 

    public User(String name) { 
     this.name = name; 
    } 

    public User(String email, String name, Integer age) { 
     this.email = email; 
     this.name = name; 
     this.age = age; 
    } 

    // Getter and setter methods 

    public long getId() { 
     return id; 
    } 

    public void setId(long value) { 
     this.id = value; 
    } 

    public String getEmail() { 
     return email; 
    } 

    public void setEmail(String value) { 
     this.email = value; 
    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String value) { 
     this.name = value; 
    } 

    public Integer getAge() { 
     return age; 
    } 

    public void setAge(Integer value) { 
     this.age = value; 
    } 

    @OneToOne(cascade = CascadeType.ALL) 
    @JoinColumn(name = "car_id") 
    private Car car; 
    public Car getCar() { 
     return car; 
    } 

    public void setCar(Car car) { 
     this.car = car; 
    } 

    @OneToMany(targetEntity=App.class, mappedBy="user", fetch=FetchType.EAGER, cascade=CascadeType.ALL) 
    private Set<App> apps; 

    public Set<App> getApps() { 
     return apps; 
    } 

    public void setApps(Set<App> apps) { 
     this.apps= apps; 
    } 

    public void addApps(Set<App> apps) { 
     this.apps.addAll(apps); 
    } 

    @Override 
    public String toString() { 
     String result = String.format(
       "User[id=%d, name='%s']%n", 
       id, name); 
     if (apps != null) { 
      for(App app : apps) { 
       result += String.format(
         "app[id=%d, name='%s']%n", 
         app.getId(), app.getName()); 
      } 
     } 

     return result; 
    } 
} // class User 

AppDao.java

@Transactional 
public interface AppDao extends JpaRepository<App, Long> { 

    /** 
    * This method will find an User instance in the database by its email. 
    * Note that this method is not implemented and its working code will be 
    * automagically generated from its signature by Spring Data JPA. 
    */ 

} 

AppController.java

@RestController 
@RequestMapping("/apps") 
public class AppController { 

    @Autowired 
    private AppDao appDao; 

    @RequestMapping("/") 
    public List<App> getAll() { 
     List<App> apps = appDao.findAll(); 
     return apps; 
    } 
} 

メインのJava：

その後、

@SpringBootApplication 
@EnableAutoConfiguration 
public class MysqlDemoApplication implements CommandLineRunner { 

    public static void main(String[] args) { 
     SpringApplication.run(MysqlDemoApplication.class, args); 
    } 

    @Override 
    @Transactional 
    public void run(String... strings) throws Exception { 
    } 

} 

訪問：http://localhost:8080/apps/ネストされた例外を取得：なぜ？

バックトレース：

com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:693) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:675) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:157) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:693) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:675) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:157) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:149) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:111) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:693) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:675) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:157) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:693) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:675) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:157) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:149) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:111) ~[jackson-databind-2.6.6.jar:2.6.6] 
     at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:24) ~[jackson-databind-2.6.6.jar:2.6.6] 

    2016-06-28 11:01:18.675 ERROR 90592 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet dispatcherServlet threw exception 

    java.lang.IllegalStateException: getOutputStream() has already been called for this response 
     at org.apache.catalina.connector.Response.getWriter(Response.java:564) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:212) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:109) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$SpelView.render(ErrorMvcAutoConfiguration.java:195) ~[spring-boot-autoconfigure-1.3.5.RELEASE.jar:1.3.5.RELEASE] 
     at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1246) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1029) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:973) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:858) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:720) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:584) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:523) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:439) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:304) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:399) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:179) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1502) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1458) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     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-8.0.33.jar:8.0.33] 
     at java.lang.Thread.run(Thread.java:745) [na:1.8.0_65] 

    2016-06-28 11:01:18.678 ERROR 90592 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost]   : Exception Processing ErrorPage[errorCode=0, location=/error] 

    org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.IllegalStateException: getOutputStream() has already been called for this response 
     at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:979) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:858) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:720) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:584) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:523) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:439) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:304) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:399) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:179) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1502) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1458) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_65] 
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_65] 
     at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.0.33.jar:8.0.33] 
     at java.lang.Thread.run(Thread.java:745) [na:1.8.0_65] 
    Caused by: java.lang.IllegalStateException: getOutputStream() has already been called for this response 
     at org.apache.catalina.connector.Response.getWriter(Response.java:564) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:212) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:109) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
     at org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$SpelView.render(ErrorMvcAutoConfiguration.java:195) ~[spring-boot-autoconfigure-1.3.5.RELEASE.jar:1.3.5.RELEASE] 
     at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1246) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1029) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:973) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
     ... 37 common frames omitted 

Answer 1

まず、あなたはControllerクラスから直接DAOコードを呼び出すのですか？それは悪い習慣とみなされます - あなたはそれらの間にサービスクラスを持っているべきです。

第2に、アプリケーションがパス/エラーの下でエラー画面を表示しようとしている間、あなたが提供したスタックトレースは、エラーです。これの前にスタックトレースがありますか？あなたの問題をよる

- すなわち、この方法であなたのRequestMappingにHTTPメソッドを指定しよう：

@RequestMapping(path = "/", method = RequestMethod.GET) 

を、これは動作しない場合は、あなたのSpring構成で何らかのエラーがなければならない、あなたは正しくへのパッケージを指定してくださいコンポーネントをスキャンしますか？ @SpringBootApplicationを使用しているときのSpringブートでは、スキャンするすべてのパッケージは、このアノテーションを持つクラスの下になければなりません。

UPDATE

は、RESTのWebサービスを経由して循環依存を持つエンティティを返さないでください - 新しいDTOクラス、データベースからフェッチされたマップのエンティティを作成し、Webサービスでそれを返します。ここ

さらに詳しい情報：もちろんhttp://www.baeldung.com/entity-to-and-from-dto-for-a-java-spring-application

あなたは別のマッピングライブラリを使用することができますしたい場合は、私の個人的な好みは、あなたが間違って使用されているようヘッダを受け入れオリカ（http://orika-mapper.github.io/orika-docs/intro.html）

Answer 2

が見えるです。あなたはウェブブラウザからサービスを要求しようとしている場合、この要求はアプリケーション/ XHTML + xmlの値と標準ヘッダ値を持つことになりますし、それはあなたが/例アプリケーションにJSONで正しいヘッダ値を持っている必要があり、問題

を引き起こしjson。郵便配達員のようなリクエストには他のツールを使用してください