求前辈给小妹看一段代码

Question

java
sqlserver数据库public Vector getTree(){
Vector vec=new Vector();
System.out.print("第一步");
//这一句出错了
List<DzswFl> treelist=dzswSpService.findFl();
vec.add(treelist);
return vec;
}请问下，为何到了List<DzswFl> treelist=dzswSpService.findFl();
这一句就报错呢？
java.lang.NullPointerException
dzswSpService这个方面找其余类里面用过，是可以查到数据的！现在就是请问下是我哪里的写法有问题吗？先谢谢了

Answer 1

dzswSpService是不是这个对象没初始化呃

Answer 2

明显是dzswSpService为空 是不是用的spring没有set
或者配置文件没有ref

Answer 3

初始化下dzswSpService对象或者走到哪一步F5看能进去那个方法不...

Answer 4

public class TreeList {
private DzswSpService dzswSpService;

public Vector getTree(){
Vector vec=new Vector();
System.out.print("第一步");
List<DzswFl> treelist=dzswSpService.findFl();
vec.add(treelist);
return vec;
}
}

Answer 5

你这样改试试：public Vector getTree(){
        Vector vec=new Vector();
        System.out.print("第一步");
         List<DzswFl> treelist = new ArrayList<DzswFl> ();
        treelist =dzswSpService.findFl();
        vec.add(treelist);
        return vec;
    }

Answer 6

dzswSpService要有对应的set方法，spring配置文件中看下是否注入了

Answer 7

注意导入包哦
import java.util.ArrayList;

Answer 8

还是空指针异常吗？
导入import java.util.ArrayList;这个包了吧

Answer 9

dzswSpService，如果是用spring注入，请为它生成get，set方法。

Answer 10

public void setDzswSpService(DzswSpService dzswSpService) {
this.dzswSpService = dzswSpService;
}

Answer 11

弱弱的说句：
我都加@Autowired的

Answer 12

弱弱的回答，我也加了package com.direct.news.dzsw.tree;import java.util.ArrayList;
import java.util.List;
import java.util.Vector;import org.springframework.beans.factory.annotation.Autowired;import com.direct.news.dzsw.dao.po.*;
import com.direct.news.dzsw.service.*;public class TreeList {
private DzswSpService dzswSpService;
@Autowired
public void setDzswSpService(DzswSpService dzswSpService) {
this.dzswSpService = dzswSpService;
}
public Vector getTree(){
Vector vec=new Vector();
System.out.print("到这里了");
List<DzswFl> treelist = new ArrayList<DzswFl> ();
        treelist =dzswSpService.findFl();
System.out.print("的值是是是:");
vec.add(treelist);
return vec;
}
}

Answer 13

1、确定配置没有错
2、debug
3、findFl代码贴出来
4、贴出所有的错误信息

Answer 14

话说我换了种写法，可以查出数据来着！为何我这样就报错呢？
所以确定findFl是对的，所有的错误信息java.lang.NullPointerException
com.direct.news.dzsw.tree.TreeList.getTree(TreeList.java:27)
org.apache.jsp.dzsw.tree.tree_jsp._jspService(tree_jsp.java:107)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:389)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:927)
org.apache.jasper.runtime.PageContextImpl.doInclude(PageContextImpl.java:684)
org.apache.jasper.runtime.PageContextImpl.include(PageContextImpl.java:678)
org.apache.tiles.jsp.context.JspTilesRequestContext.include(JspTilesRequestContext.java:103)
org.apache.tiles.jsp.context.JspTilesRequestContext.dispatch(JspTilesRequestContext.java:96)
org.apache.tiles.renderer.impl.TemplateAttributeRenderer.write(TemplateAttributeRenderer.java:44)
org.apache.tiles.renderer.impl.AbstractBaseAttributeRenderer.render(AbstractBaseAttributeRenderer.java:106)
org.apache.tiles.renderer.impl.ChainedDelegateAttributeRenderer.write(ChainedDelegateAttributeRenderer.java:76)
org.apache.tiles.renderer.impl.AbstractBaseAttributeRenderer.render(AbstractBaseAttributeRenderer.java:106)
org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:670)
org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:336)
org.apache.tiles.template.InsertAttributeModel.renderAttribute(InsertAttributeModel.java:210)
org.apache.tiles.template.InsertAttributeModel.end(InsertAttributeModel.java:126)
org.apache.tiles.jsp.taglib.InsertAttributeTag.doTag(InsertAttributeTag.java:311)
org.apache.jsp.dzsw.layouts.standard_jsp._jspx_meth_tiles_005finsertAttribute_005f0(standard_jsp.java:681)
org.apache.jsp.dzsw.layouts.standard_jsp._jspService(standard_jsp.java:189)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:389)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.tiles.servlet.context.ServletTilesRequestContext.forward(ServletTilesRequestContext.java:241)
org.apache.tiles.servlet.context.ServletTilesRequestContext.dispatch(ServletTilesRequestContext.java:222)
org.apache.tiles.renderer.impl.TemplateAttributeRenderer.write(TemplateAttributeRenderer.java:44)
org.apache.tiles.renderer.impl.AbstractBaseAttributeRenderer.render(AbstractBaseAttributeRenderer.java:106)
org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:670)
org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:690)
org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:644)
org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:627)
org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:321)
org.springframework.web.servlet.view.tiles2.TilesView.renderMergedOutputModel(TilesView.java:124)
org.springframework.js.ajax.tiles2.AjaxTilesView.renderMergedOutputModel(AjaxTilesView.java:131)
org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250)
org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1120)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:890)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:792)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:851)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:756)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:328)
org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:116)
org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:95)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:100)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:79)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:35)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:119)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:187)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:80)
org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:340)
org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:175)
org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

Answer 15

一是可能没注入service 二是可能你查得数据可能完整性是否有问题。

Answer 16

空异常，没New对象，设断点，调试一下看看吧，很easy！

Answer 17

你先确定问题在那，打印dzswSpService如果为null 那就说明没有注入成功，那就找Spring配置。

Answer 18

既然findFl是对的，换成返回List吧
 真是个奇怪的问题

Answer 19

java.lang.NullPointerException
不会飞の天使

Answer 20

public class TreeList {
    private DzswSpService dzswSpService;    
    public Vector getTree(){
        Vector vec=new Vector();
        System.out.print("第一步");
        List<DzswFl> treelist=dzswSpService.findFl();
        vec.add(treelist);
        return vec;
    }
}
普通类就NEW  注入的话 就看看配置

Answer 21

你这个错误是空指针异常，说明你这list中没值

Answer 22

CSDN的帖子带个小妹字眼，回帖量绝对杠杠的