spring空指针异常，前辈给小妹解释解释

Question

先贴错误：
exception org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:408)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:350)
javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause java.lang.NullPointerException
com.test.cmd.testCmd.handleRequest(testCmd.java:24)
org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:45)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:820)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:755)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:396)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:350)
javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)下面是applicationContext.xml
<?xml version="1.0" encoding="GBK"?><!DOCTYPE beans PUBLIC
          "-//SPRING//DTD BEAN//EN"
          "http://www.springframework.org/dtd/spring-beans.dtd"><beans>
 <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
   <property name="driverClassName">
     <value>com.microsoft.sqlserver.jdbc.SQLServerDriver</value>
   </property>
   <property name="url">
     <value>jdbc:sqlserver://localhost:1433;databaseName=sap_finance</value>
   </property>
   <property name="username">
     <value>sa</value>
   </property>
   <property name="password">
     <value>123</value>
   </property>
 </bean>
 <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
         <property name="dataSource" ref="dataSource"/>
  </bean>
 
 <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
   <property name="dataSource">
     <ref local="dataSource"/>
   </property>
 </bean><bean id="testDao" class="com.test.dao.testDao">
  <property name="jdbcTemplate">
    <ref local="jdbcTemplate"/>
  </property>
</bean> 
</beans>
testDaopublic class testDao {
  private JdbcTemplate jdbcTemplate;
  
  public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
    this.jdbcTemplate = jdbcTemplate;
  }   public JdbcTemplate getJdbcTemplate() {
    return this.jdbcTemplate;
  }}
testCmd
public class testCmd extends testDao implements Controller{
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
    throws Exception{
JdbcTemplate jdbcTemplate =getJdbcTemplate();
String sql="select * from test";
List sqlList=jdbcTemplate.queryForList(sql);
System.out.print(sqlList);
request.setAttribute("sqlList", sqlList);
return new ModelAndView("test/test.jsp");
    }

Answer 1

 = = 。。你的web.xml怎么写的。。

Answer 2

web.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/etc/applicationContext.xml
</param-value>
</context-param>
<listener>
  <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
        <servlet-name>dispatcherServlet</servlet-name>        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <load-on-startup>0</load-on-startup>    </servlet>    <!--为DispatcherServlet建立映射 -->    <servlet-mapping>         <servlet-name>dispatcherServlet</servlet-name>         <url-pattern>*.do2</url-pattern>    </servlet-mapping>
  <filter>
    <filter-name>Set Character Encoding</filter-name>
    <filter-class>com.utils.EncodeFilter</filter-class>
    <init-param>
      <param-name>ignore</param-name>
      <param-value>true</param-value>
    </init-param>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>GB2312</param-value>
    </init-param>
  </filter>  <filter-mapping>
    <filter-name>Set Character Encoding</filter-name>
    <url-pattern>*.do</url-pattern>
  </filter-mapping>
<!--
   <listener>
  <listener-class>com.utils.ActiveUserListener</listener-class>
 </listener>
-->
<servlet>          <servlet-name>TimeServlet</servlet-name>
          <servlet-class>com.utils.TimeTrackerPlugin</servlet-class>
          <load-on-startup>1</load-on-startup>
     </servlet>
  <servlet>
     <servlet-name>action</servlet-name>
    <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
    <init-param>
    
      <param-name>debug</param-name>
      <param-value>2</param-value>
    </init-param>
    <init-param>
      
      <param-name>config</param-name>
      <param-value>/WEB-INF/struts-config.xml</param-value>
    </init-param>
    <init-param>
      <param-name>application</param-name>
      <param-value>ApplicationResources</param-value>
    </init-param>
    <load-on-startup>2</load-on-startup>
  </servlet>
  <servlet>
    <servlet-name>debugjsp</servlet-name>
    <description>Added to compile JSPs with debug info</description>
    <servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
    <init-param>
      <param-name>classdebuginfo</param-name>
      <param-value>true</param-value>
    </init-param>
    <load-on-startup>3</load-on-startup>
  </servlet>   <servlet>
       <servlet-name>DisplayChart</servlet-name>
       <servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class>
     </servlet>  <servlet-mapping>
    <servlet-name>action</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>debugjsp</servlet-name>
    <url-pattern>*.jsp</url-pattern>
  </servlet-mapping>
 <session-config>
    <session-timeout>100</session-timeout>
  </session-config>
  <taglib>
    <taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-bean.tld</taglib-location>
  </taglib>
  <taglib>
    <taglib-uri>/WEB-INF/struts-html.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-html.tld</taglib-location>
  </taglib>
  <taglib>
    <taglib-uri>/WEB-INF/struts-logic.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-logic.tld</taglib-location>
  </taglib>
  <taglib>
    <taglib-uri>/WEB-INF/struts-template.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-template.tld</taglib-location>
  </taglib>
  
</web-app>

Answer 3

testCmd这个都没有在xml里面配置，spring怎么注入啊??

Answer 4

 = = 。。嗯。。楼上所说是正确的。。的确是testCmd没有配置，，相反testDao其实是不用配置的

Answer 5

以上正解，把你testDao配置注入的地方改成testCmd楼主小妹试试

Answer 6

*.do2是什么？你用的Struts1对吗？
用Spring时候时你有到了Spring的JDBC是吧
你的代码我看了半天，我才明白！
众多人认为testDao是null，因为没有注入！
先在我不管这个是否为null
因为在testCmd这个类里没有testDao
所以要知道java.lang.NullPointerException是在哪抛出来的
你必须把testCmd这个类的第24行代码标明出来！这样才方便找...

Answer 7

这行是：
List sqlList=jdbcTemplate.queryForList(sql);