使用Spring REST服務獲得NPE

我正在構建REST服務以切換true和false之間的切換。它作爲一個Singleton工作，但我試圖將其轉換爲Spring應用程序。任何幫助表示讚賞。我做了一個乾淨的-U，刪除了整個mvn倉庫，並且在訪問該標誌時我仍然得到了NPE。使用Spring REST服務獲得NPE

當我做了一個得到 - 我沒有得到任何迴應或NPE，如果我嘗試訪問它當我做了後我回來我發送但仍不知道它是否正在更新。

我有兩個類：

SwitchFlag.java

import org.springframework.stereotype.Service; 

@Service 
public class SwitchFlag { 

    private boolean flag; 

    public boolean getFlag() { 
     return flag; 
    } 

    public void setFlag(boolean flag) { 
     this.flag = flag; 
    } 

    @Override 
    public String toString() { 
     return "{\"flag\":" + flag +"}"; 
    } 
}

SwitchFlagService.java

import javax.ws.rs.Consumes; 
import javax.ws.rs.GET; 
import javax.ws.rs.POST; 
import javax.ws.rs.Path; 
import javax.ws.rs.Produces; 
import javax.ws.rs.core.MediaType; 
import javax.ws.rs.core.Response; 

import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.stereotype.Controller; 

@Path("/flag") 
public class SwitchFlagService { 

    @Autowired 
    SwitchFlag switchFlag; 

    @GET 
    @Path("/get") 
    @Produces(MediaType.APPLICATION_JSON) 
    public SwitchFlag getFlag() { 
     return switchFlag; 
    } 

    @POST 
    @Path("/post") 
    @Consumes(MediaType.APPLICATION_JSON) 
    public Response setFlag(SwitchFlag flag) { 
     return Response.status(201).entity(flag).build(); 
    } 
}

我的web.xml

<?xml version="1.0" encoding="UTF-8"?> 

<web-app id="SwitchFlag" version="2.4" 
    xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> 
    <display-name>Flag Control</display-name> 

    <context-param> 
     <param-name>resteasy.resources</param-name> 
     <param-value>SwitchFlagService</param-value> 
    </context-param> 

    <listener> 
     <listener-class> 
      org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap</listener-class> 
    </listener> 
    <servlet> 
     <servlet-name>resteasy-servlet</servlet-name> 
     <servlet-class> 
      org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher</servlet-class> 
    </servlet> 

    <servlet-mapping> 
     <servlet-name>resteasy-servlet</servlet-name> 
     <url-pattern>/*</url-pattern> 
    </servlet-mapping> 

</web-app>

最後的一個片斷我的pom.xml - 我刪除了VED一些不需要依賴於顯示如httpcomponents和JSON

<dependencies> 
     <dependency> 
      <groupId>org.jboss.resteasy</groupId> 
      <artifactId>resteasy-jaxrs</artifactId> 
      <version>3.0.19.Final</version> 
     </dependency> 
     <dependency> 
      <groupId>org.jboss.resteasy</groupId> 
      <artifactId>resteasy-jackson-provider</artifactId> 
      <version>3.0.19.Final</version> 
     </dependency> 

     <dependency> 
      <groupId>org.springframework</groupId> 
      <artifactId>spring-context</artifactId> 
      <version>4.3.3.RELEASE</version> 
     </dependency> 
     <dependency> 
      <groupId>org.springframework</groupId> 
      <artifactId>spring-core</artifactId> 
      <version>4.3.3.RELEASE</version> 
     </dependency> 

    </dependencies> 

    <build>  
     <plugins> 
      <plugin> 
       <artifactId>maven-compiler-plugin</artifactId> 
       <version>3.5.1</version> 
       <configuration> 
        <source>1.7</source> 
        <target>1.7</target> 
       </configuration> 
      </plugin> 
     </plugins> 
    </build>

很多幫助表示讚賞

而且堆棧跟蹤:)

2016-11-10 17:02:17.808:WARN:oejs.ServletHandler:qtp953305190-13: /LogFlag/flag/get 
org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException 
    at org.jboss.resteasy.core.ExceptionHandler.handleApplicationException(ExceptionHandler.java:77) 
    at org.jboss.resteasy.core.ExceptionHandler.handleException(ExceptionHandler.java:220) 
    at org.jboss.resteasy.core.SynchronousDispatcher.writeException(SynchronousDispatcher.java:175) 
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:418) 
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:209) 
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:221) 
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56) 
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) 
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:808) 
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587) 
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) 
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:577) 
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223) 
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127) 
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515) 
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185) 
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061) 
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) 
    at org.eclipse.jetty.server.handler.HandlerList.handle(HandlerList.java:52) 
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97) 
    at org.eclipse.jetty.server.Server.handle(Server.java:499) 
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310) 
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257) 
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540) 
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635) 
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555) 
    at java.lang.Thread.run(Thread.java:745) 
Caused by: 
java.lang.NullPointerException 
    at com.bcn.rest.SwitchFlagService.getFlag(SwitchFlagService.java:25) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:606) 
    at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:139) 
    at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:295) 
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:249) 
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:236) 
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:402) 
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:209) 
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:221) 
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56) 
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) 
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:808) 
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587) 
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) 
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:577) 
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223) 
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127) 
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515) 
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185) 
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061) 
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) 
    at org.eclipse.jetty.server.handler.HandlerList.handle(HandlerList.java:52) 
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97) 
    at org.eclipse.jetty.server.Server.handle(Server.java:499) 
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310) 
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257) 
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540) 
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635) 
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555) 
    at java.lang.Thread.run(Thread.java:745)

來源

2016-11-10 sometimes24

Spring容器不能注入豆到你的SwitchFlagService，因爲它被註釋爲@Path即，Spring容器只掃描像@Controller，@Component，@Service等構造型來注入bean。

你需要改變你的SwitchFlagService，如下圖所示：

@RestController 
public class SwitchFlagService { 

    @Autowired 
    SwitchFlag switchFlag; 

    @RequestMapping(value="/get", method=RequestMethod.GET) 
    public SwitchFlag getFlag() { 
     return switchFlag; 
    } 

    @RequestMapping(value="/post", method=RequestMethod.POST) 
    public ResponseEntity<SwitchFlag> setFlag(SwitchFlag flag) { 
     return new ResponseEntity<SwitchFlag>(flag, HttpStatus.CREATED); 
    } 
}

來源

2016-11-10 22:08:15 developer

這給了我一個java.lang.NoClassDefFoundError：組織/ springframework的/ HTTP/ResponseEntity錯誤。我添加了spring-web依賴項 – sometimes24

使用Spring REST服務獲得NPE

回答

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