java - 尝试从 java webservice 中的 json 对象获取值时出现异常

Question

当我尝试从 java webservice 端的 json 对象获取值时，我收到一些运行时异常，请找到下面出现的异常:
当我尝试从 java webservice 端的 json 对象获取值时，我收到一些运行时异常，请在下面找到我的 json 对象:

{"data":[{"userid":657,"name":"Eliina","username":"Admin","aim_name":" Eliina ","aim_title":"Administrator","password":"eli456456","role":1,"rolename":"Client Ain","clientno":"540","id":8,"client_name":"Eliina","defaulturl":"clientsettings.htm","attempts":0,"aimaccess":1}]}

请找到我写的java方法:

public void insertList(String ip, JSONObject loginresult) 
{  
    try{
        String n = loginresult.getString("data");
    } catch( JSONException je ) {
        je.printStackTrace();
    }
}

请找出我在下面遇到的异常:

30-Sep-2015 10:27:11.007 INFO [http-nio-8084-exec-10] org.apache.catalina.startup.HostConfig.deployDescriptor Deployment of configuration descriptor /home/ty02/.netbeans/8.0.2/apache-tomcat-8.0.15.0_base/conf/Catalina/localhost/MobileService.xml has finished in 2,217 ms
org.codehaus.jettison.json.JSONException: JSONObject["username"] not found.
    at org.codehaus.jettison.json.JSONObject.get(JSONObject.java:360)
    at org.codehaus.jettison.json.JSONObject.getString(JSONObject.java:487)
    at com.zimmer.mobileservice.resources.Login.insertauditList(Login.java:84)
    at com.zimmer.mobileservice.resources.Login.checkLogin(Login.java:71)
    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 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.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:725)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:537)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1085)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1556)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1513)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

Answer 1

您的输入 JSON 是，

{"data":[{"userid":657,"name":"Eliina","username":"Admin","aim_name":" Eliina ","aim_title":"Administrator","password":"eli456456","role":1,"rolename":"Client Ain","clientno":"540","id":8,"client_name":"Eliina","defaulturl":"clientsettings.htm","attempts":0,"aimaccess":1}]}

因此，这意味着对于键数据，值是JSONArray，但是您试图将JSONArray作为String获取，所以您面临这样的情况异常(exception)。你需要做的是，需要像 JSONArray 那样获取值，

JSONArray value = loginresult.getJSONArray("data");

编辑答案:

现在，值 JSONArray 包含数组对象，您可以从中获取 key，例如，

JSONArray value = loginresult.getJSONArray("data");
String userId = ((JSONObject) value.get(0)).getString("userid");

最好检查hasKey检查和数组大小检查以避免出现令人讨厌的异常。