在开发中我们经常使用json进行数据的传输，数据轻量传输速度快，但是使用JSONObject将数据转化为json数据的时候需要注意，
例如，将以下的类的对象转化为json数据
<span style="font-family: Arial,sans-serif; font-size: 12px; background-color: rgb(255,255);"></span><pre name="code" class="java">public class PayStatus {
private String shipId ;
private String shipName ;
private String escrowId ;
private Integer paid ;
private Date insertTime ;
public String getShipId() {
return shipId;
}
public void setShipId(String shipId) {
this.shipId = shipId;
}
public String getShipName() {
return shipName;
}
public void setShipName(String shipName) {
this.shipName = shipName;
}
public String getEscrowId() {
return escrowId;
}
public void setEscrowId(String escrowId) {
this.escrowId = escrowId;
}
public Integer getPaid() {
return paid;
}
public void setPaid(Integer paid) {
this.paid = paid;
}
public Date getInsertTime() {
return insertTime;
}
public void setInsertTime(Date insertTime) {
this.insertTime = insertTime;
}
}
上面的类中insertTime字段是java.util.Date 数据类型并不是一个基本类型的数据，如果这一项在查找的时候没有响应的数据，就会是空置，在struts中进行json数据的输出的时候就会出现如下的错误：
[ERROR] 2014-11-04 10:59:56,248(53301) --> [http-bio-8080-exec-3] com.opensymphony.xwork2.util.logging.commons.CommonsLogger.error(CommonsLogger.java:38): Exception occurred during processing request: java.lang.reflect.InvocationTargetException org.apache.struts2.json.JSONException: java.lang.reflect.InvocationTargetException at org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:246) at org.apache.struts2.json.JSONWriter.processCustom(JSONWriter.java:178) at org.apache.struts2.json.JSONWriter.process(JSONWriter.java:168) at org.apache.struts2.json.JSONWriter.value(JSONWriter.java:134) at org.apache.struts2.json.JSONWriter.map(JSONWriter.java:436) at org.apache.struts2.json.JSONWriter.process(JSONWriter.java:154) at org.apache.struts2.json.JSONWriter.value(JSONWriter.java:134) at org.apache.struts2.json.JSONWriter.array(JSONWriter.java:481) at org.apache.struts2.json.JSONWriter.process(JSONWriter.java:158) at org.apache.struts2.json.JSONWriter.value(JSONWriter.java:134) at org.apache.struts2.json.JSONWriter.map(JSONWriter.java:436) at org.apache.struts2.json.JSONWriter.process(JSONWriter.java:154) at org.apache.struts2.json.JSONWriter.value(JSONWriter.java:134) at org.apache.struts2.json.JSONWriter.write(JSONWriter.java:102) at org.apache.struts2.json.JSONUtil.serialize(JSONUtil.java:116) at org.apache.struts2.json.JSONResult.createJSONString(JSONResult.java:202) at org.apache.struts2.json.JSONResult.execute(JSONResult.java:176) at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:371) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:275) at cn.cttic.action.LoginInterceptor.intercept(LoginInterceptor.java:45) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at org.apache.struts2.interceptor.DeprecationInterceptor.intercept(DeprecationInterceptor.java:41) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:167) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265) at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:249) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:249) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at org.apache.struts2.interceptor.CheckBoxInterceptor.intercept(CheckBoxInterceptor.java:91) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:252) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:139) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246) at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54) at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:562) at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77) at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:722) Caused by: java.lang.reflect.InvocationTargetException 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 org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:226) ... 85 more Caused by: net.sf.json.JSONException: Object is null at net.sf.json.JSONNull.isEmpty(JSONNull.java:69) ... 90 more
像这样的错误在代码的过程中需要尤其的注意，有些地方可以再初始化的时候直接创建一个类的对象，或使数据库相应的字段设置为非空。
<span style="font-family: Arial,255);"> </span>