YQL：yahoo.finance.quotes表并不总是工作

Question

我的RESTful应用程序使用JAXB从yahoo.finance.quotes表中解组YQL响应，但有时我得到NullPointerException，我真的无法从堆栈中弄清楚跟踪。

该代码大部分时间在tomcat7中工作。

static { 
    try{ 
     JAXBContext jc=JAXBContext.newInstance(Quotes.class); 
     unmarshaller = jc.createUnmarshaller(); 
    } catch (JAXBException e) { 
     e.printStackTrace(); 
    } 
} 
public static Quotes getQuotes(String symbols){ 
    Quotes quotes = new Quotes(); 
    try { 
     URL url = new URL(getYQLUrl(symbols)); 
     InputStream yqlStream = url.openStream(); 
     quotes = (Quotes) unmarshaller.unmarshal(yqlStream); 
    } catch (JAXBException e) { 
     e.printStackTrace(); 
    } catch (MalformedURLException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 
    return quotes; 
} 

Jul 01, 2013 4:07:57 PM com.sun.jersey.spi.container.ContainerResponse mapMappableContainerException 
SEVERE: The RuntimeException could not be mapped to a response, re-throwing to the HTTP container 
java.lang.NullPointerException 
    at com.kunxia.portfolio.service.PortfolioService.getPositions(PortfolioService.java:70) 
    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:601) 
    at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60) 
    at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$TypeOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:185) 
    at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75) 
    at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288) 
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147) 
    at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108) 
    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147) 
    at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84) 
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469) 
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400) 
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349) 
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339) 
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416) 
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537) 
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:708) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) 
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589) 
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) 
    at java.lang.Thread.run(Thread.java:722) 

Answer 1

你代码抛出NullPointerException。它在堆栈跟踪中非常清楚地表示。所以，你需要解决什么是错的

com.kunxia.portfolio.service.PortfolioService.getPositions(PortfolioService.java:70)