在做对两个参数的查询时,有时会出现以下错误:
javax.servlet.ServletException: java.lang.NullPointerException
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:515)
org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419)
然后说代码是错在这:
- Java code
public String execute() throws Exception { Map request = (Map) ActionContext.getContext().get("request"); if ( this.getUsername_c().equals("") || this.getCustomerid_c().equals("") ) { request.put("list", service.findAll()); } else { allRecorders = service.findUsersByUsernameCustomerid_count( this.getUsername_c() , this.getCustomerid_c() ) ; request.put("currentPage",new Integer(currentPage)) ; //当前页 request.put("allRecorders",new Integer(allRecorders)) ;//总记录总数 request.put("list", service.findUsersByUsernameCustomerid( this.getUsername_c() , this.getCustomerid_c() ,this.getCurrentPage(),lineSize)); } return SUCCESS; }说是其中
- Java code
if ( this.getUsername_c().equals("") || this.getCustomerid_c().equals("") )这句设计到空指针.想问下为什么?而且好像有时候正确有时候会报错
------解决方案--------------------------------------------------------
this.getUsername_c().equals("") || this.getCustomerid_c().equals("")
这行代码有问题。要么前面的没获取到值，要么后面的没有获取到值。
你可以把位置稍微调换一下。为：
("").equals(this.getUsername_c()) || ("").equals(this.getCustomerid_c())
这样可以避免NullPointException。
所谓的NullPointException就是当你引用了一个空的对象的时候，来进行这个空对象的操作就会报NullPointException
------解决方案--------------------------------------------------------
if ("" == this.getUsername_c() || "" == this.getCustomerid_c())
------解决方案--------------------------------------------------------
楼主代码格式有问题，判断控制正或者字符串控制的格式应该是这样的
- Java code
if(null != str && !"".equal(str)){}
------解决方案--------------------------------------------------------
"".equals(this.getUsername_c()) || "".equals(this.getCustomerid_c())