空指针异常,如何解决
环境: Myeclipse2014 , win8.1操作系统, JDK7, tomcat7
运行 top.jsp文件,发生异常,错误信息如下:
org.apache.jasper.JasperException: java.lang.NullPointerException
上次的错误信息也是 Exception(只是指明了错误行在下面红色的代码),这次重启myeclipes后无法重现上次的error报错信息了,只是报错:org.apache.jasper.JasperException: java.lang.NullPointerException。上次报错能定位到 文件 top.jsp的代码,信息是:
<%BasetableFactory bf=BasetableFactory.getInstance();%>
<table id="cpdd" class='box' style='display:none' onMouseOver="popmenu(this)" onMouseOut="popmenu(this)" align="center" >
<%Collection cpdd=bf.ListSsort("");
if((cpdd!=null)&&(cpdd.size()>0))
{ Iterator it=cpdd.iterator();
while(it.hasNext())
{
Ssort s=(Ssort)it.next();
%>
BasetableFactory.java相关代码如下:
public abstract class BasetableFactory {
private static final String classname = "com.dao.DbBasetableFactory";
private static BasetableFactory factory;
public static BasetableFactory getInstance() {
if (factory == null) {
try {
Class c = Class.forName(classname);
factory = (BasetableFactory) c.newInstance();
} catch (ClassNotFoundException ex) {
ex.printStackTrace();
} catch (IllegalAccessException ex1) {
ex1.printStackTrace();
} catch (InstantiationException ex1) {
ex1.printStackTrace();
}
}
return new BasetableFactoryProxy(factory);
}
请各位高手帮忙看看: top.jsp这行代码([color=#FF0000] <%Collection cpdd=bf.ListSsort("");)到底是哪里有问题,如何修改,谢谢?[/color]